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Subject: Is this a kernel BUG? ///Re: [Question] Can we use SIGRTMIN when vdso
 disabled on X86?
To:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86l <x86@kernel.org>,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Andy Lutomirski <luto@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <5B1672FE.4050705@huawei.com>
CC:     <yaomin2@huawei.com>
From:   "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
Message-ID: <5B1792C9.8010203@huawei.com>
Date:   Wed, 6 Jun 2018 15:52:41 +0800
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On 2018/6/5 19:24, Leizhen (ThunderTown) wrote:
> After I executed "echo 0 > /proc/sys/abi/vsyscall32" to disable vdso, the rt_sigaction01 test case from ltp_2015 failed.
> The test case source code please refer to the attachment, and the output as blow:
> 
> -----------------
> ./rt_sigaction01
> rt_sigaction01    0  TINFO  :  signal: 34
> rt_sigaction01    1  TPASS  :  rt_sigaction call succeeded: result = 0
> rt_sigaction01    0  TINFO  :  sa.sa_flags = SA_RESETHAND|SA_SIGINFO
> rt_sigaction01    0  TINFO  :  Signal Handler Called with signal number 34
> 
> Segmentation fault
> ------------------
> 
> 
> Is this the desired result? In function ia32_setup_rt_frame, I found below code:
> 
> 	if (ksig->ka.sa.sa_flags & SA_RESTORER)
> 		restorer = ksig->ka.sa.sa_restorer;
> 	else
> 		restorer = current->mm->context.vdso +
> 			vdso_image_32.sym___kernel_rt_sigreturn;
> 	put_user_ex(ptr_to_compat(restorer), &frame->pretcode);
> 
> Because the vdso is disabled, so current->mm->context.vdso is NULL, which cause the result of frame->pretcode invalid.
> 
> I'm not sure whether this is a kernel bug or just an error of test case itself. Can anyone help me?
> 

-- 
Thanks!
BestRegards