Commit f4068af3 authored by Brian Foster's avatar Brian Foster Committed by Andrew Morton
Browse files

proc: save LOC in vsyscall test 

Do one fork in vsyscall detection code and let SIGSEGV handler exit and
carry information to the parent saving LOC.

[adobriyan@gmail.com: redo original patch, delete unnecessary variables, minimise code changes]
Link: https://lkml.kernel.org/r/YvoWzAn5dlhF75xa@localhost.localdomain


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: default avatarBrian Foster <bfoster@redhat.com>
Reviewed-by: default avatarBrian Foster <bfoster@redhat.com>
Tested-by: default avatarBrian Foster <bfoster@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4f1d2a03

tools/testing/selftests/proc/proc-pid-vm.c

+16 −40
Original line number Diff line number Diff line
@@ -213,22 +213,22 @@ static int make_exe(const uint8_t *payload, size_t len) 


/*

 * 0: vsyscall VMA doesn't exist	vsyscall=none

 * 1: vsyscall VMA is r-xp		vsyscall=emulate

 * 2: vsyscall VMA is --xp		vsyscall=xonly

 * 1: vsyscall VMA is --xp		vsyscall=xonly

 * 2: vsyscall VMA is r-xp		vsyscall=emulate

 */

static int g_vsyscall;

static volatile int g_vsyscall;

static const char *str_vsyscall;



static const char str_vsyscall_0[] = "";

static const char str_vsyscall_1[] =

"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]\n";

static const char str_vsyscall_2[] =

"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0                  [vsyscall]\n";

static const char str_vsyscall_2[] =

"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]\n";



#ifdef __x86_64__

static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___)

{

	_exit(1);

	_exit(g_vsyscall);

}



/*
@@ -255,6 +255,7 @@ static void vsyscall(void) 
		act.sa_sigaction = sigaction_SIGSEGV;

		(void)sigaction(SIGSEGV, &act, NULL);



		g_vsyscall = 0;

		/* gettimeofday(NULL, NULL); */

		asm volatile (

			"call %P0"
@@ -262,45 +263,20 @@ static void vsyscall(void) 
			: "i" (0xffffffffff600000), "D" (NULL), "S" (NULL)

			: "rax", "rcx", "r11"

		);

		exit(0);

	}

	waitpid(pid, &wstatus, 0);

	if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0) {

		/* vsyscall page exists and is executable. */

	} else {

		/* vsyscall page doesn't exist. */

		g_vsyscall = 0;

		return;

	}



	pid = fork();

	if (pid < 0) {

		fprintf(stderr, "fork, errno %d\n", errno);

		exit(1);

	}

	if (pid == 0) {

		struct rlimit rlim = {0, 0};

		(void)setrlimit(RLIMIT_CORE, &rlim);



		/* Hide "segfault at ffffffffff600000" messages. */

		struct sigaction act;

		memset(&act, 0, sizeof(struct sigaction));

		act.sa_flags = SA_SIGINFO;

		act.sa_sigaction = sigaction_SIGSEGV;

		(void)sigaction(SIGSEGV, &act, NULL);



		g_vsyscall = 1;

		*(volatile int *)0xffffffffff600000UL;

		exit(0);



		g_vsyscall = 2;

		exit(g_vsyscall);

	}

	waitpid(pid, &wstatus, 0);

	if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0) {

		/* vsyscall page is readable and executable. */

		g_vsyscall = 1;

		return;

	if (WIFEXITED(wstatus)) {

		g_vsyscall = WEXITSTATUS(wstatus);

	} else {

		fprintf(stderr, "error: wstatus %08x\n", wstatus);

		exit(1);

	}



	/* vsyscall page is executable but unreadable. */

	g_vsyscall = 2;

}



int main(void)