On 09/10/2015 04:30 AM, Kees Cook wrote:
The syscall ABI is inconsistent on aarch64 compat, so at least we should document it in the seccomp_bpf tests. Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- Can someone with access to native aarch64 double-check this for me? I think we need to change these tests to pass if it's expected, but the compat behavior seems bad. It means compat code will break under an aarch64 kernel, when dealing with syscalls, like through seccomp. --- tools/testing/selftests/seccomp/seccomp_bpf.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index 770f47adf295..866ff42e000d 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -33,6 +33,10 @@ #include <unistd.h> #include <sys/syscall.h> +#if defined(__aarch64__) && !defined(__NR_poll) +# define __NR_poll 0x49 +#endif + #include "test_harness.h" #ifndef PR_SET_PTRACER @@ -2124,10 +2128,17 @@ TEST(syscall_restart) ASSERT_EQ(SIGTRAP, WSTOPSIG(status)); ASSERT_EQ(PTRACE_EVENT_SECCOMP, (status >> 16)); ASSERT_EQ(0, ptrace(PTRACE_GETEVENTMSG, child_pid, NULL, &msg)); - ASSERT_EQ(0x200, msg); + + /* + * FIXME: + * - native ARM does not expose true syscall. + * - compat ARM on ARM64 does expose true syscall. + * - native ARM64 hides true syscall even from seccomp.
Are you sure about the last line? The kernel pushes __NR_compat_restart_syscall to w7 in compat mode, while __NR_restart_syscall to x8 in native mode. But it is the only difference, as far as I understand, in terms of restarting a system call. So the behavior should be basically the same. -Takahiro AKASHI
+ */ + ASSERT_EQ(0x200, msg); /* This will fail on native arm64. */ ret = get_syscall(_metadata, child_pid); #if defined(__arm__) - /* FIXME: ARM does not expose true syscall in registers. */ + /* This will fail on arm64 in compat mode. */ EXPECT_EQ(__NR_poll, ret); #else EXPECT_EQ(__NR_restart_syscall, ret);
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