From patchwork Tue Mar 21 08:46:49 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: pengdonglin X-Patchwork-Id: 13182395 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3555FC74A5B for ; Tue, 21 Mar 2023 08:47:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=9gxiWCAtU4WbXvx57nKXfs6h/lgsnXikuT0GlXYjfUk=; b=ynOs1MjBn4HYlY gZowuf3UIhnIOAdnNA746sA//LW87zGyaqZDryKuirMHaDxCFU12V2fbULo6X+JvqciTEmP2UfGYT SxV8ECmPpQtdysKijNJv03qz1IO1fR3XIy2ArPE81dbf6QMobCW2vx8j2RdNAMD89t31i1uVoFsBi VxlcSJ847j7Wt8PN2c2WFa5ZCFTamXthkVBpe9cKysnLk0LpXkvmxCEfTlY4gn+AUXMt9rsy1MtLS 5+9+TTAD0ngxkYKT+r/a72nVSmqzM7oG1cE43OeptCrt6cwOReIn2M5zGsLnpi498We8kUDiJlwiT BMorKKxXnvq9bpJtesuA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1peXeb-00Bkmj-1S; Tue, 21 Mar 2023 08:47:37 +0000 Received: from mail-m118111.qiye.163.com ([115.236.118.111]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1peXeF-00BkcI-0Y; Tue, 21 Mar 2023 08:47:20 +0000 Received: from ubuntu.localdomain (unknown [117.133.56.22]) by mail-m118111.qiye.163.com (Hmail) with ESMTPA id 9A2385807BE; Tue, 21 Mar 2023 16:47:05 +0800 (CST) From: Donglin Peng To: mhiramat@kernel.org, rostedt@goodmis.org, linux@armlinux.org.uk, mark.rutland@arm.com, will@kernel.org, catalin.marinas@arm.com, palmer@dabbelt.com, paul.walmsley@sifive.com, tglx@linutronix.de, dave.hansen@linux.intel.com, x86@kernel.org, mingo@redhat.com, peterz@infradead.org, xiehuan09@gmail.com, dinghui@sangfor.com.cn, huangcun@sangfor.com.cn, dolinux.peng@gmail.com Cc: linux-trace-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Donglin Peng Subject: [PATCH v6 1/2] function_graph: Support recording and printing the return value of function Date: Tue, 21 Mar 2023 01:46:49 -0700 Message-Id: <20230321084650.769212-2-pengdonglin@sangfor.com.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230321084650.769212-1-pengdonglin@sangfor.com.cn> References: <20230321084650.769212-1-pengdonglin@sangfor.com.cn> MIME-Version: 1.0 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFITzdXWS1ZQUlXWQ8JGhUIEh9ZQVkZGU4YVk4eThkYSUJMTB5OHVUTARMWGhIXJBQOD1 lXWRgSC1lBWUpKTFVKSEhVTk1VSUlZV1kWGg8SFR0UWUFZT0tIVUpKS09ISFVKS0tVS1kG X-HM-Sender-Digest: e1kMHhlZQR0aFwgeV1kSHx4VD1lBWUc6Ngw6Nyo5Qz0STBc2DyIWMAg1 QgxPFBpVSlVKTUxCSENDT0lMS0hKVTMWGhIXVQseFRwfFBUcFxIVOwgaFRwdFAlVGBQWVRgVRVlX WRILWUFZSkpMVUpISFVOTVVJSVlXWQgBWUFJS05DSjcG X-HM-Tid: 0a870359c0d42eb7kusn9a2385807be X-HM-MType: 1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230321_014715_555899_24B47AE2 X-CRM114-Status: GOOD ( 29.31 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org When using the function_graph tracer to analyze system call failures, it can be time-consuming to analyze the trace logs and locate the kernel function that first returns an error. This change aims to simplify the process by recording the function return value to the 'retval' member of 'ftrace_graph_ent' and printing it when outputing the trace log. New trace options are introduced: funcgraph-retval and graph_retval_hex. The former is used to control whether to display the return value, while the latter is used to control the display format. Note that even if a function's return type is void, a return value will still be printed, so just ignore it. Currently, this modification supports the following commonly used processor architectures: x86_64, x86, arm64, arm, riscv. Here is an example: I want to attach the demo process to a cpu cgroup, but it failed: echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks -bash: echo: write error: Invalid argument The strace logs tells that the write system call returned -EINVAL(-22): ... write(1, "273\n", 4) = -1 EINVAL (Invalid argument) ... Use the following commands to capture trace logs when calling the