BSD syscall#444
svc · unix #444
change_fdguard_np
Attaches, removes or rotates a guard value on an existing file descriptor.
Prototype
int change_fdguard_np(int fd, const guardid_t *guard, u_int guardflags, const guardid_t *nguard, u_int nguardflags, int *fdflagsp);Returns: int
Arguments
| Name | Type | Dir | Description |
|---|---|---|---|
| fd | int | - | |
| guard | const guardid_t | - | |
| guardflags | u_int | - | |
| nguard | const guardid_t | - | |
| nguardflags | u_int | - | |
| fdflagsp | int | - |
Version history
| XNU tag | macOS | # |
|---|---|---|
| xnu-2422.115.4 | macOS 10.9 Mavericks | 444 |
| xnu-2782.40.9 | macOS 10.10 Yosemite | 444 |
| xnu-3247.1.106 | macOS 10.11 El Capitan | 444 |
| xnu-3789.1.32 | macOS 10.12 Sierra | 444 |
| xnu-4570.1.46 | macOS 10.13 High Sierra | 444 |
| xnu-4903.221.2 | macOS 10.14 Mojave | 444 |
| xnu-6153.11.26 | macOS 10.15 Catalina | 444 |
| xnu-7195.50.7.100.1 | macOS 11.0 Big Sur | 444 |
| xnu-8019.41.5 | macOS 12.0 Monterey | 444 |
| xnu-8792.41.9 | macOS 13.0 Ventura | 444 |
| xnu-10002.1.13 | macOS 14.0 Sonoma | 444 |
| xnu-11215.1.10 | macOS 15.0 Sequoia | 444 |
| xnu-11417.101.15 | macOS 15.4 Sequoia | 444 |
| xnu-12377.1.9 | macOS 26.0 Tahoe | 444 |
| xnu-10002.41.9 | — | 444 |
| xnu-10002.61.3 | — | 444 |
| xnu-10002.81.5 | — | 444 |
| xnu-10063.101.15 | — | 444 |
| xnu-10063.121.3 | — | 444 |
| xnu-10063.141.1 | — | 444 |
| xnu-11215.41.3 | — | 444 |
| xnu-11215.61.5 | — | 444 |
| xnu-11215.81.4 | — | 444 |
| xnu-11417.121.6 | — | 444 |
| xnu-11417.140.69 | — | 444 |
| xnu-12377.101.15 | — | 444 |
| xnu-12377.41.6 | — | 444 |
| xnu-12377.61.12 | — | 444 |
| xnu-12377.81.4 | — | 444 |
| xnu-2422.1.72 | — | 444 |
| xnu-2422.100.13 | — | 444 |
| xnu-2422.110.17 | — | 444 |
| xnu-2422.90.20 | — | 444 |
| xnu-2782.1.97 | — | 444 |
| xnu-2782.10.72 | — | 444 |
| xnu-2782.20.48 | — | 444 |
| xnu-2782.30.5 | — | 444 |
| xnu-3247.10.11 | — | 444 |
| xnu-3248.20.55 | — | 444 |
| xnu-3248.30.4 | — | 444 |
| xnu-3248.40.184 | — | 444 |
| xnu-3248.50.21 | — | 444 |
| xnu-3248.60.10 | — | 444 |
| xnu-3789.21.4 | — | 444 |
| xnu-3789.31.2 | — | 444 |
| xnu-3789.41.3 | — | 444 |
| xnu-3789.51.2 | — | 444 |
| xnu-3789.60.24 | — | 444 |
| xnu-3789.70.16 | — | 444 |
| xnu-4570.20.62 | — | 444 |
| xnu-4570.31.3 | — | 444 |
| xnu-4570.41.2 | — | 444 |
| xnu-4570.51.1 | — | 444 |
| xnu-4570.61.1 | — | 444 |
| xnu-4570.71.2 | — | 444 |
| xnu-4903.231.4 | — | 444 |
| xnu-4903.241.1 | — | 444 |
| xnu-4903.270.47 | — | 444 |
| xnu-6153.101.6 | — | 444 |
| xnu-6153.121.1 | — | 444 |
| xnu-6153.141.1 | — | 444 |
| xnu-6153.41.3 | — | 444 |
| xnu-6153.61.1 | — | 444 |
| xnu-6153.81.5 | — | 444 |
| xnu-7195.101.1 | — | 444 |
| xnu-7195.121.3 | — | 444 |
| xnu-7195.141.2 | — | 444 |
| xnu-7195.60.75 | — | 444 |
| xnu-7195.81.3 | — | 444 |
| xnu-8019.61.5 | — | 444 |
| xnu-8019.80.24 | — | 444 |
| xnu-8020.101.4 | — | 444 |
| xnu-8020.121.3 | — | 444 |
| xnu-8020.140.41 | — | 444 |
| xnu-8792.61.2 | — | 444 |
| xnu-8792.81.2 | — | 444 |
| xnu-8796.101.5 | — | 444 |
| xnu-8796.121.2 | — | 444 |
| xnu-8796.141.3 | — | 444 |
Notes
Guarded fds carry a 64-bit cookie that must be presented on every operation; violations raise EXC_GUARD and typically terminate the process. change_fdguard_np lets a process upgrade a plain fd into a guarded one, swap one guard for another, or downgrade. The new guard's flags (GUARD_CLOSE, GUARD_DUP, GUARD_FILEPORT, GUARD_WRITE) determine which operations will trap.
Detection
Resulting EXC_GUARD exceptions are visible to ReportCrash and to any Mach exception port subscriber (CrashReporter, debuggers, EDR exception observers). DTrace fbt::change_fdguard_np:entry is the proactive observation point.
Related APIs
guarded_close_npguarded_kqueue_npguarded_open_npguarded_pwrite_np