Commit 9aaa131a authored Mar 21, 2009 by Paul Mackerras Committed by Ingo Molnar Apr 06, 2009

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>

parent db4fb5ac

arch/powerpc/kernel/perf_counter.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -602,12 +602,13 @@ hw_perf_counter_init(struct perf_counter *counter)
		return NULL;
		if ((s64)counter->hw_event.irq_period < 0)
		return NULL;
		if (!counter->hw_event.raw_type) {
		ev = counter->hw_event.event_id;
		if (!counter->hw_event.raw) {
		if (ev >= ppmu->n_generic \|\|
		ppmu->generic_events[ev] == 0)
		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;

include/linux/perf_counter.h

+12 −0

Original line number	Diff line number	Diff line
		@@ -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;
		};