Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932908AbcLHWrE (ORCPT ); Thu, 8 Dec 2016 17:47:04 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:34265 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932469AbcLHWrD (ORCPT ); Thu, 8 Dec 2016 17:47:03 -0500 Date: Thu, 8 Dec 2016 22:46:55 +0000 From: Abel Vesa To: Abel Vesa Cc: linux@armlinux.org.uk, rostedt@goodmis.org, mingo@redhat.com, viro@zeniv.linux.org.uk, jjhiblot@traphandler.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, pmladek@suse.com, robin.murphy@arm.com, zhouchengming1@huawei.com Subject: Re: [PATCH] arm: ftrace: Adds support for CONFIG_DYNAMIC_FTRACE_WITH_REGS Message-ID: <20161208224655.GA6319@gce> References: <1481233595-22112-1-git-send-email-abelvesa@linux.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1481233595-22112-1-git-send-email-abelvesa@linux.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7743 Lines: 241 On Thu, Dec 08, 2016 at 09:46:35PM +0000, Abel Vesa wrote: > From: Jean-Jacques Hiblot > > From: Jean-Jacques Hiblot >From statement twice in the commit message. Will resend. > > The DYNAMIC_FTRACE_WITH_REGS configuration makes it possible for a ftrace > operation to specify if registers need to saved/restored by the ftrace handler. > This is needed by kgraft and possibly other ftrace-based tools, and the ARM > architecture is currently lacking this feature. It would also be the first step > to support the "Kprobes-on-ftrace" optimization on ARM. > > This patch introduces a new ftrace handler that stores the registers on the > stack before calling the next stage. The registers are restored from the stack > before going back to the instrumented function. > > A side-effect of this patch is to activate the support for ftrace_modify_call() > as it defines ARCH_SUPPORTS_FTRACE_OPS for the ARM architecture > > Signed-off-by: Jean-Jacques Hiblot > Signed-off-by: Abel Vesa > --- > arch/arm/Kconfig | 2 ++ > arch/arm/include/asm/ftrace.h | 4 +++ > arch/arm/kernel/entry-ftrace.S | 78 ++++++++++++++++++++++++++++++++++++++++++ > arch/arm/kernel/ftrace.c | 33 ++++++++++++++++++ > 4 files changed, 117 insertions(+) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index b5d529f..87f1a9f 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -50,6 +50,7 @@ config ARM > select HAVE_DMA_API_DEBUG > select HAVE_DMA_CONTIGUOUS if MMU > select HAVE_DYNAMIC_FTRACE if (!XIP_KERNEL) && !CPU_ENDIAN_BE32 && MMU > + select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE > select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU > select HAVE_EXIT_THREAD > select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL) > @@ -90,6 +91,7 @@ config ARM > select PERF_USE_VMALLOC > select RTC_LIB > select SYS_SUPPORTS_APM_EMULATION > + select FRAME_POINTER if DYNAMIC_FTRACE_WITH_REGS && FUNCTION_GRAPH_TRACER > # Above selects are sorted alphabetically; please add new ones > # according to that. Thanks. > help > diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h > index bfe2a2f..f434ce9 100644 > --- a/arch/arm/include/asm/ftrace.h > +++ b/arch/arm/include/asm/ftrace.h > @@ -1,6 +1,10 @@ > #ifndef _ASM_ARM_FTRACE > #define _ASM_ARM_FTRACE > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > +#define ARCH_SUPPORTS_FTRACE_OPS 1 > +#endif > + > #ifdef CONFIG_FUNCTION_TRACER > #define MCOUNT_ADDR ((unsigned long)(__gnu_mcount_nc)) > #define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ > diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S > index c73c403..fd75bae 100644 > --- a/arch/arm/kernel/entry-ftrace.S > +++ b/arch/arm/kernel/entry-ftrace.S > @@ -92,12 +92,73 @@ > 2: mcount_exit > .endm > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > + > +.macro __ftrace_regs_caller > + > + add ip, sp, #4 @ move in IP the value of SP as it was > + @ before the push {lr} of the mcount mechanism > + stmdb sp!, {ip,lr,pc} > + stmdb sp!, {r0-r11,lr} > + > + @ stack content at this point: > + @ 0 4 44 48 52 56 60 64 > + @ RO | R1 | ... | R11 | LR | SP + 4 | LR | PC | previous LR | > + > + mov r3, sp @ struct pt_regs* > + ldr r2, =function_trace_op > + ldr r2, [r2] @ pointer