write system call: cd /sys/kernel/debug/tracing/ echo 0 > tracing_on echo > trace echo *sys_write > set_graph_function echo *spin* > set_graph_notrace echo *rcu* >> set_graph_notrace echo *alloc* >> set_graph_notrace echo preempt* >> set_graph_notrace echo kfree* >> set_graph_notrace echo $$ > set_ftrace_pid echo function_graph > current_tracer echo 1 > tracing_on echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks echo 0 > tracing_on echo 1 > options/funcgraph-retval cat trace > ~/trace.log Search the error code -22 directly in the file trace.log and find the first function that return -22, then read the function code to get the root cause. ... 1) | cgroup_migrate() { 1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */ 1) | cgroup_migrate_execute() { 1) | cpu_cgroup_can_attach() { 1) | cgroup_taskset_first() { 1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */ 1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */ 1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */ 1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */ 1) 4.369 us | } /* cgroup_migrate_execute = -22 */ 1) 7.143 us | } /* cgroup_migrate = -22 */ ... Signed-off-by: Donglin Peng Acked-by: Masami Hiramatsu (Google) --- v6: - Remove the conversion code for short and char types, because these two types are rarely used to store an error code. v5: - Pass both the return values to ftrace_return_to_handler - Modify the parameter sequence of ftrace_return_to_handler to decrease the modification of assembly code, thanks to Russell King - Wrap __ftrace_return_to_handler with ftrace_return_to_handler for compatible v4: - Modify commit message - Introduce new option graph_retval_hex to control display format - Introduce macro CONFIG_FUNCTION_GRAPH_RETVAL and CONFIG_HAVE_FUNCTION_GRAPH_RETVAL - Add related arch maintainers to review v3: - Modify the commit message: add trace logs processed with the btf tool v2: - Modify the commit message: use BTF to get the return type of function --- arch/arm/Kconfig | 1 + arch/arm/kernel/entry-ftrace.S | 8 +++ arch/arm64/Kconfig | 1 + arch/arm64/kernel/entry-ftrace.S | 8 +++ arch/riscv/Kconfig | 1 + arch/riscv/kernel/mcount.S | 12 +++- arch/x86/Kconfig | 1 + arch/x86/kernel/ftrace_32.S | 8 +++ arch/x86/kernel/ftrace_64.S | 10 +++ include/linux/ftrace.h | 3 + kernel/trace/Kconfig | 8 +++ kernel/trace/fgraph.c | 25 +++++++- kernel/trace/trace.h | 2 + kernel/trace/trace_entries.h | 26 ++++++++ kernel/trace/trace_functions_graph.c | 93 +++++++++++++++++++++++++--- 15 files changed, 195 insertions(+), 12 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index e24a9820e12f..ad03fc868f34 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -99,6 +99,7 @@ config ARM select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_ERROR_INJECTION select HAVE_FUNCTION_GRAPH_TRACER + select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER if !XIP_KERNEL select HAVE_GCC_PLUGINS select HAVE_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7) diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S index 3e7bcaca5e07..ba1986e27af8 100644 --- a/arch/arm/kernel/entry-ftrace.S +++ b/arch/arm/kernel/entry-ftrace.S @@ -258,7 +258,15 @@ ENDPROC(ftrace_graph_regs_caller) #ifdef CONFIG_FUNCTION_GRAPH_TRACER ENTRY(return_to_handler) stmdb sp!, {r0-r3} +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* + * Pass both the function return values in the register r0 and r1 + * to ftrace_return_to_handler + */ + add r2, sp, #16 @ sp at exit of instrumented routine +#else add r0, sp, #16 @ sp at exit of instrumented routine +#endif bl ftrace_return_to_handler mov lr, r0 @ r0 has real ret addr ldmia sp!, {r0-r3} diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 