From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752709Ab0BWNUy (ORCPT ); Tue, 23 Feb 2010 08:20:54 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:63277 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751592Ab0BWNUu (ORCPT ); Tue, 23 Feb 2010 08:20:50 -0500 X-Authority-Analysis: v=1.0 c=1 a=TmnEcBdXtfUA:10 a=HvM9zIr2IIqlL4hpBGgA:9 a=e0wJVsH4CcxC3K0uCu4A:7 a=9LKtwND0vJ7YPY1PawkVdtPBjQMA:4 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.89.75 Subject: Re: [PATCH 04/10] ARM: ftrace: allow building without frame pointers From: Steven Rostedt To: Frederic Weisbecker Cc: Rabin Vincent , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Ingo Molnar , Abhishek Sagar , Uwe =?ISO-8859-1?Q?Kleine-K=F6nig?= In-Reply-To: <20100222190516.GJ5055@nowhere> References: <1266090518-31120-1-git-send-email-rabin@rab.in> <1266090518-31120-5-git-send-email-rabin@rab.in> <20100222190516.GJ5055@nowhere> Content-Type: text/plain Date: Tue, 23 Feb 2010 08:18:33 -0500 Message-Id: <1266931113.19540.5.camel@frodo> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 (2.26.3-1.fc11) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2010-02-22 at 20:05 +0100, Frederic Weisbecker wrote: > > Btw, you described that mcount is used in some gcc versions and > __gnu_mcount_nc in newers. > Shouldn't we have a gcc version dependency here? (not sure we can > do this from Kconfig though). > Maybe we can add something to recordmcount.pl? > > > > config DEBUG_USER > > bool "Verbose user fault messages" > > help > > diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c > > index 8214bfe..e5e1e53 100644 > > --- a/arch/arm/kernel/armksyms.c > > +++ b/arch/arm/kernel/armksyms.c > > @@ -165,6 +165,8 @@ EXPORT_SYMBOL(_find_next_bit_be); > > #endif > > > > #ifdef CONFIG_FUNCTION_TRACER > > +#ifdef CONFIG_OLD_MCOUNT > > EXPORT_SYMBOL(mcount); > > +#endif > > EXPORT_SYMBOL(__gnu_mcount_nc); > > #endif > > diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S > > index d412d7c..c98e3a3 100644 > > --- a/arch/arm/kernel/entry-common.S > > +++ b/arch/arm/kernel/entry-common.S > > @@ -169,6 +169,12 @@ gnu_trace: > > ldmia sp!, {r0-r3, ip, lr} > > mov pc, ip > > > > +#ifdef CONFIG_OLD_MCOUNT > > +/* > > + * This is under an ifdef in order to force link-time errors for people trying > > + * to build with !FRAME_POINTER with a GCC which doesn't use the new-style > > + * mcount. > > + */ > > ENTRY(mcount) > > stmdb sp!, {r0-r3, lr} > > ldr r0, =ftrace_trace_function > > @@ -187,6 +193,7 @@ trace: > > mov pc, r2 > > ldr lr, [fp, #-4] @ restore lr > > ldmia sp!, {r0-r3, pc} > > +#endif > > > > #endif /* CONFIG_DYNAMIC_FTRACE */ > > > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > > index 6c22d8a..7468ffe 100644 > > --- a/kernel/trace/Kconfig > > +++ b/kernel/trace/Kconfig > > @@ -126,7 +126,7 @@ if FTRACE > > config FUNCTION_TRACER > > bool "Kernel Function Tracer" > > depends on HAVE_FUNCTION_TRACER > > - select FRAME_POINTER > > + select FRAME_POINTER if (!ARM_UNWIND) > > > So, if I understand well. If people have ARM_UNWIND but > FUNCTION_TRACER, it might crash at link time in case > they don't have a recent enough gcc version to > support the new -pg style? > > That doesn't look good. > > Ideally, we need HAVE_FUNCTION_TRACER to be enabled in arm > only if (old gcc && frame pointers) || new gcc > > And then, we need config OLD_MCOUNT: > old gcc && FUNCTION_TRACER > > and config NEW_MCOUNT: > new gcc && FUNCTION_TRACER > > so that we can selectively build mcount or __gnu_mcount_nc. > > Hmm, I fear we can't check gcc version from Kconfig, as I'm > grepping on