From patchwork Mon Jul 31 07:30:14 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13333929 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2E03C04A94 for ; Mon, 31 Jul 2023 07:31:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230272AbjGaHbo (ORCPT ); Mon, 31 Jul 2023 03:31:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230342AbjGaHb2 (ORCPT ); Mon, 31 Jul 2023 03:31:28 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3AA110DF; Mon, 31 Jul 2023 00:30:19 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6266360F4B; Mon, 31 Jul 2023 07:30:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD863C433C8; Mon, 31 Jul 2023 07:30:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690788618; bh=KReumcvfAA7aUU41c/MWj+LowvbdvMSmvuGEweZl3FI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Yk5RC9/Eey4v3uiQbcxGeVcd3OuTXzhbNndT/RueCZlJsms0vRpd1YfQkIkLh4LP7 vBWFVfEHIqnrcGaEQrKqF2NRPyIwHvPpAqQpvp/nP1SZOeMbDX/UKR5p6AsanAn7ek IRsiecm4Acy7QJcEhLm1GWC35FOOTfZ01D2qLx3gHcyGniENbPlzSAMc3YyukX+6ET /REU4J6j26tkrqeMH4Nz83yr9DSMYkbOw1jHx2USxThk5Qb7GRUwfJp4R9gGDwFJVH 9EApAghejIX2UnYkmCpzjRSLsKuOLqpKAVXO4cIBEQ1gTneftq0mgSR8TTPFfYevgR Kv7mUOuIr9qpg== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v4 1/9] tracing/probes: Support BTF argument on module functions Date: Mon, 31 Jul 2023 16:30:14 +0900 Message-Id: <169078861390.173706.6123335543895839788.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169078860386.173706.3091034523220945605.stgit@devnote2> References: <169078860386.173706.3091034523220945605.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Since the btf returned from bpf_get_btf_vmlinux() only covers functions in the vmlinux, BTF argument is not available on the functions in the modules. Use bpf_find_btf_id() instead of bpf_get_btf_vmlinux()+btf_find_name_kind() so that BTF argument can find the correct struct btf and btf_type in it. With this fix, fprobe events can use `$arg*` on module functions as below # grep nf_log_ip_packet /proc/kallsyms ffffffffa0005c00 t nf_log_ip_packet [nf_log_syslog] ffffffffa0005bf0 t __pfx_nf_log_ip_packet [nf_log_syslog] # echo 'f nf_log_ip_packet $arg*' > dynamic_events # cat dynamic_events f:fprobes/nf_log_ip_packet__entry nf_log_ip_packet net=net pf=pf hooknum=hooknum skb=skb in=in out=out loginfo=loginfo prefix=prefix To support the module's btf which is removable, the struct btf needs to be ref-counted. So this also records the btf in the traceprobe_parse_context and returns the refcount when the parse has done. Suggested-by: Alexei Starovoitov Signed-off-by: Masami Hiramatsu (Google) --- Changes in v3: - Newly added. --- include/linux/btf.h | 1 kernel/bpf/btf.c | 2 - kernel/trace/trace_eprobe.c | 4 -- kernel/trace/trace_fprobe.c | 1 kernel/trace/trace_kprobe.c | 1 kernel/trace/trace_probe.c | 100 +++++++++++++++++++++++++------------------ kernel/trace/trace_probe.h | 14 +++++- kernel/trace/trace_uprobe.c | 1 8 files changed, 75 insertions(+), 49 deletions(-) diff --git a/include/linux/btf.h b/include/linux/btf.h index cac9f304e27a..dbfe41a09c4b 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -211,6 +211,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec); bool btf_type_is_void(const struct btf_type *t); s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind); +s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p); const struct btf_type *btf_type_skip_modifiers(const struct btf *btf, u32 id, u32 *res_id); const struct btf_type *btf_type_resolve_ptr(const struct btf *btf, diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 817204d53372..b9b0eb1189bb 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -552,7 +552,7 @@ s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind) return -ENOENT; } -static s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p) +s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p) { struct btf *btf; s32 ret; diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c index a0a704ba27db..09bac836d72b 100644 --- a/kernel/trace/trace_eprobe.c +++ b/kernel/trace/trace_eprobe.c @@ -807,13 +807,11 @@ static int trace_eprobe_tp_update_arg(struct trace_eprobe *ep, const char *argv[ int ret; ret = traceprobe_parse_probe_arg(&ep->tp, i, argv[i], &ctx); - if (ret) - return ret; - /* Handle symbols "@" */ if (!ret) ret = traceprobe_update_arg(&ep->tp.args[i]); + traceprobe_finish_parse(&ctx); return ret; } diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c index dfe2e546acdc..8f43f1f65b1b 100644 --- a/kernel/trace/trace_fprobe.c +++ b/kernel/trace/trace_fprobe.c @@ -1096,6 +1096,7 @@ static int __trace_fprobe_create(int argc, const char *argv[]) } out: + traceprobe_finish_parse(&ctx); trace_probe_log_clear(); kfree(new_argv); kfree(symbol); diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 23dba01831f7..cc822f69bfe8 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -907,6 +907,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) } out: + traceprobe_finish_parse(&ctx); trace_probe_log_clear(); kfree(new_argv); kfree(symbol); diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index c68a72707852..ecbe28f8d676 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -304,16 +304,6 @@ static int parse_trace_event_arg(char *arg, struct fetch_insn *code, #ifdef CONFIG_PROBE_EVENTS_BTF_ARGS -static struct btf *traceprobe_get_btf(void) -{ - struct btf *btf = bpf_get_btf_vmlinux(); - - if (IS_ERR_OR_NULL(btf)) - return NULL; - - return btf; -} - static u32 btf_type_int(const struct btf_type *t) { return *(u32 *)(t + 1); @@ -371,42 +361,49 @@ static const char *type_from_btf_id(struct btf *btf, s32 id) return NULL; } -static const struct btf_type *find_btf_func_proto(const char *funcname) +static const struct btf_type *find_btf_func_proto(const char *funcname, + struct btf **btf_p) { - struct btf *btf = traceprobe_get_btf(); const struct btf_type *t; + struct btf *btf = NULL; s32 id; - if (!btf || !funcname) + if (!funcname) return ERR_PTR(-EINVAL); - id = btf_find_by_name_kind(btf, funcname, BTF_KIND_FUNC); + id = bpf_find_btf_id(funcname, BTF_KIND_FUNC, &btf); if (id <= 0) return ERR_PTR(-ENOENT); /* Get BTF_KIND_FUNC type */ t = btf_type_by_id(btf, id); if (!t || !btf_type_is_func(t)) - return ERR_PTR(-ENOENT); + goto err; /* The type of BTF_KIND_FUNC is BTF_KIND_FUNC_PROTO */ t = btf_type_by_id(btf, t->type); if (!t || !btf_type_is_func_proto(t)) - return ERR_PTR(-ENOENT); + goto err; + *btf_p = btf; return t; + +err: + btf_put(btf); + return ERR_PTR(-ENOENT); } static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr, - bool tracepoint) + struct btf **btf_p, bool tracepoint) { const struct btf_param *param; const struct btf_type *t; + struct btf *btf; if (!funcname || !nr) return ERR_PTR(-EINVAL); - t = find_btf_func_proto(funcname); + t = find_btf_func_proto(funcname, &btf); if (IS_ERR(t)) return (const struct btf_param *)t; @@ -419,29 +416,37 @@ static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr param++; } - if (*nr > 0) + if (*nr > 0) { + *btf_p = btf; return param; - else - return NULL; + } + + btf_put(btf); + return NULL; +} + +static void clear_btf_context(struct traceprobe_parse_context *ctx) +{ + if (ctx->btf) { + btf_put(ctx->btf); + ctx->btf = NULL; + ctx->params = NULL; + ctx->nr_params = 0; + } } static int parse_btf_arg(const char *varname, struct fetch_insn *code, struct traceprobe_parse_context *ctx) { - struct btf *btf = traceprobe_get_btf(); const struct btf_param *params; int i; - if (!btf) { - trace_probe_log_err(ctx->offset, NOSUP_BTFARG); - return -EOPNOTSUPP; - } - if (WARN_ON_ONCE(!ctx->funcname)) return -EINVAL; if (!ctx->params) { - params = find_btf_func_param(ctx->funcname, &ctx->nr_params, + params = find_btf_func_param(ctx->funcname, + &ctx->nr_params, &ctx->btf, ctx->flags & TPARG_FL_TPOINT); if (IS_ERR_OR_NULL(params)) { trace_probe_log_err(ctx->offset, NO_BTF_ENTRY); @@ -452,7 +457,7 @@ static int parse_btf_arg(const char *varname, struct fetch_insn *code, params = ctx->params; for (i = 0; i < ctx->nr_params; i++) { - const char *name = btf_name_by_offset(btf, params[i].name_off); + const char *name = btf_name_by_offset(ctx->btf, params[i].name_off); if (name && !strcmp(name, varname)) { code->op = FETCH_OP_ARG; @@ -470,7 +475,7 @@ static int parse_btf_arg(const char *varname, struct fetch_insn *code, static const struct fetch_type *parse_btf_arg_type(int arg_idx, struct traceprobe_parse_context *ctx) { - struct btf *btf = traceprobe_get_btf(); + struct btf *btf = ctx->btf; const char *typestr = NULL; if (btf && ctx->params) { @@ -485,14 +490,17 @@ static const struct fetch_type *parse_btf_arg_type(int arg_idx, static const struct fetch_type *parse_btf_retval_type( struct traceprobe_parse_context *ctx) { - struct btf *btf = traceprobe_get_btf(); const char *typestr = NULL; const struct btf_type *t; + struct btf *btf; - if (btf && ctx->funcname) { - t = find_btf_func_proto(ctx->funcname); - if (!IS_ERR(t)) + if (ctx->funcname) { + /* Do not use ctx->btf, because