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

Message ID 1421902378-3634-2-git-send-email-victor.kamensky@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Victor Kamensky Jan. 22, 2015, 4:52 a.m. UTC 
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@linaro.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Avi Kivity <avi@cloudius-systems.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Dave Martin <Dave.Martin@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
---
 tools/perf/util/symbol-elf.c | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Russell King - ARM Linux Jan. 22, 2015, 3:27 p.m. UTC | #1 
On Wed, Jan 21, 2015 at 08:52:56PM -0800, Victor Kamensky wrote:
> 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.

I thought I'd commented that this should probably use the same test that
we already have established elsewhere in the kernel, namely in the
kallsyms and module code:

/*
 * This ignores the intensely annoying "mapping symbols" found
 * in ARM ELF files: $a, $t and $d.
 */
static inline int is_arm_mapping_symbol(const char *str)
{ 
        return str[0] == '$' && strchr("axtd", str[1])
               && (str[2] == '\0' || str[2] == '.');
}

We really shouldn't be writing the same check for the same symbols in
different ways.
diff mbox

Patch

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;