[PATCH V2 0/3] perf symbols: debuglink and arm mapping symbols changes

[PATCH V2 0/3] perf symbols: debuglink and arm mapping symbols changes

[Victor Kamensky]

Hi Folks,

Here is second version of mini-series that addresses couple issues
in perf symbols handling.

Changes since V1:

o 'perf symbols: Ignore mapping symbols on aarch64': based on feedback
from Will Deacon and Russell King [1] added code that handles ARM/Aarch64
mapping symbols like "$d.<any>". Code uses similar snipet to handle
ARM mapping symbols as in another places in kernel, but it has its
own version of the code. Added proper Acked-by.

o 'perf symbols: debuglink should take symfs option into account':
based on feedback from David Ahern [2] picked more simple version that
does not make malloced copy of 'filename', that makes patch simpler.
Added proper 'Acked-and-tested-by'.

[1] https://lkml.org/lkml/2015/1/13/507

[2] https://lkml.org/lkml/2015/1/13/508

Victor Kamensky (3):
  perf symbols: Ignore mapping symbols on aarch64
  perf symbols: improve abi compliance in arm mapping symbols handling
  perf symbols: debuglink should take symfs option into account

 tools/perf/util/dso.c        |  6 +++---
 tools/perf/util/symbol-elf.c | 13 ++++++++++---
 2 files changed, 13 insertions(+), 6 deletions(-)

-- 
1.9.3

[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@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(+)

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

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

[Russell King - ARM Linux]

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.

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.

[PATCH V2 2/3] perf symbols: improve abi compliance in arm mapping symbols handling

[Victor Kamensky]

Both Arm and Aarch64 ELF ABI allow mapping symbols be in from
either "$d" or "$d.<any>". But current code that handles mapping
symbols only deals with the first, dollar character and a single
letter, case.

The patch adds handling of the second case with period
followed by any characters.

Suggested-by: Russell King <linux@arm.linux.org.uk>
Suggested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Victor Kamensky <victor.kamensky@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
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: Dave Martin <Dave.Martin@arm.com>
---
 tools/perf/util/symbol-elf.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 1e188dd..7fd35d6 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -857,17 +857,16 @@ int dso__load_sym(struct dso *dso, struct map *map,
 		 * 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, "$t"))
+			if (elf_name[0] == '$' && strchr("adt", elf_name[1])
+			    && (elf_name[2] == '\0' || elf_name[2] == '.'))
 				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"))
+			if (elf_name[0] == '$' && strchr("dx", elf_name[1])
+			    && (elf_name[2] == '\0' || elf_name[2] == '.'))
 				continue;
 		}
 
-- 
1.9.3

Re: [PATCH V2 2/3] perf symbols: improve abi compliance in arm mapping symbols handling

[Russell King - ARM Linux]

On Wed, Jan 21, 2015 at 08:52:57PM -0800, Victor Kamensky wrote:
> Both Arm and Aarch64 ELF ABI allow mapping symbols be in from
> either "$d" or "$d.<any>". But current code that handles mapping
> symbols only deals with the first, dollar character and a single
> letter, case.
> 
> The patch adds handling of the second case with period
> followed by any characters.
> 
> Suggested-by: Russell King <linux@arm.linux.org.uk>
> Suggested-by: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Victor Kamensky <victor.kamensky@linaro.org>
> Acked-by: Will Deacon <will.deacon@arm.com>
> 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: Dave Martin <Dave.Martin@arm.com>
> ---
>  tools/perf/util/symbol-elf.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> index 1e188dd..7fd35d6 100644
> --- a/tools/perf/util/symbol-elf.c
> +++ b/tools/perf/util/symbol-elf.c
> @@ -857,17 +857,16 @@ int dso__load_sym(struct dso *dso, struct map *map,
>  		 * 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, "$t"))
> +			if (elf_name[0] == '$' && strchr("adt", elf_name[1])
> +			    && (elf_name[2] == '\0' || elf_name[2] == '.'))
>  				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"))
> +			if (elf_name[0] == '$' && strchr("dx", elf_name[1])
> +			    && (elf_name[2] == '\0' || elf_name[2] == '.'))
>  				continue;
>  		}

Why not fix this first?  Then, all you'd need to do would be to change
the test for EM_ARM to EM_ARM or EM_AARCH64, and add the 'x' into the
strchr() string.

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.

