From patchwork Mon Jul 17 15:24:07 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: 13315925 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 61A78AD26 for ; Mon, 17 Jul 2023 15:24:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ECED0C433C8; Mon, 17 Jul 2023 15:24:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689607452; bh=HNw7NmAJWJoLfuOb7lcwr0tG/Yg91E6W1MXYrCfkES8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BUWZzB8ih/Pn17MNMbs4bLT6F3qq7F/IIIg66MNQnM/DH93rG0K9UG221F0zupoZZ O8oW/qK3mGyNFuNNcZkDuie4iQeVW++xBPymTfa82sLjllXjEsGcNw5l2PsHu/PRvx wF05Fc0Ew3ZII0weMaCacrFY2FKt74DBReB0ND1/u87o8reC3fXiDsXcraOkeRYLGK GqGnDPhFHYD1elbCbub6fi9URBamkp6az5E8dpcjqCzL+r13FIzSxRRUbdxMHXsKyJ QnfxwukYukf9m52v9zeqdsOAM7niAy1zWZ0hxrqZEeaI5gtH3xyW8K9mb1kbkFMScI VYQVMZlWdIX6w== 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 v2 5/9] tracing/probes: Support BTF field access from $retval Date: Tue, 18 Jul 2023 00:24:07 +0900 Message-Id: <168960744719.34107.443329109565685838.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <168960739768.34107.15145201749042174448.stgit@devnote2> References: <168960739768.34107.15145201749042174448.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Masami Hiramatsu (Google) Support BTF argument on '$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. --- kernel/trace/trace_probe.c | 98 +++++++++++++++++--------------------------- 1 file changed, 37 insertions(+), 61 deletions(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index dd646d35637d..4442ff9c2728 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -536,6 +536,22 @@ static int parse_btf_arg(char *varname, return -EOPNOTSUPP; } + if (ctx->flags & TPARG_FL_RETURN) { + if (strcmp(varname, "$retval") != 0) { + trace_probe_log_err(ctx->offset, NO_BTFARG); + return -ENOENT; + } + /* Check whether the function return type is not void */ + type = btf_find_func_proto(btf, ctx->funcname); + if (!IS_ERR_OR_NULL(type) && type->type == 0) { + trace_probe_log_err(ctx->offset, NO_RETVAL); + return -ENOENT; + } + code->op = FETCH_OP_RETVAL; + tid = type->type; + goto found; + } + if (!ctx->params) { params = find_btf_func_param(ctx->funcname, &ctx->nr_params, ctx->flags & TPARG_FL_TPOINT); @@ -556,7 +572,6 @@ static int parse_btf_arg(char *varname, code->param = i + 1; else code->param = i; - tid = params[i].type; goto found; } @@ -581,7 +596,7 @@ 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 = traceprobe_get_btf(); @@ -593,26 +608,6 @@ 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) -{ - struct btf *btf = traceprobe_get_btf(); - const char *typestr = NULL; - const struct btf_type *type; - s32 tid; - - if (btf && ctx->funcname) { - type = btf_find_func_proto(btf, ctx->funcname); - if (!IS_ERR_OR_NULL(type)) { - type = btf_type_skip_modifiers(btf, type->type, &tid); - if (!IS_ERR_OR_NULL(type)) - typestr = fetch_type_from_btf_type(btf, type, ctx); - } - } - - return find_fetch_type(typestr, ctx->flags); -} - static int parse_btf_bitfield(struct fetch_insn **pcode, struct traceprobe_parse_context *ctx) { @@ -635,20 +630,6 @@ static int parse_btf_bitfield(struct fetch_insn **pcode, return 0; } -static bool is_btf_retval_void(const char *funcname) -{ - struct btf *btf = traceprobe_get_btf(); - const struct btf_type *t; - - if (!btf) - return false; - - t = btf_find_func_proto(btf, funcname); - if (IS_ERR_OR_NULL(t)) - return false; - - return t->type == 0; -} #else static struct btf *traceprobe_get_btf(void) { @@ -676,24 +657,23 @@ 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; @@ -712,18 +692,17 @@ 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"); @@ -825,7 +804,7 @@ 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 */ @@ -1122,12 +1101,9 @@ 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 */