In preparation for setting syscall nr and ret values separately, refactor the helpers to take a pointer to a value, so that a NULL can indicate "do not change this respective value". This is done to keep the regset read/write happening once and in one code path.
Signed-off-by: Kees Cook keescook@chromium.org --- tools/testing/selftests/seccomp/seccomp_bpf.c | 59 +++++++++++++++---- 1 file changed, 47 insertions(+), 12 deletions(-)
diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index c0311b4c736b..98ce5e8a6398 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -1888,27 +1888,47 @@ int get_syscall(struct __test_metadata *_metadata, pid_t tracee) }
/* Architecture-specific syscall changing routine. */ -void change_syscall(struct __test_metadata *_metadata, - pid_t tracee, int syscall, int result) +void __change_syscall(struct __test_metadata *_metadata, + pid_t tracee, long *syscall, long *ret) { ARCH_REGS orig, regs;
+ /* Do not get/set registers if we have nothing to do. */ + if (!syscall && !ret) + return; + EXPECT_EQ(0, ARCH_GETREGS(regs)) { return; } orig = regs;
- SYSCALL_NUM_SET(regs, syscall); + if (syscall) + SYSCALL_NUM_SET(regs, *syscall);
- /* If syscall is skipped, change return value. */ - if (syscall == -1) - SYSCALL_RET_SET(regs, result); + if (ret) + SYSCALL_RET_SET(regs, *ret);
/* Flush any register changes made. */ if (memcmp(&orig, ®s, sizeof(orig)) != 0) EXPECT_EQ(0, ARCH_SETREGS(regs)); }
+/* Change only syscall number. */ +void change_syscall_nr(struct __test_metadata *_metadata, + pid_t tracee, long syscall) +{ + __change_syscall(_metadata, tracee, &syscall, NULL); +} + +/* Change syscall return value (and set syscall number to -1). */ +void change_syscall_ret(struct __test_metadata *_metadata, + pid_t tracee, long ret) +{ + long syscall = -1; + + __change_syscall(_metadata, tracee, &syscall, &ret); +} + void tracer_seccomp(struct __test_metadata *_metadata, pid_t tracee, int status, void *args) { @@ -1924,17 +1944,17 @@ void tracer_seccomp(struct __test_metadata *_metadata, pid_t tracee, case 0x1002: /* change getpid to getppid. */ EXPECT_EQ(__NR_getpid, get_syscall(_metadata, tracee)); - change_syscall(_metadata, tracee, __NR_getppid, 0); + change_syscall_nr(_metadata, tracee, __NR_getppid); break; case 0x1003: /* skip gettid with valid return code. */ EXPECT_EQ(__NR_gettid, get_syscall(_metadata, tracee)); - change_syscall(_metadata, tracee, -1, 45000); + change_syscall_ret(_metadata, tracee, 45000); break; case 0x1004: /* skip openat with error. */ EXPECT_EQ(__NR_openat, get_syscall(_metadata, tracee)); - change_syscall(_metadata, tracee, -1, -ESRCH); + change_syscall_ret(_metadata, tracee, -ESRCH); break; case 0x1005: /* do nothing (allow getppid) */ @@ -1961,6 +1981,8 @@ void tracer_ptrace(struct __test_metadata *_metadata, pid_t tracee, int ret; unsigned long msg; static bool entry; + long syscall_nr_val, syscall_ret_val; + long *syscall_nr = NULL, *syscall_ret = NULL; FIXTURE_DATA(TRACE_syscall) *self = args;
/* @@ -1987,17 +2009,30 @@ void tracer_ptrace(struct __test_metadata *_metadata, pid_t tracee, else return;
+ syscall_nr = &syscall_nr_val; + syscall_ret = &syscall_ret_val; + + /* Now handle the actual rewriting cases. */ switch (self->syscall_nr) { case __NR_getpid: - change_syscall(_metadata, tracee, __NR_getppid, 0); + syscall_nr_val = __NR_getppid; + /* Never change syscall return for this case. */ + syscall_ret = NULL; break; case __NR_gettid: - change_syscall(_metadata, tracee, -1, 45000); + syscall_nr_val = -1; + syscall_ret_val = 45000; break; case __NR_openat: - change_syscall(_metadata, tracee, -1, -ESRCH); + syscall_nr_val = -1; + syscall_ret_val = -ESRCH; break; + default: + /* Unhandled, do nothing. */ + return; } + + __change_syscall(_metadata, tracee, syscall_nr, syscall_ret); }
FIXTURE_VARIANT(TRACE_syscall) {