Syscalls

Userspace enters the kernel through SYSCALL, and the kernel returns through SYSRET. There is no interrupt gate for system calls and no argument block on the stack: the call number goes in rax, and up to six arguments go in registers.

Register	Carries
rax	the call number on the way in, the result on the way out
rdi, rsi, rdx, r10, r8, r9	arguments one through six
rcx, r11	clobbered by the instruction itself: return address and RFLAGS

The fourth argument is in r10 rather than rcx for the reason the last row gives: SYSCALL puts the return address in rcx before any handler runs, so an argument left there would be gone.

// The whole of the userspace side, from programs/edos_lib/src/sys.rs.
pub unsafe fn syscall2(num: u64, arg1: u64, arg2: u64) -> u64 {
    let ret: u64;
    unsafe {
        asm!(
            "syscall",
            in("rax") num,
            in("rdi") arg1,
            in("rsi") arg2,
            lateout("rax") ret,
            lateout("rcx") _,
            lateout("r11") _,
            options(nostack),
        );
    }
    ret
}

Reporting failure

There is no errno global and no negative-value convention shared across the table. A call that returns a u64 signals failure with u64::MAX; one that returns a signed value signals it with -1. Either way the number itself carries no detail, so the failing handler stores a code on the calling thread and userspace reads it back with call 0x400.

The code is per thread, and every handler that can fail clears it before doing any work, so a stale value from an earlier call cannot be mistaken for a fresh one. A call that succeeds leaves it cleared.

Paths are NUL-terminated and are rejected past 1024 bytes. Every pointer userspace hands over is copied through checked helpers rather than dereferenced: a bad address is EFAULT, not a kernel fault.

The table

/

102 calls

All102I/O18Filesystem30Process11Memory3Shared memory5Sync2Network15Window9Time4System5

1. 0readRead from a descriptor into a user buffer, advancing its offset.I/O

   Reg	Argument	Type	Meaning
   rdi	fd	u64	File descriptor.
   rsi	buf	*mut u8	Destination buffer.
   rdx	count	usize	Bytes to read.

   Returnsi64 — bytes read, 0 at end of file, -1 on error

   ErrorsEFAULTEINVALENOTCONNplus any filesystem failure, mapped from FsError

   Sourcekernel/src/syscalls/io.rs

   Blocks on a pipe, a pty or a tty with nothing buffered. Files are served from the page cache, so a hit never reaches the disk.

2. 1writeWrite a user buffer to a descriptor.I/O

   Reg	Argument	Type	Meaning
   rdi	fd	u64	File descriptor.
   rsi	buf	*const u8	Source buffer.
   rdx	count	usize	Bytes to write.

   Returnsu64 — bytes written, u64::MAX on error

   ErrorsEFAULTEINVALEIOENOTCONNEPIPE

   Sourcekernel/src/syscalls/io.rs

   A zero-length write returns 0 without touching the descriptor.

3. 2openOpen a path and install it in the descriptor table.I/O

   Reg	Argument	Type	Meaning
   rdi	path	*const u8	NUL-terminated path, at most 1024 bytes.
   rsi	flags	u64	Access mode and creation flags.

   Returnsi64 — new descriptor, -1 on error

   ErrorsEFAULTEINVALplus any filesystem failure, mapped from FsError

   Sourcekernel/src/syscalls/io.rs

   The low two bits are the access mode: 0 O_RDONLY, 1 O_WRONLY, 2 O_RDWR. 0x40 is O_CREAT, 0x200 O_TRUNC, 0x400 O_APPEND. An append offset is resolved per write rather than at open time.

4. 3closeRelease a descriptor.I/O

   Reg	Argument	Type	Meaning
   rdi	fd	u64	File descriptor.

   Returnsi32 — 0 on success, -1 on error

   ErrorsEINVAL

   Sourcekernel/src/syscalls/io.rs
5. 4list_dirPack a directory listing into a user buffer.Filesystem

   Reg	Argument	Type	Meaning
   rdi	path	*const u8	Directory to list.
   rsi	buf	*mut u8	Destination buffer.
   rdx	buf_size	usize	Buffer capacity in bytes.

   Returnsi64 — bytes written, -1 on error

   ErrorsEFAULTEINVALplus any filesystem failure, mapped from FsError

   Sourcekernel/src/syscalls/io.rs

   Entries are fixed-size headers each followed by a name; the return value is a byte count, not an entry count.

6. 5getcwdCopy the working directory out as a NUL-terminated path.Filesystem

   Reg	Argument	Type	Meaning
   rdi	buf	*mut u8	Destination buffer.
   rsi	size	usize	Buffer capacity in bytes.

   Returnsi64 — bytes written including the NUL, -1 on error

   ErrorsEFAULTEINVAL

   Sourcekernel/src/syscalls/io.rs
7. 6chdirChange the working directory of the calling process.Filesystem

   Reg	Argument	Type	Meaning
   rdi	path	*const u8	Directory to move to.

   Returnsi64 — 0 on success, -1 on error

   ErrorsEFAULTEINVAL

   Sourcekernel/src/syscalls/io.rs
8. 7pollWait until one of a set of descriptors is ready.I/O

   Reg	Argument	Type	Meaning
   rdi	fds	*mut SelectFd	Array of descriptors and interests; results are written back in place.
   rsi	count	usize	Number of entries.
   rdx	timeout_ms	u64	Timeout in milliseconds.

   Returnsi64 — number of ready descriptors, -1 on error

   ErrorsEFAULTEINVAL

   Sourcekernel/src/syscalls/io.rs

   SelectFd is { fd: u64, interests: PollState, result: PollState }, and PollState is five bools: readable, writable, error, hangup, invalid.

9. 8fstatMetadata for an open descriptor.Filesystem

   Reg	Argument	Type	Meaning
   rdi	fd	u64	File descriptor.
   rsi	statbuf	*mut FstatEntry	Destination struct.

