[PATCH V2 1/3] perf symbols: Ignore mapping symbols on aarch64

[Victor Kamensky]

Aarch64 ELF files use mapping symbols with special names $x, $d
to identify regions of Aarch64 code (see Aarch64 ELF ABI - "ARM
IHI 0056B", section "4.5.4 Mapping symbols").

The patch filters out these symbols at load time, similar to
"696b97a perf symbols: Ignore mapping symbols on ARM" changes
done for ARM before V8.

Signed-off-by: Victor Kamensky <victor.kamensky at linaro.org>
Cc: Peter Zijlstra <a.p.zijlstra at chello.nl>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Arnaldo Carvalho de Melo <acme at kernel.org>
Cc: Adrian Hunter <adrian.hunter at intel.com>
Cc: Jiri Olsa <jolsa at redhat.com>
Cc: Namhyung Kim <namhyung at kernel.org>
Cc: Avi Kivity <avi at cloudius-systems.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt at hitachi.com>
Cc: Anton Blanchard <anton at samba.org>
Cc: David Ahern <dsahern at gmail.com>
Cc: Will Deacon <will.deacon at arm.com>
Cc: Dave Martin <Dave.Martin at arm.com>
Acked-by: Will Deacon <will.deacon at arm.com>
---
 tools/perf/util/symbol-elf.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 06fcd1b..1e188dd 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -862,6 +862,14 @@ int dso__load_sym(struct dso *dso, struct map *map,
 			    !strcmp(elf_name, "$t"))
 				continue;
 		}
+		/* Reject Aarch64 ELF "mapping symbols": these aren't unique and
+		 * don't identify functions, so will confuse the profile
+		 * output: */
+		if (ehdr.e_machine == EM_AARCH64) {
+			if (!strcmp(elf_name, "$x") ||
+			    !strcmp(elf_name, "$d"))
+				continue;
+		}
 
 		if (runtime_ss->opdsec && sym.st_shndx == runtime_ss->opdidx) {
 			u32 offset = sym.st_value - syms_ss->opdshdr.sh_addr;
-- 
1.9.3