Kconfig files... I would not check gcc version through KCONFIG, but you can have the gcc version checked and define another macro in a header somewhere, like asm/ftrace.h. Then we could do something different while it is compiling. Disclaimer: I have to go back and read the entire thread, to know what exactly is going on ;-) -- Steve From mboxrd@z Thu Jan 1 00:00:00 1970 From: rostedt@goodmis.org (Steven Rostedt) Date: Tue, 23 Feb 2010 08:18:33 -0500 Subject: [PATCH 04/10] ARM: ftrace: allow building without frame pointers In-Reply-To: <20100222190516.GJ5055@nowhere> References: <1266090518-31120-1-git-send-email-rabin@rab.in> <1266090518-31120-5-git-send-email-rabin@rab.in> <20100222190516.GJ5055@nowhere> Message-ID: <1266931113.19540.5.camel@frodo> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, 2010-02-22 at 20:05 +0100, Frederic Weisbecker wrote: > > Btw, you described that mcount is used in some gcc versions and > __gnu_mcount_nc in newers. > Shouldn't we have a gcc version dependency here? (not sure we can > do this from Kconfig though). > Maybe we can add something to recordmcount.pl? > > > > config DEBUG_USER > > bool "Verbose user fault messages" > > help > > diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c > > index 8214bfe..e5e1e53 100644 > > --- a/arch/arm/kernel/armksyms.c > > +++ b/arch/arm/kernel/armksyms.c > > @@ -165,6 +165,8 @@ EXPORT_SYMBOL(_find_next_bit_be); > > #endif > > > > #ifdef CONFIG_FUNCTION_TRACER > > +#ifdef CONFIG_OLD_MCOUNT > > EXPORT_SYMBOL(mcount); > > +#endif > > EXPORT_SYMBOL(__gnu_mcount_nc); > > #endif > > diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S > > index d412d7c..c98e3a3 100644 > > --- a/arch/arm/kernel/entry-common.S > > +++ b/arch/arm/kernel/entry-common.S > > @@ -169,6 +169,12 @@ gnu_trace: > > ldmia sp!, {r0-r3, ip, lr} > > mov pc, ip > > > > +#ifdef CONFIG_OLD_MCOUNT > > +/* > > + * This is under an ifdef in order to force link-time errors for people trying > > + * to build with !FRAME_POINTER with a GCC which doesn't use the new-style > > + * mcount. > > + */ > > ENTRY(mcount) > > stmdb sp!, {r0-r3, lr} > > ldr r0, =ftrace_trace_function > > @@ -187,6 +193,7 @@ trace: > > mov pc, r2 > > ldr lr, [fp, #-4] @ restore lr > > ldmia sp!, {r0-r3, pc} > > +#endif > > > > #endif /* CONFIG_DYNAMIC_FTRACE */ > > > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > > index 6c22d8a..7468ffe 100644 > > --- a/kernel/trace/Kconfig > > +++ b/kernel/trace/Kconfig > > @@ -126,7 +126,7 @@ if FTRACE > > config FUNCTION_TRACER > > bool "Kernel Function Tracer" > > depends on HAVE_FUNCTION_TRACER > > - select FRAME_POINTER > > + select FRAME_POINTER if (!ARM_UNWIND) > > > So, if I understand well. If people have ARM_UNWIND but > FUNCTION_TRACER, it might crash at link time in case > they don't have a recent enough gcc version to > support the new -pg style? > > That doesn't look good. > > Ideally, we need HAVE_FUNCTION_TRACER to be enabled in arm > only if (old gcc && frame pointers) || new gcc > > And then, we need config OLD_MCOUNT: > old gcc && FUNCTION_TRACER > > and config NEW_MCOUNT: > new gcc && FUNCTION_TRACER > > so that we can selectively build mcount or __gnu_mcount_nc. > > Hmm, I fear we can't check gcc version from Kconfig, as I'm > grepping on Kconfig files... I would not check gcc version through KCONFIG, but you can have the gcc version checked and define another macro in a header somewhere, like asm/ftrace.h. Then we could do something different while it is compiling. Disclaimer: I have to go back and read the entire thread, to know what exactly is going on ;-) -- Steve