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-rw-r--r--tools/testing/selftests/x86/test_vsyscall.c22
1 files changed, 20 insertions, 2 deletions
diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
index c41f24b517f4..65c141ebfbbd 100644
--- a/tools/testing/selftests/x86/test_vsyscall.c
+++ b/tools/testing/selftests/x86/test_vsyscall.c
@@ -462,6 +462,17 @@ static int test_vsys_x(void)
return 0;
}
+/*
+ * Debuggers expect ptrace() to be able to peek at the vsyscall page.
+ * Use process_vm_readv() as a proxy for ptrace() to test this. We
+ * want it to work in the vsyscall=emulate case and to fail in the
+ * vsyscall=xonly case.
+ *
+ * It's worth noting that this ABI is a bit nutty. write(2) can't
+ * read from the vsyscall page on any kernel version or mode. The
+ * fact that ptrace() ever worked was a nice courtesy of old kernels,
+ * but the code to support it is fairly gross.
+ */
static int test_process_vm_readv(void)
{
#ifdef __x86_64__
@@ -477,8 +488,12 @@ static int test_process_vm_readv(void)
remote.iov_len = 4096;
ret = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);
if (ret != 4096) {
- printf("[OK]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", ret, errno);
- return 0;
+ /*
+ * We expect process_vm_readv() to work if and only if the
+ * vsyscall page is readable.
+ */
+ printf("[%s]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", vsyscall_map_r ? "FAIL" : "OK", ret, errno);
+ return vsyscall_map_r ? 1 : 0;
}
if (vsyscall_map_r) {
@@ -488,6 +503,9 @@ static int test_process_vm_readv(void)
printf("[FAIL]\tIt worked but returned incorrect data\n");
return 1;
}
+ } else {
+ printf("[FAIL]\tprocess_rm_readv() succeeded, but it should have failed in this configuration\n");
+ return 1;
}
#endif