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>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index a4b76c0175f3..98f5990be1e1 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;
         };