From 77072f09eab19326dd2424c8dad0a443341a228f Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Fri, 29 Sep 2017 11:23:35 +0200 Subject: x86/stacktrace: Avoid recording save_stack_trace() wrappers The save_stack_trace() and save_stack_trace_tsk() wrappers of __save_stack_trace() add themselves to the call stack, and thus appear in the recorded stacktraces. This is redundant and wasteful when we have limited space to record the useful part of the backtrace with e.g. page_owner functionality. Fix this by making sure __save_stack_trace() is noinline (which matches the current gcc decision) and bumping the skip in the wrappers (save_stack_trace_tsk() only when called for the current task). This is similar to what was done for arm in 3683f44c42e9 ("ARM: stacktrace: avoid listing stacktrace functions in stacktrace") and is pending for arm64. Also make sure that __save_stack_trace_reliable() doesn't get this problem in the future by marking it __always_inline (which matches current gcc decision), per Josh Poimboeuf. Signed-off-by: Vlastimil Babka Acked-by: Josh Poimboeuf Cc: Linus Torvalds Cc: Miroslav Benes Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20170929092335.2744-1-vbabka@suse.cz Signed-off-by: Ingo Molnar --- arch/x86/kernel/stacktrace.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c index 8dabd7bf1673..77835bc021c7 100644 --- a/arch/x86/kernel/stacktrace.c +++ b/arch/x86/kernel/stacktrace.c @@ -30,7 +30,7 @@ static int save_stack_address(struct stack_trace *trace, unsigned long addr, return 0; } -static void __save_stack_trace(struct stack_trace *trace, +static void noinline __save_stack_trace(struct stack_trace *trace, struct task_struct *task, struct pt_regs *regs, bool nosched) { @@ -56,6 +56,7 @@ static void __save_stack_trace(struct stack_trace *trace, */ void save_stack_trace(struct stack_trace *trace) { + trace->skip++; __save_stack_trace(trace, current, NULL, false); } EXPORT_SYMBOL_GPL(save_stack_trace); @@ -70,6 +71,8 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) if (!try_get_task_stack(tsk)) return; + if (tsk == current) + trace->skip++; __save_stack_trace(trace, tsk, NULL, true); put_task_stack(tsk); @@ -88,8 +91,9 @@ EXPORT_SYMBOL_GPL(save_stack_trace_tsk); } \ }) -static int __save_stack_trace_reliable(struct stack_trace *trace, - struct task_struct *task) +static int __always_inline +__save_stack_trace_reliable(struct stack_trace *trace, + struct task_struct *task) { struct unwind_state state; struct pt_regs *regs; -- cgit v1.2.3