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

Leizhen (ThunderTown)
2018-06-05T11:27:11Z

[-- Attachment #1: Type: text/plain, Size: 1092 bytes --]

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

[-- Attachment #2: rt_sigaction01.c --]
[-- Type: text/plain, Size: 4191 bytes --]

/******************************************************************************/
/* 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@in.ibm.com> */
/******************************************************************************/

/******************************************************************************/
/* 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();
}