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Message-ID: <20150715121337.3b31aa84@gandalf.local.home>
Date: Wed, 15 Jul 2015 12:13:37 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc: Jungseok Lee <jungseoklee85@...il.com>, catalin.marinas@....com,
will.deacon@....com, olof@...om.net, broonie@...nel.org,
david.griego@...aro.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/3] arm64: refactor save_stack_trace()
On Wed, 15 Jul 2015 10:55:36 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
> I'll take a look at it and try to clean up the code.
Does the following patch make sense for you?
-- Steve
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 3f34496244e9..9384647d07c3 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -18,12 +18,6 @@
#define STACK_TRACE_ENTRIES 500
-#ifdef CC_USING_FENTRY
-# define fentry 1
-#else
-# 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];
@@ -35,7 +29,7 @@ static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
*/
static struct stack_trace max_stack_trace = {
.max_entries = STACK_TRACE_ENTRIES - 1,
- .entries = &stack_dump_trace[1],
+ .entries = &stack_dump_trace[0],
};
static unsigned long max_stack_size;
@@ -77,7 +71,7 @@ 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;
+ int i, x;
this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
this_size = THREAD_SIZE - this_size;
@@ -105,26 +99,20 @@ check_stack(unsigned long ip, unsigned long *stack)
max_stack_size = this_size;
max_stack_trace.nr_entries = 0;
-
- if (using_ftrace_ops_list_func())
- max_stack_trace.skip = 4;
- else
- max_stack_trace.skip = 3;
+ max_stack_trace.skip = 0;
save_stack_trace(&max_stack_trace);
- /*
- * 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.
- */
- stack_dump_trace[0] = ip;
- max_stack_trace.nr_entries++;
+ /* Skip over the overhead of the stack tracer itself */
+ for (i = 0; i < max_stack_trace.nr_entries; i++) {
+ if (stack_dump_trace[i] == ip)
+ break;
+ }
/*
* Now find where in the stack these are.
*/
- i = 0;
+ x = 0;
start = stack;
top = (unsigned long *)
(((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
@@ -139,12 +127,13 @@ check_stack(unsigned long ip, unsigned long *stack)
while (i < max_stack_trace.nr_entries) {
int found = 0;
- stack_dump_index[i] = this_size;
+ stack_dump_index[x] = this_size;
p = start;
for (; p < top && i < max_stack_trace.nr_entries; p++) {
if (*p == stack_dump_trace[i]) {
- this_size = stack_dump_index[i++] =
+ stack_dump_trace[x] = stack_dump_trace[i++];
+ this_size = stack_dump_index[x++] =
(top - p) * sizeof(unsigned long);
found = 1;
/* Start the search from here */
@@ -168,6 +157,9 @@ check_stack(unsigned long ip, unsigned long *stack)
i++;
}
+ for (; x < max_stack_trace.nr_entries; x++)
+ stack_dump_trace[x] = ULONG_MAX;
+
if (task_stack_end_corrupted(current)) {
print_max_stack();
BUG();
@@ -192,24 +184,7 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip,
if (per_cpu(trace_active, cpu)++ != 0)
goto out;
- /*
- * 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;
+ ip += MCOUNT_INSN_SIZE;
check_stack(ip, &stack);
--
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