it must be used with ctx->param */ + t = find_btf_func_proto(ctx->funcname, &btf); + if (!IS_ERR(t)) { typestr = type_from_btf_id(btf, t->type); + btf_put(btf); + } } return find_fetch_type(typestr, ctx->flags); @@ -501,21 +509,25 @@ static const struct fetch_type *parse_btf_retval_type( static bool is_btf_retval_void(const char *funcname) { const struct btf_type *t; + struct btf *btf; + bool ret; - t = find_btf_func_proto(funcname); + t = find_btf_func_proto(funcname, &btf); if (IS_ERR(t)) return false; - return t->type == 0; + ret = (t->type == 0); + btf_put(btf); + return ret; } #else -static struct btf *traceprobe_get_btf(void) +static void clear_btf_context(struct traceprobe_parse_context *ctx) { - return NULL; + ctx->btf = NULL; } static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr, - bool tracepoint) + struct btf **btf_p, bool tracepoint) { return ERR_PTR(-EOPNOTSUPP); } @@ -1231,7 +1243,6 @@ static int sprint_nth_btf_arg(int idx, const char *type, char *buf, int bufsize, struct traceprobe_parse_context *ctx) { - struct btf *btf = traceprobe_get_btf(); const char *name; int ret; @@ -1239,7 +1250,7 @@ static int sprint_nth_btf_arg(int idx, const char *type, trace_probe_log_err(0, NO_BTFARG); return -ENOENT; } - name = btf_name_by_offset(btf, ctx->params[idx].name_off); + name = btf_name_by_offset(ctx->btf, ctx->params[idx].name_off); if (!name) { trace_probe_log_err(0, NO_BTF_ENTRY); return -ENOENT; @@ -1271,7 +1282,7 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[], return NULL; } - params = find_btf_func_param(ctx->funcname, &nr_params, + params = find_btf_func_param(ctx->funcname, &nr_params, &ctx->btf, ctx->flags & TPARG_FL_TPOINT); if (IS_ERR_OR_NULL(params)) { if (args_idx != -1) { @@ -1337,6 +1348,11 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[], return ERR_PTR(ret); } +void traceprobe_finish_parse(struct traceprobe_parse_context *ctx) +{ + clear_btf_context(ctx); +} + int traceprobe_update_arg(struct probe_arg *arg) { struct fetch_insn *code = arg->code; diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 01ea148723de..4dc91460a75d 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -383,9 +383,11 @@ static inline bool tparg_is_function_entry(unsigned int flags) struct traceprobe_parse_context { struct trace_event_call *event; - const struct btf_param *params; - s32 nr_params; - const char *funcname; + /* BTF related parameters */ + const char *funcname; /* Function name in BTF */ + const struct btf_param *params; /* Parameter of the function */ + s32 nr_params; /* The number of the parameters */ + struct btf *btf; /* The BTF to be used */ unsigned int flags; int offset; }; @@ -400,6 +402,12 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[], extern int traceprobe_update_arg(struct probe_arg *arg); extern void traceprobe_free_probe_arg(struct probe_arg *arg); +/* + * If either traceprobe_parse_probe_arg() or traceprobe_expand_meta_args() is called, + * this MUST be called for clean up the context and return a resource. + */ +void traceprobe_finish_parse(struct traceprobe_parse_context *ctx); + extern int traceprobe_split_symbol_offset(char *symbol, long *offset); int traceprobe_parse_event_name(const char **pevent, const char **pgroup, char *buf, int offset); diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 688bf579f2f1..9790f8f0a32d 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -693,6 +693,7 @@ static int __trace_uprobe_create(int argc, const char **argv) trace_probe_log_set_index(i + 2); ret = traceprobe_parse_probe_arg(&tu->tp, i, argv[i], &ctx); + traceprobe_finish_parse(&ctx); if (ret) goto error; } From patchwork Mon Jul 31 07:30:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13333930 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 293F9C001DE for ; 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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690788629; bh=SVaKMsm5wi9MtePH615CD5h2bQfFDb6xVagKrZjtk0U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LdZJ7fD3T+xhrnDmL+T7tHHUuFYDGmrM0yS8YzfN7su2DNxMmUwE6wd0weiynMwWM bZtsOuDuv09Q99o9hdOxijhLTUDclWHnM3cBEoOw5kIGaAZijCZrOpAqfIPG4ANZ+2 Lv62sx5inwIHaXGJYAc3vjj4m2SLW4vZH6LFTL6IWyz8Wd9AxUNb24y8xWLWRkKrXw md/vTfZyIR3H2GN3e9nsdrJsR0DqveTwZ+9uOOwPfF0/ScgqnrE/sIHs48vzdeZAgr 2SANoGKJTxFs+ncRbd5UV7l9YfrukVMYifnrtCenO1uU5LL3NlIv/oE0z2lcoM/6lL oqo1JY5YBc4OQ== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v4 2/9] bpf/btf: tracing: Move finding func-proto API and getting func-param API to BTF Date: Mon, 31 Jul 2023 16:30:24 +0900 Message-Id: <169078862446.173706.13484451284649857042.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169078860386.173706.3091034523220945605.stgit@devnote2> References: <169078860386.173706.3091034523220945605.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Move generic function-proto find API and getting function parameter API to BTF library code from trace_probe.c. This will avoid redundant efforts on different feature. Signed-off-by: Masami Hiramatsu (Google) --- Changes in v3: - Remove perameter check. - Fix a typo. - Add a type check for btf_get_func_param() and add comment for that. - Use bpf_find_btf_id() and add bpf_put(). - Move the code before btf_show() related code. --- include/linux/btf.h | 4 ++++ kernel/bpf/btf.c | 47 +++++++++++++++++++++++++++++++++++++++++ kernel/trace/trace_probe.c | 50 +++++++++----------------------------------- 3 files changed, 61 insertions(+), 40 deletions(-) diff --git a/include/linux/btf.h b/include/linux/btf.h index dbfe41a09c4b..20e3a07eef8f 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -222,6 +222,10 @@ const struct btf_type * btf_resolve_size(const struct btf *btf, const struct btf_type *type, u32 *type_size); const char *btf_type_str(const struct btf_type *t); +const struct btf_type *btf_find_func_proto(const char *func_name, + struct btf **btf_p); +const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, + s32 *nr); #define for_each_member(i, struct_type, member) \ for (i = 0, member = btf_type_member(struct_type); \ diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index b9b0eb1189bb..f7b25c615269 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -911,6 +911,53 @@ static const struct btf_type *btf_type_skip_qualifiers(const struct btf *btf, return t; } +/* + * Find a function proto type by name, and return the btf_type with its btf + * in *@btf_p. Return NULL if not found. + * Note that caller has to call btf_put(*@btf_p) after using the btf_type. + */ +const struct btf_type *btf_find_func_proto(const char *func_name, struct btf **btf_p) +{ + const struct btf_type *t; + s32 id; + + id = bpf_find_btf_id(func_name, BTF_KIND_FUNC, btf_p); + if (id < 0) + return NULL; + + /* Get BTF_KIND_FUNC type */ + t = btf_type_by_id(*btf_p, id); + if (!t || !btf_type_is_func(t)) + goto err; + + /* The type of BTF_KIND_FUNC is BTF_KIND_FUNC_PROTO */ + t = btf_type_by_id(*btf_p, t->type); + if (!t || !btf_type_is_func_proto(t)) + goto err; + + return t; +err: + btf_put(*btf_p); + return NULL; +} + +/* + * Get function parameter with the number of parameters. + * This can return NULL if the function has no parameters. + * It can return -EINVAL if the @func_proto is not a function proto type. + */ +const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s32 *nr) +{ + if (!btf_type_is_func_proto(func_proto)) + return ERR_PTR(-EINVAL); + + *nr = btf_type_vlen(func_proto); + if (*nr > 0) + return (const struct btf_param *)(func_proto + 1); + else + return NULL; +} + #define BTF_SHOW_MAX_ITER 10 #define BTF_KIND_BIT(kind) (1ULL << kind) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index ecbe28f8d676..21a228d88ebb 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -361,38 +361,6 @@ static const char *type_from_btf_id(struct btf *btf, s32 id) return NULL; } -static const struct btf_type *find_btf_func_proto(const char *funcname, - struct btf **btf_p) -{ - const struct btf_type *t; - struct btf *btf = NULL; - s32 id; - - if (!funcname) - return ERR_PTR(-EINVAL); - - id = bpf_find_btf_id(funcname, BTF_KIND_FUNC, &btf); - if (id <= 0) - return ERR_PTR(-ENOENT); - - /* Get BTF_KIND_FUNC type */ - t = btf_type_by_id(btf, id); - if (!t || !btf_type_is_func(t)) - goto err; - - /* The type of BTF_KIND_FUNC is BTF_KIND_FUNC_PROTO */ - t = btf_type_by_id(btf, t->type); - if (!t || !btf_type_is_func_proto(t)) - goto err; - - *btf_p = btf; - return t; - -err: - btf_put(btf); - return ERR_PTR(-ENOENT); -} - static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr, struct btf **btf_p, bool tracepoint) { @@ -403,12 +371,13 @@ static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr if (!funcname || !nr) return ERR_PTR(-EINVAL); - t = find_btf_func_proto(funcname, &btf); - if (IS_ERR(t)) + t = btf_find_func_proto(funcname, &btf); + if (!t) return (const struct btf_param *)t; - *nr = btf_type_vlen(t); - param = (const struct btf_param *)(t + 1); + param = btf_get_func_param(t, nr); + if (IS_ERR_OR_NULL(param)) + goto