From: Jiri Olsa <[email protected]>
Introducing perf_output_skip function to be able to skip data within the
perf ring buffer.
When writing data into perf ring buffer we first reserve needed place in
ring buffer and then copy the actual data.
There's a possibility we won't be able to fill all the reserved size
with data, so we need a way to skip the remaining bytes.
This is going to be useful when storing the user stack dump, where we
might end up with less data than we originally requested.
Signed-off-by: Jiri Olsa <[email protected]>
Acked-by: Frederic Weisbecker <[email protected]>
Cc: "Frank Ch. Eigler" <[email protected]>
Cc: Arun Sharma <[email protected]>
Cc: Benjamin Redelings <[email protected]>
Cc: Corey Ashford <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: Frank Ch. Eigler <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Robert Richter <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Tom Zanussi <[email protected]>
Cc: Ulrich Drepper <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
include/linux/perf_event.h | 2 ++
kernel/events/internal.h | 4 ++++
kernel/events/ring_buffer.c | 6 ++++++
3 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d41394a..8a73f75 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1321,6 +1321,8 @@ extern int perf_output_begin(struct perf_output_handle *handle,
extern void perf_output_end(struct perf_output_handle *handle);
extern unsigned int perf_output_copy(struct perf_output_handle *handle,
const void *buf, unsigned int len);
+extern unsigned int perf_output_skip(struct perf_output_handle *handle,
+ unsigned int len);
extern int perf_swevent_get_recursion_context(void);
extern void perf_swevent_put_recursion_context(int rctx);
extern void perf_event_enable(struct perf_event *event);
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 7fd5408..ce7bdfc 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -114,6 +114,10 @@ static inline int memcpy_common(void *dst, const void *src, size_t n)
DEFINE_OUTPUT_COPY(__output_copy, memcpy_common)
+#define MEMCPY_SKIP(dst, src, n) (n)
+
+DEFINE_OUTPUT_COPY(__output_skip, MEMCPY_SKIP)
+
#ifndef arch_perf_out_copy_user
#define arch_perf_out_copy_user __copy_from_user_inatomic
#endif
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index b4c2ad3..23cb34f 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -188,6 +188,12 @@ unsigned int perf_output_copy(struct perf_output_handle *handle,
return __output_copy(handle, buf, len);
}
+unsigned int perf_output_skip(struct perf_output_handle *handle,
+ unsigned int len)
+{
+ return __output_skip(handle, NULL, len);
+}
+
void perf_output_end(struct perf_output_handle *handle)
{
perf_output_put_handle(handle);
--
1.7.1