Ping^2 !
On 10/04/2013 03:35 PM, Vineet Gupta 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
>
> 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 <vgu...@synopsys.com>
> Cc: Baruch Siach <bar...@tkos.co.il>
> ---
> include/netdb.h | 2 +-
> libc/misc/internals/__errno_location.c | 2 +-
> libc/misc/internals/__h_errno_location.c | 2 +-
> libc/sysdeps/linux/common/bits/errno.h | 2 +-
> 4 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/netdb.h b/include/netdb.h
> index 14cf3d24dae0..8fdfa0fccc7d 100644
> --- a/include/netdb.h
> +++ b/include/netdb.h
> @@ -59,7 +59,7 @@ __BEGIN_DECLS
> /* Function to get address of global `h_errno' variable. */
> extern int *__h_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 *__h_errno_location(void);
> # endif
> #endif
> diff --git a/libc/misc/internals/__errno_location.c
> b/libc/misc/internals/__errno_location.c
> index dec913f3031d..be7a9093efa3 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/misc/internals/__h_errno_location.c
> b/libc/misc/internals/__h_errno_location.c
> index 41353d74a648..6653681cbf09 100644
> --- a/libc/misc/internals/__h_errno_location.c
> +++ b/libc/misc/internals/__h_errno_location.c
> @@ -16,4 +16,4 @@ int *__h_errno_location(void)
> {
> return &h_errno;
> }
> -libc_hidden_def(__h_errno_location)
> +libc_hidden_weak(__h_errno_location)
> diff --git a/libc/sysdeps/linux/common/bits/errno.h
> b/libc/sysdeps/linux/common/bits/errno.h
> index 7ef1b9440a34..777338fb1e0a 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
>
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