err; /* Hide the first 'data' argument of tracepoint */ if (tracepoint) { @@ -421,6 +390,7 @@ static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr return param; } +err: btf_put(btf); return NULL; } @@ -496,8 +466,8 @@ static const struct fetch_type *parse_btf_retval_type( if (ctx->funcname) { /* Do not use ctx->btf, because it must be used with ctx->param */ - t = find_btf_func_proto(ctx->funcname, &btf); - if (!IS_ERR(t)) { + t = btf_find_func_proto(ctx->funcname, &btf); + if (t) { typestr = type_from_btf_id(btf, t->type); btf_put(btf); } @@ -512,8 +482,8 @@ static bool is_btf_retval_void(const char *funcname) struct btf *btf; bool ret; - t = find_btf_func_proto(funcname, &btf); - if (IS_ERR(t)) + t = btf_find_func_proto(funcname, &btf); + if (!t) return false; ret = (t->type == 0); From patchwork Mon Jul 31 07:30:34 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13333931 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82B0EC001DF for ; Mon, 31 Jul 2023 07:32:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231483AbjGaHcB (ORCPT ); Mon, 31 Jul 2023 03:32:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231481AbjGaHbf (ORCPT ); Mon, 31 Jul 2023 03:31:35 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2669610C; Mon, 31 Jul 2023 00:30:40 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B872760F07; Mon, 31 Jul 2023 07:30:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2BE2DC433C7; Mon, 31 Jul 2023 07:30:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690788639; bh=ZxqLQEDqyrTI+b7ozLCG2peyd8pHZudlPd6y62zwtWQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hpZUtMBGR106BHm0aj2xR7/CzYRk5wdguE7xIfK2kjju17dMC1Ve8PY4G1GNYkn8P 2LV0DgD+0uZ2JB2OfOKjP2TNXSwEacmeNU3iq2kQ+BM124AGnkMCwl8LK9dVJYNTbC eFZeK+jAz/1F9dBubKz5HaIaUNZyIsrk24FSMnmUWFXms6R1GFjXeVNp/oo5KiJ3di U3q5sCGsPnRGezK13vAsoxDPYLDL5D05+ljYET+h3qXjCOkCteT/bH7ZnIA/brGmOm pqUNLdUbGklzV2bIIs7RMX7T6iRZx6uu6BEa2Kx/6E0Ss/2t35rnt8vNq0+atuBnuJ dnNS988aIFc4A== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v4 3/9] bpf/btf: Add a function to search a member of a struct/union Date: Mon, 31 Jul 2023 16:30:34 +0900 Message-Id: <169078863449.173706.2322042687021909241.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169078860386.173706.3091034523220945605.stgit@devnote2> References: <169078860386.173706.3091034523220945605.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Add btf_find_struct_member() API to search a member of a given data structure or union from the member's name. Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Alan Maguire --- Changes in v3: - Remove simple input check. - Fix unneeded IS_ERR_OR_NULL() check for btf_type_by_id(). - Move the code next to btf_get_func_param(). - Use for_each_member() macro instead of for-loop. - Use btf_type_skip_modifiers() instead of btf_type_by_id(). Changes in v4: - Use a stack for searching in anonymous members instead of nested call. --- include/linux/btf.h | 3 +++ kernel/bpf/btf.c | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 43 insertions(+) diff --git a/include/linux/btf.h b/include/linux/btf.h index 20e3a07eef8f..4b10d57ceee0 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -226,6 +226,9 @@ const struct btf_type *btf_find_func_proto(const char *func_name, struct btf **btf_p); const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s32 *nr); +const struct btf_member *btf_find_struct_member(struct btf *btf, + const struct btf_type *type, + const char *member_name); #define for_each_member(i, struct_type, member) \ for (i = 0, member = btf_type_member(struct_type); \ diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index f7b25c615269..8d81a4ffa67b 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -958,6 +958,46 @@ const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s3 return NULL; } +#define BTF_ANON_STACK_MAX 16 + +/* + * Find a member of data structure/union by name and return it. + * Return NULL if not found, or -EINVAL if parameter is invalid. + */ +const struct btf_member *btf_find_struct_member(struct btf *btf, + const struct btf_type *type, + const char *member_name) +{ + const struct btf_type *anon_stack[BTF_ANON_STACK_MAX]; + const struct btf_member *member; + const char *name; + int i, top = 0; + +retry: + if (!btf_type_is_struct(type)) + return ERR_PTR(-EINVAL); + + for_each_member(i, type, member) { + if (!member->name_off) { + /* Anonymous union/struct: push it for later use */ + type = btf_type_skip_modifiers(btf, member->type, NULL); + if (type && top < BTF_ANON_STACK_MAX) + anon_stack[top++] = type; + } else { + name = btf_name_by_offset(btf, member->name_off); + if (name && !strcmp(member_name, name)) + return member; + } + } + if (top > 0) { + /* Pop from the anonymous stack and retry */ + type = anon_stack[--top]; + goto retry; + } + + return NULL; +} + #define BTF_SHOW_MAX_ITER 10 #define BTF_KIND_BIT(kind) (1ULL << kind) From patchwork Mon Jul 31 07:30:44 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13333932 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8EF7C04A94 for ; Mon, 31 Jul 2023 07:32:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229880AbjGaHcC (ORCPT ); Mon, 31 Jul 2023 03:32:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40368 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229665AbjGaHbh (ORCPT ); Mon, 31 Jul 2023 03:31:37 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E51BD189; Mon, 31 Jul 2023 00:30:49 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7606F60F07; Mon, 31 Jul 2023 07:30:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38F48C433C8; Mon, 31 Jul 2023 07:30:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690788648; bh=I2UbfdQQupa3O44BbXXMZ2gOuSLCUPSbCpadML6QpNE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZNCWIK8AHIpgvShQCZWobmRbkNHn8B+w8OCcv6Drj4HSGSqsI1A59YIkXybk5twQP TN4XE/Gj05gidVfKI9WYan5cLYCO3ItUjRnkke9KHVo0MXYSlVPMTMope4RKGnYRtO qta722rvjhnF23k2UpEE2GGgnFg/haTNk1MLsb8cKk9bM+Njw3I+phDndmL8A8s1D9 bxLhMsXeReinecm4PO2Dc4jBBCVSPgGBO93iiH1eFQa88ym2dBe3u3arn8/f64CGeI uwYhJmjm+g+gTdHXoVEi+UcaRZrMKowUsl6ZbIM8JlQ5vSl9JQTPQJTRR1AdJJRKBv q2zQCw/Pb5ndQ== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v4 4/9] tracing/probes: Support BTF based data structure field access Date: Mon, 31 Jul 2023 16:30:44 +0900 Message-Id: <169078864454.173706.15170839555232465528.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169078860386.173706.3091034523220945605.stgit@devnote2> References: <169078860386.173706.3091034523220945605.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Using BTF to access the fields of a data structure. You can use this for accessing the field with '->' or '.' operation with BTF argument. # echo 't sched_switch next=next->pid vruntime=next->se.vruntime' \ > dynamic_events # echo 1 > events/tracepoints/sched_switch/enable # head -n 40 trace | tail -0 [000] d..3. 272.565382: sched_switch: (__probestub_sched_switch+0x4/0x10) next=26 vruntime=956533179 kcompactd0-26 [000] d..3. 272.565406: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0 -0 [000] d..3. 273.069441: sched_switch: (__probestub_sched_switch+0x4/0x10) next=9 vruntime=956533179 kworker/0:1-9 [000] d..3. 273.069464: sched_switch: (__probestub_sched_switch+0x4/0x10) next=26 vruntime=956579181 kcompactd0-26 [000] d..3. 273.069480: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0 -0 [000] d..3. 273.141434: sched_switch: (__probestub_sched_switch+0x4/0x10) next=22 vruntime=956533179 kworker/u2:1-22 [000] d..3. 273.141461: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0 -0 [000] d..3. 273.480872: sched_switch: (__probestub_sched_switch+0x4/0x10) next=22 vruntime=956585857 kworker/u2:1-22 [000] d..3. 273.480905: sched_switch: (__probestub_sched_switch+0x4/0x10) next=70 vruntime=959533179 sh-70 [000] d..3. 273.481102: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0 Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Alan Maguire --- Changes in v2: - Use new BTF API for finding the member. Changes in v3: - Update according to previous changes in the series. --- kernel/trace/trace_probe.c | 226 +++++++++++++++++++++++++++++++++++++++----- kernel/trace/trace_probe.h | 11 ++ 2 files changed, 210 insertions(+), 27 deletions(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 21a228d88ebb..f6b855de4256 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -309,16 +309,14 @@ static u32 btf_type_int(const struct btf_type *t) return *(u32 *)(t + 1); } -static const char *type_from_btf_id(struct btf *btf, s32 id) +static const char *fetch_type_from_btf_type(struct btf *btf, + const struct btf_type *type, + struct traceprobe_parse_context *ctx) { - const struct btf_type *t; u32 intdata; - s32 tid; /* TODO: const char * could be converted as a string */ - t = btf_type_skip_modifiers(btf, id, &tid); - - switch (BTF_INFO_KIND(t->info)) { + switch (BTF_INFO_KIND(type->info)) { case BTF_KIND_ENUM: /* enum is "int", so convert to "s32" */ return "s32"; @@ -331,7 +329,7 @@ static const char *type_from_btf_id(struct btf *btf, s32 id) else return "x32"; case BTF_KIND_INT: - intdata = btf_type_int(t); + intdata = btf_type_int(type); if (BTF_INT_ENCODING(intdata) & BTF_INT_SIGNED) { switch (BTF_INT_BITS(intdata)) { case 8: @@ -354,6 +352,10 @@ static const char *type_from_btf_id(struct btf *btf, s32 id) case 64: return "u64"; } + /* bitfield, size is encoded in the type */ + ctx->last_bitsize = BTF_INT_BITS(intdata); + ctx->last_bitoffs += BTF_INT_OFFSET(intdata); + return "u64"; } } /* TODO: support other types */ @@ -405,15 +407,132 @@ static void clear_btf_context(struct traceprobe_parse_context *ctx) } } -static int parse_btf_arg(const char *varname, struct fetch_insn *code, +/* Return 1 if the field separater is arrow operator ('->') */ +static int split_next_field(char *varname, char **next_field, + struct traceprobe_parse_context *ctx) +{ + char *field; + int ret = 0; + + field = strpbrk(varname, ".