Messages in this thread | | | Date | Mon, 6 Feb 2012 16:22:08 -0200 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v5 16/18] perf: enable reading of perf.data files from different ABI rev |
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Em Thu, Feb 02, 2012 at 01:54:46PM +0100, Stephane Eranian escreveu: > 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 a perf.data file which is using a newer version of the ABI than 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.
Anshuman, can I have your Acked-by or Reviewed-by since you spotted problems in this and your suggestions were taken into account? Is this OK now?
- Arnaldo
> Signed-off-by: Stephane Eranian <eranian@google.com> > --- > tools/perf/util/header.c | 49 ++++++++++++++++++++++++++++++++++++++++++++- > 1 files changed, 47 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c > index 6f4187d..8d6c18d 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) > + 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) { > + /* bigger than what we know about */ > + sz = our_sz; > + > + /* skip what we do not know about */ > + lseek(fd, SEEK_CUR, attr->size - our_sz); > + } > + /* 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); > + if (ret <= 0) > + return -1; > + } > + /* read the ids */ > + ret = readn(fd, &f_attr->ids, sizeof(struct perf_file_section)); > + return ret <= 0 ? -1 : 0; > +} > + > int perf_session__read_header(struct perf_session *session, int fd) > { > struct perf_header *header = &session->header; > @@ -1979,14 +2024,14 @@ int perf_session__read_header(struct perf_session *session, int fd) > 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) > -- > 1.7.4.1
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