On Feb 28, 2019, at 4:18 PM, Steve Muckle smuckle@google.com wrote:

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.

NAK. If you want an old buggy kernel to pass a test, please either patch the kernel or run an old test.

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