1023e896d46b..5ad53d565f2b 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -196,6 +196,7 @@ config ARM64 select HAVE_FUNCTION_TRACER select HAVE_FUNCTION_ERROR_INJECTION select HAVE_FUNCTION_GRAPH_TRACER + select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER select HAVE_GCC_PLUGINS select HAVE_HW_BREAKPOINT if PERF_EVENTS select HAVE_IOREMAP_PROT diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S index 350ed81324ac..d1a5d76e6d72 100644 --- a/arch/arm64/kernel/entry-ftrace.S +++ b/arch/arm64/kernel/entry-ftrace.S @@ -276,7 +276,15 @@ SYM_CODE_START(return_to_handler) stp x4, x5, [sp, #32] stp x6, x7, [sp, #48] +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* + * Pass both the function return values in the register x0 and x1 + * to ftrace_return_to_handler. + */ + mov x2, x29 // parent's fp +#else mov x0, x29 // parent's fp +#endif bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp); mov x30, x0 // restore the original return address diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index c5e42cc37604..3efa4f645a39 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -139,6 +139,7 @@ config RISCV select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_GRAPH_TRACER + select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION config ARCH_MMAP_RND_BITS_MIN diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S index 30102aadc4d7..bba2f3835592 100644 --- a/arch/riscv/kernel/mcount.S +++ b/arch/riscv/kernel/mcount.S @@ -69,8 +69,18 @@ ENTRY(return_to_handler) mv t6, s0 #endif SAVE_RET_ABI_STATE -#ifdef HAVE_FUNCTION_GRAPH_FP_TEST +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* + * Pass both the function return values in the register a0 and a1 + * to ftrace_return_to_handler + */ + #ifdef HAVE_FUNCTION_GRAPH_FP_TEST + mv a2, t6 + #endif +#else + #ifdef HAVE_FUNCTION_GRAPH_FP_TEST mv a0, t6 + #endif #endif call ftrace_return_to_handler mv a2, a0 diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index a825bf031f49..af80f3c75a54 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -215,6 +215,7 @@ config X86 select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE select HAVE_FTRACE_MCOUNT_RECORD select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE) + select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER select HAVE_GCC_PLUGINS select HAVE_HW_BREAKPOINT diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S index a0ed0e4a2c0c..ae8f215d9820 100644 --- a/arch/x86/kernel/ftrace_32.S +++ b/arch/x86/kernel/ftrace_32.S @@ -184,7 +184,15 @@ SYM_CODE_END(ftrace_graph_caller) return_to_handler: pushl %eax pushl %edx +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* + * Pass both the function return values in the register eax and edx + * to ftrace_return_to_handler + */ + movl $0, %ecx +#else movl $0, %eax +#endif call ftrace_return_to_handler movl %eax, %ecx popl %edx diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index 1265ad519249..2eefa82814dc 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -347,7 +347,17 @@ SYM_CODE_START(return_to_handler) /* Save the return values */ movq %rax, (%rsp) movq %rdx, 8(%rsp) +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* + * Pass both the function return values in the register rax and rdx + * to ftrace_return_to_handler + */ + movq %rax, %rdi + movq %rdx, %rsi + movq %rbp, %rdx +#else movq %rbp, %rdi +#endif call ftrace_return_to_handler diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 366c730beaa3..be662a11cd13 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -1032,6 +1032,9 @@ struct ftrace_graph_ent { */ struct ftrace_graph_ret { unsigned long func; /* Current function */ +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + unsigned long