-"); + if (field) { + if (field[0] == '-' && field[1] == '>') { + field[0] = '\0'; + field += 2; + ret = 1; + } else if (field[0] == '.') { + field[0] = '\0'; + field += 1; + } else { + trace_probe_log_err(ctx->offset + field - varname, BAD_HYPHEN); + return -EINVAL; + } + *next_field = field; + } + + return ret; +} + +/* + * Parse the field of data structure. The @type must be a pointer type + * pointing the target data structure type. + */ +static int parse_btf_field(char *fieldname, const struct btf_type *type, + struct fetch_insn **pcode, struct fetch_insn *end, + struct traceprobe_parse_context *ctx) +{ + struct fetch_insn *code = *pcode; + const struct btf_member *field; + u32 bitoffs; + char *next; + int is_ptr; + s32 tid; + + do { + /* Outer loop for solving arrow operator ('->') */ + if (BTF_INFO_KIND(type->info) != BTF_KIND_PTR) { + trace_probe_log_err(ctx->offset, NO_PTR_STRCT); + return -EINVAL; + } + /* Convert a struct pointer type to a struct type */ + type = btf_type_skip_modifiers(ctx->btf, type->type, &tid); + if (!type) { + trace_probe_log_err(ctx->offset, BAD_BTF_TID); + return -EINVAL; + } + + bitoffs = 0; + do { + /* Inner loop for solving dot operator ('.') */ + next = NULL; + is_ptr = split_next_field(fieldname, &next, ctx); + if (is_ptr < 0) + return is_ptr; + + field = btf_find_struct_member(ctx->btf, type, fieldname); + if (!field) { + trace_probe_log_err(ctx->offset, NO_BTF_FIELD); + return -ENOENT; + } + + /* Accumulate the bit-offsets of the dot-connected fields */ + if (btf_type_kflag(type)) { + bitoffs += BTF_MEMBER_BIT_OFFSET(field->offset); + ctx->last_bitsize = BTF_MEMBER_BITFIELD_SIZE(field->offset); + } else { + bitoffs += field->offset; + ctx->last_bitsize = 0; + } + + type = btf_type_skip_modifiers(ctx->btf, field->type, &tid); + if (!type) { + trace_probe_log_err(ctx->offset, BAD_BTF_TID); + return -EINVAL; + } + + ctx->offset += next - fieldname; + fieldname = next; + } while (!is_ptr && fieldname); + + if (++code == end) { + trace_probe_log_err(ctx->offset, TOO_MANY_OPS); + return -EINVAL; + } + code->op = FETCH_OP_DEREF; /* TODO: user deref support */ + code->offset = bitoffs / 8; + *pcode = code; + + ctx->last_bitoffs = bitoffs % 8; + ctx->last_type = type; + } while (fieldname); + + return 0; +} + +static int parse_btf_arg(char *varname, + struct fetch_insn **pcode, struct fetch_insn *end, struct traceprobe_parse_context *ctx) { + struct fetch_insn *code = *pcode; const struct btf_param *params; - int i; + const struct btf_type *type; + char *field = NULL; + int i, is_ptr; + u32 tid; if (WARN_ON_ONCE(!ctx->funcname)) return -EINVAL; + is_ptr = split_next_field(varname, &field, ctx); + if (is_ptr < 0) + return is_ptr; + if (!is_ptr && field) { + /* dot-connected field on an argument is not supported. */ + trace_probe_log_err(ctx->offset + field - varname, + NOSUP_DAT_ARG); + return -EOPNOTSUPP; + } + if (!ctx->params) { params = find_btf_func_param(ctx->funcname, &ctx->nr_params, &ctx->btf, @@ -435,24 +554,39 @@ static int parse_btf_arg(const char *varname, struct fetch_insn *code, code->param = i + 1; else code->param = i; - return 0; + + tid = params[i].type; + goto found; } } trace_probe_log_err(ctx->offset, NO_BTFARG); return -ENOENT; + +found: + type = btf_type_skip_modifiers(ctx->btf, tid, &tid); + if (!type) { + trace_probe_log_err(ctx->offset, BAD_BTF_TID); + return -EINVAL; + } + /* Initialize the last type information */ + ctx->last_type = type; + ctx->last_bitoffs = 0; + ctx->last_bitsize = 0; + if (field) { + ctx->offset += field - varname; + return parse_btf_field(field, type, pcode, end, ctx); + } + return 0; } -static const struct fetch_type *parse_btf_arg_type(int arg_idx, +static const struct fetch_type *parse_btf_arg_type( struct traceprobe_parse_context *ctx) { struct btf *btf = ctx->btf; const char *typestr = NULL; - if (btf && ctx->params) { - if (ctx->flags & TPARG_FL_TPOINT) - arg_idx--; - typestr = type_from_btf_id(btf, ctx->params[arg_idx].type); - } + if (btf && ctx->last_type) + typestr = fetch_type_from_btf_type(btf, ctx->last_type, ctx); return find_fetch_type(typestr, ctx->flags); } @@ -461,14 +595,16 @@ static const struct fetch_type *parse_btf_retval_type( struct traceprobe_parse_context *ctx) { const char *typestr = NULL; - const struct btf_type *t; + const struct btf_type *type; struct btf *btf; if (ctx->funcname) { /* Do not use ctx->btf, because it must be used with ctx->param */ - t = btf_find_func_proto(ctx->funcname, &btf); - if (t) { - typestr = type_from_btf_id(btf, t->type); + type = btf_find_func_proto(ctx->funcname, &btf); + if (type) { + type = btf_type_skip_modifiers(btf, type->type, NULL); + if (!IS_ERR_OR_NULL(type)) + typestr = fetch_type_from_btf_type(btf, type, ctx); btf_put(btf); } } @@ -476,6 +612,28 @@ static const struct fetch_type *parse_btf_retval_type( return find_fetch_type(typestr, ctx->flags); } +static int parse_btf_bitfield(struct fetch_insn **pcode, + struct traceprobe_parse_context *ctx) +{ + struct fetch_insn *code = *pcode; + + if ((ctx->last_bitsize % 8 == 0) && ctx->last_bitoffs == 0) + return 0; + + code++; + if (code->op != FETCH_OP_NOP) { + trace_probe_log_err(ctx->offset, TOO_MANY_OPS); + return -EINVAL; + } + *pcode = code; + + code->op = FETCH_OP_MOD_BF; + code->lshift = 64 - (ctx->last_bitsize + ctx->last_bitoffs); + code->rshift = 64 - ctx->last_bitsize; + code->basesize = 64 / 8; + return 0; +} + static bool is_btf_retval_void(const char *funcname) { const struct btf_type *t; @@ -502,14 +660,22 @@ static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr return ERR_PTR(-EOPNOTSUPP); } -static int parse_btf_arg(const char *varname, struct fetch_insn *code, +static int parse_btf_arg(char *varname, + struct fetch_insn **pcode, struct fetch_insn *end, struct traceprobe_parse_context *ctx) { trace_probe_log_err(ctx->offset, NOSUP_BTFARG); return -EOPNOTSUPP; } -#define parse_btf_arg_type(idx, ctx) \ +static int parse_btf_bitfield(struct fetch_insn **pcode, + struct traceprobe_parse_context *ctx) +{ + trace_probe_log_err(ctx->offset, NOSUP_BTFARG); + return -EOPNOTSUPP; +} + +#define parse_btf_arg_type(ctx) \ find_fetch_type(NULL, ctx->flags) #define parse_btf_retval_type(ctx) \ @@ -777,6 +943,8 @@ parse_probe_arg(char *arg, const struct fetch_type *type, code->op = deref; code->offset = offset; + /* Reset the last type if used */ + ctx->last_type = NULL; } break; case '\\': /* Immediate value */ @@ -800,7 +968,7 @@ parse_probe_arg(char *arg, const struct fetch_type *type, trace_probe_log_err(ctx->offset, NOSUP_BTFARG); return -EINVAL; } - ret = parse_btf_arg(arg, code, ctx); + ret = parse_btf_arg(arg, pcode, end, ctx); break; } } @@ -946,6 +1114,7 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size, goto out; code[FETCH_INSN_MAX - 1].op = FETCH_OP_END; + ctx->last_type = NULL; ret = parse_probe_arg(arg, parg->type, &code, &code[FETCH_INSN_MAX - 1], ctx); if (ret) @@ -953,9 +1122,9 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size, /* Update storing type if BTF is available */ if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && !t) { - if (code->op == FETCH_OP_ARG) - parg->type = parse_btf_arg_type(code->param, ctx); - else if (code->op == FETCH_OP_RETVAL) + if (ctx->last_type) + parg->type = parse_btf_arg_type(ctx); + else if (ctx->flags & TPARG_FL_RETURN) parg->type = parse_btf_retval_type(ctx); } @@ -1030,6 +1199,11 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size, trace_probe_log_err(ctx->offset + t - arg, BAD_BITFIELD); goto fail; } + } else if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && + ctx->last_type) { + ret = parse_btf_bitfield(&code, ctx); + if (ret) + goto fail; } ret = -EINVAL; /* Loop(Array) operation */ diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 4dc91460a75d..6111f1ffca6c 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -388,6 +388,9 @@ struct traceprobe_parse_context { const struct btf_param *params; /* Parameter of the function */ s32 nr_params; /* The number of the parameters */ struct