   Returnsi64 — 0 on success, -1 on error

   ErrorsEBADFEFAULTplus any filesystem failure, mapped from FsError

   Sourcekernel/src/syscalls/fs.rs
10. 9mmapMap anonymous, file-backed or physical memory into the address space.Memory

    Reg	Argument	Type	Meaning
    rdi	addr	u64	Requested address, or 0 to let the kernel choose.
    rsi	length	u64	Length in bytes.
    rdx	prot	u32	PROT_READ 0x1, PROT_WRITE 0x2, PROT_EXEC 0x4.
    r10	flags	u32	MAP_SHARED 0x01, MAP_PRIVATE 0x02, MAP_FIXED 0x10, MAP_ANONYMOUS 0x20, MAP_PHYSICAL 0x40, MAP_WRITE_COMBINING 0x80.
    r8	phys_or_fd	u64	Physical address for MAP_PHYSICAL, descriptor for a file-backed mapping.
    r9	file_offset	u64	Offset into the file; file-backed mappings only.

    Returnsu64 — mapping address, u64::MAX on error

    ErrorsEACCESEBADFEINVALENOMEMEPERM

    Sourcekernel/src/syscalls/memory.rs

    Pages are faulted in on demand. MAP_PHYSICAL is how a driver in userspace reaches device memory, and it is the reason this call can return EPERM.

11. 10statMetadata for a path.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Path to inspect.
    rsi	path_len	usize	Length of the path in bytes.
    rdx	statbuf	*mut FstatEntry	Destination struct.

    Returnsi64 — 0 on success, -1 on error

    ErrorsEFAULTplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs
12. 11munmapRemove a mapping and shoot down the stale TLB entries.Memory

    Reg	Argument	Type	Meaning
    rdi	addr	u64	Start of the mapping.
    rsi	length	u64	Length in bytes.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/memory.rs
13. 12lseekMove the offset of a file descriptor.I/O

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	offset	i64	Signed displacement.
    rdx	whence	u32	0 SEEK_SET, 1 SEEK_CUR, 2 SEEK_END.

    Returnsi64 — the new offset, -1 on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/io.rs

    Only regular files carry an offset; anything else is rejected.

14. 13ftruncateSet the length of an open file.Filesystem

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	size	u64	New length in bytes.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/io.rs
15. 14fsyncFlush one file, data and metadata, to stable storage.Filesystem

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEINVALEIOplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/io.rs
16. 15isattyReport whether a descriptor is a terminal.I/O

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.

    Returnsu64 — 1 for a terminal, 0 otherwise

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/io.rs
17. 16ioctlDevice-specific control, for ptys and for devfs nodes.I/O

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	request	u64	Device-defined request code.
    rdx	arg	u64	Inline value, or a pointer when arg_len is non-zero.
    r10	arg_len	usize	Size of the buffer arg points at.
    r8	flags	u64	IOCTL_FLAG_READ 1 copies the buffer in, IOCTL_FLAG_WRITE 2 copies it back out.

    Returnsi64 — the device’s own value, -1 on error

    ErrorsEBADFEFAULTEINVALplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/ioctl/mod.rs

    The buffer is bounced through the kernel rather than handed to the driver, so a device never touches a user pointer. devfs nodes are dispatched directly instead of through the filesystem mailbox.

18. 17preadRead at an explicit offset, leaving the descriptor offset alone.I/O

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	buf	*mut u8	Destination buffer.
    rdx	count	usize	Bytes to read.
    r10	offset	u64	Absolute file offset.

    Returnsi64 — bytes read, 0 at end of file, -1 on error

    ErrorsEBADFEFAULTEINVALESPIPEplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/io.rs

    Threads of one process share a descriptor table, so they share one offset per descriptor: lseek followed by read races by construction. This call is the fix, and it is ESPIPE on anything without an offset.

19. 18pwriteWrite at an explicit offset, leaving the descriptor offset alone.I/O

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	buf	*const u8	Source buffer.
    rdx	count	usize	Bytes to write.
    r10	offset	u64	Absolute file offset.

    Returnsi64 — bytes written, -1 on error

    ErrorsEBADFEFAULTEINVALESPIPE

    Sourcekernel/src/syscalls/io.rs

    O_APPEND is deliberately not consulted: a positional write that silently lands somewhere else is worse than no call at all.

20. 19readvRead into a list of buffers, filling each before moving to the next.I/O

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	iov	*const IoVec	Array of { base, len } pairs.
    rdx	iovcnt	usize	Number of entries, at most IOV_MAX (1024).

    Returnsi64 — total bytes read, 0 at end of file, -1 on error

    ErrorsEFAULTEINVALplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/io.rs

    Each buffer is a separate underlying read, so the buffers fill in order but the sequence is not atomic against a concurrent reader. A short read ends the sequence, and an error after a partial transfer returns the partial count with errno cleared, as POSIX requires.

21. 20writevWrite a list of buffers in order.I/O

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	iov	*const IoVec	Array of { base, len } pairs.
    rdx	iovcnt	usize	Number of entries, at most IOV_MAX (1024).

    Returnsi64 — total bytes written, -1 on error

    ErrorsEFAULTEINVALplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/io.rs

    A zero-length entry is skipped rather than ending the run. A total length past i64::MAX is rejected before anything is written.

22. 21accessTest a path for existence and readability.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Path, not NUL-terminated.
    rsi	path_len	usize	Length in bytes.
    rdx	mode	u32	F_OK 0, X_OK 1, W_OK 2, R_OK 4.

    Returnsi32 — 0 if the access would be permitted, -1 otherwise

    ErrorsEACCESEINVALplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    Delegates to faccessat with AT_FDCWD. There is one user id, so only the read-only attribute can actually deny anything; undefined mode bits are EINVAL rather than ignored.

