perf header: Add ability to keep feature sections

Many feature sections should not be re-written during perf inject. In
preparation to support that, add callbacks that a tool can use to copy
a feature section from elsewhere. perf inject will use this facility to
copy features sections from the input file.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20220520132404.25853-2-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index a27132e..b0c57a1 100644 (file)
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3462,9 +3462,22 @@ int perf_header__fprintf_info(struct perf_session *session, FILE *fp, bool full)
        return 0;
 }
 
+struct header_fw {
+       struct feat_writer      fw;
+       struct feat_fd          *ff;
+};
+
+static int feat_writer_cb(struct feat_writer *fw, void *buf, size_t sz)
+{
+       struct header_fw *h = container_of(fw, struct header_fw, fw);
+
+       return do_write(h->ff, buf, sz);
+}
+
 static int do_write_feat(struct feat_fd *ff, int type,
                         struct perf_file_section **p,
-                        struct evlist *evlist)
+                        struct evlist *evlist,
+                        struct feat_copier *fc)
 {
        int err;
        int ret = 0;
@@ -3478,7 +3491,23 @@ static int do_write_feat(struct feat_fd *ff, int type,
 
                (*p)->offset = lseek(ff->fd, 0, SEEK_CUR);
 
-               err = feat_ops[type].write(ff, evlist);
+               /*
+                * Hook to let perf inject copy features sections from the input
+                * file.
+                */
+               if (fc && fc->copy) {
+                       struct header_fw h = {
+                               .fw.write = feat_writer_cb,
+                               .ff = ff,
+                       };
+
+                       /* ->copy() returns 0 if the feature was not copied */
+                       err = fc->copy(fc, type, &h.fw);
+               } else {
+                       err = 0;
+               }
+               if (!err)
+                       err = feat_ops[type].write(ff, evlist);
                if (err < 0) {
                        pr_debug("failed to write feature %s\n", feat_ops[type].name);
 
@@ -3494,7 +3523,8 @@ static int do_write_feat(struct feat_fd *ff, int type,
 }
 
 static int perf_header__adds_write(struct perf_header *header,
-                                  struct evlist *evlist, int fd)
+                                  struct evlist *evlist, int fd,
+                                  struct feat_copier *fc)
 {
        int nr_sections;
        struct feat_fd ff;
@@ -3523,7 +3553,7 @@ static int perf_header__adds_write(struct perf_header *header,
        lseek(fd, sec_start + sec_size, SEEK_SET);
 
        for_each_set_bit(feat, header->adds_features, HEADER_FEAT_BITS) {
-               if (do_write_feat(&ff, feat, &p, evlist))
+               if (do_write_feat(&ff, feat, &p, evlist, fc))
                        perf_header__clear_feat(header, feat);
        }
 
@@ -3561,9 +3591,10 @@ int perf_header__write_pipe(int fd)
        return 0;
 }
 
-int perf_session__write_header(struct perf_session *session,
-                              struct evlist *evlist,
-                              int fd, bool at_exit)
+static int perf_session__do_write_header(struct perf_session *session,
+                                        struct evlist *evlist,
+                                        int fd, bool at_exit,
+                                        struct feat_copier *fc)
 {
        struct perf_file_header f_header;
        struct perf_file_attr   f_attr;
@@ -3615,7 +3646,7 @@ int perf_session__write_header(struct perf_session *session,
        header->feat_offset = header->data_offset + header->data_size;
 
        if (at_exit) {
-               err = perf_header__adds_write(header, evlist, fd);
+               err = perf_header__adds_write(header, evlist, fd, fc);
                if (err < 0)
                        return err;
        }
@@ -3648,6 +3679,13 @@ int perf_session__write_header(struct perf_session *session,
        return 0;
 }
 
+int perf_session__write_header(struct perf_session *session,
+                              struct evlist *evlist,
+                              int fd, bool at_exit)
+{
+       return perf_session__do_write_header(session, evlist, fd, at_exit, NULL);
+}
+
 static int perf_header__getbuffer64(struct perf_header *header,
                                    int fd, void *buf, size_t size)
 {

diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
index 0eb4bc2..e76ab02 100644 (file)
--- a/tools/perf/util/header.h
+++ b/tools/perf/util/header.h
@@ -121,6 +121,16 @@ int perf_session__write_header(struct perf_session *session,
                               int fd, bool at_exit);
 int perf_header__write_pipe(int fd);
 
+/* feat_writer writes a feature section to output */
+struct feat_writer {
+       int (*write)(struct feat_writer *fw, void *buf, size_t sz);
+};
+
+/* feat_copier copies a feature section using feat_writer to output */
+struct feat_copier {
+       int (*copy)(struct feat_copier *fc, int feat, struct feat_writer *fw);
+};
+
 void perf_header__set_feat(struct perf_header *header, int feat);
 void perf_header__clear_feat(struct perf_header *header, int feat);
 bool perf_header__has_feat(const struct perf_header *header, int feat);