diff options
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/trace_stack.c | 75 |
1 files changed, 54 insertions, 21 deletions
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index ea28e4b0ed5..aab277b67fa 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -20,27 +20,24 @@ #define STACK_TRACE_ENTRIES 500 -/* - * If fentry is used, then the function being traced will - * jump to fentry directly before it sets up its stack frame. - * We need to ignore that one and record the parent. Since - * the stack frame for the traced function wasn't set up yet, - * the stack_trace wont see the parent. That needs to be added - * manually to stack_dump_trace[] as the first element. - */ #ifdef CC_USING_FENTRY -# define add_func 1 +# define fentry 1 #else -# define add_func 0 +# define fentry 0 #endif static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] = { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX }; static unsigned stack_dump_index[STACK_TRACE_ENTRIES]; +/* + * Reserve one entry for the passed in ip. This will allow + * us to remove most or all of the stack size overhead + * added by the stack tracer itself. + */ static struct stack_trace max_stack_trace = { - .max_entries = STACK_TRACE_ENTRIES - add_func, - .entries = &stack_dump_trace[add_func], + .max_entries = STACK_TRACE_ENTRIES - 1, + .entries = &stack_dump_trace[1], }; static unsigned long max_stack_size; @@ -58,10 +55,14 @@ check_stack(unsigned long ip, unsigned long *stack) { unsigned long this_size, flags; unsigned long *p, *top, *start; + static int tracer_frame; + int frame_size = ACCESS_ONCE(tracer_frame); int i; this_size = ((unsigned long)stack) & (THREAD_SIZE-1); this_size = THREAD_SIZE - this_size; + /* Remove the frame of the tracer */ + this_size -= frame_size; if (this_size <= max_stack_size) return; @@ -73,6 +74,10 @@ check_stack(unsigned long ip, unsigned long *stack) local_irq_save(flags); arch_spin_lock(&max_stack_lock); + /* In case another CPU set the tracer_frame on us */ + if (unlikely(!frame_size)) + this_size -= tracer_frame; + /* a race could have already updated it */ if (this_size <= max_stack_size) goto out; @@ -85,15 +90,12 @@ check_stack(unsigned long ip, unsigned long *stack) save_stack_trace(&max_stack_trace); /* - * When fentry is used, the traced function does not get - * its stack frame set up, and we lose the parent. - * Add that one in manally. We set up save_stack_trace() - * to not touch the first element in this case. + * Add the passed in ip from the function tracer. + * Searching for this on the stack will skip over + * most of the overhead from the stack tracer itself. */ - if (add_func) { - stack_dump_trace[0] = ip; - max_stack_trace.nr_entries++; - } + stack_dump_trace[0] = ip; + max_stack_trace.nr_entries++; /* * Now find where in the stack these are. @@ -123,6 +125,18 @@ check_stack(unsigned long ip, unsigned long *stack) found = 1; /* Start the search from here */ start = p + 1; + /* + * We do not want to show the overhead + * of the stack tracer stack in the + * max stack. If we haven't figured + * out what that is, then figure it out + * now. + */ + if (unlikely(!tracer_frame) && i == 1) { + tracer_frame = (p - stack) * + sizeof(unsigned long); + max_stack_size -= tracer_frame; + } } } @@ -149,7 +163,26 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip, if (per_cpu(trace_active, cpu)++ != 0) goto out; - check_stack(parent_ip, &stack); + /* + * When fentry is used, the traced function does not get + * its stack frame set up, and we lose the parent. + * The ip is pretty useless because the function tracer + * was called before that function set up its stack frame. + * In this case, we use the parent ip. + * + * By adding the return address of either the parent ip + * or the current ip we can disregard most of the stack usage + * caused by the stack tracer itself. + * + * The function tracer always reports the address of where the + * mcount call was, but the stack will hold the return address. + */ + if (fentry) + ip = parent_ip; + else + ip += MCOUNT_INSN_SIZE; + + check_stack(ip, &stack); out: per_cpu(trace_active, cpu)--; |