| 41 | #endif |
| 42 | |
| 43 | int openat2_usable(void) |
| 44 | { |
| 45 | #if defined(__ANDROID__) && defined(HAVE_OPENAT2) |
| 46 | static int cached = -1; |
| 47 | struct sigaction sa, old_sa; |
| 48 | |
| 49 | if (cached >= 0) |
| 50 | return cached; |
| 51 | |
| 52 | memset(&sa, 0, sizeof sa); |
| 53 | sa.sa_handler = openat2_probe_handler; |
| 54 | sigemptyset(&sa.sa_mask); |
| 55 | if (sigaction(SIGSYS, &sa, &old_sa) != 0) |
| 56 | return cached = 0; |
| 57 | |
| 58 | if (sigsetjmp(openat2_probe_env, 1) != 0) { |
| 59 | /* SIGSYS delivered: openat2 is blocked by a seccomp filter. */ |
| 60 | cached = 0; |
| 61 | } else { |
| 62 | struct open_how how; |
| 63 | int fd; |
| 64 | memset(&how, 0, sizeof how); |
| 65 | how.flags = O_RDONLY | O_DIRECTORY; |
| 66 | how.resolve = RESOLVE_BENEATH | RESOLVE_NO_MAGICLINKS; |
| 67 | fd = syscall(SYS_openat2, AT_FDCWD, ".", &how, sizeof how); |
| 68 | if (fd >= 0) |
| 69 | close(fd); |
| 70 | /* Usable only if the probe actually succeeded. Any failure -- |
| 71 | * ENOSYS (kernel < 5.6), a seccomp SECCOMP_RET_ERRNO denial |
| 72 | * (EPERM/EACCES), or EINVAL (RESOLVE_BENEATH unsupported) -- |
| 73 | * means we must fall back to the portable O_NOFOLLOW walk. */ |
| 74 | cached = fd >= 0; |
| 75 | } |
| 76 | |
| 77 | sigaction(SIGSYS, &old_sa, NULL); |
| 78 | return cached; |
| 79 | #else |
| 80 | return 1; |
| 81 | #endif |
| 82 | } |
no test coverage detected