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perf_counter: sanity check on the output API

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Ensure we never write more than we said we would.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113316.921433024@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-03-25 12:30:24 +01:00 committed by Ingo Molnar
parent 5c14819432
commit 63e35b25d6
1 changed files with 4 additions and 0 deletions
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4
kernel/perf_counter.c
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@ -1422,6 +1422,7 @@ struct perf_output_handle {
struct perf_counter *counter;
struct perf_mmap_data *data;
unsigned int offset;
unsigned int head;
int wakeup;
};
@ -1447,6 +1448,7 @@ static int perf_output_begin(struct perf_output_handle *handle,
handle->counter = counter;
handle->data = data;
handle->offset = offset;
handle->head = head;
handle->wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT);
return 0;
@ -1485,6 +1487,8 @@ static void perf_output_copy(struct perf_output_handle *handle,
} while (len);
handle->offset = offset;
WARN_ON_ONCE(handle->offset > handle->head);
}
#define perf_output_put(handle, x) \