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perf_counter: fix type/event_id layout on big-endian systems 

Impact: build fix for powerpc

Commit db3a944aca35ae61 ("perf_counter: revamp syscall input ABI")
expanded the hw_event.type field into a union of structs containing
bitfields.  In particular it introduced a type field and a raw_type
field, with the intention that the 1-bit raw_type field should
overlay the most-significant bit of the 8-bit type field, and in fact
perf_counter_alloc() now assumes that (or at least, assumes that
raw_type doesn't overlay any of the bits that are 1 in the values of
PERF_TYPE_{HARDWARE,SOFTWARE,TRACEPOINT}).

Unfortunately this is not true on big-endian systems such as PowerPC,
where bitfields are laid out from left to right, i.e. from most
significant bit to least significant.  This means that setting
hw_event.type = PERF_TYPE_SOFTWARE will set hw_event.raw_type to 1.

This fixes it by making the layout depend on whether or not
__BIG_ENDIAN_BITFIELD is defined.  It's a bit ugly, but that's what
we get for using bitfields in a user/kernel ABI.

Also, that commit didn't fix up some places in arch/powerpc/kernel/
perf_counter.c where hw_event.raw and hw_event.event_id were used.
This fixes them too.

Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Paul Mackerras 2009-03-21 15:31:47 +11:00 committed by Ingo Molnar
parent db4fb5acf2
commit 9aaa131a27
2 changed files with 17 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
arch/powerpc/kernel/perf_counter.c
View File

@ -602,12 +602,13 @@ hw_perf_counter_init(struct perf_counter *counter)
return NULL;
if ((s64)counter->hw_event.irq_period < 0)
return NULL;
ev = counter->hw_event.event_id;
if (!counter->hw_event.raw) {
if (ev >= ppmu->n_generic ||
ppmu->generic_events[ev] == 0)
if (!counter->hw_event.raw_type) {
ev = counter->hw_event.event_id;
if (ev >= ppmu->n_generic || ppmu->generic_events[ev] == 0)
return NULL;
ev = ppmu->generic_events[ev];
} else {
ev = counter->hw_event.raw_event_id;
}
counter->hw.config_base = ev;
counter->hw.idx = 0;

12
include/linux/perf_counter.h
View File

@ -15,6 +15,7 @@
#include <linux/types.h>
#include <linux/ioctl.h>
#include <asm/byteorder.h>
/*
* User-space ABI bits:
@ -86,6 +87,7 @@ enum perf_counter_record_type {
*/
struct perf_counter_hw_event {
union {
#ifndef __BIG_ENDIAN_BITFIELD
struct {
__u64 event_id : 56,
type : 8;
@ -94,6 +96,16 @@ struct perf_counter_hw_event {
__u64 raw_event_id : 63,
raw_type : 1;
};
#else
struct {
__u64 type : 8,
event_id : 56;
};
struct {
__u64 raw_type : 1,
raw_event_id : 63;
};
#endif /* __BIT_ENDIAN_BITFIELD */
__u64 event_config;
};