23. 22pipeCreate a pipe and return both ends.I/O

    Reg	Argument	Type	Meaning
    rdi	pipefd	*mut [u64; 2]	Receives [read_fd, write_fd].

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEFAULT

    Sourcekernel/src/syscalls/mod.rs

    If the copy back to userspace faults, both descriptors are closed rather than leaked.

24. 32dupDuplicate a descriptor onto the lowest free number.I/O

    Reg	Argument	Type	Meaning
    rdi	oldfd	u64	Descriptor to duplicate.

    Returnsu64 — the new descriptor, u64::MAX on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/mod.rs
25. 33dup2Duplicate a descriptor onto a chosen number, closing whatever was there.I/O

    Reg	Argument	Type	Meaning
    rdi	oldfd	u64	Descriptor to duplicate.
    rsi	newfd	u64	Target number.

    Returnsu64 — newfd, u64::MAX on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/mod.rs
26. 34msyncFlush the dirty pages of a MAP_SHARED range to storage.Memory

    Reg	Argument	Type	Meaning
    rdi	addr	u64	Start of the range.
    rsi	len	u64	Length in bytes.
    rdx	flags	u32	MS_ASYNC 0x1, MS_SYNC 0x2, MS_INVALIDATE 0x4.

    Returnsi64 — 0 on success, -1 on error

    ErrorsEINVALEIO

    Sourcekernel/src/syscalls/memory.rs

    The VMA lock collects the work and is dropped before any disk I/O runs.

27. 35nanosleepSleep for a duration given in nanoseconds.Time

    Reg	Argument	Type	Meaning
    rdi	req	*const Timespec	Requested duration; tv_nsec must be under 1e9.
    rsi	rem	*mut Timespec	Accepted and validated, never written.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEFAULTEINVAL

    Sourcekernel/src/syscalls/mod.rs

    A sleep ends on any wake, so the kernel loops until the deadline passes. `rem` stays unwritten because there are no userspace signal handlers yet, which makes an early return unobservable.

28. 39getpidProcess ID of the caller.Process

    Takes no arguments.

    Returnsu64 — the pid

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/mod.rs
29. 40waitpidWait for a child to exit and collect its status.Process

    Reg	Argument	Type	Meaning
    rdi	pid	u64	Child to wait for.
    rsi	block	u64	1 parks until the child exits, anything else polls.
    rdx	status	*mut i32	Receives the exit code; may be null.

    Returnsu64 — the pid, 0 if it has not exited and block was 0, u64::MAX on error

    ErrorsEFAULT

    Sourcekernel/src/syscalls/mod.rs
30. 57spawnLoad a program as a new process with three inherited descriptors.Process

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Program to load.
    rsi	argv	*const *const u8	NULL-terminated argument vector.
    rdx	stdin_fd	u64	Descriptor to install as stdin.
    r10	stdout_fd	u64	Descriptor to install as stdout.
    r8	stderr_fd	u64	Descriptor to install as stderr.

    Returnsu64 — the child pid, u64::MAX on error

    ErrorsEFAULTEINVAL

    Sourcekernel/src/syscalls/mod.rs

    Registers are scarce, so anything richer than three descriptors goes through spawn2.

31. 59execveReplace this process’s image, keeping its pid.Process

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Program to load.
    rsi	argv	*const *const u8	NULL-terminated argument vector.
    rdx	envp	*const *const u8	NULL-terminated environment.

    Returnsdoes not return on success; u64::MAX on error

    ErrorsEAGAINEFAULTEINVALENOENTENOEXEC

    Sourcekernel/src/syscalls/mod.rs

    One rule dictates the order of the whole implementation: nothing observable changes until the point of no return, and nothing after that point may fail.

32. 60exitTerminate the calling thread.Process

    Reg	Argument	Type	Meaning
    rdi	code	i32	Exit status.

    Returnsdoes not return

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/mod.rs
33. 72fcntlDescriptor flags and duplication.I/O

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	cmd	u64	F_DUPFD 0, F_GETFD 1, F_SETFD 2, F_DUPFD_CLOEXEC 1030.
    rdx	arg	u64	Command-specific argument.

    Returnsi64 — command-specific, -1 on error

    ErrorsEBADFEINVAL

    Sourcekernel/src/syscalls/mod.rs

    F_GETFL and F_SETFL return EINVAL rather than a plausible-looking zero: there is no O_NONBLOCK here, and a caller told it succeeded would then rely on it.

34. 76truncateSet a file length by path.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Path, not NUL-terminated.
    rsi	path_len	usize	Length in bytes.
    rdx	size	u64	New length in bytes.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEFAULTEINVALEISDIRplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    Growing a file creates a hole: the blocks it names are never allocated and read back as zeros. Shrinking zeroes the surviving tail of the last cached page, so a later grow cannot resurrect the old bytes.

35. 78getdentsStream a directory listing from an entry index.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Directory to list.
    rsi	path_len	usize	Length in bytes.
    rdx	buf	*mut u8	Destination buffer.
    r10	buf_size	usize	Buffer capacity in bytes.
    r8	start	usize	Index of the first entry to pack.

    Returnsi64 — bytes written, 0 once `start` is past the last entry, -1 on error

    ErrorsEFAULTEINVALplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/io.rs

    The caller advances `start` by the number of entries it decoded, so there is no in/out cursor to keep. An entry that cannot fit on its own is EINVAL, not 0, because 0 means end of directory and would silently drop the tail.

