[PATCH] perf, ibs: Check syscall attribute flags

[Robert Richter]

Current implementation simply ignores attribute flags. Thus, there is
no notification to userland of unsupported features. Check syscall's
attribute flags to let userland know if a feature is supported by the
kernel. This is also needed to distinguish between future kernels what
might support a feature.

Cc: <stable@xxxxxxxxxxxxxxx> v3.5..
Signed-off-by: Robert Richter <robert.richter@xxxxxxx>
---
 arch/x86/kernel/cpu/perf_event_amd_ibs.c |   12 ++++++++++++
 include/linux/perf_event.h               |    2 ++
 2 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
index 7bfb5be..eebd5ff 100644
--- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c
+++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
@@ -209,6 +209,15 @@ static int perf_ibs_precise_event(struct perf_event *event, u64 *config)
 	return -EOPNOTSUPP;
 }
 
+static const struct perf_event_attr ibs_notsupp = {
+	.exclude_user	= 1,
+	.exclude_kernel	= 1,
+	.exclude_hv	= 1,
+	.exclude_idle	= 1,
+	.exclude_host	= 1,
+	.exclude_guest	= 1,
+};
+
 static int perf_ibs_init(struct perf_event *event)
 {
 	struct hw_perf_event *hwc = &event->hw;
@@ -229,6 +238,9 @@ static int perf_ibs_init(struct perf_event *event)
 	if (event->pmu != &perf_ibs->pmu)
 		return -ENOENT;
 
+	if (perf_flags(&event->attr) & perf_flags(&ibs_notsupp))
+		return -EINVAL;
+
 	if (config & ~perf_ibs->config_mask)
 		return -EINVAL;
 
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 28f9cee..c36a04f 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -304,6 +304,8 @@ struct perf_event_attr {
 	__u32	__reserved_2;
 };
 
+#define perf_flags(attr)	(*(&(attr)->read_format + 1))
+
 /*
  * Ioctls that can be done on a perf event fd:
  */
-- 
1.7.8.6




-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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