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: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Tested-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/proc/proc-pid-vm.c b/tools/testing/selftests/proc/proc-pid-vm.c
index e5962f4..69551bf 100644 (file)
--- a/tools/testing/selftests/proc/proc-pid-vm.c
+++ b/tools/testing/selftests/proc/proc-pid-vm.c
@@ -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)