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Subject[PATCH v3] perf: disable PERF_RECORD_MMAP2 support

For now, we disable the extended MMAP record support (MMAP2).
We have identified cases where it would not report the correct
mapping information, clone(VM_CLONE) but with separate pids.
We will revisit the support once we find a solution for this case.

The patch changes the kernel to return EINVAL if attr->mmap2
is set. The patch also modifies the perf tool to use regular PERF_RECORD_MMAP
for synthetic events and it also prevents the tool from requesting attr->mmap2
mode because the kernel would reject it.

The support will be revisited once the kenrel interface is updated.

In V2, we reduce the patch to the strict minimum.
In V3, we avoid calling perf_event_open() with mmap2 set because we
know it will fail and require fallback retry.

Signed-off-by: Stephane Eranian <eranian@google.com>
---
kernel/events/core.c | 4 ++++
tools/perf/util/event.c | 30 +++++++++++++-----------------
tools/perf/util/evsel.c | 1 -
3 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index c716385..5bd7fe4 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6773,6 +6773,10 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
if (ret)
return -EFAULT;

+ /* disabled for now */
+ if (attr->mmap2)
+ return -EINVAL;
+
if (attr->__reserved_1)
return -EINVAL;

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 9b393e7..63df031 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -187,7 +187,7 @@ static int perf_event__synthesize_mmap_events(struct perf_tool *tool,
return -1;
}

- event->header.type = PERF_RECORD_MMAP2;
+ event->header.type = PERF_RECORD_MMAP;
/*
* Just like the kernel, see __perf_event_mmap in kernel/perf_event.c
*/
@@ -198,7 +198,6 @@ static int perf_event__synthesize_mmap_events(struct perf_tool *tool,
char prot[5];
char execname[PATH_MAX];
char anonstr[] = "//anon";
- unsigned int ino;
size_t size;
ssize_t n;

@@ -209,13 +208,10 @@ static int perf_event__synthesize_mmap_events(struct perf_tool *tool,
strcpy(execname, "");

/* 00400000-0040c000 r-xp 00000000 fd:01 41038 /bin/cat */
- n = sscanf(bf, "%"PRIx64"-%"PRIx64" %s %"PRIx64" %x:%x %u %s\n",
- &event->mmap2.start, &event->mmap2.len, prot,
- &event->mmap2.pgoff, &event->mmap2.maj,
- &event->mmap2.min,
- &ino, execname);
-
- event->mmap2.ino = (u64)ino;
+ n = sscanf(bf, "%"PRIx64"-%"PRIx64" %s %"PRIx64" %*x:%*x %*u %s\n",
+ &event->mmap.start, &event->mmap.len, prot,
+ &event->mmap.pgoff,
+ execname);

if (n != 8)
continue;
@@ -227,15 +223,15 @@ static int perf_event__synthesize_mmap_events(struct perf_tool *tool,
strcpy(execname, anonstr);

size = strlen(execname) + 1;
- memcpy(event->mmap2.filename, execname, size);
+ memcpy(event->mmap.filename, execname, size);
size = PERF_ALIGN(size, sizeof(u64));
- event->mmap2.len -= event->mmap.start;
- event->mmap2.header.size = (sizeof(event->mmap2) -
- (sizeof(event->mmap2.filename) - size));
- memset(event->mmap2.filename + size, 0, machine->id_hdr_size);
- event->mmap2.header.size += machine->id_hdr_size;
- event->mmap2.pid = tgid;
- event->mmap2.tid = pid;
+ event->mmap.len -= event->mmap.start;
+ event->mmap.header.size = (sizeof(event->mmap) -
+ (sizeof(event->mmap.filename) - size));
+ memset(event->mmap.filename + size, 0, machine->id_hdr_size);
+ event->mmap.header.size += machine->id_hdr_size;
+ event->mmap.pid = tgid;
+ event->mmap.tid = pid;

if (process(tool, event, &synth_sample, machine) != 0) {
rc = -1;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index bfebc1e..bab6775 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -678,7 +678,6 @@ void perf_evsel__config(struct perf_evsel *evsel,
attr->sample_type |= PERF_SAMPLE_WEIGHT;

attr->mmap = track;
- attr->mmap2 = track && !perf_missing_features.mmap2;
attr->comm = track;

if (opts->sample_transaction)
--
1.7.9.5


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