From patchwork Wed Mar 15 13:39:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: pengdonglin X-Patchwork-Id: 13175891 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 D12D5C6FD1D for ; Wed, 15 Mar 2023 13:39:57 +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=3Hno4olMSgy0wduChWHjzxj3D/vI3gqiR2kRBiVLqkQ=; b=airGTV4L94b9af EWmILzNH/6SvAn/843Pru4J1YxEX+VxqBTOGUIr/y7WCoeg+o7s1y+TutyETqU7FbrGAzNfPgcDh9 vRHms4H7ufba56qrMBdRW9pi+TyCSThLApOfTSG9yF/yY0qoJ4EvnI97b6dU3hJwAnBlBqwDKZMcU hgcU7bL4XscQbUSU9LKELT0M0Y9K/x0rrxfKvhxz2jSk+WjErqaSN12XSRkfkF5cExFKZRxTWmp2l GWvDh2ZKUrHXLUlOolJZygkvkSPIdmZIdiKtCqwS4pFDQEptgFk+89bEjBWT27S+9x3zJRujdafAj AlXdfQ5de0XfqEWni5xw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pcRM6-00DTcV-1B; Wed, 15 Mar 2023 13:39:50 +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 1pcRLq-00DTS8-26; Wed, 15 Mar 2023 13:39:39 +0000 Received: from ubuntu.localdomain (unknown [121.32.254.146]) by mail-m118111.qiye.163.com (Hmail) with ESMTPA id 26E3F5801DC; Wed, 15 Mar 2023 21:39:17 +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, 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 v4 1/2] function_graph: Support recording and printing the return value of function Date: Wed, 15 Mar 2023 06:39:10 -0700 Message-Id: <20230315133911.958741-2-pengdonglin@sangfor.com.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230315133911.958741-1-pengdonglin@sangfor.com.cn> References: <20230315133911.958741-1-pengdonglin@sangfor.com.cn> MIME-Version: 1.0 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFITzdXWS1ZQUlXWQ8JGhUIEh9ZQVkZSRoaVkMZSU9CS0tMHk5PTFUTARMWGhIXJBQOD1 lXWRgSC1lBWUpJSlVISVVJTk9VSk9NWVdZFhoPEhUdFFlBWU9LSFVKSktPSEhVSktLVUtZBg++ X-HM-Sender-Digest: e1kMHhlZQR0aFwgeV1kSHx4VD1lBWUc6OhQ6Fio6PT0UMRo9OSwyTk4R TwEKCTlVSlVKTUxDQ0NMTk5DTktLVTMWGhIXVQseFRwfFBUcFxIVOwgaFRwdFAlVGBQWVRgVRVlX WRILWUFZSklKVUhJVUlOT1VKT01ZV1kIAVlBSkNDQk03Bg++ X-HM-Tid: 0a86e57f1b022eb7kusn26e3f5801dc X-HM-MType: 1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230315_063935_370933_EF0A9DD0 X-CRM114-Status: GOOD ( 29.64 ) 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. Two 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 of the reutrn value. 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: x64, 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 --- 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 each 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 | 4 ++ arch/arm64/Kconfig | 1 + arch/arm64/kernel/entry-ftrace.S | 6 +- arch/riscv/Kconfig | 1 + arch/riscv/kernel/mcount.S | 4 ++ arch/x86/Kconfig | 1 + arch/x86/kernel/ftrace_32.S | 4 ++ arch/x86/kernel/ftrace_64.S | 4 ++ include/linux/ftrace.h | 3 + kernel/trace/Kconfig | 8 +++ kernel/trace/fgraph.c | 5 +- kernel/trace/trace.h | 2 + kernel/trace/trace_entries.h | 26 ++++++++ kernel/trace/trace_functions_graph.c | 94 +++++++++++++++++++++++++--- 15 files changed, 152 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..0151d2ce9958 100644 --- a/arch/arm/kernel/entry-ftrace.S +++ b/arch/arm/kernel/entry-ftrace.S @@ -258,6 +258,10 @@ ENDPROC(ftrace_graph_regs_caller) #ifdef CONFIG_FUNCTION_GRAPH_TRACER ENTRY(return_to_handler) stmdb sp!, {r0-r3} +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* Pass the function return value to ftrace_return_to_handler */ + mov r1, r0 +#endif add r0, sp, #16 @ sp at exit of instrumented routine bl ftrace_return_to_handler mov lr, r0 @ r0 has real ret addr 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..6633bd52c2df 100644 --- a/arch/arm64/kernel/entry-ftrace.S +++ b/arch/arm64/kernel/entry-ftrace.S @@ -276,8 +276,12 @@ SYM_CODE_START(return_to_handler) stp x4, x5, [sp, #32] stp x6, x7, [sp, #48] +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* Pass the function return value to ftrace_return_to_handler */ + mov x1, x0 +#endif mov x0, x29 // parent's fp - bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp); + bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp, retval); mov x30, x0 // restore the original return address /* restore return value regs */ 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..2935cbb2c7a5 100644 --- a/arch/riscv/kernel/mcount.S +++ b/arch/riscv/kernel/mcount.S @@ -69,6 +69,10 @@ ENTRY(return_to_handler) mv t6, s0 #endif SAVE_RET_ABI_STATE +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* Pass the function return value to ftrace_return_to_handler */ + mv a1, a0 +#endif #ifdef HAVE_FUNCTION_GRAPH_FP_TEST mv a0, t6 #endif 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..44a773d9de82 100644 --- a/arch/x86/kernel/ftrace_32.S +++ b/arch/x86/kernel/ftrace_32.S @@ -184,6 +184,10 @@ SYM_CODE_END(ftrace_graph_caller) return_to_handler: pushl %eax pushl %edx +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* Pass the function return value to ftrace_return_to_handler*/ + movl %eax, %edx +#endif movl $0, %eax call ftrace_return_to_handler movl %eax, %ecx diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index 1265ad519249..35ac9c58dc77 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -348,6 +348,10 @@ SYM_CODE_START(return_to_handler) movq %rax, (%rsp) movq %rdx, 8(%rsp) movq %rbp, %rdi +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + /* Pass the function return value to ftrace_return_to_handler */ + movq %rax, %rsi +#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..e9336cf09022 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -240,12 +240,15 @@ static struct notifier_block ftrace_suspend_notifier = { * Send the trace to the ring-buffer. * @return the original return address. */ -unsigned long ftrace_return_to_handler(unsigned long frame_pointer) +unsigned long ftrace_return_to_handler(unsigned long frame_pointer, unsigned long retval) { struct ftrace_graph_ret trace; unsigned long ret; ftrace_pop_return_trace(&trace, &ret, frame_pointer); +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL + trace.retval = retval; +#endif trace.rettime = trace_clock_local(); ftrace_graph_return(&trace); /* 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..d230de6698e5 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 +625,57 @@ 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; + + /* Guess whether the retval looks like an error code */ + if ((retval & BIT(7)) && (retval >> 8) == 0) + err_code = (unsigned long)(s8)retval; + else if ((retval & BIT(15)) && (retval >> 16) == 0) + err_code = (unsigned long)(s16)retval; + else if ((retval & BIT(31)) && (((u64)retval) >> 32) == 0) + 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 +720,15 @@ 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 +1007,25 @@ 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 Wed Mar 15 13:39:11 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: pengdonglin X-Patchwork-Id: 13175889 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 E9C5EC7618B for ; Wed, 15 Mar 2023 13:39:44 +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=nSSLOkK5JShj8BL2h8v/bqiVK0LFo9SO++IPo7ZLmVA=; b=3Y7krYekcJa+i9 T3kSbOLT6P4xnGDm4LOiLpJgVHaV2YmFogu/TOXa1mgSg9XI9AMBQWu4zP4v/6Pqrnl+pK9plvria OgzeF6Oqt5mn5t9OjubYZ4Eur8EXoqAvntJUPWUnO1N15inRdZrRgo9JwFDw21n/+Y4MlifsR46Yl ParxFToWUwEYAc/JGTGeKSGJyWQmcXmv9Xe9mHHRp4wawIG1BHWQmxZDmOXF5AocC54US4AkNWz3d iff3N5st+CEuMURv1BHUk1B5XMg+FdeOf6R3WQlXvEZVTq/TJp9pn9zfZwpwGRQJ4wkToW0u8jUXa AuYp0ntH45nZCinFMrQQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pcRLu-00DTW2-1c; Wed, 15 Mar 2023 13:39:38 +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 1pcRLp-00DTSB-2Z; Wed, 15 Mar 2023 13:39:36 +0000 Received: from ubuntu.localdomain (unknown [121.32.254.146]) by mail-m118111.qiye.163.com (Hmail) with ESMTPA id 8DAFC58022F; Wed, 15 Mar 2023 21:39:18 +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, 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 v4 2/2] tracing: Add documentation for funcgraph-retval and graph_retval_hex Date: Wed, 15 Mar 2023 06:39:11 -0700 Message-Id: <20230315133911.958741-3-pengdonglin@sangfor.com.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230315133911.958741-1-pengdonglin@sangfor.com.cn> References: <20230315133911.958741-1-pengdonglin@sangfor.com.cn> MIME-Version: 1.0 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFITzdXWS1ZQUlXWQ8JGhUIEh9ZQVkaTkxMVkxDGRhKThpPHkkfSVUTARMWGhIXJBQOD1 lXWRgSC1lBWUpJSlVISVVJTk9VSk9NWVdZFhoPEhUdFFlBWU9LSFVKSEpCSE9VSktLVUtZBg++ X-HM-Sender-Digest: e1kMHhlZQR0aFwgeV1kSHx4VD1lBWUc6NSI6MTo*FT0TNRpNEy0aTT8Q Kh9PCi1VSlVKTUxDQ0NMTk5CTENNVTMWGhIXVQseFRwfFBUcFxIVOwgaFRwdFAlVGBQWVRgVRVlX WRILWUFZSklKVUhJVUlOT1VKT01ZV1kIAVlBTUtKSTcG X-HM-Tid: 0a86e57f20912eb7kusn8dafc58022f X-HM-MType: 1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230315_063934_495710_94D6E4F9 X-CRM114-Status: GOOD ( 13.33 ) 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 --- Documentation/trace/ftrace.rst | 55 ++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index b927fb2b94dc..8ebe8d0b8838 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 event will include the function and + its return value. Note that even if the function return + type is void, a return value will also be printed, you + should ignore it. This option is off by default. + + graph_retval_hex + Depend on function-retval. When set, the function return + value will be printed in hexadecimal format. If this is not + set and the return value looks like an error code, it will + be printed in signed decimal format, else in hexadecimal + format. This option is off by default. + sleep-time When running function graph tracer, to include the time a task schedules out in its function. @@ -2673,6 +2686,48 @@ It is default disabled. 0) 1.757 us | } /* kmem_cache_free() */ 0) 2.861 us | } /* putname() */ +The kernel function return value can be displayed. Note that even if the +function return type is void, the return value is will still be printed. +However you should ignore it. You can use this feature to locate kernel +functions those return errors. + + - 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 */ + +By default, if the return value looks like an error code, it will be printed in +signed decimal format. In other cases, it will be printed in hexadecimal format. + + - hexadecimal or signed decimal (default): echo nograph_retval_hex > trace_options + - hexadecimal: 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 */ + 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