[PATCH] Fix weak/strong attribute of __errno_location and it's __GI alias

[Bernhard Reutner-Fischer]

On 1 October 2013 14:21:44 Vineet Gupta <Vineet.Gupta1 at synopsys.com> wrote:
> A simple statically linked hello world program was segfaulting for ARC
> in linuxthreads.old configuration (although the root casue applies
> cross-arch for NPTL as well as linuxthreads.old as described)
>
> The crash was due to branch to NULL in _stdio_init

is this gcc.gnu.org/PR32219 ?
See GCC ML for proposed patches..
Thanks,
>
>   0001026c <_stdio_init>:
>      1026c:    push_s     blink
>      1026e:    st.a       r13,[sp,-8]
>      10272:    bl.d       0  --> supposed call to __errno_location
>
> The call was NOT getting patched to libc internal only alias
> __GI___errno_location, because it was weak while it's exported cousin,
> __errno_location was strong/normal.
>
>   arc-linux-uclibc-nm libc/misc/internals/__errno_location.os
>
>   00000000 W __GI___errno_location
>   00000000 T __errno_location
>
> This is exactly opposite to what is expected.
>
> Quoting Peter S. Mazinger, commit 87936cd013041 "errno and *_init cleanup"
>
>  | The rule adopted:
>  | for enabled threads we make in libc the __GI_x() variants strong, x() weak
>  | and (should) provide another strong x() in libpthread.
>  | If threads are disabled, even the __GI_x() variants are weak.
>
> With the fix, we see the right settings as below
>
>   00000000 T __GI___errno_location
>   00000000 W __errno_location
>
> Note that problem won't show up in a static busybox build as it references
> errno and that seems to elide the issue.
>
> I can confirm the same/more issues with latest ARM buildroot builds w/o
> my fix.
>
> (1). linuxthreads.old (broken just like ARC)
>
>   arm-linux-nm uclibc-snapshot/libc/misc/internals/__errno_location.os
>
>   00000000 W __GI___errno_location
>   00000000 T __errno_location
>
>   But presumably the issue there is NOT catestrophic because ARM linker is
>   likely smarter and patches a NOP instead of NULL branch.
>
>   00008388 <_stdio_init>:
>       8388:	e92d4038 	push	{r3, r4, r5, lr}
>       838c:	e320f000 	nop	{0}
>
> (2) NPTL build (exported version is not weak)
>
>   00000000 T __GI___errno_location
>   00000000 T __errno_location
>
>   This causes a static link with libpthread and test program
>   referencing errno to fail to link.
>
>   #include <errno.h>
>   int main(void)
>   {
>       printf("%d\n", errno);
>   }
>
>   arm-linux-gcc -static -pthread -o tst tst.o
>
>   arm-buildroot-linux-uclibcgnueabi/sysroot/usr/lib/libc.a(__errno_location.os):
>   In function `__errno_location':  __errno_location.c:(.text+0x0):
>                            multiple definition of `__errno_location'
>   arm-buildroot-linux-uclibcgnueabi/sysroot/usr/lib/libpthread.a
>             (errno_location.os):errno_location.c:(.text+0x0): first defined here
>
> Signed-off-by: Vineet Gupta <vgupta at synopsys.com>
> ---
>  libc/misc/internals/__errno_location.c | 2 +-
>  libc/sysdeps/linux/common/bits/errno.h | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/libc/misc/internals/__errno_location.c 
> b/libc/misc/internals/__errno_location.c
> index dec913f..be7a909 100644
> --- a/libc/misc/internals/__errno_location.c
> +++ b/libc/misc/internals/__errno_location.c
> @@ -16,4 +16,4 @@ int *__errno_location(void)
>  {
>      return &errno;
>  }
> -libc_hidden_def(__errno_location)
> +libc_hidden_weak(__errno_location)
> diff --git a/libc/sysdeps/linux/common/bits/errno.h 
> b/libc/sysdeps/linux/common/bits/errno.h
> index 7ef1b94..777338f 100644
> --- a/libc/sysdeps/linux/common/bits/errno.h
> +++ b/libc/sysdeps/linux/common/bits/errno.h
> @@ -43,7 +43,7 @@
>  /* Function to get address of global `errno' variable.  */
>  extern int *__errno_location (void) __THROW __attribute__ ((__const__));
>  #  ifdef _LIBC
> -#   ifndef __UCLIBC_HAS_TLS__
> +#   if !defined(__UCLIBC_HAS_TLS__) && !defined(__UCLIBC_HAS_THREADS__)
>  extern int weak_const_function *__errno_location(void);
>  #   endif
>  #  endif
> --
> 1.8.1.2
>
> _______________________________________________
> uClibc mailing list
> uClibc at uclibc.org
> http://lists.busybox.net/mailman/listinfo/uclibc



Sent with AquaMail for Android
http://www.aqua-mail.com