Re: [PATCH] ftrace: Get the true parent ip for function tracer
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2024-08-21 13:58:42
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On Wed, 21 Aug 2024 21:27:55 +0800 Jeff Xie [off-list ref] wrote: Hi Jeff, Thanks for the patch.
quoted hunk ↗ jump to hunk
Signed-off-by: Jeff Xie <redacted> --- kernel/trace/trace_functions.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index 3b0cea37e029..273b8c7eeb2d 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c@@ -176,6 +176,19 @@ static void function_trace_start(struct trace_array *tr) tracing_reset_online_cpus(&tr->array_buffer); } +static unsigned long +function_get_true_parent_ip(unsigned long parent_ip, struct ftrace_regs *fregs)
I wonder if we should make this inline, or even __always_inline, as this will be called in a very hot path, and I want to make sure that the compiler always inlines it. It likely should, but we should also give the compiler a hint that it should. -- Steve
quoted hunk ↗ jump to hunk
+{ + unsigned long true_parent_ip; + int idx = 0; + + true_parent_ip = parent_ip; + if (unlikely(parent_ip == (unsigned long)&return_to_handler)) + true_parent_ip = ftrace_graph_ret_addr(current, &idx, parent_ip, + (unsigned long *)fregs->regs.sp); + return true_parent_ip; +} + static void function_trace_call(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct ftrace_regs *fregs)@@ -193,6 +206,8 @@ function_trace_call(unsigned long ip, unsigned long parent_ip, if (bit < 0) return; + parent_ip = function_get_true_parent_ip(parent_ip, fregs); + trace_ctx = tracing_gen_ctx(); cpu = smp_processor_id();@@ -241,6 +256,7 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip, * recursive protection is performed. */ local_irq_save(flags); + parent_ip = function_get_true_parent_ip(parent_ip, fregs); cpu = raw_smp_processor_id(); data = per_cpu_ptr(tr->array_buffer.data, cpu); disabled = atomic_inc_return(&data->disabled);@@ -309,6 +325,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip, if (bit < 0) return; + parent_ip = function_get_true_parent_ip(parent_ip, fregs); cpu = smp_processor_id(); data = per_cpu_ptr(tr->array_buffer.data, cpu); if (atomic_read(&data->disabled))@@ -356,6 +373,7 @@ function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip, * recursive protection is performed. */ local_irq_save(flags); + parent_ip = function_get_true_parent_ip(parent_ip, fregs); cpu = raw_smp_processor_id(); data = per_cpu_ptr(tr->array_buffer.data, cpu); disabled = atomic_inc_return(&data->disabled);