36. 82renameRename or move an entry.Filesystem

    Reg	Argument	Type	Meaning
    rdi	old_path	*const u8	Existing path.
    rsi	new_path	*const u8	Destination path.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEFAULTEINVAL

    Sourcekernel/src/syscalls/io.rs
37. 88symlinkCreate a symbolic link.Filesystem

    Reg	Argument	Type	Meaning
    rdi	target	*const u8	What the link points at, stored verbatim.
    rsi	target_len	usize	Length in bytes.
    rdx	path	*const u8	Where the link is created.
    r10	path_len	usize	Length in bytes.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEEXISTEFAULTEINVALplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    Delegates to symlinkat with AT_FDCWD. Targets are stored inline in the inode on EFS. Path resolution follows links up to eight hops before returning ELOOP; unlinking a link frees its inode in the same transaction as the detach, since nothing can hold a reference to one.

38. 89readlinkRead a symbolic link target without following it.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	The link itself.
    rsi	path_len	usize	Length in bytes.
    rdx	buf	*mut u8	Destination buffer.
    r10	buf_len	usize	Buffer capacity in bytes.

    Returnsi64 — bytes written, -1 on error

    ErrorsEFAULTEINVALplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    Truncates rather than failing when the buffer is short, and no terminator is written. A path that is not a link is an error, not an empty read.

39. 102getuidReal user id of the calling process.System

    Takes no arguments.

    Returnsu64 — the uid

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/mod.rs
40. 104getgidReal group id of the calling process.System

    Takes no arguments.

    Returnsu64 — the gid

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/mod.rs
41. 162syncFlush every dirty block cache page to disk.Filesystem

    Takes no arguments.

    Returnsu64 — always 0

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/io.rs

    Errors are the writeback thread’s to log; the caller is told nothing because it can do nothing.

42. 169rebootSync every filesystem, then stop or restart the machine.System

    Reg	Argument	Type	Meaning
    rdi	cmd	u64	0 power off, 1 reset, 2 halt.

    Returnsdoes not return on success; -1 on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/mod.rs

    Soft-off with no AML interpreter: PM1a/PM1b_CNT come from the FADT and SLP_TYPa is decoded structurally out of the DSDT’s \_S5_ package, with emulator ports as a fallback. Reset drives RST_CNT then pulses the 8042. Progress prints to the serial port rather than the log ring, because the kthread that drains the ring will not run again.

43. 202mountMount a partition at a path.Filesystem

    Reg	Argument	Type	Meaning
    rdi	device_id	u64	Block device index.
    rsi	partition_idx	u64	Partition within that device.
    rdx	path	*const u8	Mount point.
    r10	fs_type	*const u8	Filesystem name, e.g. efs or fat32.

    Returnsi64 — 0 on success, -1 on error

    ErrorsENOENTENOTDIRplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs
44. 203list_partitionsDescribe every partition the kernel enumerated, as text.Filesystem

    Reg	Argument	Type	Meaning
    rdi	buf	*mut u8	Destination buffer.
    rsi	size	u64	Buffer capacity in bytes.

    Returnsi64 — bytes written, -1 on error

    ErrorsEFAULTEIO

    Sourcekernel/src/syscalls/fs.rs
45. 204mkdirCreate a directory.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Directory to create.

    Returnsi64 — 0 on success, -1 on error

    Errorsplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs
46. 205rmdirRemove an empty directory.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Directory to remove.

    Returnsi64 — 0 on success, -1 on error

    Errorsplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs
47. 206rmdir_allRemove a directory and everything under it.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Root of the subtree to remove.

    Returnsi64 — 0 on success, -1 on error

    Errorsplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    The recursion lives in the kernel because a userspace walk would race with anyone else writing into the tree.

48. 207unlinkRemove a file.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	File to remove.

    Returnsi64 — 0 on success, -1 on error

    Errorsplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs
49. 208list_mountsDescribe the mount table as text.Filesystem

    Reg	Argument	Type	Meaning
    rdi	buf	*mut u8	Destination buffer.
    rsi	size	usize	Buffer capacity in bytes.

    Returnsi64 — bytes written, -1 on error

    ErrorsEFAULT

    Sourcekernel/src/syscalls/fs.rs
50. 209sleep_msPark the calling thread for a duration.Time

    Reg	Argument	Type	Meaning
    rdi	milliseconds	u64	How long to sleep.

    Returnsu64 — always 0

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/mod.rs
51. 210monotonic_timeNanoseconds since boot, from the HPET.Time

    Takes no arguments.

    Returnsu64 — nanoseconds

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/mod.rs

    Monotonic with microsecond resolution, scaled to nanoseconds. It never goes backwards and never jumps with the wall clock.

52. 211cloneStart a thread in the calling process’s address space.Process

    Reg	Argument	Type	Meaning
    rdi	func	u64	Entry point.
    rsi	arg	u64	Value passed to the entry point.
    rdx	flags	u64	Clone flags.
    r10	child_stack	u64	Top of the stack the child runs on.

    Returnsu64 — the child thread id, u64::MAX on error

    ErrorsEINVALENOMEM

    Sourcekernel/src/syscalls/mod.rs

    The child shares the address space, the descriptor table and the heap break, and gets its own TLS block and stack.

53. 212futex_waitSleep while a word in memory still holds an expected value.Sync

    Reg	Argument	Type	Meaning
    rdi	addr	*const u32	Word to watch.
    rsi	expected	u32	Value to sleep on.
    rdx	timeout_ns	u64	Timeout in nanoseconds; u64::MAX waits forever.

    Returnsu64 — 0 woken with the value changed, 1 value did not match or a spurious wake, 2 timed out, u64::MAX on error

    ErrorsEFAULT

    Sourcekernel/src/syscalls/sync.rs

    Keyed by the address space plus the address, so two processes sharing a mapping share a queue. The wait queue is dropped when its last waiter leaves.

54. 213futex_wakeWake waiters parked on a word.Sync

    Reg	Argument	Type	Meaning
    rdi	addr	*const u32	Word waiters are parked on.
    rsi	count	u32	How many to wake.

