From patchwork Thu Sep 21 08:51:31 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johannes Berg X-Patchwork-Id: 13394127 X-Patchwork-Delegate: johannes@sipsolutions.net 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 5408BE7D0A2 for ; Thu, 21 Sep 2023 17:26:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229663AbjIUR0G (ORCPT ); Thu, 21 Sep 2023 13:26:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229874AbjIURZf (ORCPT ); Thu, 21 Sep 2023 13:25:35 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:242:246e::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2024559E1; Thu, 21 Sep 2023 10:09:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sipsolutions.net; s=mail; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Content-Type:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-To: Resent-Cc:Resent-Message-ID; bh=3zuye6cuN/UXKpEDGt76GmiwBqKZcclp/r7kmn7YPt8=; t=1695316191; x=1696525791; b=YLEJXpBmqRgzWnGLLIg3lfq3TZDW0FXsGGDdlYK2wl0F4Kw qOgd83ieNnwUKZ2GELAfvipv7AwWkkgGvce8wwrb6/BAl9M961J0cyccxYCVzJ7V0ggCcnzZYnAV7 EqAIwponONEfRnvMStrGKLvYEIXwzlpKKJ2OQILkeOtryJ4rHLmRpmAsk1NCSSrvQRJCsNamhy0fV ek5oTp0D+z0CeXDIaxLOjKuL+yqc9oVoFUSjg9xOlH2N1gqGdzQUuh9A68w1qa3FP2bAU7J3zRjUN 0ccg3gbT1pPu6ocy6vQ6hye9HFTTj7kRUA76UxIrXX7BlxaOAfBqIwPr30Ziwc8w==; Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1qjFPl-00D3lb-18; Thu, 21 Sep 2023 10:52:01 +0200 From: Johannes Berg To: linux-kernel@vger.kernel.org Cc: linux-trace-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, Johannes Berg Subject: [RFC PATCH 1/4] tracing: add __print_sym() to replace __print_symbolic() Date: Thu, 21 Sep 2023 10:51:31 +0200 Message-ID: <20230921105129.cd040deee13e.I9bd2617499f0d170df58471bc51379742190f92d@changeid> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230921085129.261556-5-johannes@sipsolutions.net> References: <20230921085129.261556-5-johannes@sipsolutions.net> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org From: Johannes Berg The way __print_symbolic() works is limited and inefficient in multiple ways: - you can only use it with a static list of symbols, but e.g. the SKB dropreasons are now a dynamic list - it builds the list in memory _three_ times, so it takes a lot of memory: - The print_fmt contains the list (since it's passed to the macro there). This actually contains the names _twice_, which is fixed up at runtime. - TRACE_DEFINE_ENUM() puts a 24-byte struct trace_eval_map for every entry, plus the string pointed to by it, which cannot be deduplicated with the strings in the print_fmt - The in-kernel symbolic printing creates yet another list of struct trace_print_flags for trace_print_symbols_seq() - it also requires runtime fixup during init, which is a lot of string parsing due to the print_fmt fixup Introduce __print_sym() to - over time - replace the old one. We can easily extend this also to __print_flags later, but I cared more about the SKB dropreasons for now. This new __print_sym() requires only a single list of items, created by TRACE_DEFINE_SYM_LIST(), for can even use another already existing list by using TRACE_DEFINE_SYM_FNS() with lookup and show methods. Then, instead of doing an init-time fixup, just do this at the time when userspace reads the print_fmt. This way, dynamically updated lists are possible. For userspace, nothing actually changes, because the print_fmt is shown exactly the same way the old __print_symbolic() was. This adds about 4k .text in my test builds, but that'll be more than paid for by the actual conversions. OPEN QUESTIONS: - do we need TRACE_EVENT_FL_DYNPRINT or should we just always go through