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Subject[PATCH] perfcounters: 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 is in the master branch of my perfcounters.git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/paulus/perfcounters.git master

arch/powerpc/kernel/perf_counter.c | 9 +++++----
include/linux/perf_counter.h | 12 ++++++++++++
2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/perf_counter.c b/arch/powerpc/kernel/perf_counter.c
index 830ca9c..6413d9c 100644
--- a/arch/powerpc/kernel/perf_counter.c
+++ b/arch/powerpc/kernel/perf_counter.c
@@ -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;
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index a4b76c0..98f5990 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -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;
};

--
1.5.6.3

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