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Date: Wed, 9 Jun 2010 15:53:13 +0300
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Subject: Re: [tip:perf/core] perf: Add non-exec mmap() tracking
From: Pekka Enberg <penberg@cs.helsinki.fi>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@redhat.com, hpa@zytor.com, anton@samba.org, acme@redhat.com,
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On Wed, Jun 9, 2010 at 3:22 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, 2010-06-09 at 13:44 +0300, Pekka Enberg wrote:
>> > @@ -3830,6 +3834,14 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
>> > ? ? ? ? ? ? ? ?if (!vma->vm_mm) {
>> > ? ? ? ? ? ? ? ? ? ? ? ?name = strncpy(tmp, "[vdso]", sizeof(tmp));
>> > ? ? ? ? ? ? ? ? ? ? ? ?goto got_name;
>> > + ? ? ? ? ? ? ? } else if (vma->vm_start <= vma->vm_mm->start_brk &&
>> > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? vma->vm_end >= vma->vm_mm->brk) {
>> > + ? ? ? ? ? ? ? ? ? ? ? name = strncpy(tmp, "[heap]", sizeof(tmp));
>> > + ? ? ? ? ? ? ? ? ? ? ? goto got_name;
>> > + ? ? ? ? ? ? ? } else if (vma->vm_start <= vma->vm_mm->start_stack &&
>> > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? vma->vm_end >= vma->vm_mm->start_stack) {
>> > + ? ? ? ? ? ? ? ? ? ? ? name = strncpy(tmp, "[stack]", sizeof(tmp));
>> > + ? ? ? ? ? ? ? ? ? ? ? goto got_name;
>> > ? ? ? ? ? ? ? ?}
>> >
>> > ? ? ? ? ? ? ? ?name = strncpy(tmp, "//anon", sizeof(tmp));
>>
>> Doesn't this change here break the JIT generated code region detection
>> in map__new() of tools/perf/util/map.c? We generate a new
>> "/tmp/perf-<pid>.map" filename for anonymous memory regions and check
>> for that in dso__load() of tools/perf/util/symbol.c.
>
> Not unless you stick your executable code in the heap or on the stack.

Right, I misread the patch. Thanks for the clarification, Peter!

> If you use something like mmap(NULL, size, PROT_READ|PROT_WRITE|
> PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); to allocate your memory
> everything should be fine.

Sure, that's what I do.
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