btf *btf; /* The BTF to be used */ + const struct btf_type *last_type; /* Saved type */ + u32 last_bitoffs; /* Saved bitoffs */ + u32 last_bitsize; /* Saved bitsize */ unsigned int flags; int offset; }; @@ -503,7 +506,13 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, C(BAD_VAR_ARGS, "$arg* must be an independent parameter without name etc."),\ C(NOFENTRY_ARGS, "$arg* can be used only on function entry"), \ C(DOUBLE_ARGS, "$arg* can be used only once in the parameters"), \ - C(ARGS_2LONG, "$arg* failed because the argument list is too long"), + C(ARGS_2LONG, "$arg* failed because the argument list is too long"), \ + C(ARGIDX_2BIG, "$argN index is too big"), \ + C(NO_PTR_STRCT, "This is not a pointer to union/structure."), \ + C(NOSUP_DAT_ARG, "Non pointer structure/union argument is not supported."),\ + C(BAD_HYPHEN, "Failed to parse single hyphen. Forgot '>'?"), \ + C(NO_BTF_FIELD, "This field is not found."), \ + C(BAD_BTF_TID, "Failed to get BTF type info."), #undef C #define C(a, b) TP_ERR_##a From patchwork Mon Jul 31 07:30:54 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13333933 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48338C001DE for ; Mon, 31 Jul 2023 07:32:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231660AbjGaHcD (ORCPT ); Mon, 31 Jul 2023 03:32:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231495AbjGaHbi (ORCPT ); Mon, 31 Jul 2023 03:31:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1990D1AD; Mon, 31 Jul 2023 00:30:59 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9257760F29; Mon, 31 Jul 2023 07:30:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D0A1C433C7; Mon, 31 Jul 2023 07:30:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690788658; bh=MEwRLs52A6mbWMV633WSoZvf7gtbSq9T0CrWmcVCrQw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RYSSDeeab7dS/kZ4Db9OMxQn35b8l2tqXf8H6VCsP/YZtH2eseldsfv0ZUTDu1Voj LWbuWGxSEpb1ypo6UVXSiAnlhHqpR1/0nhdoE2SRbTD38VVpND+Hukg20gj1sO0JZ4 x1s9+SthzuX/Igv3doVhONPZcjRmw+c9y6IMkCzE75cZ3BzuBhNzR4rbwCBrxwsahy xKA6kZMpklAmD4Sz9yv/8S7+5BA9vsN7D3mKltjIvydOqUt64TGHHVsK12uUzq9PGm 5RH39ywrFExEHqL+XKfpjNDfsR3ipibOgX+hQzsevZLKHZXPOfTmJZ3xgJYonuqsmP nDaRcmpNDABaw== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v4 5/9] tracing/probes: Support BTF field access from $retval Date: Mon, 31 Jul 2023 16:30:54 +0900 Message-Id: <169078865417.173706.16364911655090306732.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169078860386.173706.3091034523220945605.stgit@devnote2> References: <169078860386.173706.3091034523220945605.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Support BTF argument on '$retval' for function return events including kretprobe and fprobe for accessing the return value. This also allows user to access its fields if the return value is a pointer of a data structure. E.g. # echo 'f getname_flags%return +0($retval->name):string' \ > dynamic_events # echo 1 > events/fprobes/getname_flags__exit/enable # ls > /dev/null # head -n 40 trace | tail ls-87 [000] ...1. 8067.616101: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./function_profile_enabled" ls-87 [000] ...1. 8067.616108: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./trace_stat" ls-87 [000] ...1. 8067.616115: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_graph_notrace" ls-87 [000] ...1. 8067.616122: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_graph_function" ls-87 [000] ...1. 8067.616129: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_ftrace_notrace" ls-87 [000] ...1. 8067.616135: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_ftrace_filter" ls-87 [000] ...1. 8067.616143: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./touched_functions" ls-87 [000] ...1. 8067.616237: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./enabled_functions" ls-87 [000] ...1. 8067.616245: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./available_filter_functions" ls-87 [000] ...1. 8067.616253: getname_flags__exit: (vfs_fstatat+0x3c/0x70 <- getname_flags) arg1="./set_ftrace_notrace_pid" Signed-off-by: Masami Hiramatsu (Google) --- Changes in v2: - Use '$retval' instead of 'retval' because it is confusing. Changes in v3: - Introduce query_btf_context() to cache the btf related data (function prototype) for using common field analyzing code with function parameters. Changes in v3.1: - Return int error code from query_btf_context() if !CONFIG_PROBE_EVENTS_BTF_ARGS Changes in v4: - Fix wrong BTF access if query_btf_context() is failed in parse_btf_arg(). - Return error if $retval accesses a field but BTF is not found. --- kernel/trace/trace_probe.c | 187 ++++++++++++++++++++------------------------ kernel/trace/trace_probe.h | 1 2 files changed, 86 insertions(+), 102 deletions(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index f6b855de4256..8ce7d8f04849 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -363,38 +363,46 @@ static const char *fetch_type_from_btf_type(struct btf *btf, return NULL; } -static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr, - struct btf **btf_p, bool tracepoint) +static int query_btf_context(struct traceprobe_parse_context *ctx) { const struct btf_param *param; - const struct btf_type *t; + const struct btf_type *type; struct btf *btf; + s32 nr; - if (!funcname || !nr) - return ERR_PTR(-EINVAL); + if (ctx->btf) + return 0; - t = btf_find_func_proto(funcname, &btf); - if (!t) - return (const struct btf_param *)t; + if (!ctx->funcname) + return -EINVAL; - param = btf_get_func_param(t, nr); - if (IS_ERR_OR_NULL(param)) - goto err; + type = btf_find_func_proto(ctx->funcname, &btf); + if (!type) + return -ENOENT; - /* Hide the first 'data' argument of tracepoint */ - if (tracepoint) { - (*nr)--; - param++; + ctx->btf = btf; + ctx->proto = type; + + /* ctx->params is optional, since func(void) will not have params. */ + nr = 0; + param = btf_get_func_param(type, &nr); + if (!IS_ERR_OR_NULL(param)) { + /* Hide the first 'data' argument of tracepoint */ + if (ctx->flags & TPARG_FL_TPOINT) { + nr--; + param++; + } } - if (*nr > 0) { - *btf_p = btf; - return param; + if (nr > 0) { + ctx->nr_params = nr; + ctx->params = param; + } else { + ctx->nr_params = 0; + ctx->params = NULL; } -err: - btf_put(btf); - return NULL; + return 0; } static void clear_btf_context(struct traceprobe_parse_context *ctx) @@ -402,6 +410,7 @@ static void clear_btf_context(struct traceprobe_parse_context *ctx) if (ctx->btf) { btf_put(ctx->btf); ctx->btf = NULL; + ctx->proto = NULL; ctx->params = NULL; ctx->nr_params = 0; } @@ -517,7 +526,7 @@ static int parse_btf_arg(char *varname, const struct btf_param *params; const struct btf_type *type; char *field = NULL; - int i, is_ptr; + int i, is_ptr, ret; u32 tid; if (WARN_ON_ONCE(!ctx->funcname)) @@ -533,17 +542,37 @@ static int parse_btf_arg(char *varname, return -EOPNOTSUPP; } - if (!ctx->params) { - params = find_btf_func_param(ctx->funcname, - &ctx->nr_params, &ctx->btf, - ctx->flags & TPARG_FL_TPOINT); - if (IS_ERR_OR_NULL(params)) { + if (ctx->flags & TPARG_FL_RETURN) { + if (strcmp(varname, "$retval") != 0) { + trace_probe_log_err(ctx->offset, NO_BTFARG); + return -ENOENT; + } + code->op = FETCH_OP_RETVAL; + /* Check whether the function return type is not void */ + if (query_btf_context(ctx) == 0) { + if (ctx->proto->type == 0) { + trace_probe_log_err(ctx->offset, NO_RETVAL); + return -ENOENT; + } + tid = ctx->proto->type; + goto found; + } + if (field) { + trace_probe_log_err(ctx->offset + field - varname, + NO_BTF_ENTRY); + return -ENOENT; + } + return 0; + } + + if (!ctx->btf) { + ret = query_btf_context(ctx); + if (ret < 0 || ctx->nr_params == 0) { trace_probe_log_err(ctx->offset, NO_BTF_ENTRY); return PTR_ERR(params); } - ctx->params = params; - } else - params = ctx->params; + } + params = ctx->params; for (i = 0; i < ctx->nr_params; i++) { const char *name = btf_name_by_offset(ctx->btf, params[i].name_off); @@ -554,7 +583,6 @@ static int parse_btf_arg(char *varname, code->param = i + 1; else code->param = i; - tid = params[i].type; goto found; } @@ -579,7 +607,7 @@ static int parse_btf_arg(char *varname, return 0; } -static const struct fetch_type *parse_btf_arg_type( +static const struct fetch_type *find_fetch_type_from_btf_type( struct traceprobe_parse_context *ctx) { struct btf *btf = ctx->btf; @@ -591,27 +619,6 @@ static const struct fetch_type *parse_btf_arg_type( return find_fetch_type(typestr, ctx->flags); } -static const struct fetch_type *parse_btf_retval_type( - struct traceprobe_parse_context *ctx) -{ - const char *typestr = NULL; - const struct btf_type *type; - struct btf *btf; - - if (ctx->funcname) { - /* Do not use ctx->btf, because it must be used with ctx->param */ - type = btf_find_func_proto(ctx->funcname, &btf); - if (type) { - type = btf_type_skip_modifiers(btf, type->type, NULL); - if (!IS_ERR_OR_NULL(type)) - typestr = fetch_type_from_btf_type(btf, type, ctx); - btf_put(btf); - } - } - - return find_fetch_type(typestr, ctx->flags); -} - static