retval; +#endif int depth; /* Number of functions that overran the depth limit for current task */ unsigned int overrun; diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index a856d4a34c67..319eb6dc2250 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -31,6 +31,9 @@ config HAVE_FUNCTION_GRAPH_TRACER help See Documentation/trace/ftrace-design.rst +config HAVE_FUNCTION_GRAPH_RETVAL + bool + config HAVE_DYNAMIC_FTRACE bool help @@ -227,6 +230,11 @@ config FUNCTION_GRAPH_TRACER the return value. This is done by setting the current return address on the current task structure into a stack of calls. +config FUNCTION_GRAPH_RETVAL + def_bool y + depends on HAVE_FUNCTION_GRAPH_RETVAL + depends on FUNCTION_GRAPH_TRACER + config DYNAMIC_FTRACE bool "enable/disable function tracing dynamically" depends on FUNCTION_TRACER diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index 218cd95bf8e4..f40b10fc6561 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -238,14 +238,24 @@ static struct notifier_block ftrace_suspend_notifier = { /* * Send the trace to the ring-buffer. + * + * For double register return, need to pass both register values. + * However only the first one is saved currently. + * + * @retval_1st: the first return value + * @retval_2nd: the second return value * @return the original return address. */ -unsigned long ftrace_return_to_handler(unsigned long frame_pointer) +static unsigned long __ftrace_return_to_handler(unsigned long retval_1st, + unsigned long retval_2nd, unsigned long frame_pointer) { struct ftrace_graph_ret trace; unsigned long ret; ftrace_pop_return_trace(&trace, &ret, frame_pointer); +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + trace.retval = retval_1st; +#endif trace.rettime = trace_clock_local(); ftrace_graph_return(&trace); /* @@ -266,6 +276,19 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer) return ret; } +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL +unsigned long ftrace_return_to_handler(unsigned long retval_1st, + unsigned long retval_2nd, unsigned long frame_pointer) +{ + return __ftrace_return_to_handler(retval_1st, retval_2nd, frame_pointer); +} +#else +unsigned long ftrace_return_to_handler(unsigned long frame_pointer) +{ + return __ftrace_return_to_handler(0, 0, frame_pointer); +} +#endif + /** * ftrace_graph_get_ret_stack - return the entry of the shadow stack * @task: The task to read the shadow stack from diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 616e1aa1c4da..0a3c4582df10 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -831,6 +831,8 @@ static __always_inline bool ftrace_hash_empty(struct ftrace_hash *hash) #define TRACE_GRAPH_PRINT_TAIL 0x100 #define TRACE_GRAPH_SLEEP_TIME 0x200 #define TRACE_GRAPH_GRAPH_TIME 0x400 +#define TRACE_GRAPH_PRINT_RETVAL 0x800 +#define TRACE_GRAPH_PRINT_RETVAL_HEX 0x1000 #define TRACE_GRAPH_PRINT_FILL_SHIFT 28 #define TRACE_GRAPH_PRINT_FILL_MASK (0x3 << TRACE_GRAPH_PRINT_FILL_SHIFT) diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h index cd41e863b51c..340b2fa98218 100644 --- a/kernel/trace/trace_entries.h +++ b/kernel/trace/trace_entries.h @@ -86,6 +86,30 @@ FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry, ); /* Function return entry */ +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + +FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry, + + TRACE_GRAPH_RET, + + F_STRUCT( + __field_struct( struct ftrace_graph_ret, ret ) + __field_packed( unsigned long, ret, func ) + __field_packed( unsigned long, ret, retval ) + __field_packed( int, ret, depth ) + __field_packed( unsigned int, ret, overrun ) + __field_packed( unsigned long long, ret, calltime) + __field_packed( unsigned long long, ret, rettime ) + ), + + F_printk("<-- %ps (%d) (start: %llx end: %llx) over: %d retval: %lx", + (void *)__entry->func, __entry->depth, + __entry->calltime, __entry->rettime, + __entry->depth, __entry->retval) +); + +#else + FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry, TRACE_GRAPH_RET, @@ -105,6 +129,8 @@ FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry, __entry->depth) ); +#endif + /* * Context switch trace entry - which task (and prio) we switched from/to: * diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c index 203204cadf92..100973d25dfc 100644 --- a/kernel/trace/trace_functions_graph.c +++ b/kernel/trace/trace_functions_graph.c @@ -58,6 +58,12 @@ static struct tracer_opt trace_opts[] = { { TRACER_OPT(funcgraph-irqs, TRACE_GRAPH_PRINT_IRQS) }, /* Display function name after trailing } */ { TRACER_OPT(funcgraph-tail, TRACE_GRAPH_PRINT_TAIL) }, +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* Display function return value ? */ + { TRACER_OPT(funcgraph-retval, TRACE_GRAPH_PRINT_RETVAL) }, + /* Display function return value in hexadecimal format ? */ + { TRACER_OPT(graph_retval_hex, TRACE_GRAPH_PRINT_RETVAL_HEX) }, +#endif /* Include sleep time (scheduled out) between entry and return */ { TRACER_OPT(sleep-time, TRACE_GRAPH_SLEEP_TIME) }, @@ -619,6 +625,56 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration, trace_seq_puts(s, "| "); } +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + +#define __TRACE_GRAPH_PRINT_RETVAL TRACE_GRAPH_PRINT_RETVAL + +static void print_graph_retval(struct trace_seq *s, unsigned long retval, + bool leaf, void *func, bool hex_format) +{ + unsigned long err_code = 0; + + if (retval == 0 || hex_format) + goto done; + + /* Check if the return value matches the negative format */ + if (IS_ENABLED(CONFIG_64BIT) && (retval & BIT(31)) && + (((u64)retval) >> 32) == 0) { + /* sign extension */ + err_code = (unsigned long)(s32)retval; + } else { + err_code = retval; + } + + if (!IS_ERR_VALUE(err_code)) + err_code = 0; + +done: + if (leaf) { + if (hex_format || (err_code == 0)) + trace_seq_printf(s, "%ps(); /* = 0x%lx */\n", + func, retval); + else + trace_seq_printf(s, "%ps(); /* = %ld */\n", + func, err_code); + } else { + if (hex_format || (err_code == 0)) + trace_seq_printf(s, "} /* %ps = 0x%lx */\n", + func, retval); + else + trace_seq_printf(s, "} /* %ps = %ld */\n", + func, err_code); + } +} + +#else + +#define __TRACE_GRAPH_PRINT_RETVAL 0 + +#define print_graph_retval(_seq, _retval, _leaf, _func, _format) do {} while (0) + +#endif + /* Case of a leaf function on its call entry */ static enum print_line_t print_graph_entry_leaf(struct trace_iterator *iter, @@ -663,7 +719,15 @@ print_graph_entry_leaf(struct trace_iterator *iter, for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++) trace_seq_putc(s, ' '); - trace_seq_printf(s, "%ps();\n", (void *)call->func); + /* + * Write out the function return value if the option function-retval is + * enabled. + */ + if (flags & __TRACE_GRAPH_PRINT_RETVAL) + print_graph_retval(s, graph_ret->retval, true, (void *)call->func, + !!(flags & TRACE_GRAPH_PRINT_RETVAL_HEX)); + else + trace_seq_printf(s, "%ps();\n", (void *)call->func); print_graph_irq(iter, graph_ret->func, TRACE_GRAPH_RET, cpu, iter->ent->pid, flags); @@ -942,16 +1006,25 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s, trace_seq_putc(s, ' '); /* - * If the return function does not have a matching entry, - * then the entry was lost. Instead of just printing - * the '}' and letting the user guess what function this - * belongs to, write out the function name. Always do - * that if the funcgraph-tail option is enabled. + * Always write out the function name and its return value if the + * function-retval option is enabled. */ - if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL)) - trace_seq_puts(s, "}\n"); - else - trace_seq_printf(s, "} /* %ps */\n", (void *)trace->func); + if (flags & __TRACE_GRAPH_PRINT_RETVAL) { + print_graph_retval(s, trace->retval, false, (void *)trace->func, + !!