Re: [PATCH V2 2/3] perf symbols: improve abi compliance in arm mapping symbols handling

[Victor Kamensky]

On 22 January 2015 at 07:29, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> On Wed, Jan 21, 2015 at 08:52:57PM -0800, Victor Kamensky wrote:
>> Both Arm and Aarch64 ELF ABI allow mapping symbols be in from
>> either "$d" or "$d.<any>". But current code that handles mapping
>> symbols only deals with the first, dollar character and a single
>> letter, case.
>>
>> The patch adds handling of the second case with period
>> followed by any characters.
>>
>> Suggested-by: Russell King <linux@arm.linux.org.uk>
>> Suggested-by: Will Deacon <will.deacon@arm.com>
>> Signed-off-by: Victor Kamensky <victor.kamensky@linaro.org>
>> Acked-by: Will Deacon <will.deacon@arm.com>
>> 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: Dave Martin <Dave.Martin@arm.com>
>> ---
>>  tools/perf/util/symbol-elf.c | 9 ++++-----
>>  1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
>> index 1e188dd..7fd35d6 100644
>> --- a/tools/perf/util/symbol-elf.c
>> +++ b/tools/perf/util/symbol-elf.c
>> @@ -857,17 +857,16 @@ int dso__load_sym(struct dso *dso, struct map *map,
>>                * 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, "$t"))
>> +                     if (elf_name[0] == '$' && strchr("adt", elf_name[1])
>> +                         && (elf_name[2] == '\0' || elf_name[2] == '.'))
>>                               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"))
>> +                     if (elf_name[0] == '$' && strchr("dx", elf_name[1])
>> +                         && (elf_name[2] == '\0' || elf_name[2] == '.'))
>>                               continue;
>>               }
>
> Why not fix this first?  Then, all you'd need to do would be to change
> the test for EM_ARM to EM_ARM or EM_AARCH64, and add the 'x' into the
> strchr() string.

In previously discussed [1] I proposed two variants and ask
for people's preferences. Will replied that he did not care and
let me choose that I like.

It seems to me that you more like variant 2 (provided here
for reference again). It would replace patch 1 and patch 2 of
version 2. Please confirm. I don't practically care much and
can use either. I personally preferred variant 1 because in
variant 2 $x will be filtered on ARM V7, but V7 ABI does not
say anything about $x, only Aarch64 does. I.e special symbols
do to match between V7 and V8 exactly. But as it is
already in other places like kallsyms, I agree practically it
may not matter. If you give your node to variant 2 (as below)
I can report this miniseries: Please let me know

Variant 2:

>From c8d08ebddc61203daf21b17c891c26c1d08e14f1 Mon Sep 17 00:00:00 2001
From: Victor Kamensky <victor.kamensky@linaro.org>
Date: Mon, 12 Jan 2015 14:13:36 -0800
Subject: [PATCH 1/2] perf symbols: Ignore mapping symbols on aarch64

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.

Also added handling of mapping symbols that has format
"$d.<any>" and similar for both cases.

Note we are not making difference between EM_ARM and
EM_AARCH64 mapping symbols instead code handles superset
of both.

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: Russell King <linux@arm.linux.org.uk>
Cc: Dave Martin <Dave.Martin@arm.com>
---
 tools/perf/util/symbol-elf.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 06fcd1b..b2eb0f9 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -856,10 +856,9 @@ int dso__load_sym(struct dso *dso, struct map *map,
         /* 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, "$t"))
+        if (ehdr.e_machine == EM_ARM || ehdr.e_machine == EM_AARCH64) {
+                        if (elf_name[0] == '$' && strchr("adtx", elf_name[1])
+                        && (elf_name[2] == '\0' || elf_name[2] == '.'))
                 continue;
         }

-- 
1.9.3

Thanks,
Victor

[1] https://lkml.org/lkml/2015/1/14/1019

> --
> FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
> according to speedtest.net.

[PATCH V2 3/3] perf symbols: debuglink should take symfs option into account

[Victor Kamensky]

Currently code that tries to read corresponding debug symbol
file from .gnu_debuglink section (DSO_BINARY_TYPE__DEBUGLINK)
does not take in account symfs option, so filename__read_debuglink
function cannot open ELF file, if symfs option is used.

Fix is to add proper handling of symfs as it is done in other
places: use __symbol__join_symfs function to get real file name
of target ELF file.

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: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Waiman Long <Waiman.Long@hp.com>
Cc: David Ahern <dsahern@gmail.com>
Acked-and-tested-by: David Ahern <dsahern@gmail.com>
---
 tools/perf/util/dso.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 45be944..ca8d8d5 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -45,13 +45,13 @@ int dso__read_binary_type_filename(const struct dso *dso,
 	case DSO_BINARY_TYPE__DEBUGLINK: {
 		char *debuglink;
 
-		strncpy(filename, dso->long_name, size);
-		debuglink = filename + dso->long_name_len;
+		len = __symbol__join_symfs(filename, size, dso->long_name);
+		debuglink = filename + len;
 		while (debuglink != filename && *debuglink != '/')
 			debuglink--;
 		if (*debuglink == '/')
 			debuglink++;
-		ret = filename__read_debuglink(dso->long_name, debuglink,
+		ret = filename__read_debuglink(filename, debuglink,
 					       size - (debuglink - filename));
 		}
 		break;
-- 
1.9.3