linux-kernel - Re: Is this a kernel BUG? ///Re: [Question] Can we use SIGRTMIN when vdso disabled on X86?

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Date:   Wed, 6 Jun 2018 17:17:42 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86l <x86@...nel.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Andy Lutomirski <luto@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
CC:     <yaomin2@...wei.com>, Thunder Town <thunder.leizhen@...wei.com>
Subject: Re: Is this a kernel BUG? ///Re: [Question] Can we use SIGRTMIN when
 vdso disabled on X86?

I found that glibc has already dealt with this case. So this issue must have been met before, should it be maintained by libc/user?

	if (GLRO(dl_sysinfo_dso) == NULL)
	{
		kact.sa_flags |= SA_RESTORER;

		kact.sa_restorer = ((act->sa_flags & SA_SIGINFO)
			? &restore_rt : &restore);
	}


On 2018/6/6 15:52, Leizhen (ThunderTown) wrote:
> 
> 
> 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