(flags & TRACE_GRAPH_PRINT_RETVAL_HEX)); + } else { + /* + * If the return function does not have a matching entry, + * then the entry was lost. Instead of just printing + * the '}' and letting the user guess what function this + * belongs to, write out the function name. Always do + * that if the funcgraph-tail option is enabled. + */ + if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL)) + trace_seq_puts(s, "}\n"); + else + trace_seq_printf(s, "} /* %ps */\n", (void *)trace->func); + } /* Overrun */ if (flags & TRACE_GRAPH_PRINT_OVERRUN) From patchwork Tue Mar 21 08:46:50 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: pengdonglin X-Patchwork-Id: 13182393 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5E345C74A5B for ; Tue, 21 Mar 2023 08:47:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Im8I9eUNnVkv1NY8Clmzz4qZbj5A7+dQDE75MY6nag8=; b=mfvx0hAdf8BKzF i/3adJamkL+9VClhcMyzG8xLGICNajDknpJU7Xn//etzjKK99vrH/IDOhMcJWrF4YetwlGUjY0HHW cKK77JU0ISujUNvO98wfn2fsiMC0da8yhqGxtk+km9625QIGoDRjJeAchRETl101iBJoxcpceTTT+ emOPneMXn/H39mDPJVL4ACwqKSclX6ykku1Ot/RHNtaZkkKuBe2KuH0hJh79M/2KeGEmyGhT7Ymyp HLLwK9yFyVGByxg1n6AneFOS+VFJ0XfirBJ88DGR88SnSloDc+FmPbYnBeU7YaTnuIRlwTX3fgGMh ig2TRX1Yoo6XA+0aEiHQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1peXeN-00BkhM-0r; Tue, 21 Mar 2023 08:47:23 +0000 Received: from mail-m118111.qiye.163.com ([115.236.118.111]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1peXeF-00BkcE-0Z; Tue, 21 Mar 2023 08:47:17 +0000 Received: from ubuntu.localdomain (unknown [117.133.56.22]) by mail-m118111.qiye.163.com (Hmail) with ESMTPA id 1CF7358063F; Tue, 21 Mar 2023 16:47:07 +0800 (CST) From: Donglin Peng To: mhiramat@kernel.org, rostedt@goodmis.org, linux@armlinux.org.uk, mark.rutland@arm.com, will@kernel.org, catalin.marinas@arm.com, palmer@dabbelt.com, paul.walmsley@sifive.com, tglx@linutronix.de, dave.hansen@linux.intel.com, x86@kernel.org, mingo@redhat.com, peterz@infradead.org, xiehuan09@gmail.com, dinghui@sangfor.com.cn, huangcun@sangfor.com.cn, dolinux.peng@gmail.com Cc: linux-trace-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Donglin Peng Subject: [PATCH v6 2/2] tracing: Add documentation for funcgraph-retval and graph_retval_hex Date: Tue, 21 Mar 2023 01:46:50 -0700 Message-Id: <20230321084650.769212-3-pengdonglin@sangfor.com.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230321084650.769212-1-pengdonglin@sangfor.com.cn> References: <20230321084650.769212-1-pengdonglin@sangfor.com.cn> MIME-Version: 1.0 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFITzdXWS1ZQUlXWQ8JGhUIEh9ZQVkaGkkdVh0YGR1KHU1MQkNKHlUTARMWGhIXJBQOD1 lXWRgSC1lBWUpKTFVKSEhVTk1VSUlZV1kWGg8SFR0UWUFZT0tIVUpISkJIT1VKS0tVS1kG X-HM-Sender-Digest: e1kMHhlZQR0aFwgeV1kSHx4VD1lBWUc6NS46Azo6PT0UVhdNDyEZMBFP SDgaCi1VSlVKTUxCSENDT0lDT09OVTMWGhIXVQseFRwfFBUcFxIVOwgaFRwdFAlVGBQWVRgVRVlX WRILWUFZSkpMVUpISFVOTVVJSVlXWQgBWUFNQ05ONwY+ X-HM-Tid: 0a870359c6b12eb7kusn1cf7358063f X-HM-MType: 1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230321_014715_550837_7CB08325 X-CRM114-Status: GOOD ( 18.91 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org Add documentation for the two newly introduced options for the function_graph tracer. The new option funcgraph-retval is used to control whether or not to display the return value. The new option graph_retval_hex is used to control the display format of the return value. Signed-off-by: Donglin Peng --- v6: - Modify the limitations for funcgraph-retval - Optimize the