[PATCH 0/1] perf symbols: ignore mapping symbols on ARM

[PATCH 0/1] perf symbols: ignore mapping symbols on ARM

[Dave Martin]

Applies to linux-2.6-tip/master or acme/perf-core

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.

Addressing architecture-specific cases in this way could get
quite messy-- if one architecture-specific hack is needed in
the symbol loading loop, more might be needed over time.
Adding a generic per-architecture symbol filtering hook might
help to mitigate this if more cases need to be supported.

Switching to libbfd as a generic image-handling backend for all
architectures might be a better long-term solution, since
libelf seems to be essentially a low-level parsing library only
at this stage, and doesn't deal with all the architecture
specifics.  There's a generic bfd_is_target_special_symbol()
function which is used by binutils to filter out architecture-
specific symbols which are not "normal" symbols, which could
help us for this case.

Dave Martin (1):
  perf symbols: ignore mapping symbols on ARM

 tools/perf/util/symbol.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

[PATCH 1/1] perf symbols: ignore mapping symbols on ARM

[Dave Martin]

Applies to linux-2.6-tip/master or acme/perf-core

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.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
---
 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;
-- 
1.7.0.4

Re: [PATCH 1/1] perf symbols: ignore mapping symbols on ARM

[Arnaldo Carvalho de Melo]

Em Mon, Aug 09, 2010 at 12:21:18PM +0100, Dave Martin escreveu:
> +		/* 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;
> +		}
> +

Thanks, applied.

[tip:perf/core] perf symbols: Ignore mapping symbols on ARM

[tip-bot for Dave Martin]

Commit-ID:  696b97a5d2de9e2b22699300835e675dfffe8592
Gitweb:     http://git.kernel.org/tip/696b97a5d2de9e2b22699300835e675dfffe8592
Author:     Dave Martin <dave.martin@linaro.org>
AuthorDate: Mon, 9 Aug 2010 12:21:18 +0100
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 10 Aug 2010 16:10:36 -0300

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>
---
 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;