show_print_fmt()? If we do, we can get rid of set_event_dynprint() which is also a stupid function, and somewhat inefficient. - Is the WARN_ON() in show_print_fmt() correct? Can we have a dynamic event using this infrastructure? I don't know about dynamic events enough. - Is the double-slash (//) thing a good approach? I was looking for something that couldn't happen in C, and that's a comment so it shouldn't be possible ... It's only internal though so we could always change it. Parsing to the next , means we'd have to parse a LOT of C, so that's out of the question. - Is it correct that we can assume RCU critical section when in the lookup function? The SKB code currently does, but I may not ever have actually run this code yet. - Where should all the functions be implemented :-) Signed-off-by: Johannes Berg --- include/asm-generic/vmlinux.lds.h | 3 +- include/linux/module.h | 2 + include/linux/trace_events.h | 10 ++ include/linux/tracepoint.h | 20 ++++ include/trace/stages/init.h | 54 +++++++++ include/trace/stages/stage2_data_offsets.h | 6 + include/trace/stages/stage3_trace_output.h | 9 ++ include/trace/stages/stage7_class_define.h | 4 + kernel/module/main.c | 3 + kernel/trace/trace_events.c | 131 ++++++++++++++++++++- kernel/trace/trace_output.c | 43 +++++++ 11 files changed, 282 insertions(+), 3 deletions(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 9c59409104f6..b2b45ff0a701 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -263,7 +263,8 @@ #define FTRACE_EVENTS() \ . = ALIGN(8); \ BOUNDED_SECTION(_ftrace_events) \ - BOUNDED_SECTION_BY(_ftrace_eval_map, _ftrace_eval_maps) + BOUNDED_SECTION_BY(_ftrace_eval_map, _ftrace_eval_maps) \ + BOUNDED_SECTION(_ftrace_sym_defs) #else #define FTRACE_EVENTS() #endif diff --git a/include/linux/module.h b/include/linux/module.h index a98e188cf37b..bf14b74a872c 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -524,6 +524,8 @@ struct module { unsigned int num_trace_events; struct trace_eval_map **trace_evals; unsigned int num_trace_evals; + struct trace_sym_def **trace_sym_defs; + unsigned int num_trace_sym_defs; #endif #ifdef CONFIG_FTRACE_MCOUNT_RECORD unsigned int num_ftrace_callsites; diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index eb5c3add939b..9ab651a8fa0b 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -24,6 +24,13 @@ const char *trace_print_flags_seq(struct trace_seq *p, const char *delim, const char *trace_print_symbols_seq(struct trace_seq *p, unsigned long val, const struct trace_print_flags *symbol_array); +const char *trace_print_sym_seq(struct trace_seq *p, unsigned long long val, + const char *(*lookup)(unsigned long long val)); +const char *trace_sym_lookup(const struct trace_sym_entry *list, + size_t len, unsigned long long value); +void trace_sym_show(struct seq_file *m, + const struct trace_sym_entry *list, size_t len); + #if BITS_PER_LONG == 32 const char *trace_print_flags_seq_u64(struct trace_seq *p, const char *delim, unsigned long long flags, @@ -331,6 +338,7 @@ enum { TRACE_EVENT_FL_EPROBE_BIT, TRACE_EVENT_FL_FPROBE_BIT, TRACE_EVENT_FL_CUSTOM_BIT, + TRACE_EVENT_FL_DYNPRINT_BIT, }; /* @@ -348,6 +356,7 @@ enum { * CUSTOM - Event is a custom event (to be attached to an exsiting tracepoint) * This is set when the custom event has not been attached * to a tracepoint yet, then it is cleared when it is. + * DYNPRINT - Event has dynamic symbol prints */ enum { TRACE_EVENT_FL_FILTERED = (1 << TRACE_EVENT_FL_FILTERED_BIT), @@ -361,6 +370,7 @@ enum { TRACE_EVENT_FL_EPROBE = (1 << TRACE_EVENT_FL_EPROBE_BIT), TRACE_EVENT_FL_FPROBE = (1 << TRACE_EVENT_FL_FPROBE_BIT), TRACE_EVENT_FL_CUSTOM = (1 << TRACE_EVENT_FL_CUSTOM_BIT), + TRACE_EVENT_FL_DYNPRINT = (1 << TRACE_EVENT_FL_DYNPRINT_BIT), }; #define TRACE_EVENT_FL_UKPROBE (TRACE_EVENT_FL_KPROBE | TRACE_EVENT_FL_UPROBE) diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index 88c0ba623ee6..7650019f4347 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -31,6 +31,24 @@ struct trace_eval_map { unsigned long eval_value; }; +struct trace_sym_def { + const char *system; + const char *symbol_id; + /* may return NULL */ + const char * (*lookup)(unsigned long long); + /* + * Must print the list: ', { val, "name"}, ...' + * with no trailing comma, but with the leading ', ' + * to simplify things: + */ + void (*show)(struct seq_file *); +}; + +struct trace_sym_entry { + unsigned long long value; + const char *name; +}; + #define TRACEPOINT_DEFAULT_PRIO 10 extern struct srcu_struct tracepoint_srcu; @@ -109,6 +127,8 @@ extern void syscall_unregfunc(void); #define TRACE_DEFINE_ENUM(x) #define TRACE_DEFINE_SIZEOF(x) +#define TRACE_DEFINE_SYM_FNS(...) +#define TRACE_DEFINE_SYM_LIST(...) #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) diff --git a/include/trace/stages/init.h b/include/trace/stages/init.h index 000bcfc8dd2e..251ab22485d1 100644 --- a/include/trace/stages/init.h +++ b/include/trace/stages/init.h @@ -23,6 +23,60 @@ TRACE_MAKE_SYSTEM_STR(); __section("_ftrace_eval_map") \ *TRACE_SYSTEM##_##a = &__##TRACE_SYSTEM##_##a +/* + * Define a symbol for __print_sym by giving lookup and + * show functions. See &struct trace_sym_def. + */ +#define TRACE_DEFINE_SYM_FNS(_symbol_id, _lookup, _show) \ + _TRACE_DEFINE_SYM_FNS(TRACE_SYSTEM, _symbol_id, _lookup, _show) +#define _TRACE_DEFINE_SYM_FNS(_system, _symbol_id, _lookup, _show) \ + __TRACE_DEFINE_SYM_FNS(_system, _symbol_id, _lookup, _show) +#define __TRACE_DEFINE_SYM_FNS(_system, _symbol_id, _lookup, _show) \ + ___TRACE_DEFINE_SYM_FNS(_system ## _ ## _symbol_id, _symbol_id, \ + _lookup, _show) +#define ___TRACE_DEFINE_SYM_FNS(_name, _symbol_id, _lookup, _show) \ + static struct trace_sym_def \ + __trace_sym_def_ ## _name = { \ + .system = TRACE_SYSTEM_STRING, \ + /* need the ) for later strcmp */ \ + .symbol_id = #_symbol_id ")", \ + .lookup = _lookup, \ + .show = _show, \ + }; \ + static struct trace_sym_def \ + __section("_ftrace_sym_defs") \ + *__trace_sym_def_p_ ## _name = &__trace_sym_def_ ## _name + +/* + * Define a symbol for __print_sym by giving lookup and + * show functions. See &struct trace_sym_def. + */ +#define TRACE_DEFINE_SYM_LIST(_symbol_id, ...) \ + _TRACE_DEFINE_SYM_LIST(TRACE_SYSTEM, _symbol_id, __VA_ARGS__) +#define _TRACE_DEFINE_SYM_LIST(_system, _symbol_id, ...) \ + __TRACE_DEFINE_SYM_LIST(_system, _symbol_id, __VA_ARGS__) +#define __TRACE_DEFINE_SYM_LIST(_system, _symbol_id, ...) \ + ___TRACE_DEFINE_SYM_LIST(_system ## _ ## _symbol_id, _symbol_id,\ + __VA_ARGS__) +#define ___TRACE_DEFINE_SYM_LIST(_name, _symbol_id, ...) \ + static struct trace_sym_entry \ + __trace_sym_list_ ## _name[] = { __VA_ARGS__ }; \ + static const char * \ + __trace_sym_lookup_ ## _name(unsigned long long value) \ + { \ + return trace_sym_lookup(__trace_sym_list_ ## _name, \ + ARRAY_SIZE(__trace_sym_list_ ## _name), value); \ + } \ + static void \ + __trace_sym_show_ ## _name(struct seq_file *m) \ + { \ + trace_sym_show(m, __trace_sym_list_ ## _name, \ + ARRAY_SIZE(__trace_sym_list_ ## _name)); \ + } \ + ___TRACE_DEFINE_SYM_FNS(_name, _symbol_id, \ + __trace_sym_lookup_ ## _name, \ + __trace_sym_show_ ## _name) + #undef TRACE_DEFINE_SIZEOF #define TRACE_DEFINE_SIZEOF(a) \ static struct trace_eval_map __used __initdata \ diff --git