feat: implement utimensat and futimens syscalls #617
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Add support for the utimensat(2) and futimens(3) syscalls which allow setting file access and modification times with nanosecond precision. Changes: - Add UTIME_NOW (0x3fffffff) and UTIME_OMIT (0x3ffffffe) constants - Add Timespec helper methods for validating utimensat arguments - Add SetTimesError enum for filesystem time-setting errors - Add set_times() and fd_set_times() methods to FileSystem trait - Implement sys_utimensat() with full path resolution and flag handling - Implement sys_futimens() for fd-based timestamp modification - Support AT_SYMLINK_NOFOLLOW and AT_EMPTY_PATH flags The implementation uses the platform's TimeProvider for current time and includes proper validation of the Timespec nanosecond fields. Filesystems that don't track timestamps can use the default no-op implementations. TODO items documented in code: - AT_SYMLINK_NOFOLLOW not fully supported until symlinks are implemented - FdRelative path resolution not yet implemented - Permission checks are simplified (allow all changes)
Review feedback addressed:
1. Add EINVAL check for AT_SYMLINK_NOFOLLOW with NULL pathname
- Per Linux man page: return EINVAL when pathname is NULL, dirfd
is not AT_FDCWD, and flags contains AT_SYMLINK_NOFOLLOW
2. Return Ok(()) for pipes and sockets instead of ENOENT
- Linux silently succeeds on these fd types (no-op)
- ENOENT was semantically incorrect
3. Handle get_current_time() error gracefully
- Return EINVAL instead of panicking if clock is before Unix epoch
- Prevents crashes on misconfigured or uninitialized clocks
4. Use explicit "." for current directory path
- Clearer semantics than empty string
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🤖 SemverChecks 🤖 No breaking API changes detected Note: this does not mean API is unchanged, or even that there are no breaking changes; simply, none of the detections triggered. |
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Summary
Add support for the
utimensat(2)andfutimens(3)syscalls which allow setting file access and modification times with nanosecond precision.Changes
litebox_common_linux
UTIME_NOW(0x3fffffff) andUTIME_OMIT(0x3ffffffe) constantsTimespechelper methods:is_utime_now(),is_utime_omit(),is_valid_for_utimensat()Sysno::utimensat,Sysno::utimensat_time64, andSysno::futimenslitebox (core)
SetTimesErrorenum for filesystem time-setting errorsset_times()andfd_set_times()methods toFileSystemtraitlitebox_shim_linux
sys_utimensat()with full path resolution and flag handlingsys_futimens()for fd-based timestamp modificationAT_SYMLINK_NOFOLLOWandAT_EMPTY_PATHflagsTimeProviderfor current time whenUTIME_NOWis specifiedTesting
cargo buildpassescargo clippy --all-targets --all-featurespasses with no new warningscargo test -p liteboxpasses (85 tests)cargo test -p litebox_common_linuxpassesKnown Limitations (documented as TODOs in code)
AT_SYMLINK_NOFOLLOWflag is accepted but not fully functional until symlinks are implementedFdRelativepath resolution returnsENOSYSRelated
This addresses one of the syscalls commonly needed by applications. See
docs/link_syscall_design.mdfor context on recent syscall implementations.