perf_counter: Add forward/backward attribute ABI compatibility
Provide for means of extending the perf_counter_attr in a 'natural' way.
We allow growing the structure by appending fields at the end by specifying
the full structure size inside it.
When a new kernel sees a smaller (old) structure, it will 0 pad the tail.
When an old kernel sees a larger (new) structure, it will verify the tail
consists of 0s, otherwise fail.
If we fail due to a size-mismatch, we return -E2BIG and write the kernel's
native attribe size back into the provided structure.
Furthermore, add some attribute verification, so that we'll fail counter
creation when unknown bits are present (PERF_SAMPLE, PERF_FORMAT, or in
the __reserved fields).
(This ABI detail is introduced while keeping the existing syscall ABI.)
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 7c4f32f..1b3118a 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -120,6 +120,8 @@
PERF_SAMPLE_ID = 1U << 6,
PERF_SAMPLE_CPU = 1U << 7,
PERF_SAMPLE_PERIOD = 1U << 8,
+
+ PERF_SAMPLE_MAX = 1U << 9, /* non-ABI */
};
/*
@@ -131,17 +133,26 @@
PERF_FORMAT_TOTAL_TIME_ENABLED = 1U << 0,
PERF_FORMAT_TOTAL_TIME_RUNNING = 1U << 1,
PERF_FORMAT_ID = 1U << 2,
+
+ PERF_FORMAT_MAX = 1U << 3, /* non-ABI */
};
+#define PERF_ATTR_SIZE_VER0 64 /* sizeof first published struct */
+
/*
* Hardware event to monitor via a performance monitoring counter:
*/
struct perf_counter_attr {
+
/*
* Major type: hardware/software/tracepoint/etc.
*/
__u32 type;
- __u32 __reserved_1;
+
+ /*
+ * Size of the attr structure, for fwd/bwd compat.
+ */
+ __u32 size;
/*
* Type specific configuration information.
@@ -168,12 +179,12 @@
comm : 1, /* include comm data */
freq : 1, /* use freq, not period */
- __reserved_2 : 53;
+ __reserved_1 : 53;
__u32 wakeup_events; /* wakeup every n events */
- __u32 __reserved_3;
+ __u32 __reserved_2;
- __u64 __reserved_4;
+ __u64 __reserved_3;
};
/*