    Returnsu64 — waiters actually woken, u64::MAX on error

    ErrorsEFAULT

    Sourcekernel/src/syscalls/sync.rs
55. 214getrandomFill a buffer with random bytes.System

    Reg	Argument	Type	Meaning
    rdi	buf	*mut u8	Destination buffer.
    rsi	len	usize	Bytes to generate, at most 1 MiB.
    rdx	flags	u64	Must be 0.

    Returnsi64 — bytes written, -1 on error

    ErrorsEFAULTEINVAL

    Sourcekernel/src/syscalls/io.rs
56. 215shm_createCreate a shared memory region.Shared memory

    Reg	Argument	Type	Meaning
    rdi	size	u64	Size in bytes.

    Returnsi64 — the region id, -1 on error

    ErrorsEINVALENOMEM

    Sourcekernel/src/syscalls/shm.rs
57. 216shm_mapMap a shared region into the calling process.Shared memory

    Reg	Argument	Type	Meaning
    rdi	shm_id	u64	Region id.
    rsi	addr_hint	u64	Suggested address, or 0 to let the kernel choose.
    rdx	prot	u64	PROT_READ 0x1, PROT_WRITE 0x2, PROT_EXEC 0x4.

    Returnsu64 — the mapping address, u64::MAX on error

    ErrorsEINVALENOMEM

    Sourcekernel/src/syscalls/shm.rs

    This is what a window buffer is: the client draws into the region and the compositor reads the same frames.

58. 217shm_unmapUnmap a shared region from the calling process.Shared memory

    Reg	Argument	Type	Meaning
    rdi	addr	u64	Address the region was mapped at.

    Returnsi64 — 0 on success, -1 on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/shm.rs
59. 218shm_destroyDestroy a shared region.Shared memory

    Reg	Argument	Type	Meaning
    rdi	shm_id	u64	Region id.

    Returnsi64 — 0 on success, -1 on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/shm.rs

    Refused while any mapping is still live.

60. 219window_createRegister a window with the kernel.Window

    Reg	Argument	Type	Meaning
    rdi	x	i64	Position, x.
    rsi	y	i64	Position, y.
    rdx	width	u64	Width in pixels.
    r10	height	u64	Height in pixels.

    Returnsu64 — the window id, u64::MAX on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/window.rs

    The kernel owns the registry and routes input to it. Decoration, stacking and everything else people call a window manager is userspace.

61. 220window_destroyRemove a window from the registry.Window

    Reg	Argument	Type	Meaning
    rdi	window_id	u64	Window id.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsENOENTEPERM

    Sourcekernel/src/syscalls/window.rs
62. 221window_setSet a window property.Window

    Reg	Argument	Type	Meaning
    rdi	window_id	u64	Window id.
    rsi	prop	u64	VISIBLE 1, X 2, Y 3, WIDTH 4, HEIGHT 5, TITLE_PTR 6, BUFFER_SHM 7, FLAGS 8.
    rdx	value	u64	The value, or a pointer for TITLE_PTR.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEFAULTEINVALENOENTEPERM

    Sourcekernel/src/syscalls/window.rs

    FLAGS carries FLAG_DOCK 1, the undecorated, undraggable window the taskbar uses.

63. 222window_getRead a window property.Window

    Reg	Argument	Type	Meaning
    rdi	window_id	u64	Window id.
    rsi	prop	u64	Property id, as for window_set.

    Returnsu64 — the property value, u64::MAX on error

    ErrorsEINVALENOENT

    Sourcekernel/src/syscalls/window.rs
64. 223window_pollDrain pending events for a window.Window

    Reg	Argument	Type	Meaning
    rdi	window_id	u64	Window id.
    rsi	events	*mut WindowEvent	Destination array.
    rdx	max	u64	Capacity of that array.

    Returnsu64 — events copied, u64::MAX on error

    ErrorsEFAULTENOENTEPERM

    Sourcekernel/src/syscalls/window.rs
65. 224window_listList every window, for the compositor.Window

    Reg	Argument	Type	Meaning
    rdi	buf	*mut WindowListEntry	Destination array.
    rsi	max	u64	Capacity of that array.

    Returnsu64 — entries written, u64::MAX on error

    ErrorsEFAULT

    Sourcekernel/src/syscalls/window.rs
66. 225window_send_eventPost an event to a window the caller does not own.Window

    Reg	Argument	Type	Meaning
    rdi	window_id	u64	Target window.
    rsi	event	*const WindowEvent	Event to deliver.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEFAULTENOENT

    Sourcekernel/src/syscalls/window.rs

    How the window manager asks a client to close itself.

67. 226clock_gettimeNanoseconds since the Unix epoch.Time

    Reg	Argument	Type	Meaning
    rdi	buf	*mut u8	Eight-byte buffer receiving a little-endian u64.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEFAULTEINVAL

    Sourcekernel/src/syscalls/mod.rs

    Answered from the monotonic counter plus a wall-clock offset sampled at boot, so it costs a counter read rather than several RTC port round-trips.

68. 227openptyOpen a pty master and slave pair.I/O

    Reg	Argument	Type	Meaning
    rdi	fds	*mut [u64; 2]	Receives [master_fd, slave_fd].

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEFAULT

    Sourcekernel/src/syscalls/io.rs

    What the terminal emulator opens before it spawns a shell.

69. 228spawn2Spawn with arguments, an environment and three descriptors.Process

    Reg	Argument	Type	Meaning
    rdi	args	*const SpawnArgs	Struct of { path, argv, envp, stdin_fd, stdout_fd, stderr_fd }.

