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Subject[PATCH v2] 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.

Signed-off-by: Stephane Eranian <eranian@google.com>
---
kernel/events/core.c | 4 ++++
tools/perf/util/event.c | 30 +++++++++++++-----------------
2 files changed, 17 insertions(+), 17 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;
--
1.7.9.5


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