linux-kernel - [Question] Can we use SIGRTMIN when vdso disabled on X86?

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Message-ID: <5B1672FE.4050705@huawei.com>
Date:   Tue, 5 Jun 2018 19:24:46 +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>
Subject: [Question] Can we use SIGRTMIN when vdso disabled on X86?

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

View attachment "rt_sigaction01.c" of type "text/plain" (4191 bytes)