    Returnsu64 — the child pid, u64::MAX on error

    ErrorsEFAULTEINVAL

    Sourcekernel/src/syscalls/mod.rs
70. 229killSend a signal to a process.Process

    Reg	Argument	Type	Meaning
    rdi	pid	u64	Target process.
    rsi	signum	u32	Signal number, 1 to 31.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/mod.rs
71. 230sigactionInstall a signal disposition.Process

    Reg	Argument	Type	Meaning
    rdi	signum	u32	Signal number, 1 to 31; SIGKILL is rejected.
    rsi	handler	u32	0 SIG_DFL, 1 SIG_IGN, otherwise a handler address.

    Returnsu64 — the previous disposition, u64::MAX on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/mod.rs
72. 231shm_sizeSize of a shared region.Shared memory

    Reg	Argument	Type	Meaning
    rdi	shm_id	u64	Region id.

    Returnsi64 — size in bytes, -1 on error

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/shm.rs
73. 232window_damageTell the compositor a window has repainted its buffer.Window

    Reg	Argument	Type	Meaning
    rdi	window_id	u64	Window id.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsCannot fail.

    Sourcekernel/src/syscalls/window.rs
74. 233sigprocmaskRead and change the calling thread’s blocked signal mask.Process

    Reg	Argument	Type	Meaning
    rdi	how	u32	SIG_BLOCK 0, SIG_UNBLOCK 1, SIG_SETMASK 2.
    rsi	mask	u32	The set to apply.

    Returnsu64 — the previous mask, u64::MAX on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/mod.rs

    Sets are 32 bits, so the mask goes in and the old one comes back by value rather than through pointers, matching sigaction. A signal sent while blocked is recorded pending without killing or waking the target; widening the mask delivers it immediately, and SIGKILL is dropped from the mask rather than making the call fail.

75. 234window_grant_shellAppoint another process as part of the shell.Window

    Reg	Argument	Type	Meaning
    rdi	pid	u64	Process to appoint.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEINVALEPERM

    Sourcekernel/src/syscalls/window.rs

    Moving, resizing, framing, minimizing and posting events to a window belong to a shell, not to the window’s owner, so they cannot be gated on ownership. They are gated on this instead. Only a process that already holds the privilege may grant it, and the kernel seeds exactly one: `bin/edos-init`, the only process it starts, which appoints the compositor and the panel. The grant is per pid, follows a process’s threads, and is dropped when the process exits.

76. 240socketCreate a socket and install it in the descriptor table.Network

    Reg	Argument	Type	Meaning
    rdi	domain	u64	AF_INET 2.
    rsi	type	u64	SOCK_STREAM 1, SOCK_DGRAM 2.
    rdx	protocol	u64	Ignored; implied by the type.

    Returnsu64 — the new descriptor, u64::MAX on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/net.rs
77. 241bindBind a socket to a local address.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	addr	*const SockAddrIn	Local address.
    rdx	addr_len	u64	Size of that struct.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEADDRINUSEEBADFEFAULTEINVAL

    Sourcekernel/src/syscalls/net.rs
78. 242connectOpen a connection to a remote address.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	addr	*const SockAddrIn	Remote address.
    rdx	addr_len	u64	Size of that struct.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEBADFECONNREFUSEDEFAULTEINVAL

    Sourcekernel/src/syscalls/net.rs

    Blocks through the TCP handshake.

79. 243listenMark a bound socket as accepting connections.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	backlog	u32	Pending connection queue depth.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEBADFEINVAL

    Sourcekernel/src/syscalls/net.rs
80. 244acceptTake the next established connection off a listening socket.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	addr	*mut SockAddrIn	Receives the peer address; may be null.
    rdx	addr_len	*mut u32	In and out length for that struct.

    Returnsu64 — descriptor for the new connection, u64::MAX on error

    ErrorsEAGAINEBADFEFAULTEINVAL

    Sourcekernel/src/syscalls/net.rs
81. 245sendtoSend on a socket, with an explicit destination for datagrams.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	buf	*const u8	Payload.
    rdx	len	u64	Payload length.
    r10	flags	u64	Unused.
    r8	addr	*const SockAddrIn	Destination; null on a connected socket.
    r9	addr_len	u64	Size of that struct.

    Returnsu64 — bytes sent, u64::MAX on error

    ErrorsEBADFEFAULTEINVALEIO

    Sourcekernel/src/syscalls/net.rs
82. 246recvfromReceive on a socket, optionally reporting the sender.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	buf	*mut u8	Destination buffer.
    rdx	len	u64	Buffer capacity.
    r10	flags	u64	Unused.
    r8	addr	*mut SockAddrIn	Receives the sender address; may be null.
    r9	addr_len	*mut u32	In and out length for that struct.

    Returnsu64 — bytes received, u64::MAX on error

    ErrorsEAGAINEBADFEFAULT

    Sourcekernel/src/syscalls/net.rs
83. 247shutdownClose one or both directions of a connection.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	how	u64	0 read, 1 write, 2 both.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEBADFEINVAL

    Sourcekernel/src/syscalls/net.rs
84. 248setsockoptSet a socket option.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	level	i32	Option level.
    rdx	optname	i32	Option name.
    r10	val	*const u8	Option value.
    r8	val_len	u32	Length of that value.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEBADFEFAULTEINVAL

    Sourcekernel/src/syscalls/net.rs
85. 249pingSend an ICMP echo request and wait for the reply.Network

    Reg	Argument	Type	Meaning
    rdi	dst_ip	*const [u8; 4]	Destination address.
    rsi	id	u16	ICMP identifier.
    rdx	seq	u16	ICMP sequence number.
    r10	timeout_ms	u64	Timeout in milliseconds; 0 means 5000.

    Returnsu64 — round-trip time in microseconds, u64::MAX on timeout or error

    ErrorsEFAULTEINVAL

    Sourcekernel/src/syscalls/mod.rs

    A raw socket API would be the general answer; this is the one ICMP case userspace actually needs.

86. 250netinfoDescribe the network interfaces as text.Network

    Reg	Argument	Type	Meaning
    rdi	buf	*mut u8	Destination buffer.
    rsi	len	usize	Buffer capacity in bytes.