to the current > + @ function tracing op > + ldr r1, [sp, #64] @ lr of instrumented func > + mcount_adjust_addr r0, lr @ instrumented function > + > + .globl ftrace_regs_call > +ftrace_regs_call: > + bl ftrace_stub > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > + .globl ftrace_graph_regs_call > +ftrace_graph_regs_call: > + mov r0, r0 > +#endif > + ldr lr, [sp, #64] @ get the previous LR value from stack > + ldmia sp, {r0-r11, ip, sp} @ pop the saved registers INCLUDING > + @ the stack pointer > + ret ip > +.endm > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > +.macro __ftrace_graph_regs_caller > + > + sub r0, fp, #4 @ lr of instrumented routine (parent) > + > + @ called from __ftrace_regs_caller > + ldr r1, [sp, #56] @ instrumented routine (func) > + mcount_adjust_addr r1, r1 > + > + mov r2, fp @ frame pointer > + bl prepare_ftrace_return > + > + ldr lr, [fp, #-4] @ restore lr from the stack > + ldmia sp, {r0-r11, ip, sp} @ restore r0 through sp > + ret ip > +.endm > +#endif > +#endif > + > .macro __ftrace_caller suffix > mcount_enter > > mcount_get_lr r1 @ lr of instrumented func > mcount_adjust_addr r0, lr @ instrumented function > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > + ldr r2, =function_trace_op > + ldr r2, [r2] @ pointer to the current > + @ function tracing op > + mov r3, #0 @ regs is NULL > +#endif > + > .globl ftrace_call\suffix > ftrace_call\suffix: > bl ftrace_stub > @@ -212,6 +273,15 @@ UNWIND(.fnstart) > __ftrace_caller > UNWIND(.fnend) > ENDPROC(ftrace_caller) > + > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > +ENTRY(ftrace_regs_caller) > +UNWIND(.fnstart) > + __ftrace_regs_caller > +UNWIND(.fnend) > +ENDPROC(ftrace_regs_caller) > +#endif > + > #endif > > #ifdef CONFIG_FUNCTION_GRAPH_TRACER > @@ -220,6 +290,14 @@ UNWIND(.fnstart) > __ftrace_graph_caller > UNWIND(.fnend) > ENDPROC(ftrace_graph_caller) > + > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > +ENTRY(ftrace_graph_regs_caller) > +UNWIND(.fnstart) > + __ftrace_graph_regs_caller > +UNWIND(.fnend) > +ENDPROC(ftrace_graph_regs_caller) > +#endif > #endif > > .purgem mcount_enter > diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c > index 3f17594..d8d4753 100644 > --- a/arch/arm/kernel/ftrace.c > +++ b/arch/arm/kernel/ftrace.c > @@ -139,6 +139,15 @@ int ftrace_update_ftrace_func(ftrace_func_t func) > > ret = ftrace_modify_code(pc, 0, new, false); > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > + if (!ret) { > + pc = (unsigned long)&ftrace_regs_call; > + new = ftrace_call_replace(pc, (unsigned long)func); > + > + ret = ftrace_modify_code(pc, 0, new, false); > + } > +#endif > + > #ifdef CONFIG_OLD_MCOUNT > if (!ret) { > pc = (unsigned long)&ftrace_call_old; > @@ -157,6 +166,20 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) > unsigned long ip = rec->ip; > > old = ftrace_nop_replace(rec); > + > + new = ftrace_call_replace(ip, adjust_address(rec, addr)); > + > + return ftrace_modify_code(rec->ip, old, new, true); > +} > + > +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, > + unsigned long addr) > +{ > + unsigned long new, old; > + unsigned long ip = rec->ip; > + > + old = ftrace_call_replace(ip, adjust_address(rec, old_addr)); > + > new = ftrace_call_replace(ip, adjust_address(rec, addr)); > > return ftrace_modify_code(rec->ip, old, new, true); > @@ -229,6 +252,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, > extern unsigned long ftrace_graph_call; > extern unsigned long ftrace_graph_call_old; > extern void ftrace_graph_caller_old(void); > +extern unsigned long ftrace_graph_regs_call; > +extern void ftrace_graph_regs_caller(void); > > static int __ftrace_modify_caller(unsigned long *callsite, > void (*func) (void), bool enable) > @@ -251,6 +276,14 @@ static int ftrace_modify_graph_caller(bool enable) > ftrace_graph_caller, > enable); > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > + if (!ret) > + ret = __ftrace_modify_caller(&ftrace_graph_regs_call, > + ftrace_graph_regs_caller, > + enable); > +#endif > + > + > #ifdef CONFIG_OLD_MCOUNT > if (!ret) > ret = __ftrace_modify_caller(&ftrace_graph_call_old, > -- > 2.7.4 >