From mboxrd@z Thu Jan 1 00:00:00 1970 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 8DBA8C7EE25 for ; Mon, 12 Jun 2023 11:05:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237948AbjFLLF4 (ORCPT ); Mon, 12 Jun 2023 07:05:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42416 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238931AbjFLLF2 (ORCPT ); Mon, 12 Jun 2023 07:05:28 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 31EE4A266; Mon, 12 Jun 2023 03:53:37 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 869F81FB; Mon, 12 Jun 2023 02:57:42 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.27.163]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1998B3F663; Mon, 12 Jun 2023 02:56:54 -0700 (PDT) Date: Mon, 12 Jun 2023 10:56:52 +0100 From: Mark Rutland To: Steven Rostedt Cc: LKML , Linux Trace Kernel , Masami Hiramatsu , Andrew Morton , Thomas Gleixner , Peter Zijlstra , Kees Cook , Miguel Ojeda , Nick Desaulniers , Ingo Molnar , Song Liu , Josh Poimboeuf Subject: Re: [PATCH v2] ftrace: Allow inline functions not inlined to be traced Message-ID: References: <20230609174422.04824a9e@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230609174422.04824a9e@gandalf.local.home> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 09, 2023 at 05:44:22PM -0400, Steven Rostedt wrote: > From: "Steven Rostedt (Google)" > > Over 10 years ago there were many bugs that caused function tracing to > crash because some inlined function was not inlined and should not have > been traced. This made it hard to debug because when the developer tried > to reproduce it, if their compiler still inlined the function, the bug > would not trigger. The solution back then was simply to add "notrace" to > "inline" which would make sure all functions that are marked inline are > never traced even when the compiler decides to not inline them. > > A lot has changed over the last 10 years. > > 1) ftrace_test_recursion_trylock() is now used by all ftrace hooks which > will prevent the recursive crashes from happening that was caused by > inlined functions being traced. > > 2) noinstr is now used to mark pretty much all functions that would also > cause problems if they are traced. > > Today, it is no longer a problem if an inlined function is not inlined and > is traced, at least on x86. Removing notrace from inline has been requested > several times over the years. I believe it is now safe to do so. > > Currently only x86 uses this. > > Acked-by: Song Liu > Acked-by: Josh Poimboeuf > Signed-off-by: Steven Rostedt (Google) Acked-by: Mark Rutland > --- > Changes since v1: https://lore.kernel.org/linux-trace-kernel/20230502164102.1a51cdb4@gandalf.local.home > > - have it opted in by architecture. Currently only x86 adds it. (Mark Rutland) I'll add auditing/fixing arm64 on my queue of things to do; thanks for adding the config option in the mean time! Mark. > > arch/x86/Kconfig | 1 + > include/linux/compiler_types.h | 16 +++++++++++++--- > kernel/trace/Kconfig | 7 +++++++ > 3 files changed, 21 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index da5c081d64a5..1ddebf832534 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -61,6 +61,7 @@ config X86 > select ACPI_LEGACY_TABLES_LOOKUP if ACPI > select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI > select ARCH_32BIT_OFF_T if X86_32 > + select ARCH_CAN_TRACE_INLINE > select ARCH_CLOCKSOURCE_INIT > select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE > select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > index 547ea1ff806e..f827e2a98500 100644 > --- a/include/linux/compiler_types.h > +++ b/include/linux/compiler_types.h > @@ -169,6 +169,16 @@ struct ftrace_likely_data { > #define notrace __attribute__((__no_instrument_function__)) > #endif > > +/* > + * If all inline code not marked as __always_inline is safe to trace, > + * then allow the architecture to do so. > + */ > +#ifdef CONFIG_ARCH_CAN_TRACE_INLINE > +#define __notrace_inline > +#else > +#define __notrace_inline notrace > +#endif > + > /* > * it doesn't make sense on ARM (currently the only user of __naked) > * to trace naked functions because then mcount is called without > @@ -184,7 +194,7 @@ struct ftrace_likely_data { > * of extern inline functions at link time. > * A lot of inline functions can cause havoc with function tracing. > */ > -#define inline inline __gnu_inline __inline_maybe_unused notrace > +#define inline inline __gnu_inline __inline_maybe_unused __notrace_inline > > /* > * gcc provides both __inline__ and __inline as alternate spellings of > @@ -230,7 +240,7 @@ struct ftrace_likely_data { > * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 > * '__maybe_unused' allows us to avoid defined-but-not-used warnings. > */ > -# define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused > +# define __no_kasan_or_inline __no_sanitize_address __notrace_inline __maybe_unused > # define __no_sanitize_or_inline __no_kasan_or_inline > #else > # define __no_kasan_or_inline __always_inline > @@ -247,7 +257,7 @@ struct ftrace_likely_data { > * disable all instrumentation. See Kconfig.kcsan where this is mandatory. > */ > # define __no_kcsan __no_sanitize_thread __disable_sanitizer_instrumentation > -# define __no_sanitize_or_inline __no_kcsan notrace __maybe_unused > +# define __no_sanitize_or_inline __no_kcsan __notrace_inline __maybe_unused > #else > # define __no_kcsan > #endif > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > index abe5c583bd59..b66ab0e6ce19 100644 > --- a/kernel/trace/Kconfig > +++ b/kernel/trace/Kconfig > @@ -106,6 +106,13 @@ config HAVE_BUILDTIME_MCOUNT_SORT > An architecture selects this if it sorts the mcount_loc section > at build time. > > +config ARCH_CAN_TRACE_INLINE > + bool > + help > + It is safe for an architecture to trace any function marked > + as inline (not __always_inline) that the compiler decides to > + not inline. > + > config BUILDTIME_MCOUNT_SORT > bool > default y > -- > 2.39.2 >