The patch titled
Subject: proc: save LOC in vsyscall test
has been added to the -mm mm-nonmm-unstable branch. Its filename is
proc-save-loc-in-vsyscall-test.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/proc-save-loc-in-vsyscall-test.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Brian Foster <bfoster@xxxxxxxxxx>
Subject: proc: save LOC in vsyscall test
Date: Mon, 15 Aug 2022 12:50:04 +0300
Do one fork in vsyscall detection code and let SIGSEGV handler exit and
carry information to the parent saving LOC.
[adobriyan@xxxxxxxxx: redo original patch, delete unnecessary variables, minimise code changes]
Link: https://lkml.kernel.org/r/YvoWzAn5dlhF75xa@localhost.localdomain
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Tested-by: Brian Foster <bfoster@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/proc/proc-pid-vm.c | 56 +++++--------------
1 file changed, 16 insertions(+), 40 deletions(-)
--- a/tools/testing/selftests/proc/proc-pid-vm.c~proc-save-loc-in-vsyscall-test
+++ a/tools/testing/selftests/proc/proc-pid-vm.c
@@ -213,22 +213,22 @@ static int make_exe(const uint8_t *paylo
/*
* 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)
_
Patches currently in -mm which might be from bfoster@xxxxxxxxxx are
proc-save-loc-in-vsyscall-test.patch