a/include/trace/stages/stage2_data_offsets.h b/include/trace/stages/stage2_data_offsets.h index 469b6a64293d..83a287f78501 100644 --- a/include/trace/stages/stage2_data_offsets.h +++ b/include/trace/stages/stage2_data_offsets.h @@ -5,6 +5,12 @@ #undef TRACE_DEFINE_ENUM #define TRACE_DEFINE_ENUM(a) +#undef TRACE_DEFINE_SYM_FNS +#define TRACE_DEFINE_SYM_FNS(_symbol_id, _lookup, _show) + +#undef TRACE_DEFINE_SYM_LIST +#define TRACE_DEFINE_SYM_LIST(_symbol_id, ...) + #undef TRACE_DEFINE_SIZEOF #define TRACE_DEFINE_SIZEOF(a) diff --git a/include/trace/stages/stage3_trace_output.h b/include/trace/stages/stage3_trace_output.h index c1fb1355d309..d2c6458b62dc 100644 --- a/include/trace/stages/stage3_trace_output.h +++ b/include/trace/stages/stage3_trace_output.h @@ -79,6 +79,15 @@ trace_print_symbols_seq(p, value, symbols); \ }) +#undef __print_sym +#define __print_sym(value, symbol_id) \ + ___print_sym(TRACE_SYSTEM, value, symbol_id) +#define ___print_sym(sys, value, symbol_id) \ + ____print_sym(sys, value, symbol_id) +#define ____print_sym(sys, value, symbol_id) \ + trace_print_sym_seq(p, value, \ + __trace_sym_def_p_ ## sys ## _ ## symbol_id->lookup) + #undef __print_flags_u64 #undef __print_symbolic_u64 #if BITS_PER_LONG == 32 diff --git a/include/trace/stages/stage7_class_define.h b/include/trace/stages/stage7_class_define.h index bcb960d16fc0..ce802172b5d7 100644 --- a/include/trace/stages/stage7_class_define.h +++ b/include/trace/stages/stage7_class_define.h @@ -25,6 +25,10 @@ #undef __print_hex_dump #undef __get_buf +#undef __print_sym +/* use // as the separator since it'd be a comment in C */ +#define __print_sym(value, symbol_id) __print_sym(value\/\/symbol_id) + /* * The below is not executed in the kernel. It is only what is * displayed in the print format for userspace to parse. diff --git a/kernel/module/main.c b/kernel/module/main.c index 98fedfdb8db5..7752c3883cd2 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -2161,6 +2161,9 @@ static int find_module_sections(struct module *mod, struct load_info *info) mod->trace_evals = section_objs(info, "_ftrace_eval_map", sizeof(*mod->trace_evals), &mod->num_trace_evals); + mod->trace_sym_defs = section_objs(info, "_ftrace_sym_defs", + sizeof(*mod->trace_sym_defs), + &mod->num_trace_sym_defs); #endif #ifdef CONFIG_TRACING mod->trace_bprintk_fmt_start = section_objs(info, "__trace_printk_fmt", diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index ed367d713be0..38eaa7dce078 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -1559,6 +1559,104 @@ static void *f_next(struct seq_file *m, void *v, loff_t *pos) return node; } +extern struct trace_sym_def *__start_ftrace_sym_defs[]; +extern struct trace_sym_def *__stop_ftrace_sym_defs[]; + +static void show_sym_list(struct seq_file *m, struct trace_event_call *call, + const char *name) +{ + struct trace_sym_def **sym_defs; + unsigned int n_sym_defs, i; + + if (call->module) { + struct module *mod = call->module; + + sym_defs = mod->trace_sym_defs; + n_sym_defs = mod->num_trace_sym_defs; + } else { + sym_defs = __start_ftrace_sym_defs; + n_sym_defs = __stop_ftrace_sym_defs - __start_ftrace_sym_defs; + } + + for (i = 0; i < n_sym_defs; i++) { + if (!sym_defs[i]) + continue; + if (sym_defs[i]->system != call->class->system) + continue; + if (strncmp(name, sym_defs[i]->symbol_id, + strlen(sym_defs[i]->symbol_id))) + continue; + if (sym_defs[i]->show) + sym_defs[i]->show(m); + break; + } +} + +static void show_print_fmt(struct seq_file *m, struct trace_event_call *call) +{ + char *ptr = call->print_fmt; + int quote = 0; + int wait_for_doubleslash = 0; + + if (!