perf symbols: Ignore mapping symbols on ARM

ARM ELF files use symbols with special names $a, $t, $d to identify regions of
ARM code, Thumb code and data within code sections.  This can cause confusing
output from the perf tools, especially for partially stripped binaries, or
binaries containing user-added zero-sized symbols (which may occur in
hand-written assembler which hasn't been fully annotated with .size
directives).

This patch filters out these symbols at load time.

LKML-Reference: <1281352878-8735-2-git-send-email-dave.martin@linaro.org>
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index b6f5970f9106..1a367734e016 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1079,6 +1079,16 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
                 if (!is_label && !elf_sym__is_a(&sym, map->type))
                         continue;
 
+                /* Reject ARM ELF "mapping symbols": these aren't unique and
+                 * don't identify functions, so will confuse the profile
+                 * output: */
+                if (ehdr.e_machine == EM_ARM) {
+                        if (!strcmp(elf_name, "$a") ||
+                            !strcmp(elf_name, "$d") ||
+                            !strcmp(elf_name, "$t"))
+                                continue;
+                }
+
                 if (opdsec && sym.st_shndx == opdidx) {
                         u32 offset = sym.st_value - opdshdr.sh_addr;
                         u64 *opd = opddata->d_buf + offset;