English expression v5: - Describe the limitations of funcgraph-retval --- Documentation/trace/ftrace.rst | 73 ++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index b927fb2b94dc..1807f7752037 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -1328,6 +1328,19 @@ Options for function_graph tracer: only a closing curly bracket "}" is displayed for the return of a function. + funcgraph-retval + When set, the return value of each traced function + will be printed after an equal sign "=". By default + this is off. + + graph_retval_hex + When set, the return value will always be printed + in hexadecimal format. If the option is not set and + the return value is an error code, it will be printed + in signed decimal format; otherwise it will also be + printed in hexadecimal format. By default, this option + is off. + sleep-time When running function graph tracer, to include the time a task schedules out in its function. @@ -2673,6 +2686,66 @@ It is default disabled. 0) 1.757 us | } /* kmem_cache_free() */ 0) 2.861 us | } /* putname() */ +The return value of each traced function can be displayed after +an equal sign "=". When encountering system call failures, it +can be verfy helpful to quickly locate the function that first +returns an error code. + + - hide: echo nofuncgraph-retval > trace_options + - show: echo funcgraph-retval > trace_options + + Example with funcgraph-retval:: + + 1) | cgroup_migrate() { + 1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */ + 1) | cgroup_migrate_execute() { + 1) | cpu_cgroup_can_attach() { + 1) | cgroup_taskset_first() { + 1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */ + 1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */ + 1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */ + 1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */ + 1) 4.369 us | } /* cgroup_migrate_execute = -22 */ + 1) 7.143 us | } /* cgroup_migrate = -22 */ + +The above example shows that the function cpu_cgroup_can_attach +returned the error code -22 firstly, then we can read the code +of this function to get the root cause. + +When the option graph_retval_hex is not set, the return value can +be displayed in a smart way. Specifically, if it is an error code, +it will be printed in signed decimal format, otherwise it will +printed in hexadecimal format. + + - smart: echo nograph_retval_hex > trace_options + - hexadecimal always: echo graph_retval_hex > trace_options + + Example with graph_retval_hex:: + + 1) | cgroup_migrate() { + 1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */ + 1) | cgroup_migrate_execute() { + 1) | cpu_cgroup_can_attach() { + 1) | cgroup_taskset_first() { + 1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */ + 1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */ + 1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */ + 1) 2.335 us | } /* cpu_cgroup_can_attach = 0xffffffea */ + 1) 4.369 us | } /* cgroup_migrate_execute = 0xffffffea */ + 1) 7.143 us | } /* cgroup_migrate = 0xffffffea */ + +There are some limitations when using the funcgraph-retval currently: + +- Even if the function return type is void, a return value will still + be printed, and you can just ignore it. + +- Even if return values are stored in two registers, only the value of + the first return register will be recorded and printed. For example, + in x86 architecture, both eax and edx are used to store a 64-bit + return value. Eax stores the low 32 bits, and edx stores the high + 32 bits. However, only the value stored in eax will be recorded and + printed. + You can put some comments on specific functions by using trace_printk() For example, if you want to put a comment inside the __might_sleep() function, you just have to include