(call->flags & TRACE_EVENT_FL_DYNPRINT) || + /* WARN because dynamic events have no module */ + WARN_ON_ONCE(call->flags & TRACE_EVENT_FL_DYNAMIC)) { + seq_printf(m, "\nprint fmt: %s\n", call->print_fmt); + return; + } + + seq_puts(m, "\nprint fmt: "); + while (*ptr) { + if (*ptr == '\\') { + seq_putc(m, *ptr); + ptr++; + /* paranoid */ + if (!*ptr) + break; + goto next; + } + if (*ptr == '"') { + quote ^= 1; + goto next; + } + if (quote) + goto next; + + if (wait_for_doubleslash == 1 && *ptr == '/') { + wait_for_doubleslash = 2; + ptr++; + continue; + } else if (wait_for_doubleslash == 2 && *ptr != '/') { + seq_putc(m, '/'); + wait_for_doubleslash = 1; + goto next; + } else if (wait_for_doubleslash == 2 && *ptr == '/') { + const char *name; + + ptr++; + name = ptr; + /* skip the name */ + while (*ptr && *ptr != ')') + ptr++; + wait_for_doubleslash = 0; + show_sym_list(m, call, name); + continue; + } + + if (strncmp(ptr, "__print_sym(", 12) == 0) { + ptr += 12; + seq_puts(m, "__print_symbolic("); + wait_for_doubleslash = 1; + continue; + } +next: + seq_putc(m, *ptr); + ptr++; + } + + seq_putc(m, '\n'); +} + static int f_show(struct seq_file *m, void *v) { struct trace_event_call *call = event_file_data(m->private); @@ -1577,8 +1675,7 @@ static int f_show(struct seq_file *m, void *v) return 0; case FORMAT_PRINTFMT: - seq_printf(m, "\nprint fmt: %s\n", - call->print_fmt); + show_print_fmt(m, call); return 0; } @@ -2552,6 +2649,32 @@ static int event_init(struct trace_event_call *call) return ret; } +static void set_event_dynprint(struct trace_event_call *call) +{ + char *ptr; + int quote = 0; + + for (ptr = call->print_fmt; *ptr; ptr++) { + if (*ptr == '\\') { + ptr++; + /* paranoid */ + if (!*ptr) + break; + continue; + } + if (*ptr == '"') { + quote ^= 1; + continue; + } + if (quote) + continue; + if (strncmp(ptr, "__print_sym(", 12) == 0) { + call->flags |= TRACE_EVENT_FL_DYNPRINT; + break; + } + } +} + static int __register_event(struct trace_event_call *call, struct module *mod) { @@ -2567,6 +2690,8 @@ __register_event(struct trace_event_call *call, struct module *mod) else call->module = mod; + set_event_dynprint(call); + return 0; } @@ -3810,6 +3935,8 @@ static __init int event_trace_enable(void) ret = event_init(call); if (!ret) list_add(&call->list, &ftrace_events); + + set_event_dynprint(call); } register_trigger_cmds(); diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index db575094c498..9196f408a1d2 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -124,6 +124,49 @@ trace_print_symbols_seq(struct trace_seq *p, unsigned long val, } EXPORT_SYMBOL(trace_print_symbols_seq); +const char *trace_sym_lookup(const struct trace_sym_entry *list, + size_t len, unsigned long long value) +{ + size_t i; + + for (i = 0; i < len; i++) { + if (list[i].value == value) + return list[i].name; + } + return NULL; +} +EXPORT_SYMBOL(trace_sym_lookup); + +void trace_sym_show(struct seq_file *m, + const struct trace_sym_entry *list, size_t len) +{ + size_t i; + + for (i = 0; i < len; i++) + seq_printf(m, ", { %lld, \"%s\" }", + list[i].value, list[i].name); +} +EXPORT_SYMBOL(trace_sym_show); + +const char * +trace_print_sym_seq(struct trace_seq *p, unsigned long long val, + const char *(*lookup)(unsigned long long val)) +{ + const char *ret = trace_seq_buffer_ptr(p); + const char *name; + + name = lookup(val); + if (name) + trace_seq_puts(p, name); + else + trace_seq_printf(p, "0x%llx", val); + + trace_seq_putc(p, 0); + + return ret; +} +EXPORT_SYMBOL(trace_print_sym_seq); + #if BITS_PER_LONG == 32 const char * trace_print_flags_seq_u64(struct trace_seq *p, const char *delim,