Messages in this thread Patch in this message | | | From | Stephane Eranian <> | Subject | [PATCH v5 16/18] perf: enable reading of perf.data files from different ABI rev | Date | Thu, 2 Feb 2012 13:54:46 +0100 |
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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 Similarly, perf must be able to cope with a perf.data file which is using a newer version of the ABI than what it knows about.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 | 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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