Messages in this thread | | | Date | Thu, 9 Feb 2012 23:41:10 +0100 | Subject | Re: [PATCH v6 16/18] perf: enable reading of perf.data files from different ABI rev | From | Stephane Eranian <> |
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On Thu, Feb 9, 2012 at 11:39 PM, David Ahern <dsahern@gmail.com> wrote: > 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 a perf.data file which is using a newer version of the ABI than 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. >
No, They are needed to get the offsets of the ids[] table. The field name are confusing. This is not reading the ids[], but just the offset of where the table is. Without that you get bogus offsets. I ran into that bug during testing...
> 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; >> } >> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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