Initial commit: Schunix as it stands before the SchOS rename

An x86-64 operating system built from xv6, now largely rewritten: SMP,
a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF
rasteriser, and a Linux-numbered syscall ABI.

No history before this point -- the tree was never under version control.
This commit exists so the rename that follows has something to undo to.

include/posix.h

@@ -0,0 +1,289 @@
+// SPDX-License-Identifier: Apache-2.0
+// Schunix — POSIX-compatibility types used by kernel syscall handlers.
+#pragma once
+#include "types.h"
+#include "date.h"
+
+struct iovec {
+    void   *iov_base;
+    uint64  iov_len;
+};
+
+// Linux's IOV_MAX. readv/writev used to cap iovcnt at 16 -- which is legal,
+// since POSIX only requires 16 -- and returned EINVAL above it. But programs
+// are written against the platform they run on, and on Linux that limit is
+// 1024: toybox's `yes` builds a 256-entry iovec and writev()s it in a loop,
+// so `yes | head -2` failed with "Invalid argument" before producing a single
+// byte. Nothing here costs per-entry memory; the count is just a loop bound.
+#define UIO_MAXIOV 1024
+
+// Simplified termios (matches Linux x86_64 layout enough for basic use).
+struct termios {
+    uint32 c_iflag;
+    uint32 c_oflag;
+    uint32 c_cflag;
+    uint32 c_lflag;
+    uint8  c_line;
+    uint8  c_cc[19];
+    uint32 c_ispeed;
+    uint32 c_ospeed;
+};
+
+// Terminal flags, with Linux's values. The kernel honours the ones marked
+// below; the rest are accepted and stored so a program that sets them and
+// reads them back sees what it wrote, which is what cfmakeraw() and every
+// line-editing library actually check.
+//
+// c_iflag
+#define IGNBRK  0000001
+#define BRKINT  0000002
+#define IGNPAR  0000004
+#define PARMRK  0000010
+#define INPCK   0000020
+#define ISTRIP  0000040   // honoured: strip the eighth bit
+#define INLCR   0000100   // honoured: NL -> CR on input
+#define IGNCR   0000200   // honoured: drop CR
+#define ICRNL   0000400   // honoured: CR -> NL on input
+#define IUCLC   0001000
+#define IXON    0002000
+#define IXANY   0004000
+#define IXOFF   0010000
+#define IMAXBEL 0020000
+#define IUTF8   0040000
+
+// c_oflag
+#define OPOST   0000001   // honoured: enable output processing
+#define OLCUC   0000002
+#define ONLCR   0000004   // honoured: NL -> CR NL on output
+#define OCRNL   0000010
+#define ONOCR   0000020
+#define ONLRET  0000040
+
+// c_cflag
+#define CS8     0000060
+#define CREAD   0000200
+#define HUPCL   0002000
+#define CLOCAL  0004000
+
+// c_lflag
+#define ISIG    0000001   // honoured: INTR/QUIT/SUSP generate signals
+#define ICANON  0000002   // honoured: line-at-a-time with editing
+#define ECHO    0000010   // honoured
+#define ECHOE   0000020   // honoured: ERASE rubs the character out
+#define ECHOK   0000040
+#define ECHONL  0000100   // honoured: echo NL even with ECHO off
+#define NOFLSH  0000200
+#define TOSTOP  0000400
+#define IEXTEN  0100000
+
+// c_cc indices (Linux order). VMIN/VTIME share slots with VEOF/VEOL, which is
+// why they are only meaningful in the mode the other pair is not.
+#define VINTR    0
+#define VQUIT    1
+#define VERASE   2
+#define VKILL    3
+#define VEOF     4
+#define VTIME    5
+#define VMIN     6
+#define VSWTC    7
+#define VSTART   8
+#define VSTOP    9
+#define VSUSP   10
+#define VEOL    11
+#define VREPRINT 12
+#define VDISCARD 13
+#define VWERASE 14
+#define VLNEXT  15
+#define VEOL2   16
+
+struct winsize {
+    uint16 ws_row;
+    uint16 ws_col;
+    uint16 ws_xpixel;
+    uint16 ws_ypixel;
+};
+
+struct rlimit {
+    uint64 rlim_cur;
+    uint64 rlim_max;
+};
+
+// Linux ioctl codes we handle.
+#define TCGETS      0x5401
+#define TCSETS      0x5402
+#define TCSETSW     0x5403
+#define TCSETSF     0x5404
