linux-kernel - [PATCH 6/9] perf symbols: Ignore mapping symbols on ARM

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Date:	Tue, 10 Aug 2010 17:15:36 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, Dave Martin <dave.martin@...aro.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 6/9] perf symbols: Ignore mapping symbols on ARM

From: Dave Martin <dave.martin@...aro.org>

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@...aro.org>
Signed-off-by: Dave Martin <dave.martin@...aro.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/symbol.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index b6f5970..1a36773 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;
-- 
1.6.2.5

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