Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754606AbZKNGgj (ORCPT ); Sat, 14 Nov 2009 01:36:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754343AbZKNGgh (ORCPT ); Sat, 14 Nov 2009 01:36:37 -0500 Received: from mail-px0-f180.google.com ([209.85.216.180]:33554 "EHLO mail-px0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754182AbZKNGge (ORCPT ); Sat, 14 Nov 2009 01:36:34 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=Jb67QucxBDw3++BbxXETiSpMUuv5ZCaZgCaVQzjA4wXaj+twKf0avq4fmCg1kmztli IwHHXTZlzssGz7g9ZaS6Zt66n94ezHG29DXgRIF6r+4D+9o0XGQuKdVcP7zDUWnoXIuY Q1hwFGIG05dF/+E9wNBF75Wblq1ZNJf6EAcWc= From: Wu Zhangjin To: rostedt@goodmis.org, Ralf Baechle Cc: Wu Zhangjin , Frederic Weisbecker , Ingo Molnar , Nicholas Mc Guire , David Daney , Richard Sandiford , Patrik Kluba , Thomas Gleixner , Michal Simek , "Maciej W . Rozycki" , linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, zhangfx@lemote.com, zhouqg@gmail.com Subject: [PATCH v8 16/16] tracing: make function graph tracer work with -mmcount-ra-address Date: Sat, 14 Nov 2009 14:33:31 +0800 Message-Id: X-Mailer: git-send-email 1.6.2.1 In-Reply-To: <5fac5676cfadccf569cab72094f365b130b181ed.1258177321.git.wuzhangjin@gmail.com> References: <9dc81a7a9e5a292cccdf465c533a2b08d19d6021.1258177321.git.wuzhangjin@gmail.com> <8f579e2cece16cd22358a4ec143ef6a8c462639b.1258177321.git.wuzhangjin@gmail.com> <7c7568247ad6cc109ec20387cfc3ca258d1d430f.1258177321.git.wuzhangjin@gmail.com> <3fcaffcfb3c8c8cd3015151ed5b7480ccaecde0f.1258177321.git.wuzhangjin@gmail.com> <48676d84140dbafd46e530611766121e18abc4ef.1258177321.git.wuzhangjin@gmail.com> <99ebd8fcb19e4cccd702fca966405ffc45f8540b.1258177321.git.wuzhangjin@gmail.com> <8a7987bba58526a0e156f531dba31d9a65d3d744.1258177321.git.wuzhangjin@gmail.com> <24733f375d853dd6dc44138c53f2f57493915d8f.1258177321.git.wuzhangjin@gmail.com> <5fac5676cfadccf569cab72094f365b130b181ed.1258177321.git.wuzhangjin@gmail.com> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6288 Lines: 166 From: Wu Zhangjin That thread "MIPS: Add option to pass return address location to _mcount" from "David Daney " have added a new option -mmcount-ra-address to gcc(4.5) for MIPS to transfer the location of the return address to _mcount. Benefit from this new feature, function graph tracer on MIPS will be easier and safer to hijack the return address of the kernel function, which will save some overhead and make the whole thing more reliable. In this patch, at first, try to enable the option -mmcount-ra-address in arch/mips/Makefile with cc-option, if gcc support it, it will be enabled, otherwise, no side effect. and then, we need to support this new option of gcc 4.5 and also support the old gcc versions. with _mcount in the old gcc versions, it's not easy to get the location of return address(tracing: add function graph tracer support for MIPS), so, we do it in a C function: ftrace_get_parent_addr(ftrace.c), but with -mmcount-ra-address, only several instructions need to get what we want, so, I put into asm(mcount.S). and also, as the $12(t0) is used by -mmcount-ra-address for transferring the localtion of return address to _mcount, we need to save it into the stack and restore it when enabled dynamic function tracer, 'Cause we have called "ftrace_call" before "ftrace_graph_caller", which may destroy $12(t0). (Thanks to David for providing that -mcount-ra-address and giving the idea of KBUILD_MCOUNT_RA_ADDRESS, both of them have made the whole thing more beautiful!) Signed-off-by: Wu Zhangjin --- arch/mips/Makefile | 7 +++++++ arch/mips/kernel/ftrace.c | 24 +++++++++++++++++------- arch/mips/kernel/mcount.S | 14 ++++++++++++++ 3 files changed, 38 insertions(+), 7 deletions(-) diff --git a/arch/mips/Makefile b/arch/mips/Makefile index 0a2073e..50039e8 100644 --- a/arch/mips/Makefile +++ b/arch/mips/Makefile @@ -51,6 +51,13 @@ endif ifndef CONFIG_FUNCTION_TRACER cflags-y := -ffunction-sections endif +ifdef CONFIG_FUNCTION_GRAPH_TRACER + ifndef KBUILD_MCOUNT_RA_ADDRESS + ifeq ($(call cc-option-yn,-mmcount-ra-address), y) + cflags-y += -mmcount-ra-address -DKBUILD_MCOUNT_RA_ADDRESS + endif + endif +endif cflags-y += $(call cc-option, -mno-check-zero-division) ifdef CONFIG_32BIT diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c index e363fc6..68b0670 100644 --- a/arch/mips/kernel/ftrace.c +++ b/arch/mips/kernel/ftrace.c @@ -148,6 +148,7 @@ int ftrace_disable_ftrace_graph_caller(void) #endif /* !CONFIG_DYNAMIC_FTRACE */ +#ifndef KBUILD_MCOUNT_RA_ADDRESS #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */ #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */ #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */ @@ -201,6 +202,8 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr, return 0; } +#endif + /* * Hook the return address and push it in the stack of return addrs * in current thread info. @@ -218,19 +221,26 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, return; /* "parent" is the stack address saved the return address of the caller - * of _mcount, for a leaf function not save the return address in the - * stack address, so, we "emulate" one in _mcount's stack space, and - * hijack it directly, but for a non-leaf function, it will save the - * return address to the its stack space, so, we can not hijack the - * "parent" directly, but need to find the real stack address, + * of _mcount. + * + * if the gcc < 4.5, a leaf function does not save the return address + * in the stack address, so, we "emulate" one in _mcount's stack space, + * and hijack it directly, but for a non-leaf function, it save the + * return address to the its own stack space, we can not hijack it + * directly, but need to find the real stack address, * ftrace_get_parent_addr() does it! + * + * if gcc>= 4.5, with the new -mmcount-ra-address option, for a + * non-leaf function, the location of the return address will be saved + * to $12 for us, and for a leaf function, only put a zero into $12. we + * do it in ftrace_graph_caller of mcount.S. */ /* old = *parent; */ safe_load_stack(old, parent, faulted); if (unlikely(faulted)) goto out; - +#ifndef KBUILD_MCOUNT_RA_ADDRESS parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old, (unsigned long)parent, fp); @@ -238,7 +248,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, * ra, stop function graph tracer and return */ if (parent == 0) goto out; - +#endif /* *parent = return_hooker; */ safe_store_stack(return_hooker, parent, faulted); if (unlikely(faulted)) diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S index 522e91c..0a9cfdb 100644 --- a/arch/mips/kernel/mcount.S +++ b/arch/mips/kernel/mcount.S @@ -70,6 +70,9 @@ _mcount: nop MCOUNT_SAVE_REGS +#ifdef KBUILD_MCOUNT_RA_ADDRESS + PTR_S t0, PT_R12(sp) /* t0 saved the location of the return address(at) by -mmcount-ra-address */ +#endif move a0, ra /* arg1: next ip, selfaddr */ .globl ftrace_call @@ -133,11 +136,22 @@ ftrace_stub: NESTED(ftrace_graph_caller, PT_SIZE, ra) #ifdef CONFIG_DYNAMIC_FTRACE PTR_L a1, PT_R31(sp) /* load the original ra from the stack */ +#ifdef KBUILD_MCOUNT_RA_ADDRESS + PTR_L t0, PT_R12(sp) /* load the original t0 from the stack */ +#endif #else MCOUNT_SAVE_REGS move a1, ra /* arg2: next ip, selfaddr */ #endif + +#ifdef KBUILD_MCOUNT_RA_ADDRESS + bnez t0, 1f /* non-leaf func: t0 saved the location of the return address */ + nop + PTR_LA t0, PT_R1(sp) /* leaf func: get the location of at(old ra) from our own stack */ +1: move a0, t0 /* arg1: the location of the return address */ +#else PTR_LA a0, PT_R1(sp) /* arg1: &AT -> a0 */ +#endif jal prepare_ftrace_return #ifdef CONFIG_FRAME_POINTER move a2, fp /* arg3: frame pointer */ -- 1.6.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/