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perf_counter: Add forward/backward attribute ABI compatibility

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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>
This commit is contained in:
Peter Zijlstra 2009-06-12 12:46:55 +02:00 • committed by Ingo Molnar
commit 974802eaa1
4 changed files with 105 additions and 10 deletions
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19
include/linux/perf_counter.h
View file

@ -120,6 +120,8 @@ enum perf_counter_sample_format {
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 @@ enum perf_counter_read_format {
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 @@ struct perf_counter_attr {
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;
};
/*

2
include/linux/syscalls.h
View file

@ -758,6 +758,6 @@ int kernel_execve(const char *filename, char *const argv[], char *const envp[]);
asmlinkage long sys_perf_counter_open(
const struct perf_counter_attr __user *attr_uptr,
struct perf_counter_attr __user *attr_uptr,
pid_t pid, int cpu, int group_fd, unsigned long flags);
#endif