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[61.205.7.47]) by smtp.googlemail.com with ESMTPSA id xr8sm1685523pab.26.2015.11.17.22.44.47 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 17 Nov 2015 22:44:50 -0800 (PST) From: AKASHI Takahiro To: catalin.marinas@arm.com, will.deacon@arm.com, rostedt@goodmis.org Subject: [PATCH v6 3/6] arm64: ftrace: fix a stack tracer's output under function graph tracer Date: Wed, 18 Nov 2015 15:43:06 +0900 Message-Id: <1447828989-4980-4-git-send-email-takahiro.akashi@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1447828989-4980-1-git-send-email-takahiro.akashi@linaro.org> References: <1447828989-4980-1-git-send-email-takahiro.akashi@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20151117_224513_512892_8AC4DC03 X-CRM114-Status: GOOD ( 17.57 ) X-Spam-Score: -2.6 (--) X-Spam-Report: SpamAssassin version 3.4.0 on bombadil.infradead.org summary: Content analysis details: (-2.6 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [2607:f8b0:400e:c03:0:0:0:235 listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jungseoklee85@gmail.com, AKASHI Takahiro , broonie@kernel.org, yalin.wang2010@gmail.com, david.griego@linaro.org, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org Function graph tracer modifies a return address (LR) in a stack frame to hook a function return. This will result in many useless entries (return_to_handler) showing up in a) a stack tracer's output b) perf call graph (with perf record -g) c) dump_backtrace (at panic et al.) For example, in case of a), $ echo function_graph > /sys/kernel/debug/tracing/current_tracer $ echo 1 > /proc/sys/kernel/stack_trace_enabled $ cat /sys/kernel/debug/tracing/stack_trace Depth Size Location (54 entries) ----- ---- -------- 0) 4504 16 gic_raise_softirq+0x28/0x150 1) 4488 80 smp_cross_call+0x38/0xb8 2) 4408 48 return_to_handler+0x0/0x40 3) 4360 32 return_to_handler+0x0/0x40 ... In case of b), $ echo function_graph > /sys/kernel/debug/tracing/current_tracer $ perf record -e mem:XXX:x -ag -- sleep 10 $ perf report ... | | |--0.22%-- 0x550f8 | | | 0x10888 | | | el0_svc_naked | | | sys_openat | | | return_to_handler | | | return_to_handler ... In case of c), $ echo function_graph > /sys/kernel/debug/tracing/current_tracer $ echo c > /proc/sysrq-trigger ... Call trace: [] sysrq_handle_crash+0x24/0x30 [] return_to_handler+0x0/0x40 [] return_to_handler+0x0/0x40 ... This patch replaces such entries with real addresses preserved in current->ret_stack[] at unwind_frame(). This way, we can cover all the cases. Signed-off-by: AKASHI Takahiro --- arch/arm64/include/asm/ftrace.h | 2 ++ arch/arm64/include/asm/stacktrace.h | 3 +++ arch/arm64/kernel/perf_callchain.c | 3 +++ arch/arm64/kernel/process.c | 3 +++ arch/arm64/kernel/return_address.c | 3 +++ arch/arm64/kernel/stacktrace.c | 17 +++++++++++++++++ arch/arm64/kernel/time.c | 3 +++ arch/arm64/kernel/traps.c | 3 +++ 8 files changed, 37 insertions(+) -- 1.7.9.5 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h index c5534fa..3c60f37 100644 --- a/arch/arm64/include/asm/ftrace.h +++ b/arch/arm64/include/asm/ftrace.h @@ -28,6 +28,8 @@ struct dyn_arch_ftrace { extern unsigned long ftrace_graph_call; +extern void return_to_handler(void); + static inline unsigned long ftrace_call_adjust(unsigned long addr) { /* diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index 6fb61c5..801a16db 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -22,6 +22,9 @@ struct stackframe { unsigned long fp; unsigned long sp; unsigned long pc; +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + unsigned int graph; +#endif }; extern int unwind_frame(struct task_struct *tsk, struct stackframe *frame); diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c index 797220d..ff46654 100644 --- a/arch/arm64/kernel/perf_callchain.c +++ b/arch/arm64/kernel/perf_callchain.c @@ -164,6 +164,9 @@ void perf_callchain_kernel(struct perf_callchain_entry *entry, frame.fp = regs->regs[29]; frame.sp = regs->sp; frame.pc = regs->pc; +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + frame.graph = current->curr_ret_stack; +#endif walk_stackframe(current, &frame, callchain_trace, entry); } diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 98bf546..88d742b 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -344,6 +344,9 @@ unsigned long get_wchan(struct task_struct *p) frame.fp = thread_saved_fp(p); frame.sp = thread_saved_sp(p); frame.pc = thread_saved_pc(p); +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + frame.graph = p->curr_ret_stack; +#endif stack_page = (unsigned long)task_stack_page(p); do { if (frame.sp < stack_page || diff --git a/arch/arm64/kernel/return_address.c b/arch/arm64/kernel/return_address.c index 07b37ac..1718706 100644 --- a/arch/arm64/kernel/return_address.c +++ b/arch/arm64/kernel/return_address.c @@ -43,6 +43,9 @@ void *return_address(unsigned int level) frame.fp = (unsigned long)__builtin_frame_address(0); frame.sp = current_stack_pointer; frame.pc = (unsigned long)return_address; /* dummy */ +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + frame.graph = current->curr_ret_stack; +#endif walk_stackframe(current, &frame, save_return_addr, &data); diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 9c7acf8..0a39049 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -17,6 +17,7 @@ */ #include #include +#include #include #include @@ -66,6 +67,19 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) frame->fp = *(unsigned long *)(fp); frame->pc = *(unsigned long *)(fp + 8); +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + if (tsk && tsk->ret_stack && + (frame->pc == (unsigned long)return_to_handler)) { + /* + * This is a case where function graph tracer has + * modified a return address (LR) in a stack frame + * to hook a function return. + * So replace it to an original value. + */ + frame->pc = tsk->ret_stack[frame->graph--].ret; + } +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ + /* * Check whether we are going to walk through from interrupt stack * to task stack. @@ -137,6 +151,9 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) frame.sp = current_stack_pointer; frame.pc = (unsigned long)save_stack_trace_tsk; } +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + frame.graph = tsk->curr_ret_stack; +#endif walk_stackframe(tsk, &frame, save_trace, &data); if (trace->nr_entries < trace->max_entries) diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c index 6e5c521..5977969 100644 --- a/arch/arm64/kernel/time.c +++ b/arch/arm64/kernel/time.c @@ -52,6 +52,9 @@ unsigned long profile_pc(struct pt_regs *regs) frame.fp = regs->regs[29]; frame.sp = regs->sp; frame.pc = regs->pc; +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + frame.graph = -1; /* no task info */ +#endif do { int ret = unwind_frame(NULL, &frame); if (ret < 0) diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index da45224..46053c2 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -169,6 +169,9 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) frame.sp = thread_saved_sp(tsk); frame.pc = thread_saved_pc(tsk); } +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + frame.graph = tsk->curr_ret_stack; +#endif pr_emerg("Call trace:\n"); while (1) {