+#define TIOCGPGRP   0x540F
+#define TIOCSPGRP   0x5410
+#define TIOCGWINSZ  0x5413
+#define TIOCSWINSZ  0x5414
+#define TIOCSCTTY   0x540E
+#define TIOCGSERIAL 0x541E
+#define FIONREAD    0x541B
+#define TIOCEXCL    0x540C
+#define TIOCNXCL    0x540D
+
+// arch_prctl commands
+#define ARCH_SET_GS 0x1001
+#define ARCH_SET_FS 0x1002
+#define ARCH_GET_FS 0x1003
+#define ARCH_GET_GS 0x1004
+
+// clone flags (subset)
+#define CLONE_VM      0x00000100
+#define CLONE_THREAD  0x00010000
+#define CLONE_SIGHAND 0x00000800
+
+// futex ops
+#define FUTEX_WAIT         0
+#define FUTEX_WAKE         1
+#define FUTEX_WAIT_PRIVATE 128
+#define FUTEX_WAKE_PRIVATE 129
+
+// Resource limit codes (POSIX)
+#define RLIMIT_AS     9
+#define RLIMIT_STACK  3
+#define RLIMIT_NOFILE 7
+
+// clock IDs
+#define CLOCK_REALTIME  0
+#define CLOCK_MONOTONIC 1
+
+struct timespec {
+    long tv_sec;
+    long tv_nsec;
+};
+
+struct itimerval {
+    struct timeval it_interval;
+    struct timeval it_value;
+};
+
+struct rusage {
+    struct timeval ru_utime;
+    struct timeval ru_stime;
+    long ru_maxrss;
+    long ru_ixrss;
+    long ru_idrss;
+    long ru_isrss;
+    long ru_minflt;
+    long ru_majflt;
+    long ru_nswap;
+    long ru_inblock;
+    long ru_oublock;
+    long ru_msgsnd;
+    long ru_msgrcv;
+    long ru_nsignals;
+    long ru_nvcsw;
+    long ru_nivcsw;
+};
+
+struct tms {
+    long tms_utime;
+    long tms_stime;
+    long tms_cutime;
+    long tms_cstime;
+};
+
+struct sysinfo {
+    long   uptime;
+    uint64 loads[3];
+    uint64 totalram;
+    uint64 freeram;
+    uint64 sharedram;
+    uint64 bufferram;
+    uint64 totalswap;
+    uint64 freeswap;
+    uint16 procs;
+    uint16 pad;
+    uint32 pad2;
+    uint64 totalhigh;
+    uint64 freehigh;
+    uint32 mem_unit;
+    char   _f[8];
+};
+
+struct statfs {
+    int64  f_type;
+    int64  f_bsize;
+    int64  f_blocks;
+    int64  f_bfree;
+    int64  f_bavail;
+    int64  f_files;
+    int64  f_ffree;
+    int64  f_fsid[2];
+    int64  f_namelen;
+    int64  f_frsize;
+    int64  f_flags;
+    int64  f_spare[4];
+};
+
+// at-syscall dirfd sentinel
+#define AT_FDCWD            (-100)
+#define AT_REMOVEDIR        0x200
+#define AT_SYMLINK_NOFOLLOW 0x100
+#define AT_EMPTY_PATH       0x1000
+#define AT_NO_AUTOMOUNT     0x800
+
+// prctl options
+#define PR_SET_NAME     15
+#define PR_GET_NAME     16
+#define PR_SET_DUMPABLE  4
+#define PR_GET_DUMPABLE  3
+
+// signal numbers (Linux x86_64 values), used by kill dispatch and
+// default-action classification in sigsend()
+#define SIGHUP    1
+#define SIGINT    2
+#define SIGQUIT   3
+#define SIGILL    4
+#define SIGABRT   6
+#define SIGBUS    7
+#define SIGFPE    8
+#define SIGKILL   9
+#define SIGUSR1  10
+#define SIGSEGV  11
+#define SIGUSR2  12
+#define SIGPIPE  13
+#define SIGALRM  14
+#define SIGTERM  15
+#define SIGCHLD  17
+#define SIGCONT  18
+#define SIGSTOP  19
+// Job-control and the remaining standard signals. A shell needs the TSTP/
+// TTIN/TTOU trio to implement ^Z and background-job terminal access at all;
+// they were simply absent, so any reference to them failed to compile.
+#define SIGTRAP   5
+#define SIGTSTP  20
+#define SIGTTIN  21
+#define SIGTTOU  22
+#define SIGURG   23
+#define SIGXCPU  24
+#define SIGXFSZ  25
+#define SIGVTALRM 26
+#define SIGPROF  27
+#define SIGWINCH 28
+#define SIGIO    29
+#define SIGPWR   30
+#define SIGSYS   31
+
+// getrusage who
+#define RUSAGE_SELF     0
+#define RUSAGE_CHILDREN (-1)
+
+// fallocate mode
+#define FALLOC_FL_KEEP_SIZE 1
+
+// poll(2) event bits (Linux values)
+#define POLLIN    0x001
+#define POLLPRI   0x002
+#define POLLOUT   0x004
+#define POLLERR   0x008
+#define POLLHUP   0x010
+#define POLLNVAL  0x020
+
+struct pollfd {
+    int   fd;
+    short events;
+    short revents;
+};