    Returnsu64 — bytes written, u64::MAX on error

    ErrorsEFAULT

    Sourcekernel/src/syscalls/mod.rs
87. 251getsockoptRead a socket option.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	level	i32	Option level.
    rdx	optname	i32	Option name.
    r10	val	*mut u8	Receives the value.
    r8	val_len	*mut u32	In and out length for that buffer.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEBADFEFAULT

    Sourcekernel/src/syscalls/net.rs
88. 252getpeernameAddress of the remote end of a connection.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	addr	*mut SockAddrIn	Receives the peer address.
    rdx	addr_len	*mut u32	In and out length for that struct.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEBADFEFAULTENOTCONN

    Sourcekernel/src/syscalls/net.rs
89. 253getsocknameLocal address a socket is bound to.Network

    Reg	Argument	Type	Meaning
    rdi	fd	u64	File descriptor.
    rsi	addr	*mut SockAddrIn	Receives the local address.
    rdx	addr_len	*mut u32	In and out length for that struct.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEBADFEFAULT

    Sourcekernel/src/syscalls/net.rs
90. 254statfsFilesystem statistics for the mount that holds a path.Filesystem

    Reg	Argument	Type	Meaning
    rdi	path	*const u8	Any path on the filesystem.
    rsi	buf	*mut RawStatFs	Destination struct.
    rdx	buf_len	usize	Size of that struct.

    Returnsi64 — 0 on success, -1 on error

    ErrorsEFAULTEIOENOENT

    Sourcekernel/src/syscalls/fs.rs
91. 255forkDuplicate the calling process, copy-on-write.Process

    Takes no arguments.

    Returnsi64 — the child pid in the parent, 0 in the child, -1 on error

    ErrorsEINVAL

    Sourcekernel/src/syscalls/mod.rs

    Private mappings are marked read-only in both processes and split on the first write fault.

92. 256getdnsThe resolver address the stack learned from DHCP.Network

    Reg	Argument	Type	Meaning
    rdi	addr	*mut [u8; 4]	Receives the resolver address.

    Returnsu64 — 0 on success, u64::MAX on error

    ErrorsEFAULTENOTCONN

    Sourcekernel/src/syscalls/net.rs

    A resolver is configuration, and there is no /etc/resolv.conf convention here, so userspace asks the stack that learned it.

93. 257openatOpen a path resolved against a directory descriptor.I/O

    Reg	Argument	Type	Meaning
    rdi	dirfd	i64	Directory the path is resolved against, or AT_FDCWD (-100) for the cwd. Ignored when the path is absolute.
    rsi	path	*const u8	Path, not NUL-terminated.
    rdx	path_len	usize	Length in bytes.
    r10	flags	u64	Same flag set as open.

    Returnsi64 — new descriptor, -1 on error

    ErrorsEBADFEFAULTEINVALENOTDIRplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/io.rs

    Shares its body with open, which is openat against the cwd. Taking pointer and length rather than a NUL-terminated string means userspace does not have to allocate a CString per open.

94. 258mkdiratCreate a directory relative to a directory descriptor.Filesystem

    Reg	Argument	Type	Meaning
    rdi	dirfd	i64	Directory the path is resolved against, or AT_FDCWD (-100) for the cwd. Ignored when the path is absolute.
    rsi	path	*const u8	Path, not NUL-terminated.
    rdx	path_len	usize	Length in bytes.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEBADFEEXISTEFAULTEINVALENOTDIRplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    No mode argument: there are no permission bits to observe yet.

95. 262fstatatStat a path resolved against a directory descriptor.Filesystem

    Reg	Argument	Type	Meaning
    rdi	dirfd	i64	Directory the path is resolved against, or AT_FDCWD (-100) for the cwd. Ignored when the path is absolute.
    rsi	path	*const u8	Path, not NUL-terminated.
    rdx	path_len	usize	Length in bytes.
    r10	statbuf	*mut FstatEntry	Receives the metadata.
    r8	flags	u64	Must be zero.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEBADFEFAULTEINVALENOTDIRplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    stat is this call against the cwd. A nonzero flags word is rejected rather than ignored: AT_SYMLINK_NOFOLLOW cannot be honoured while the lookup follows links.

96. 263unlinkatRemove a file or directory relative to a directory descriptor.Filesystem

    Reg	Argument	Type	Meaning
    rdi	dirfd	i64	Directory the path is resolved against, or AT_FDCWD (-100) for the cwd. Ignored when the path is absolute.
    rsi	path	*const u8	Path, not NUL-terminated.
    rdx	path_len	usize	Length in bytes.
    r10	flags	u64	0, or AT_REMOVEDIR (0x200) to remove a directory.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEBADFEFAULTEINVALENOTDIRplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    AT_REMOVEDIR is the only accepted flag; anything else is EINVAL.

97. 264renameatRename, resolving each side against its own directory descriptor.Filesystem

    Reg	Argument	Type	Meaning
    rdi	olddirfd	i64	Base for the old path, or AT_FDCWD (-100).
    rsi	oldpath	*const u8	Existing name.
    rdx	oldpath_len	usize	Length in bytes.
    r10	newdirfd	i64	Base for the new path, or AT_FDCWD (-100).
    r8	newpath	*const u8	New name.
    r9	newpath_len	usize	Length in bytes.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEBADFEFAULTEINVALENOTDIRplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    rename routes through the same body, which is what gives it real filesystem error codes instead of a flat EINVAL.

98. 266symlinkatCreate a symbolic link relative to a directory descriptor.Filesystem

    Reg	Argument	Type	Meaning
    rdi	target	*const u8	What the link points at, stored verbatim.
    rsi	target_len	usize	Length in bytes.
    rdx	newdirfd	i64	Base for the link path, or AT_FDCWD (-100).
    r10	linkpath	*const u8	Where the link is created.
    r8	linkpath_len	usize	Length in bytes.

