[PATCH] selftests: x86: add version check in test_syscall_vdso

Steve Muckle
2019-03-01T00:18:23Z

Since 4.17 registers r8-r11 are not clobbered/zeroed by a 64-bit kernel
handling a 32-bit syscall and this behavior is enforced by the
test_syscall_vdso testcase. See commit 8bb2610bc496
("x86/entry/64/compat: Preserve r8-r11 in int $0x80").

Permit the old behavior in the testcase for kernels prior to 4.17.

Signed-off-by: Steve Muckle <smuckle@google.com>
---
.../testing/selftests/x86/test_syscall_vdso.c | 30 +++++++++++++++++++
1 file changed, 30 insertions(+)

diff --git a/tools/testing/selftests/x86/test_syscall_vdso.c b/tools/testing/selftests/x86/test_syscall_vdso.c
index c9c3281077bc..f7284dc4c32b 100644
--- a/tools/testing/selftests/x86/test_syscall_vdso.c
+++ b/tools/testing/selftests/x86/test_syscall_vdso.c
@@ -30,6 +30,7 @@
#include <sys/time.h>
#include <elf.h>
#include <sys/ptrace.h>
+#include <sys/utsname.h>
#include <sys/wait.h>

#if !defined(__i386__)
@@ -71,6 +72,7 @@ struct regs64 {
};
struct regs64 regs64;
int kernel_is_64bit;
+int clobber_ok;

asm (
" .pushsection .text\n"
@@ -130,6 +132,28 @@ void print_regs64(void)
printf("12:%016llx 13:%016llx 14:%016llx 15:%016llx\n", regs64.r12, regs64.r13, regs64.r14, regs64.r15);
}

+static void get_kernel_version(int *version, int *patchlevel)
+{
+ int ret, sublevel;
+ struct utsname utsname;
+
+ ret = uname(&utsname);
+ if (ret) {
+ perror("uname");
+ exit(1);
+ }
+
+ ret = sscanf(utsname.release, "%d.%d.%d", version, patchlevel,
+ &sublevel);
+ if (ret < 0) {
+ perror("sscanf");
+ exit(1);
+ } else if (ret != 3) {
+ printf("Malformed kernel version %s\n", &utsname.release);
+ exit(1);
+ }
+}
+
int check_regs64(void)
{
int err = 0;
@@ -166,6 +190,8 @@ int check_regs64(void)
* Historically (and probably unintentionally), they
* were clobbered or zeroed.
*/
+ if (clobber_ok && *r64 == 0 && num <= 11)
+ continue;
}
printf("[FAIL]\tR%d has changed:%016llx\n", num, *r64);
err++;
@@ -385,6 +411,7 @@ int main(int argc, char **argv, char **envp)
{
int exitcode = 0;
int cs;
+ int version, patchlevel;

asm("\n"
" movl %%cs, %%eax\n"
@@ -394,6 +421,9 @@ int main(int argc, char **argv, char **envp)
if (!kernel_is_64bit)
printf("[NOTE]\tNot a 64-bit kernel, won't test R8..R15 leaks\n");

+ get_kernel_version(&version, &patchlevel);
+ clobber_ok = version < 4 || (version == 4 && patchlevel < 17);
+
/* This only works for non-static builds:
* syscall_addr = dlsym(dlopen("linux-gate.so.1", RTLD_NOW), "__kernel_vsyscall");
*/
--
2.21.0.352.gf09ad66450-goog