int parse_btf_bitfield(struct fetch_insn **pcode, struct traceprobe_parse_context *ctx) { @@ -634,30 +641,15 @@ static int parse_btf_bitfield(struct fetch_insn **pcode, return 0; } -static bool is_btf_retval_void(const char *funcname) -{ - const struct btf_type *t; - struct btf *btf; - bool ret; - - t = btf_find_func_proto(funcname, &btf); - if (!t) - return false; - - ret = (t->type == 0); - btf_put(btf); - return ret; -} #else static void clear_btf_context(struct traceprobe_parse_context *ctx) { ctx->btf = NULL; } -static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr, - struct btf **btf_p, bool tracepoint) +static int query_btf_context(struct traceprobe_parse_context *ctx) { - return ERR_PTR(-EOPNOTSUPP); + return -EOPNOTSUPP; } static int parse_btf_arg(char *varname, @@ -675,24 +667,23 @@ static int parse_btf_bitfield(struct fetch_insn **pcode, return -EOPNOTSUPP; } -#define parse_btf_arg_type(ctx) \ - find_fetch_type(NULL, ctx->flags) - -#define parse_btf_retval_type(ctx) \ +#define find_fetch_type_from_btf_type(ctx) \ find_fetch_type(NULL, ctx->flags) -#define is_btf_retval_void(funcname) (false) - #endif #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long)) -static int parse_probe_vars(char *arg, const struct fetch_type *t, - struct fetch_insn *code, +/* Parse $vars. @orig_arg points '$', which syncs to @ctx->offset */ +static int parse_probe_vars(char *orig_arg, const struct fetch_type *t, + struct fetch_insn **pcode, + struct fetch_insn *end, struct traceprobe_parse_context *ctx) { - unsigned long param; + struct fetch_insn *code = *pcode; int err = TP_ERR_BAD_VAR; + char *arg = orig_arg + 1; + unsigned long param; int ret = 0; int len; @@ -711,18 +702,17 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t, goto inval; } - if (strcmp(arg, "retval") == 0) { - if (ctx->flags & TPARG_FL_RETURN) { - if ((ctx->flags & TPARG_FL_KERNEL) && - is_btf_retval_void(ctx->funcname)) { - err = TP_ERR_NO_RETVAL; - goto inval; - } + if (str_has_prefix(arg, "retval")) { + if (!(ctx->flags & TPARG_FL_RETURN)) { + err = TP_ERR_RETVAL_ON_PROBE; + goto inval; + } + if (!(ctx->flags & TPARG_FL_KERNEL) || + !IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS)) { code->op = FETCH_OP_RETVAL; return 0; } - err = TP_ERR_RETVAL_ON_PROBE; - goto inval; + return parse_btf_arg(orig_arg, pcode, end, ctx); } len = str_has_prefix(arg, "stack"); @@ -824,7 +814,7 @@ parse_probe_arg(char *arg, const struct fetch_type *type, switch (arg[0]) { case '$': - ret = parse_probe_vars(arg + 1, type, code, ctx); + ret = parse_probe_vars(arg, type, pcode, end, ctx); break; case '%': /* named register */ @@ -1121,12 +1111,9 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size, goto fail; /* Update storing type if BTF is available */ - if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && !t) { - if (ctx->last_type) - parg->type = parse_btf_arg_type(ctx); - else if (ctx->flags & TPARG_FL_RETURN) - parg->type = parse_btf_retval_type(ctx); - } + if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && + !t && ctx->last_type) + parg->type = find_fetch_type_from_btf_type(ctx); ret = -EINVAL; /* Store operation */ @@ -1415,7 +1402,6 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[], const struct btf_param *params = NULL; int i, j, n, used, ret, args_idx = -1; const char **new_argv = NULL; - int nr_params; ret = argv_has_var_arg(argc, argv, &args_idx, ctx); if (ret < 0) @@ -1426,9 +1412,8 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[], return NULL; } - params = find_btf_func_param(ctx->funcname, &nr_params, &ctx->btf, - ctx->flags & TPARG_FL_TPOINT); - if (IS_ERR_OR_NULL(params)) { + ret = query_btf_context(ctx); + if (ret < 0 || ctx->nr_params == 0) { if (args_idx != -1) { /* $arg* requires BTF info */ trace_probe_log_err(0, NOSUP_BTFARG); @@ -1437,8 +1422,6 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[], *new_argc = argc; return NULL; } - ctx->params = params; - ctx->nr_params = nr_params; if (args_idx >= 0) *new_argc = argc + ctx->nr_params - 1; @@ -1453,7 +1436,7 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[], for (i = 0, j = 0; i < argc; i++) { trace_probe_log_set_index(i + 2); if (i == args_idx) { - for (n = 0; n < nr_params; n++) { + for (n = 0; n < ctx->nr_params; n++) { ret = sprint_nth_btf_arg(n, "", buf + used, bufsize - used, ctx); if (ret < 0) diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 6111f1ffca6c..9184c84833f8 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -385,6 +385,7 @@ struct traceprobe_parse_context { struct trace_event_call *event; /* BTF related parameters */ const char *funcname; /* Function name in BTF */ + const struct btf_type *proto; /* Prototype of the function */ const struct btf_param *params; /* Parameter of the function */ s32 nr_params; /* The number of the parameters */ struct btf *btf; /* The BTF to be used */ From patchwork Mon Jul 31 07:31:03 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13333934 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1A57C001DE for ; Mon, 31 Jul 2023 07:32:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231680AbjGaHcX (ORCPT ); Mon, 31 Jul 2023 03:32:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231637AbjGaHbm (ORCPT ); Mon, 31 Jul 2023 03:31:42 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E5B010CC; Mon, 31 Jul 2023 00:31:08 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id BEFE660F32; Mon, 31 Jul 2023 07:31:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A096C433C8; Mon, 31 Jul 2023 07:31:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690788667; bh=QCbDVf1VPNh57Ufpzf7xem7rI1/giuALEFEtHjhBjWE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RrNR1tgQgrdgasqTE6MuVSLiszRgirrlY3roSxl4LcL4xqQZaSjxnsJl3gxlDMcxN 3CqmQLrhVC73A4A398nIK5O49ocamGPUHzFv7vUsj3YaZxATgbTMQgTFFx+7nYQic7 IuR97qGalBhx/Iwwgpx8FJkGOTZ3W90Y+G/i6CISKyVYXmLJ8caqLvEpvk4GDOfyIy tEAOfuMbuJy2V3W4FgT9xUPp54QivJl5T49kw5LWY37tNZy3+9ykiIMjsORI9U7/hg FbJsfVNpYT23EliqObc/bPoKWrXvC1HMm+Db6vfdyJIz6yvZKF6Pc13oCvkoWyCVBL DlnBFTIc13DHg== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v4 6/9] tracing/probes: Add string type check with BTF Date: Mon, 31 Jul 2023 16:31:03 +0900 Message-Id: <169078866330.173706.18430839904581751211.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169078860386.173706.3091034523220945605.stgit@devnote2> References: <169078860386.173706.3091034523220945605.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Add a string type checking with BTF information if possible. This will check whether the given BTF argument (and field) is signed char array or pointer to signed char. If not, it reject the 'string' type. If it is pointer to signed char, it adds a dereference opration so that it can correctly fetch the string data from memory. # echo 'f getname_flags%return retval->name:string' >> dynamic_events # echo 't sched_switch next->comm:string' >> dynamic_events The above cases, 'struct filename::name' is 'char *' and 'struct task_struct::comm' is 'char []'. But in both case, user can specify ':string' to fetch the string data. Signed-off-by: Masami Hiramatsu (Google) --- Changes in v3: - Use ctx->btf instead of traceprobe_get_btf(). --- kernel/trace/trace_probe.c | 89 +++++++++++++++++++++++++++++++++++++++++++- kernel/trace/trace_probe.h | 3 + 2 files changed, 89 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 8ce7d8f04849..46a604f786c5 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -309,6 +309,77 @@ static u32 btf_type_int(const struct btf_type *t) return *(u32 *)(t + 1); } +static bool btf_type_is_char_ptr(struct btf *btf, const struct btf_type *type) +{ + const struct btf_type *real_type; + u32 intdata; + s32 tid; + + real_type = btf_type_skip_modifiers(btf, type->type, &tid); + if (!real_type) + return false; + + if (BTF_INFO_KIND(real_type->info) != BTF_KIND_INT) + return false; + + intdata = btf_type_int(real_type); + return !(BTF_INT_ENCODING(intdata) & BTF_INT_SIGNED) + && BTF_INT_BITS(intdata) == 8; +} + +static bool btf_type_is_char_array(struct btf *btf, const struct btf_type *type) +{ + const struct btf_type *real_type; + const struct btf_array *array; + u32 intdata; + s32 tid; + + if (BTF_INFO_KIND(type->info) != BTF_KIND_ARRAY) + return false; + + array = (const struct btf_array *)(type + 1); + + real_type = btf_type_skip_modifiers(btf, array->type, &tid); + + intdata = btf_type_int(real_type); + return !