Messages in this thread |  | | Date | Thu, 09 Feb 2012 15:39:08 -0700 | From | David Ahern <> | Subject | Re: [PATCH v6 16/18] perf: enable reading of perf.data files from different ABI rev |
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On 02/09/2012 03:21 PM, Stephane Eranian wrote: > This patch allows perf to process perf.data files generated > using an ABI that has a different perf_event_attr struct size, i.e., > a different ABI version. > > The perf_event_attr can be extended, yet perf needs to cope with > older perf.data files. Similarly, perf must be able to cope with > a perf.data file which is using a newer version of the ABI than > what it knows about. > > This patch adds read_attr(), a routine that reads a perf_event_attr > struct from a file incrementally based on its advertised size. If > the on-file struct is smaller than what perf knows, then the extra > fields are zeroed. If the on-file struct is bigger, then perf only > uses what it knows about, the rest is skipped. > > Signed-off-by: Stephane Eranian <eranian@google.com> > --- > tools/perf/util/header.c | 53 ++++++++++++++++++++++++++++++++++++++++---- > tools/perf/util/session.c | 4 +- > 2 files changed, 50 insertions(+), 7 deletions(-) > > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c > index 6f4187d..c2a3410 100644 > --- a/tools/perf/util/header.c > +++ b/tools/perf/util/header.c > @@ -1959,6 +1959,51 @@ static int perf_header__read_pipe(struct perf_session *session, int fd) > return 0; > } > > +static int read_attr(int fd, struct perf_header *ph, > + struct perf_file_attr *f_attr) > +{ > + struct perf_event_attr *attr = &f_attr->attr; > + size_t sz, left; > + size_t our_sz = sizeof(f_attr->attr); > + int ret; > + > + memset(f_attr, 0, sizeof(*f_attr)); > + > + /* read minimal guaranteed structure */ > + ret = readn(fd, attr, PERF_ATTR_SIZE_VER0); > + if (ret <= 0) { > + pr_debug("cannot read %d bytes of header attr\n", > + PERF_ATTR_SIZE_VER0); > + return -1; > + } > + > + /* on file perf_event_attr size */ > + sz = attr->size; > + if (ph->needs_swap) > + sz = bswap_32(sz); > + > + if (sz == 0) { > + /* assume ABI0 */ > + sz = PERF_ATTR_SIZE_VER0; > + } else if (sz > our_sz) { > + pr_debug("file uses a more recent and unsupported ABI" > + " (%zu bytes extra)\n", sz - our_sz); > + return -1; > + } > + /* what we have not yet read and that we know about */ > + left = sz - PERF_ATTR_SIZE_VER0; > + if (left) { > + void *ptr = attr; > + ptr += PERF_ATTR_SIZE_VER0; > + > + ret = readn(fd, ptr, left); > + } > + /* read perf_file_section, ids are read in caller */ > + ret = readn(fd, &f_attr->ids, sizeof(f_attr->ids));
I thought the above 2 lines were to be removed.
David
> + > + return ret <= 0 ? -1 : 0; > +} > + > int perf_session__read_header(struct perf_session *session, int fd) > { > struct perf_header *header = &session->header; > @@ -1974,19 +2019,17 @@ int perf_session__read_header(struct perf_session *session, int fd) > if (session->fd_pipe) > return perf_header__read_pipe(session, fd); > > - if (perf_file_header__read(&f_header, header, fd) < 0) { > - pr_debug("incompatible file format\n"); > + if (perf_file_header__read(&f_header, header, fd) < 0) > return -EINVAL; > - } > > - nr_attrs = f_header.attrs.size / sizeof(f_attr); > + nr_attrs = f_header.attrs.size / f_header.attr_size; > lseek(fd, f_header.attrs.offset, SEEK_SET); > > for (i = 0; i < nr_attrs; i++) { > struct perf_evsel *evsel; > off_t tmp; > > - if (readn(fd, &f_attr, sizeof(f_attr)) <= 0) > + if (read_attr(fd, header, &f_attr) < 0) > goto out_errno; > > if (header->needs_swap) > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > index 3f3afed..5476320 100644 > --- a/tools/perf/util/session.c > +++ b/tools/perf/util/session.c > @@ -24,7 +24,7 @@ static int perf_session__open(struct perf_session *self, bool force) > self->fd = STDIN_FILENO; > > if (perf_session__read_header(self, self->fd) < 0) > - pr_err("incompatible file format"); > + pr_err("incompatible file format (rerun with -v to learn more)"); > > return 0; > } > @@ -56,7 +56,7 @@ static int perf_session__open(struct perf_session *self, bool force) > } > > if (perf_session__read_header(self, self->fd) < 0) { > - pr_err("incompatible file format"); > + pr_err("incompatible file format (rerun with -v to learn more)"); > goto out_close; > } >
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