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

[Leizhen (ThunderTown)]

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
/******************************************************************************/
/* Copyright (c) Crackerjack Project., 2007                                   */
/*                                                                            */
/* This program is free software;  you can redistribute it and/or modify      */
/* it under the terms of the GNU General Public License as published by       */
/* the Free Software Foundation; either version 2 of the License, or          */
/* (at your option) any later version.                                        */
/*                                                                            */
/* This program is distributed in the hope that it will be useful,            */
/* but WITHOUT ANY WARRANTY;  without even the implied warranty of            */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See                  */
/* the GNU General Public License for more details.                           */
/*                                                                            */
/* You should have received a copy of the GNU General Public License          */
/* along with this program;  if not, write to the Free Software Foundation,   */
/* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA           */
/*                                                                            */
/* History:     Porting from Crackerjack to LTP is done by                    */
/*              Manas Kumar Nayak maknayak@xxxxxxxxxx>                        */
/******************************************************************************/

/******************************************************************************/
/* Description: This tests the rt_sigaction() syscall                         */
/*		rt_sigaction alters an action taken by a process on receipt   */
/* 		of a particular signal. The action is specified by the        */
/*		sigaction structure. The previous action on the signal is     */
/*		saved in oact.sigsetsize should indicate the size of a        */
/*		sigset_t type.                       			      */
/******************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <sys/syscall.h>
#include <string.h>

#include "test.h"
#include "linux_syscall_numbers.h"
#include "lapi/rt_sigaction.h"

char *TCID = "rt_sigaction01";
static int testno;
int TST_TOTAL = 1;

static void cleanup(void)
{
	tst_rmdir();
}

static void setup(void)
{
	TEST_PAUSE;
	tst_tmpdir();
}

static int test_flags[] =
    { SA_RESETHAND | SA_SIGINFO, SA_RESETHAND, SA_RESETHAND | SA_SIGINFO,
SA_RESETHAND | SA_SIGINFO, SA_NOMASK };
char *test_flags_list[] =
    { "SA_RESETHAND|SA_SIGINFO", "SA_RESETHAND", "SA_RESETHAND|SA_SIGINFO",
"SA_RESETHAND|SA_SIGINFO", "SA_NOMASK" };

static void handler(int sig)
{
	tst_resm(TINFO, "Signal Handler Called with signal number %d\n", sig);
	return;
}

static int set_handler(int sig, int sig_to_mask, int mask_flags)
{
	struct sigaction sa, oldaction;

	sa.sa_handler = (void *)handler;
	sa.sa_flags = mask_flags;
	sigemptyset(&sa.sa_mask);
	sigaddset(&sa.sa_mask, sig);

	return ltp_rt_sigaction(sig, &sa, &oldaction, SIGSETSIZE);
}

int main(int ac, char **av)
{
	unsigned int flag;
	int signal;
	int lc;

	tst_parse_opts(ac, av, NULL, NULL);

	setup();

	for (lc = 0; TEST_LOOPING(lc); ++lc) {

		tst_count = 0;

		for (testno = 0; testno < TST_TOTAL; ++testno) {

			for (signal = SIGRTMIN; signal <= SIGRTMAX; signal++) {
				for (flag = 0;
				     flag <
				     (sizeof(test_flags) /
				      sizeof(test_flags[0])); flag++) {

					TEST(set_handler
					     (signal, 0, test_flags[flag]));

					if (TEST_RETURN == 0) {
						tst_resm(TINFO, "signal: %d ",
							 signal);
						tst_resm(TPASS,
							 "rt_sigaction call succeeded: result = %ld ",
							 TEST_RETURN);
						tst_resm(TINFO,
							 "sa.sa_flags = %s ",
							 test_flags_list[flag]);
						kill(getpid(), signal);
					} else {
						tst_resm(TFAIL | TTERRNO,
							 "rt_sigaction call "
							 "failed");
					}

				}

			}

		}

	}
	cleanup();
	tst_exit();
}