(BTF_INT_ENCODING(intdata) & BTF_INT_SIGNED) + && BTF_INT_BITS(intdata) == 8; +} + +static int check_prepare_btf_string_fetch(char *typename, + struct fetch_insn **pcode, + struct traceprobe_parse_context *ctx) +{ + struct btf *btf = ctx->btf; + + if (!btf || !ctx->last_type) + return 0; + + /* char [] does not need any change. */ + if (btf_type_is_char_array(btf, ctx->last_type)) + return 0; + + /* char * requires dereference the pointer. */ + if (btf_type_is_char_ptr(btf, ctx->last_type)) { + struct fetch_insn *code = *pcode + 1; + + if (code->op == FETCH_OP_END) { + trace_probe_log_err(ctx->offset, TOO_MANY_OPS); + return -E2BIG; + } + if (typename[0] == 'u') + code->op = FETCH_OP_UDEREF; + else + code->op = FETCH_OP_DEREF; + code->offset = 0; + *pcode = code; + return 0; + } + /* Other types are not available for string */ + trace_probe_log_err(ctx->offset, BAD_TYPE4STR); + return -EINVAL; +} + static const char *fetch_type_from_btf_type(struct btf *btf, const struct btf_type *type, struct traceprobe_parse_context *ctx) @@ -670,6 +741,13 @@ static int parse_btf_bitfield(struct fetch_insn **pcode, #define find_fetch_type_from_btf_type(ctx) \ find_fetch_type(NULL, ctx->flags) +static int check_prepare_btf_string_fetch(char *typename, + struct fetch_insn **pcode, + struct traceprobe_parse_context *ctx) +{ + return 0; +} + #endif #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long)) @@ -1112,8 +1190,15 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size, /* Update storing type if BTF is available */ if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && - !t && ctx->last_type) - parg->type = find_fetch_type_from_btf_type(ctx); + ctx->last_type) { + if (!t) { + parg->type = find_fetch_type_from_btf_type(ctx); + } else if (strstr(t, "string")) { + ret = check_prepare_btf_string_fetch(t, &code, ctx); + if (ret) + goto fail; + } + } ret = -EINVAL; /* Store operation */ diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 9184c84833f8..7f929482e8d4 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -513,7 +513,8 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, C(NOSUP_DAT_ARG, "Non pointer structure/union argument is not supported."),\ C(BAD_HYPHEN, "Failed to parse single hyphen. Forgot '>'?"), \ C(NO_BTF_FIELD, "This field is not found."), \ - C(BAD_BTF_TID, "Failed to get BTF type info."), + C(BAD_BTF_TID, "Failed to get BTF type info."),\ + C(BAD_TYPE4STR, "This type does not fit for string."), #undef C #define C(a, b) TP_ERR_##a From patchwork Mon Jul 31 07:31:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13333940 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21051C001DE for ; Mon, 31 Jul 2023 07:32:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231649AbjGaHcq (ORCPT ); Mon, 31 Jul 2023 03:32:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39296 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231485AbjGaHcC (ORCPT ); Mon, 31 Jul 2023 03:32:02 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8FC5170C; Mon, 31 Jul 2023 00:31:18 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id D478760F29; Mon, 31 Jul 2023 07:31:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B9E1C433C8; Mon, 31 Jul 2023 07:31:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690788677; bh=gcAsXcNpHr2neQoiFwF9exmEBvK8RQO7NJB0uoPDuFA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PJCNZ8PJXZUOqESsO0CQvvqa2vbqiqGdT78s1Kndn+r65NM4ua0ImO263GojFQAff a+V/S6unQvLrqL4T35+oxqQZ2bvUq6GNIiclwu55ZhebUHHCWW9pP1GwsG5AW95NYZ lYd/Pgw+7nNR0aJktmDw5qYQDjAYkYhQfedHZsIvUWgAR1f5GfiiwU41+kGIf9Bm5Y kJkb3nppK+uoXOrjLq5WY5TgOeeWVTN8eAM1XydYC81tjYt/avbOv9ZtAlXpQyBf/e HKEgGzBpWG1psJoyQGQgzwrUPKaHUyNvvsC5SzRh6lqitV7W1u3uGLK1EDDl2RDfiE ZvdrF4kY8i9sQ== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v4 7/9] tracing/fprobe-event: Assume fprobe is a return event by $retval Date: Mon, 31 Jul 2023 16:31:12 +0900 Message-Id: <169078867246.173706.10461108619228856719.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169078860386.173706.3091034523220945605.stgit@devnote2> References: <169078860386.173706.3091034523220945605.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Assume the fprobe event is a return event if there is $retval is used in the probe's argument without %return. e.g. echo 'f:myevent vfs_read $retval' >> dynamic_events then 'myevent' is a return probe event. Suggested-by: Steven Rostedt Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/trace_fprobe.c | 58 +++++++++++++++----- .../ftrace/test.d/dynevent/fprobe_syntax_errors.tc | 2 - 2 files changed, 45 insertions(+), 15 deletions(-) diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c index 8f43f1f65b1b..8bfe23af9c73 100644 --- a/kernel/trace/trace_fprobe.c +++ b/kernel/trace/trace_fprobe.c @@ -898,6 +898,46 @@ static struct tracepoint *find_tracepoint(const char *tp_name) return data.tpoint; } +static int parse_symbol_and_return(int argc, const char *argv[], + char **symbol, bool *is_return, + bool is_tracepoint) +{ + char *tmp = strchr(argv[1], '%'); + int i; + + if (tmp) { + int len = tmp - argv[1]; + + if (!is_tracepoint && !strcmp(tmp, "%return")) { + *is_return = true; + } else { + trace_probe_log_err(len, BAD_ADDR_SUFFIX); + return -EINVAL; + } + *symbol = kmemdup_nul(argv[1], len, GFP_KERNEL); + } else + *symbol = kstrdup(argv[1], GFP_KERNEL); + if (!*symbol) + return -ENOMEM; + + if (*is_return) + return 0; + + /* If there is $retval, this should be a return fprobe. */ + for (i = 2; i < argc; i++) { + tmp = strstr(argv[i], "$retval"); + if (tmp && !isalnum(tmp[7]) && tmp[7] != '_') { + *is_return = true; + /* + * NOTE: Don't check is_tracepoint here, because it will + * be checked when the argument is parsed. + */ + break; + } + } + return 0; +} + static int __trace_fprobe_create(int argc, const char *argv[]) { /* @@ -927,7 +967,7 @@ static int __trace_fprobe_create(int argc, const char *argv[]) struct trace_fprobe *tf = NULL; int i, len, new_argc = 0, ret = 0; bool is_return = false; - char *symbol = NULL, *tmp = NULL; + char *symbol = NULL; const char *event = NULL, *group = FPROBE_EVENT_SYSTEM; const char **new_argv = NULL; int maxactive = 0; @@ -983,20 +1023,10 @@ static int __trace_fprobe_create(int argc, const char *argv[]) trace_probe_log_set_index(1); /* a symbol(or tracepoint) must be specified */ - symbol = kstrdup(argv[1], GFP_KERNEL); - if (!symbol) - return -ENOMEM; + ret = parse_symbol_and_return(argc, argv, &symbol, &is_return, is_tracepoint); + if (ret < 0) + goto parse_error; - tmp = strchr(symbol, '%'); - if (tmp) { - if (!is_tracepoint && !strcmp(tmp, "%return")) { - *tmp = '\0'; - is_return = true; - } else { - trace_probe_log_err(tmp - symbol, BAD_ADDR_SUFFIX); - goto parse_error; - } - } if (!is_return && maxactive) { trace_probe_log_set_index(0); trace_probe_log_err(1, BAD_MAXACT_TYPE); diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc index 812f5b3f6055..72563b2e0812 100644 --- a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc +++ b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc @@ -30,11 +30,11 @@ check_error 'f:^ vfs_read' # NO_EVENT_NAME check_error 'f:foo/^12345678901234567890123456789012345678901234567890123456789012345 vfs_read' # EVENT_TOO_LONG check_error 'f:foo/^bar.1 vfs_read' # BAD_EVENT_NAME -check_error 'f vfs_read ^$retval' # RETVAL_ON_PROBE check_error 'f vfs_read ^$stack10000' # BAD_STACK_NUM check_error 'f vfs_read ^$arg10000' # BAD_ARG_NUM +check_error 'f vfs_read $retval ^$arg1' # BAD_VAR check_error 'f vfs_read ^$none_var' # BAD_VAR check_error 'f vfs_read ^'$REG # BAD_VAR From patchwork Mon Jul 31 07:31:22 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13333941 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7D942C001DE for ; Mon, 31 Jul 2023 07:32:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231676AbjGaHct (ORCPT ); Mon, 31 Jul 2023 03:32:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39434 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230309AbjGaHcO (ORCPT ); Mon, 31 Jul 2023 03:32:14 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 522481BC9; Mon, 31 Jul 2023 00:31:28 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id DB0DE60DF0; Mon, 31 Jul 2023 07:31:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B722C433C7; Mon, 31 Jul 2023 07:31:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690788687; bh=KGJEEq13A9go4Yhd3XiG1sdw1r30ps972RCgI6Rs1/c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=a1G1qgfTsdvrtkIT3v662J7BXCoWxQlHFUC+VqEihQx14Afq1GzMqwKHyLylUK9Va aTP0YEozlL+xyyAp939Gq+RAou0Bqv5Ggs7biyQBxzUMjnHIofUjXlz9AJI5n3ol9J qUXxIZygZlW3xMn78IJei09bMJ/SzuUIyF81XRNHrclxT59OUuSo6FID0I5WRG//TR /Sm1R432P4Gg/IUBkDyltRHrxLyfTT2oWty0HT6L2JbuvPSzi0cPTzFS7w/zkKp3GP LPNx5dOcTj+D/MG6RDXTr9PNz7F1GUbxNr5usRv11lp2S9R+Cc+77SJXMX8UMOyHV9 GMHJ+XmVAaesg== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v4 8/9] selftests/ftrace: Add BTF fields access testcases Date: Mon, 31 Jul 2023 16:31:22 +0900 Message-Id: <169078868262.173706.15416052542086569996.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169078860386.173706.3091034523220945605.stgit@devnote2> References: <169078860386.173706.3091034523220945605.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Add test cases for accessing the data structure fields using BTF info. This includes the field access from parameters and retval, and accessing string information. Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Alan Maguire --- Changes in v2: - Use '$retval' instead of 'retval'. - Add a test that use both '$retval' and '$arg1' for fprobe. Changes in v3: - Change a test case with a numeric value. - Add a test case with mixed '.' and '->' operators. --- .../ftrace/test.d/dynevent/add_remove_btfarg.tc | 14 ++++++++++++++ .../ftrace/test.d/dynevent/fprobe_syntax_errors.tc | 4 ++++ 2 files changed, 18 insertions(+) diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_btfarg.tc b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_btfarg.tc index f34b14ef9781..4bfd2f45db42 100644 --- a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_btfarg.tc +++ b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_btfarg.tc @@ -21,6 +21,9 @@ echo 0 > events/enable echo > dynamic_events TP=kfree +TP2=kmem_cache_alloc +TP3=getname_flags +TP4=sched_wakeup if [ "$FPROBES" ] ; then echo "f:fpevent $TP object" >> dynamic_events @@ -33,6 +36,7 @@ echo > dynamic_events echo "f:fpevent $TP "'$arg1' >> dynamic_events grep -q "fpevent.*object=object" dynamic_events + echo > dynamic_events echo "f:fpevent $TP "'$arg*' >> dynamic_events @@ -45,6 +49,16 @@ fi echo > dynamic_events +echo "t:tpevent ${TP2} obj_size=s->object_size" >> dynamic_events +echo "f:fpevent ${TP3}%return path=\$retval->name:string" >> dynamic_events +echo "t:tpevent2 ${TP4} p->se.group_node.next->prev" >> dynamic_events + +grep -q "tpevent .*obj_size=s->object_size" dynamic_events +grep -q "fpevent.*path=\$retval->name:string" dynamic_events +grep -q 'tpevent2 .*p->se.group_node.next->prev' dynamic_events + +echo > dynamic_events + if [ "$KPROBES" ] ; then echo "p:kpevent $TP object" >> dynamic_events grep -q "kpevent.*object=object" dynamic_events diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc index 72563b2e0812..49758f77c923 100644 --- a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc +++ b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc @@ -103,6 +103,10 @@ check_error 'f vfs_read%return ^$arg*' # NOFENTRY_ARGS check_error 'f vfs_read ^hoge' # NO_BTFARG check_error 'f kfree ^$arg10' # NO_BTFARG (exceed the number of parameters) check_error 'f kfree%return ^$retval' # NO_RETVAL +check_error 'f vfs_read%return $retval->^foo' # NO_PTR_STRCT +check_error 'f vfs_read file->^foo' # NO_BTF_FIELD +check_error 'f vfs_read file^-.foo' # BAD_HYPHEN +check_error 'f vfs_read ^file:string' # BAD_TYPE4STR else check_error 'f vfs_read ^$arg*' # NOSUP_BTFARG check_error 't kfree ^$arg*' # NOSUP_BTFARG From patchwork Mon Jul 31 07:31:32 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13333942 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ED766C001DF for ; Mon, 31 Jul 2023 07:32:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231569AbjGaHcv (ORCPT ); Mon, 31 Jul 2023 03:32:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231641AbjGaHcX (ORCPT ); Mon, 31 Jul 2023 03:32:23 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45397CA; Mon, 31 Jul 2023 00:31:38 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9A43A60F0B; Mon, 31 Jul 2023 07:31:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 541EAC433C8; Mon, 31 Jul 2023 07:31:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690788697; bh=CcGORqTI9ZQHAZplK151N2vLhAMfOhssOSPkNJphVGw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=p2QBWRZedp3YFyCxsKCi6rHw3WzJzOupor1Wbq0F/GWg+lhivUFqgiE1LN9ol8x9L L/wXeIIxoMHLRDw3fodckV7Kt4ZWegulZQIFjlFcYjqvYHAP9g8ZmslPVvuXybt/kl vTwKW+lUG1+M9cXAFLGtmceiETB/aWZg6pV8rcZ80FxoXr9DR6Mg4DyYoeBhXH26wt YdOGsoL3/2rJjWebcOXLvB40QxwL7RCxIIt/NSfXbQRUm115EqNF8wVWNVjDcY0343 E70u9pIZ4vDPOBNDzq3VpIb0BDvrSWXTm/aKbGB86JJ146VVxsOYfvFdeYiqoyEF3r Qz9UymBTLNdOw== From: "Masami Hiramatsu (Google)" To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Steven Rostedt , mhiramat@kernel.org, Martin KaFai Lau , bpf@vger.kernel.org, Sven Schnelle , Alexei Starovoitov Subject: [PATCH v4 9/9] Documentation: tracing: Update fprobe event example with BTF field Date: Mon, 31 Jul 2023 16:31:32 +0900 Message-Id: <169078869266.173706.7593816583722034542.stgit@devnote2> X-Mailer: git-send-email 2.34.1 In-Reply-To: <169078860386.173706.3091034523220945605.stgit@devnote2> References: <169078860386.173706.3091034523220945605.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Update fprobe event example with BTF data structure field specification. Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Alan Maguire --- Changes in v2: - Remove 'retval' and use '$retval'. Changes in v3: - Add description about mixture of '.' and '->' usage. --- Documentation/trace/fprobetrace.rst | 64 +++++++++++++++++++++++++---------- 1 file changed, 46 insertions(+), 18 deletions(-) diff --git a/Documentation/trace/fprobetrace.rst b/Documentation/trace/fprobetrace.rst index 7297f9478459..8e9bebcf0a2e 100644 --- a/Documentation/trace/fprobetrace.rst +++ b/Documentation/trace/fprobetrace.rst @@ -79,9 +79,9 @@ automatically set by the given name. :: f:fprobes/myprobe vfs_read count=count pos=pos It also chooses the fetch type from BTF information. For example, in the above -example, the ``count`` is unsigned long, and the ``pos`` is a pointer. Thus, both -are converted to 64bit unsigned long, but only ``pos`` has "%Lx" print-format as -below :: +example, the ``count`` is unsigned long, and the ``pos`` is a pointer. Thus, +both are converted to 64bit unsigned long, but only ``pos`` has "%Lx" +print-format as below :: # cat events/fprobes/myprobe/format name: myprobe @@ -105,9 +105,47 @@ is expanded to all function arguments of the function or the tracepoint. :: # cat dynamic_events f:fprobes/myprobe vfs_read file=file buf=buf count=count pos=pos -BTF also affects the ``$retval``. If user doesn't set any type, the retval type is -automatically picked from the BTF. If the function returns ``void``, ``$retval`` -is rejected. +BTF also affects the ``$retval``. If user doesn't set any type, the retval +type is automatically picked from the BTF. If the function returns ``void``, +``$retval`` is rejected. + +You can access the data fields of a data structure using allow operator ``->`` +(for pointer type) and dot operator ``.`` (for data structure type.):: + +# echo 't sched_switch preempt prev_pid=prev->pid next_pid=next->pid' >> dynamic_events + +The field access operators, ``->`` and ``.`` can be combined for accessing deeper +members and other structure members pointed by the member. e.g. ``foo->bar.baz->qux`` +If there is non-name union member, you can directly access it as the C code does. +For example:: + + struct { + union { + int a; + int b; + }; + } *foo; + +To access ``a`` and ``b``, use ``foo->a`` and ``foo->b`` in this case. + +This data field access is available for the return value via ``$retval``, +e.g. ``$retval->name``. + +For these BTF arguments and fields, ``:string`` and ``:ustring`` change the +behavior. If these are used for BTF argument or field, it checks whether +the BTF type of the argument or the data field is ``char *`` or ``char []``, +or not. If not, it rejects applying the string types. Also, with the BTF +support, you don't need a memory dereference operator (``+0(PTR)``) for +accessing the string pointed by a ``PTR``. It automatically adds the memory +dereference operator according to the BTF type. e.g. :: + +# echo 't sched_switch prev->comm:string' >> dynamic_events +# echo 'f getname_flags%return $retval->name:string' >> dynamic_events + +The ``prev->comm`` is an embedded char array in the data structure, and +``$retval->name`` is a char pointer in the data structure. But in both +cases, you can use ``:string`` type to get the string. + Usage examples -------------- @@ -161,10 +199,10 @@ parameters. This means you can access any field values in the task structure pointed by the ``prev`` and ``next`` arguments. For example, usually ``task_struct::start_time`` is not traced, but with this -traceprobe event, you can trace it as below. +traceprobe event, you can trace that field as below. :: - # echo 't sched_switch comm=+1896(next):string start_time=+1728(next):u64' > dynamic_events + # echo 't sched_switch comm=next->comm:string next->start_time' > dynamic_events # head -n 20 trace | tail # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | @@ -176,13 +214,3 @@ traceprobe event, you can trace it as below. -0 [000] d..3. 5606.690317: sched_switch: (__probestub_sched_switch+0x4/0x10) comm="kworker/0:1" usage=1 start_time=137000000 kworker/0:1-14 [000] d..3. 5606.690339: sched_switch: (__probestub_sched_switch+0x4/0x10) comm="swapper/0" usage=2 start_time=0 -0 [000] d..3. 5606.692368: sched_switch: (__probestub_sched_switch+0x4/0x10) comm="kworker/0:1" usage=1 start_time=137000000 - -Currently, to find the offset of a specific field in the data structure, -you need to build kernel with debuginfo and run `perf probe` command with -`-D` option. e.g. -:: - - # perf probe -D "__probestub_sched_switch next->comm:string next->start_time" - p:probe/__probestub_sched_switch __probestub_sched_switch+0 comm=+1896(%cx):string start_time=+1728(%cx):u64 - -And replace the ``%cx`` with the ``next``.