* Re: [2.32] struct _Unwind_Exception alignment should not depend on compiler flags
[not found] <20201116204659.40340-1-msc@linux.ibm.com>
@ 2020-11-16 20:49 ` Matheus Castanho
0 siblings, 0 replies; only message in thread
From: Matheus Castanho @ 2020-11-16 20:49 UTC (permalink / raw)
To: tuliom, fweimer, Libc-stable Mailing List
Sorry, sent to the wrong list.
- libc-alpha
+ libc-stable
On 11/16/20 5:46 PM, Matheus Castanho via Libc-alpha wrote:
> From: Florian Weimer <fweimer@redhat.com>
>
> Hi Florian and Tulio,
>
> Could we backport this patch to the 2.32 branch? It would be helpful to fix the
> issue downstream.
>
> Thanks,
> Matheus Castanho
>
> ---8<---
>
> __attribute__((__aligned__)) selects an alignment that depends on
> the micro-architecture selected by GCC flags. Enabling vector
> extensions may increase the allignment. This is a problem when
> building glibc as a collection of ELF multilibs with different
> GCC flags because ld.so and libc.so/libpthread.so/&c may end up
> with a different layout of struct pthread because of the
> changing offset of its struct _Unwind_Exception field.
>
> Tested-By: Matheus Castanho <msc@linux.ibm.com>
>
> (cherry picked from commit 30af7c7fa13e17d82c3f1f91536384715844f432)
> ---
> sysdeps/generic/unwind.h | 24 +++++++++++++++---------
> 1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/sysdeps/generic/unwind.h b/sysdeps/generic/unwind.h
> index b667a5b652..c229603af3 100644
> --- a/sysdeps/generic/unwind.h
> +++ b/sysdeps/generic/unwind.h
> @@ -75,15 +75,21 @@ typedef void (*_Unwind_Exception_Cleanup_Fn) (_Unwind_Reason_Code,
>
> struct _Unwind_Exception
> {
> - _Unwind_Exception_Class exception_class;
> - _Unwind_Exception_Cleanup_Fn exception_cleanup;
> - _Unwind_Word private_1;
> - _Unwind_Word private_2;
> -
> - /* @@@ The IA-64 ABI says that this structure must be double-word aligned.
> - Taking that literally does not make much sense generically. Instead we
> - provide the maximum alignment required by any type for the machine. */
> -} __attribute__((__aligned__));
> + union
> + {
> + struct
> + {
> + _Unwind_Exception_Class exception_class;
> + _Unwind_Exception_Cleanup_Fn exception_cleanup;
> + _Unwind_Word private_1;
> + _Unwind_Word private_2;
> + };
> +
> + /* The IA-64 ABI says that this structure must be double-word aligned. */
> + _Unwind_Word unwind_exception_align[2]
> + __attribute__ ((__aligned__ (2 * sizeof (_Unwind_Word))));
> + };
> +};
>
>
> /* The ACTIONS argument to the personality routine is a bitwise OR of one
> --
> 2.26.2
>
^ permalink raw reply [flat|nested] only message in thread