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    SubjectRe: [PATCH 2/5] perf tools: fix piped mode read code
    Hi Stephane:

    This patch no longer applies cleanly. Can you update the series?

    David

    On 4/11/12 3:01 AM, Stephane Eranian wrote:
    > In __perf_session__process_pipe_events(), there was a risk
    > we would read more than what a union perf_event struct can
    > hold. this could happen in case, perf is reading a file which
    > contains new record types it does not know about and which are
    > larger than anything it knows about.
    >
    > In general, perf is supposed to skip records it does not
    > understand, but in pipe mode, those have to be read and ignored.
    > The fixed size header contains the size of the record, but that
    > size may be larger than union perf_event, yet it was used as
    > the backing to the read in:
    >
    > union perf_event event;
    > void *p;
    >
    > size = event->header.size;
    >
    > p =&event;
    > p += sizeof(struct perf_event_header);
    > if (size - sizeof(struct perf_event_header)) {
    > err = readn(self->fd, p, size - sizeof(struct perf_event_header));
    >
    > We fix this by allocating a buffer based on the size reported in
    > the header. We reuse the buffer as much as we can. We realloc in
    > case it becomes too small. In the common case, the performance
    > impact is negligible.
    >
    > Signed-off-by: Stephane Eranian<eranian@google.com>
    > ---
    > tools/perf/util/session.c | 35 +++++++++++++++++++++++++++--------
    > 1 files changed, 27 insertions(+), 8 deletions(-)
    >
    > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
    > index 9412e3b..d13e915 100644
    > --- a/tools/perf/util/session.c
    > +++ b/tools/perf/util/session.c
    > @@ -1056,8 +1056,9 @@ volatile int session_done;
    > static int __perf_session__process_pipe_events(struct perf_session *self,
    > struct perf_tool *tool)
    > {
    > - union perf_event event;
    > - uint32_t size;
    > + union perf_event *event;
    > + uint32_t size, cur_size = 0;
    > + void *buf = NULL;
    > int skip = 0;
    > u64 head;
    > int err;
    > @@ -1066,8 +1067,14 @@ static int __perf_session__process_pipe_events(struct perf_session *self,
    > perf_tool__fill_defaults(tool);
    >
    > head = 0;
    > + cur_size = sizeof(union perf_event);
    > +
    > + buf = malloc(cur_size);
    > + if (!buf)
    > + return -errno;
    > more:
    > - err = readn(self->fd,&event, sizeof(struct perf_event_header));
    > + event = buf;
    > + err = readn(self->fd, event, sizeof(struct perf_event_header));
    > if (err<= 0) {
    > if (err == 0)
    > goto done;
    > @@ -1077,13 +1084,23 @@ static int __perf_session__process_pipe_events(struct perf_session *self,
    > }
    >
    > if (self->header.needs_swap)
    > - perf_event_header__bswap(&event.header);
    > + perf_event_header__bswap(&event->header);
    >
    > - size = event.header.size;
    > + size = event->header.size;
    > if (size == 0)
    > size = 8;
    >
    > - p =&event;
    > + if (size> cur_size) {
    > + void *new = realloc(buf, size);
    > + if (!new) {
    > + pr_err("failed to allocate memory to read event\n");
    > + goto out_err;
    > + }
    > + buf = new;
    > + cur_size = size;
    > + event = buf;
    > + }
    > + p = event;
    > p += sizeof(struct perf_event_header);
    >
    > if (size - sizeof(struct perf_event_header)) {
    > @@ -1099,9 +1116,10 @@ static int __perf_session__process_pipe_events(struct perf_session *self,
    > }
    > }
    >
    > - if ((skip = perf_session__process_event(self,&event, tool, head))< 0) {
    > + skip = perf_session__process_event(self, event, tool, head);
    > + if (skip< 0) {
    > dump_printf("%#" PRIx64 " [%#x]: skipping unknown header type: %d\n",
    > - head, event.header.size, event.header.type);
    > + head, event->header.size, event->header.type);
    > /*
    > * assume we lost track of the stream, check alignment, and
    > * increment a single u64 in the hope to catch on again 'soon'.
    > @@ -1122,6 +1140,7 @@ static int __perf_session__process_pipe_events(struct perf_session *self,
    > done:
    > err = 0;
    > out_err:
    > + free(buf);
    > perf_session__warn_about_errors(self, tool);
    > perf_session_free_sample_buffers(self);
    > return err;



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