System calls — `int 0x80`¶

Ring-3 programs talk to the kernel through software interrupt 0x80. The syscall number goes in EAX; arguments in EBX/ECX/EDX/ESI (usage per entry below); the return value replaces EAX. Numbers are append-only: new syscalls are only ever added at the end (table in kernel/library/syscall.cpp, constants in kernel/library/header/syscall.h). Number #0 is deliberately unused — it catches "forgot to set EAX".

From ring 3, pointers must live inside the task's user region or the call fails with SYS_EFAULT (uaccess check). Most calls return a negative SYS_E* errno on failure; the convention per call is noted.

Console & input (#1–#10, #23–#24, #32–#33)¶

#	Name	Signature	Returns
1	`SYS_EXIT`	`(status)`	does not return
8	`SYS_GETKEY`	`()`	blocking key / -1
9	`SYS_READLINE`	`(buf, maxlen)`	line length
23	`SYS_POLLKEY`	`()`	non-blocking key / 0
24	`SYS_MOUSE`	`(state*)`	absolute position + buttons
32	`SYS_KEYEVENT`	`()`	press/release event + raw code
33	`SYS_MOUSEDELTA`	`(int32 dxdy[2])`	PS/2 delta, buttons

Output & text (#4, #10, #11, #28)¶

#	Name	Signature	Returns
4	`SYS_WRITE`	`(fd, buf, len)`	bytes written
10	`SYS_PRINT`	`(str)`	0
11	`SYS_PRINTINT`	`(num)`	0
28	`SYS_PRINTF`	`(fmt, int args[3])`	chars printed

Legacy whole-file I/O (#6, #7, #16–#19)¶

#	Name	Signature	Returns
6	`SYS_OPEN`	`(path)`	fd (3+), read-only
7	`SYS_CLOSE`	`(fd)`	0
16	`SYS_MKFILE`	`(path, buf, len)`	0 / errno
17	`SYS_READFILE`	`(path, buf, maxlen)`	bytes / errno
18	`SYS_FILESIZE`	`(path)`	size / errno
19	`SYS_FILEEXISTS`	`(path)`	0/1

Positional file I/O (#5, #27, #40–#48)¶

#	Name	Signature	Returns
5	`SYS_READ`	`(fd, buf, len)`	bytes / 0 = EOF
27	`SYS_LSEEK`	`(fd, off, whence)`	new position
40	`SYS_OPEN2`	`(path, flags)`	fd — flags: `O_CREAT/TRUNC/APPEND/EXCL/DIR`
41	`SYS_UNLINK`	`(path)`	0
42	`SYS_MKDIR`	`(path)`	0
43	`SYS_RMDIR`	`(path)`	0 (empty dir)
44	`SYS_RENAME`	`(old, new)`	0
45	`SYS_STAT`	`(path, morph_stat_t*)`	0
46	`SYS_READDIR`	`(fd, morph_dirent_t*)`	1 = entry / 0 = end
47	`SYS_FSTAT`	`(fd, morph_stat_t*)`	0

Per-task fd tables (cwd + args live in struct Task); writes go write-through to FAT32 on close.

Memory (#12, #48, #51)¶

#	Name	Signature	Returns
12	`SYS_MALLOC`	`(size)`	pointer / 0 (per-task MRP arena)
48	`SYS_FREE`	`(ptr)`	0
51	`SYS_MEMINFO`	`(u32 w[6])`	pool stats (total/free, faulted, reserved, zombies)

Time, misc, introspection (#13–#15, #29, #34)¶

#	Name	Signature	Returns
13	`SYS_GETTICK`	`()`	timer ticks since boot (100 Hz)
14	`SYS_SLEEP`	`(ms)`	0 — tick-precise
15	`SYS_GETARGS`	`(buf, maxlen)`	spawn args length
29	`SYS_RINGINFO`	`()`	caller CPL: 0 = kernel, 3 = user
34	`SYS_NETINFO`	`(u32 w[10])`	NIC/stack info

Graphics & audio (#20–#22, #25–#26, #30–#31, #53–#54)¶

#	Name	Signature	Returns
20	`SYS_FBINFO`	`(info*)`	framebuffer geometry
21	`SYS_PUTPIXEL`	`(x, y, color)`	0
22	`SYS_FILLRECT`	`(x\\|w<<16, y\\|h<<16, color)`	0
25	`SYS_SPEAKER`	`(freq)`	0 — 0 = off
26	`SYS_SNDBEEP`	`(freq, ms)`	queued beep
30	`SYS_BLIT`	`(src, w\\|h<<16, flags)`	8-bpp blit; flags: stretch / 4:3 letterbox (DOOM)
31	`SYS_SETPAL`	`(pal*)`	256×RGB palette
53	`SYS_SETCLIP`	`(x\\|w<<16, y\\|h<<16)`	per-task draw window
54	`SYS_DRAWLINE`	`(x0\\|y0<<16, x1\\|y1<<16, color)`	Bresenham, focus-gated

Processes (#2, #3, #36–#39, #49, #52)¶

#	Name	Signature	Returns
2	`SYS_EXEC`	`(path)`	run `.mrp` (legacy, single-arena)
3	`SYS_GETPID`	`()`	pid
36	`SYS_SPAWN`	`(path, arena_hint)`	new user task
37	`SYS_YIELD`	`()`	0
38	`SYS_TASKINFO`	`(u32 info[])`	task count (feeds `ps`)
39	`SYS_KILL`	`(pid)`	0
49	`SYS_WAIT`	`(pid, u32* status)`	child pid — blocks like waitpid
52	`SYS_SPAWN2`	`(path, hint, args)`	pid — spawn with argv

Lifecycle: spawn → run → exit → child becomes zombie (slot held for the parent) → wait reaps it; orphans are reaped when the parent dies. MAX_TASKS = 8.

Pipes & network (#35, #50)¶

#	Name	Signature	Returns
35	`SYS_NETPING`	`(ip)`	ICMP echo, 0–4 replies
50	`SYS_PIPE`	`(int fds[2])`	4 KB kernel ring, ref-counted, inherited across spawn; blocking read/write, EOF + broken-pipe detection

Errno values¶

Value	Constant	Meaning
-1	`SYS_ENOSYS`	unknown syscall / not implemented
-2	`SYS_EBADF`	invalid fd / not open
-3	`SYS_ENOENT`	path does not exist
-4	`SYS_EISDIR`	path is a directory
-5	`SYS_ENOMEM`	allocation failed / arena full
-6	`SYS_EINVAL`	invalid argument
-7	`SYS_ENOTSUP`	not supported (yet)
-8	`SYS_EMFILE`	fd table full
-9	`SYS_EBUSY`	nested exec rejected (arena busy)
-10	`SYS_EFAULT`	argument pointer outside the user region
-11	`SYS_EIO`	disk I/O error (FAT32 write-through)
-12	`SYS_EEXIST`	`O_EXCL` / mkdir / rename target exists
-13	`SYS_ECHILD`	`wait()` without a matching live child

Inspect the live table from the shell with syscalls; sctest runs a self-test of the dispatch path.

System calls — int 0x80¶