    Returnsi32 — 0 on success, -1 on error

    ErrorsEBADFEEXISTEFAULTEINVALENOTDIRplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    The descriptor places the link only. The target is never resolved at creation time, so it may dangle, and a dangling link still takes the name.

99. 267readlinkatRead a link target relative to a directory descriptor.Filesystem

    Reg	Argument	Type	Meaning
    rdi	dirfd	i64	Directory the path is resolved against, or AT_FDCWD (-100) for the cwd. Ignored when the path is absolute.
    rsi	path	*const u8	The link itself.
    rdx	path_len	usize	Length in bytes.
    r10	buf	*mut u8	Destination buffer.
    r8	buf_len	usize	Buffer capacity in bytes.

    Returnsi64 — bytes written, -1 on error

    ErrorsEBADFEFAULTEINVALENOTDIRplus any filesystem failure, mapped from FsError

    Sourcekernel/src/syscalls/fs.rs

    readlink is this call against the cwd.

100. 269faccessatTest access to a path relative to a directory descriptor.Filesystem

     Reg	Argument	Type	Meaning
     rdi	dirfd	i64	Directory the path is resolved against, or AT_FDCWD (-100) for the cwd. Ignored when the path is absolute.
     rsi	path	*const u8	Path, not NUL-terminated.
     rdx	path_len	usize	Length in bytes.
     r10	mode	u32	F_OK 0, X_OK 1, W_OK 2, R_OK 4.
     r8	flags	u64	Must be zero.

     Returnsi32 — 0 if the access would be permitted, -1 otherwise

     ErrorsEACCESEBADFEFAULTEINVALENOTDIRplus any filesystem failure, mapped from FsError

     Sourcekernel/src/syscalls/fs.rs

     Flags are rejected rather than ignored. AT_EACCESS names the only set of ids there is, and AT_SYMLINK_NOFOLLOW cannot be honoured while the lookup follows links.

101. 280utimensatSet a file’s access and modification times.Filesystem

     Reg	Argument	Type	Meaning
     rdi	dirfd	i64	Directory the path is resolved against, or AT_FDCWD (-100) for the cwd. Ignored when the path is absolute.
     rsi	path	*const u8	Path, not NUL-terminated.
     rdx	path_len	usize	Length in bytes.
     r10	times	*const [Timespec; 2]	Access time then modification time; null means both now.
     r8	flags	u64	Must be zero.

     Returnsi32 — 0 on success, -1 on error

     ErrorsEBADFEFAULTEINVALENOTDIRplus any filesystem failure, mapped from FsError

     Sourcekernel/src/syscalls/fs.rs

     UTIME_NOW stamps the current time and UTIME_OMIT leaves that field alone. EFS applies both in one journal transaction. AT_SYMLINK_NOFOLLOW is rejected, since the underlying set_times follows links.

102. 1024errnoThe error code the caller’s last failing syscall stored.System

     Takes no arguments.

     Returnsu64 — an Errno discriminant

     ErrorsCannot fail.

     Sourcekernel/src/syscalls/mod.rs

     Per thread, and cleared at the start of every handler that can fail. The value is the discriminant below, not a POSIX number.

Error codes

Errno is a plain Rust enum, and what userspace reads is its discriminant. These are not the POSIX numbers; a program that hardcodes 2 for ENOENT is reading ENOMEM.

Value	Name	Meaning
0	Clear	No error. Every handler stores this before it does any work.
1	EINVAL	Invalid argument passed to a syscall.
2	ENOMEM	Memory allocation failed or memory exhausted.
3	EFAULT	Bad memory address provided by userspace.
4	EBADF	Invalid or closed file descriptor.
5	EACCES	Operation requires permissions the caller lacks.
6	EPERM	Operation not permitted for the current caller.
7	ENOENT	Requested file or directory does not exist.
8	EEXIST	Attempted to create an entry that already exists.
9	ENOTDIR	Expected a directory but encountered a non-directory entry.
10	EISDIR	Operation required a regular file but encountered a directory.
11	ENOSPC	Device or filesystem has no space left for the operation.
12	EROFS	Write attempted on a read-only filesystem or device.
13	EIO	Generic I/O failure from the filesystem or storage layer.
14	EINTR	System call interrupted, e.g. by a signal or a kill.
15	ENOEXEC	File format is not recognized as an executable.
16	EAGAIN	Resource temporarily unavailable; the operation would block.
17	ENOTCONN	Socket is not connected.
18	ECONNREFUSED	Connection was refused by the remote host.
19	EADDRINUSE	Address already in use.
20	EPIPE	Broken pipe: a write to a closed connection.
21	EAFNOSUPPORT	Address family not supported.
22	ESPIPE	Seek on a descriptor with no file offset: pipe, socket, tty.
23	EBUSY	Device or resource in use, e.g. a disk backing a live mount.
24	UNKNOWN	Placeholder for unmapped kernel error codes.

Filesystem failures reach userspace through a mapping rather than as their own codes: FileNotFound becomes ENOENT, NotAFile becomes EISDIR, NotADir becomes ENOTDIR, Busy becomes EBUSY, InvalidFs and InvalidArgument become EINVAL, and everything else, including a corrupt filesystem and an AHCI error, becomes EIO.

Adding one

Four edits, in this order:

1. A number constant and a dispatch arm in kernel/src/syscalls/mod.rs. The arm unpacks registers and calls the implementation; it does not contain logic.
2. The implementation in the matching syscalls/*.rs, taking real types rather than registers, clearing the caller’s error code first and copying user memory through the checked helpers.
3. A wrapper in programs/edos_lib/, or in the edos_rt crate and the std fork if it has to be reachable through std.
4. A row here, since this page is transcribed from that table.