[PATCH] snd_dlsym: only do versioning checks if built --with-versioning

[PATCH] snd_dlsym: only do versioning checks if built --with-versioning

[John Spencer]

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 From 291553a0132936611d48f41e924601dff8941537 Mon Sep 17 00:00:00 2001
From: John Spencer <maillist-alsa@barfooze.de>
Date: Sat, 15 Nov 2014 13:41:00 +0100
Subject: [PATCH] snd_dlsym: only do versioning checks if built 
--with-versioning

a combination of some of the following garbage collecting LD/CFLAGS
-Os -g0 -fdata-sections -ffunction-sections -s -Wl,--gc-sections
-fno-unwind-tables -fno-asynchronous-unwind-tables
causes the symbol versioning marker symbols to be removed from BSS
since they're otherwise unreferenced. this causes dlsym failing to
find them which results in runtime breakage:

$ alsamixer
ALSA lib dlmisc.c:142:(snd_dlsym_verify) unable to verify version for 
symbol snd_config_hook_load
ALSA lib conf.c:3328:(snd_config_hooks_call) symbol snd_config_hook_load 
is not defined inside (null)
ALSA lib conf.c:3788:(snd_config_update_r) hooks failed, removing 
configuration
cannot open mixer: No such device or address

correct DSO:
$ objdump -T libasound.so.2.strip | grep 
_snd_config_hook_load_dlsym_config_hook_001
001196bc g    DO .bss   00000001 _snd_config_hook_load_dlsym_config_hook_001

incorrect DSO:
$ objdump -T libs/libasound.so.2 | grep 
_snd_config_hook_load_dlsym_config_hook_001
00000000 g    DO *ABS*  00000001 _snd_config_hook_load_dlsym_config_hook_001

since alsa was built with --without-versioning, doing those versioning
checks at all is unnecessary and harmful and thus now disabled in this case.

Signed-off-by: John Spencer <maillist-alsa@barfooze.de>

---
  src/dlmisc.c | 2 ++
  1 file changed, 2 insertions(+)


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From 291553a0132936611d48f41e924601dff8941537 Mon Sep 17 00:00:00 2001
From: John Spencer <maillist-alsa@barfooze.de>
Date: Sat, 15 Nov 2014 13:41:00 +0100
Subject: [PATCH] snd_dlsym: only do versioning checks if built --with-versioning

a combination of some of the following garbage collecting LD/CFLAGS
-Os -g0 -fdata-sections -ffunction-sections -s -Wl,--gc-sections
-fno-unwind-tables -fno-asynchronous-unwind-tables
causes the symbol versioning marker symbols to be removed from BSS
since they're otherwise unreferenced. this causes dlsym failing to
find them which results in runtime breakage:

$ alsamixer
ALSA lib dlmisc.c:142:(snd_dlsym_verify) unable to verify version for symbol snd_config_hook_load
ALSA lib conf.c:3328:(snd_config_hooks_call) symbol snd_config_hook_load is not defined inside (null)
ALSA lib conf.c:3788:(snd_config_update_r) hooks failed, removing configuration
cannot open mixer: No such device or address

correct DSO:
$ objdump -T libasound.so.2.strip | grep _snd_config_hook_load_dlsym_config_hook_001
001196bc g    DO .bss   00000001 _snd_config_hook_load_dlsym_config_hook_001

incorrect DSO:
$ objdump -T libs/libasound.so.2 | grep _snd_config_hook_load_dlsym_config_hook_001
00000000 g    DO *ABS*  00000001 _snd_config_hook_load_dlsym_config_hook_001

since alsa was built with --without-versioning, doing those versioning
checks at all is unnecessary and harmful and thus now disabled in this case.

Signed-off-by: John Spencer <maillist-alsa@barfooze.de>

---
 src/dlmisc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/dlmisc.c b/src/dlmisc.c
index 4b8a02c..62f7047 100644
--- a/src/dlmisc.c
+++ b/src/dlmisc.c
@@ -177,11 +177,13 @@ void *snd_dlsym(void *handle, const char *name, const char *version)
 	}
 #endif
 #ifdef HAVE_LIBDL
+#ifdef VERSIONED_SYMBOLS
 	if (version) {
 		err = snd_dlsym_verify(handle, name, version);
 		if (err < 0)
 			return NULL;
 	}
+#endif
 	return dlsym(handle, name);
 #else
 	return NULL;
-- 
1.8.4


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Re: [PATCH] snd_dlsym: only do versioning checks if built --with-versioning

[Takashi Iwai]

At Sat, 15 Nov 2014 13:55:54 +0100,
John Spencer wrote:
> 
>  From 291553a0132936611d48f41e924601dff8941537 Mon Sep 17 00:00:00 2001
> From: John Spencer <maillist-alsa@barfooze.de>
> Date: Sat, 15 Nov 2014 13:41:00 +0100
> Subject: [PATCH] snd_dlsym: only do versioning checks if built 
> --with-versioning
> 
> a combination of some of the following garbage collecting LD/CFLAGS
> -Os -g0 -fdata-sections -ffunction-sections -s -Wl,--gc-sections
> -fno-unwind-tables -fno-asynchronous-unwind-tables
> causes the symbol versioning marker symbols to be removed from BSS
> since they're otherwise unreferenced. this causes dlsym failing to
> find them which results in runtime breakage:
> 
> $ alsamixer
> ALSA lib dlmisc.c:142:(snd_dlsym_verify) unable to verify version for 
> symbol snd_config_hook_load
> ALSA lib conf.c:3328:(snd_config_hooks_call) symbol snd_config_hook_load 
> is not defined inside (null)
> ALSA lib conf.c:3788:(snd_config_update_r) hooks failed, removing 
> configuration
> cannot open mixer: No such device or address
> 
> correct DSO:
> $ objdump -T libasound.so.2.strip | grep 
> _snd_config_hook_load_dlsym_config_hook_001
> 001196bc g    DO .bss   00000001 _snd_config_hook_load_dlsym_config_hook_001
> 
> incorrect DSO:
> $ objdump -T libs/libasound.so.2 | grep 
> _snd_config_hook_load_dlsym_config_hook_001
> 00000000 g    DO *ABS*  00000001 _snd_config_hook_load_dlsym_config_hook_001
> 
> since alsa was built with --without-versioning, doing those versioning
> checks at all is unnecessary and harmful and thus now disabled in this case.
> 
> Signed-off-by: John Spencer <maillist-alsa@barfooze.de>

Thanks, applied.


Takashi