perf symbols: Follow .gnu_debuglink section to find separate symbols

The .gnu_debuglink section is specified to contain the filename of the
debug info file, as well as a CRC that can be used to validate it.

This doesn't currently use the checksum and relies on the usual build-id
matching for validation.

This provides more context:
http://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html

Signed-off-by: Pierre-Loup A. Griffais <pgriffais@nvidia.com>
Reported-by: Mike Sartain <mikesart@valvesoftware.com>
Tested-by: Mike Sartain <mikesart@valvesoftware.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Sartain <mikesart@valvesoftware.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4FE4BB95.3080309@nvidia.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 3e2e5ea0f03f692c41f62e8aeb1f5d3382c86ce1..994f4ffdcd055f026149aef6186eb106fa2952da 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1590,11 +1590,62 @@ out:
        return err;
 }
 
+static int filename__read_debuglink(const char *filename,
+                                   char *debuglink, size_t size)
+{
+       int fd, err = -1;
+       Elf *elf;
+       GElf_Ehdr ehdr;
+       GElf_Shdr shdr;
+       Elf_Data *data;
+       Elf_Scn *sec;
+       Elf_Kind ek;
+
+       fd = open(filename, O_RDONLY);
+       if (fd < 0)
+               goto out;
+
+       elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
+       if (elf == NULL) {
+               pr_debug2("%s: cannot read %s ELF file.\n", __func__, filename);
+               goto out_close;
+       }
+
+       ek = elf_kind(elf);
+       if (ek != ELF_K_ELF)
+               goto out_close;
+
+       if (gelf_getehdr(elf, &ehdr) == NULL) {
+               pr_err("%s: cannot get elf header.\n", __func__);
+               goto out_close;
+       }
+
+       sec = elf_section_by_name(elf, &ehdr, &shdr,
+                                 ".gnu_debuglink", NULL);
+       if (sec == NULL)
+               goto out_close;
+
+       data = elf_getdata(sec, NULL);
+       if (data == NULL)
+               goto out_close;
+
+       /* the start of this section is a zero-terminated string */
+       strncpy(debuglink, data->d_buf, size);
+
+       elf_end(elf);
+
+out_close:
+       close(fd);
+out:
+       return err;
+}
+
 char dso__symtab_origin(const struct dso *dso)
 {
        static const char origin[] = {
                [SYMTAB__KALLSYMS]            = 'k',
                [SYMTAB__JAVA_JIT]            = 'j',
+               [SYMTAB__DEBUGLINK]           = 'l',
                [SYMTAB__BUILD_ID_CACHE]      = 'B',
                [SYMTAB__FEDORA_DEBUGINFO]    = 'f',
                [SYMTAB__UBUNTU_DEBUGINFO]    = 'u',
@@ -1662,10 +1713,22 @@ int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
         */
        want_symtab = 1;
 restart:
-       for (dso->symtab_type = SYMTAB__BUILD_ID_CACHE;
+       for (dso->symtab_type = SYMTAB__DEBUGLINK;
             dso->symtab_type != SYMTAB__NOT_FOUND;
             dso->symtab_type++) {
                switch (dso->symtab_type) {
+               case SYMTAB__DEBUGLINK: {
+                       char *debuglink;
+                       strncpy(name, dso->long_name, size);
+                       debuglink = name + dso->long_name_len;
+                       while (debuglink != name && *debuglink != '/')
+                               debuglink--;
+                       if (*debuglink == '/')
+                               debuglink++;
+                       filename__read_debuglink(dso->long_name, debuglink,
+                                                size - (debuglink - name));
+                       }
+                       break;
                case SYMTAB__BUILD_ID_CACHE:
                        /* skip the locally configured cache if a symfs is given */
                        if (symbol_conf.symfs[0] ||

diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index af0752b1aca1a9097b1eb552da416683bf3394c7..a884b99017f085c0dceb47e7b766dab8527dc7df 100644 (file)
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -257,6 +257,7 @@ enum symtab_type {
        SYMTAB__KALLSYMS = 0,
        SYMTAB__GUEST_KALLSYMS,
        SYMTAB__JAVA_JIT,
+       SYMTAB__DEBUGLINK,
        SYMTAB__BUILD_ID_CACHE,
        SYMTAB__FEDORA_DEBUGINFO,
        SYMTAB__UBUNTU_DEBUGINFO,