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From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: libc-alpha@sourceware.org
Subject: Re: [PATCH] S390: Fix backtrace in vdso functions.
Date: Tue, 28 Nov 2017 13:09:00 -0000	[thread overview]
Message-ID: <6698d098-aea3-14cc-8ed7-762def848dc9@linaro.org> (raw)
In-Reply-To: <ead922fd-1eb9-3781-345d-6a2ea63ecd01@linux.vnet.ibm.com>



On 28/11/2017 10:44, Stefan Liebler wrote:
> Hi,
> 
> On s390, GDB fails to show the complete backtrace from within vdso functions. The macro INTERNAL_VSYSCALL_CALL saves the return address in r14 to r10 before branching to the vdso function. The branch-instruction updates r14 in order to let the vdso function return. Then the original address in r14 is restored from r10. Unfortunately, there are no cfi-rules and GDB fails.
> 
> Furthermore the call of the vdso function does not comply with the s390 ABI as no stack-frame for the vdso-function is generated.
> 
> This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL and the common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h is used. Then the vdso function is called via function-pointer and GCC generates a new stack-frame and emits all needed cfi-rules.
> 
> The defines CLOBBER_[0-6] are removed as they  were only used in macro INTERNAL_VSYSCALL_CALL.
> 
> The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390. The only user is power. Thus it is removed from s390 sysdep.h.

I am almost sure we can remove it for powerpc as well (I can't see
no immediate gain on doing a function call using inline assembly
as for INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc). 


> 
> ChangeLog:
> 
>     * sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
>     (INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
>      CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
>     INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
>     * sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

  reply	other threads:[~2017-11-28 13:09 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-28 12:44 Stefan Liebler
2017-11-28 13:09 ` Adhemerval Zanella [this message]
2017-11-28 14:18   ` Florian Weimer
2017-11-28 15:53     ` Adhemerval Zanella
2017-11-28 16:35       ` Adhemerval Zanella
2017-12-04  8:00   ` Stefan Liebler
2017-12-04 10:48     ` Adhemerval Zanella
2017-12-04 15:42       ` Stefan Liebler

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