From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758690AbdELVGw (ORCPT ); Fri, 12 May 2017 17:06:52 -0400 Received: from mail-wr0-f195.google.com ([209.85.128.195]:36389 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758146AbdELVGu (ORCPT ); Fri, 12 May 2017 17:06:50 -0400 From: Abel Vesa To: robin.murphy@arm.com, jjhiblot@traphandler.com, nicstange@gmail.com, Russell King , Steven Rostedt , Ingo Molnar Cc: pmladek@suse.com, mhiramat@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH] arm: ftrace: Adds support for CONFIG_DYNAMIC_FTRACE_WITH_REGS Date: Fri, 12 May 2017 22:06:47 +0100 Message-Id: <1494623207-17195-1-git-send-email-abelvesa@gmail.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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: Abel Vesa --- arch/arm/Kconfig | 1 + arch/arm/include/asm/ftrace.h | 4 ++ arch/arm/kernel/entry-ftrace.S | 100 +++++++++++++++++++++++++++++++++++++++++ arch/arm/kernel/ftrace.c | 37 +++++++++++++++ 4 files changed, 142 insertions(+) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 4c1a35f..730d456 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -56,6 +56,7 @@ 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) diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h index 22b7311..f379881 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..efcd9f2 100644 --- a/arch/arm/kernel/entry-ftrace.S +++ b/arch/arm/kernel/entry-ftrace.S @@ -92,12 +92,95 @@ 2: mcount_exit .endm +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + +.macro __ftrace_regs_caller + + sub sp, sp, #8 @ space for PC and CPSR OLD_R0, + @ OLD_R0 will overwrite previous LR + + add ip, sp, #12 @ move in IP the value of SP as it was + @ before the push {lr} of the mcount mechanism + + str lr, [sp, #0] @ store LR instead of PC + + ldr lr, [sp, #8] @ get previous LR + + str r0, [sp, #8] @ write r0 as OLD_R0 over previous LR + + stmdb sp!, {ip, lr} + stmdb sp!, {r0-r11, lr} + + @ stack content at this point: + @ 0 4 48 52 56 60 64 68 72 + @ R0 | R1 | ... | LR | SP + 4 | previous LR | LR | PSR | OLD_R0 | + + mov r3, sp @ struct pt_regs* + + ldr r2, =function_trace_op + ldr r2, [r2] @ pointer to the current + @ function tracing op + + ldr r1, [sp, #S_LR] @ lr of instrumented func + + ldr lr, [sp, #S_PC] @ get LR + + 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 + + @ pop saved regs + ldmia sp!, {r0-r12} @ restore r0 through r12 + ldr ip, [sp, #8] @ restore PC + ldr lr, [sp, #4] @ restore LR + ldr sp, [sp, #0] @ restore SP + mov pc, ip @ return +.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, #S_PC] @ instrumented routine (func) + mcount_adjust_addr r1, r1 + + mov r2, fp @ frame pointer + bl prepare_ftrace_return + + @ pop registers saved in ftrace_regs_caller + ldmia sp!, {r0-r12} @ restore r0 through r12 + ldr ip, [sp, #8] @ restore PC + ldr lr, [sp, #4] @ restore LR + ldr sp, [sp, #0] @ restore SP + mov pc, ip @ return + +.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 +295,15 @@ 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 +312,14 @@ 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 833c991..5617932 100644 --- a/arch/arm/kernel/ftrace.c +++ b/arch/arm/kernel/ftrace.c @@ -141,6 +141,15 @@ 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; @@ -159,11 +168,29 @@ 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); +} + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + +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); } +#endif + int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { @@ -231,6 +258,8 @@ 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) @@ -253,6 +282,14 @@ 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