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Date: Tue, 30 Oct 2012 20:00:20 +0400
From: Vasily Kulikov <segoon@...nwall.com>
To: owl-dev@...ts.openwall.com
Subject: Re: glibc
On Tue, Oct 30, 2012 at 05:57 +0400, Dmitry V. Levin wrote:
> On Mon, Oct 29, 2012 at 11:34:39PM +0400, Dmitry V. Levin wrote:
> > On Mon, Oct 29, 2012 at 10:17:48PM +0400, Vasily Kulikov wrote:
> > [...]
> > > 'strncmp' symbol is present on x86_64, but absent on i686:
> > >
> > > $ readelf -s logs/glibc-build-i386/elf/rtld-libc.a | grep strncmp
> > > 22: 00000000 0 NOTYPE GLOBAL DEFAULT UND strncmp
> > > File: logs/glibc-build-i386/elf/rtld-libc.a(rtld-strncmp-c.os)
> > > 1: 00000000 0 FILE LOCAL DEFAULT ABS strncmp-c.c
> > > 15: 00000000 279 FUNC GLOBAL DEFAULT 1 __strncmp_ia32
> > > 16: 00000000 279 FUNC GLOBAL DEFAULT 1 __GI_strncmp
> > >
> > > $ readelf -s logs/glibc-build-x86_64/elf/rtld-libc.a | grep strncmp
> > > 19: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND strncmp
> > > File: logs/glibc-build-x86_64/elf/rtld-libc.a(rtld-strncmp.os)
> > > 10: 0000000000000000 33 FUNC GLOBAL DEFAULT 1 strncmp
> > > File: logs/glibc-build-x86_64/elf/rtld-libc.a(rtld-strncmp-ssse3.os)
> > > 11: 0000000000000000 33 FUNC GLOBAL DEFAULT 4 __strncmp_ssse3
> >
> > The difference between x86_64 and i686 is due to STT_GNU_IFUNC.
>
> Try this:
>
> --- a/sysdeps/i386/i686/multiarch/Makefile
> +++ b/sysdeps/i386/i686/multiarch/Makefile
> @@ -24,6 +24,7 @@ sysdep_routines += bzero-sse2 memset-sse2 memcpy-ssse3 mempcpy-ssse3 \
> strcasecmp_l-c strcasecmp-c strcasecmp_l-ssse3 \
> strncase_l-c strncase-c strncase_l-ssse3 \
> strcasecmp_l-sse4 strncase_l-sse4
> +sysdep-rtld-routines += strncmp-c strncmp-ssse3 strncmp-sse4
> ifeq (yes,$(config-cflags-sse4))
> sysdep_routines += strcspn-c strpbrk-c strspn-c strstr-c strcasestr-c
> CFLAGS-varshift.c += -msse4
The same error. strncmp-c is compiled in rtld-libc.a:
$ readelf -s rtld-libc.a | grep strncmp-c.
File: rtld-libc.a(rtld-strncmp-c.os)
1: 00000000 0 FILE LOCAL DEFAULT ABS strncmp-c.c
However, strncmp-{ssse3,sse4} are not.
Btw, I see that there is no XXX symbol for any __GI_XXX symbol defined in
'readelf -s elf/rtld-libc.a'. IOW, no STT_GNU_IFUNC'ish function
wouldn't work in rtld. Weird.
(from another email)
> > The direct using of 'getenv' adds the dependency. Commenting 2 usages
> > of 'getenv' in the patch removed the linking problem.
>
> Which ones?
const char *value = getenv (cp);
and
const char *value = getenv (nextp);
from _dl_non_dynamic_init() and process_envvars(), respectively.
--
Vasiliy
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