To allow testing of vfork() support in the arm64 basic-gcs test provide an implementation for nolibc, using the vfork() syscall if one is available and otherwise clone3(). We implement in terms of clone3() since the order of the arguments for clone() varies between architectures.

Signed-off-by: Mark Brown broonie@kernel.org --- tools/include/nolibc/sys.h | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h index 9556c69a6ae1..e056da010f64 100644 --- a/tools/include/nolibc/sys.h +++ b/tools/include/nolibc/sys.h @@ -22,6 +22,7 @@ #include <linux/time.h> #include <linux/auxvec.h> #include <linux/fcntl.h> /* for O_* and AT_* */ +#include <linux/sched.h> /* for clone_args */ #include <linux/stat.h> /* for statx() */

#include "errno.h" @@ -340,6 +341,34 @@ pid_t fork(void) return __sysret(sys_fork()); }

+#ifndef sys_vfork +static __attribute__((unused)) +pid_t sys_vfork(void) +{ +#ifdef __NR_vfork + return my_syscall0(__NR_vfork); +#elif defined(__NR_clone3) + /* + * clone() could be used but has different argument orders per + * architecture. + */ + struct clone_args args = { + .flags = CLONE_VM | CLONE_VFORK, + .exit_signal = SIGCHLD, + }; + + return my_syscall2(__NR_clone3, &args, sizeof(args)); +#else + return __nolibc_enosys(__func__); +#endif +} +#endif + +static __attribute__((unused)) +pid_t vfork(void) +{ + return __sysret(sys_vfork()); +}

/* * int fsync(int fd);

Ensure that we've got at least some coverage of the special cases around vfork() by adding a test case in basic-gcs doing the same thing as the plain fork() one - vfork(), do a few checks and then return to the parent.

Signed-off-by: Mark Brown broonie@kernel.org --- tools/testing/selftests/arm64/gcs/basic-gcs.c | 63 +++++++++++++++++++++++++++ 1 file changed, 63 insertions(+)

diff --git a/tools/testing/selftests/arm64/gcs/basic-gcs.c b/tools/testing/selftests/arm64/gcs/basic-gcs.c index 3fb9742342a3..96ea51cf7163 100644 --- a/tools/testing/selftests/arm64/gcs/basic-gcs.c +++ b/tools/testing/selftests/arm64/gcs/basic-gcs.c @@ -298,6 +298,68 @@ static bool test_fork(void) return pass; }

+/* A vfork()ed process can run and exit */ +static bool test_vfork(void) +{ + unsigned long child_mode; + int ret, status; + pid_t pid; + bool pass = true; + + pid = vfork(); + if (pid == -1) { + ksft_print_msg("vfork() failed: %d\n", errno); + pass = false; + goto out; + } + if (pid == 0) { + /* In child, make sure we can call a function, read + * the GCS pointer and status and then exit */ + valid_gcs_function(); + get_gcspr(); + + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, + &child_mode, 0, 0, 0); + if (ret == 0 && !(child_mode & PR_SHADOW_STACK_ENABLE)) { + ksft_print_msg("GCS not enabled in child\n"); + ret = -EINVAL; + } + + exit(ret); + } + + /* + * In parent, check we can still do function calls then block + * for the child. + */ + valid_gcs_function(); + + ksft_print_msg("Waiting for child %d\n", pid); + + ret = waitpid(pid, &status, 0); + if (ret == -1) { + ksft_print_msg("Failed to wait for child: %d\n", + errno); + return false; + } + + if (!WIFEXITED(status)) { + ksft_print_msg("Child exited due to signal %d\n", + WTERMSIG(status)); + pass = false; + } else { + if (WEXITSTATUS(status)) { + ksft_print_msg("Child exited with status %d\n", + WEXITSTATUS(status)); + pass = false; + } + } + +out: + + return pass; +} + typedef bool (*gcs_test)(void);

static struct { @@ -314,6 +376,7 @@ static struct { { "enable_invalid", enable_invalid, true }, { "map_guarded_stack", map_guarded_stack }, { "fork", test_fork }, + { "vfork", test_vfork }, };

int main(void)