//! System calls via the `syscall` instruction. //! //! ABI (like Linux x86_64): number in rax, arguments in rdi, rsi, rdx, r10, //! r8, r9; result in rax; negative results are `-errno`. The `syscall` //! instruction itself clobbers rcx (return address) and r11 (saved //! RFLAGS); every other register is preserved for the caller. //! //! Numbers are Linux's where Linux has the same call, so `strace` output and //! man pages mostly apply. The process calls added in stage 14 (fork, //! execve, wait4, mmap, signals, dup, pipe2, fcntl, process groups) follow //! Linux exactly -- C strings, structs, flags -- so a C library can use //! them as they are. The older file calls still take paths as pointer + //! length (Linux: NUL-terminated); relative paths start at the cwd. //! //! | nr | name | arguments | note | //! |-----|-------------|-------------------------------------|------| //! | 0 | read | fd, buf, len | blocks: console until Enter, pipe until data/EOF | //! | 1 | write | fd, buf, len | to a pipe without readers: EPIPE + SIGPIPE | //! | 2 | open | path, path_len, flags | O_CREAT 0o100, O_TRUNC 0o1000, O_APPEND, O_CLOEXEC 0o2000000 | //! | 3 | close | fd | | //! | 4 | stat | path, path_len, *Stat | our own small `Stat {kind, size, mode}`; follows symlinks | //! | 5 | fstat | fd, *Stat | | //! | 8 | lseek | fd, offset, whence | SEEK_SET/CUR/END = 0/1/2 | //! | 9 | mmap | addr, len, prot, flags, fd, offset | MAP_PRIVATE/SHARED, MAP_ANONYMOUS, MAP_FIXED; files: private only | //! | 10 | mprotect | addr, len, prot | PROT_READ 1, PROT_WRITE 2, PROT_EXEC 4 | //! | 11 | munmap | addr, len | | //! | 12 | brk | addr | returns the (new) end of the heap; brk(0) = current | //! | 13 | rt_sigaction | sig, *new, *old, 8 | kernel `struct sigaction`; handlers need SA_RESTORER | //! | 14 | rt_sigprocmask | how, *set, *old, 8 | SIG_BLOCK 0 / SIG_UNBLOCK 1 / SIG_SETMASK 2 | //! | 15 | rt_sigreturn | | only from a signal handler's restorer | //! | 16 | ioctl | fd, request, arg | console: TTY_SET_RAW (ours), TIOCGPGRP, TIOCSPGRP, TIOCGWINSZ; /dev/fb0: FB_* (below) | //! | 22 | pipe | *[u32; 2] | [read end, write end] | //! | 24 | sched_yield | | | //! | 32 | dup | fd | lowest free fd | //! | 33 | dup2 | old, new | closes `new` first if open | //! | 34 | pause | | sleeps until a signal; returns EINTR | //! | 35 | sleep_ms | milliseconds | Linux's nr 35 is nanosleep(timespec); ours is simpler. EINTR on a signal | //! | 39 | getpid | | | //! | 41 | socket | domain, type, protocol | AF_INET (2) only; SOCK_STREAM (1) = TCP, SOCK_DGRAM (2) = UDP, SOCK_DGRAM + IPPROTO_ICMP (1) = ping socket | //! | 42 | connect | fd, *sockaddr_in, len | TCP: handshake, blocks (10 s timeout); UDP/ICMP: set default destination | //! | 43 | accept | fd, *sockaddr_in or 0, *u32 len or 0 | blocks for a connection (SO_RCVTIMEO applies); returns the new fd | //! | 44 | sendto | fd, buf, len, flags, *sockaddr_in or 0 | Linux has a 6th arg (addrlen); we only take 5, the address is always 16 bytes | //! | 45 | recvfrom | fd, buf, len, flags, *sockaddr_in or 0 | blocks (SO_RCVTIMEO -> EAGAIN); 0 = TCP peer closed. No addrlen pointer | //! | 49 | bind | fd, *sockaddr_in, len | sets the local port (address ignored: we have one) | //! | 50 | listen | fd, backlog | TCP; backlog 1..4 | //! | 54 | setsockopt | fd, level, name, *value, len | only SOL_SOCKET (1) / SO_RCVTIMEO (20) with a `struct timeval` | //! | 56 | clone | flags, stack, ... | only fork-like flags: SIGCHLD + optional CLONE_VFORK (else ENOSYS) | //! | 57 | fork | | copy-on-write; parent gets the pid, child 0 | //! | 58 | vfork | | fork + the parent waits until the child execs or exits | //! | 59 | execve | path, argv, envp (C strings) | Linux's stack layout: argc, argv, envp, auxv | //! | 60 | exit | code | | //! | 61 | wait4 | pid, *status, options, *rusage | WNOHANG 1, WUNTRACED 2, WCONTINUED 8; rusage must be 0 | //! | 62 | kill | pid, sig | pid 0 = my group, -1 = all, < -1 = group -pid | //! | 63 | uname | *utsname | Linux's `struct utsname` (6 x 65-byte strings) | //! | 72 | fcntl | fd, cmd, arg | F_DUPFD 0, F_GETFD 1, F_SETFD 2, F_GETFL 3, F_SETFL 4, F_DUPFD_CLOEXEC 1030 | //! | 79 | getcwd | buf, len | returns the length (no NUL) | //! | 80 | chdir | path, path_len | | //! | 83 | mkdir | path, path_len | | //! | 84 | rmdir | path, path_len | only empty directories | //! | 87 | unlink | path, path_len | files and symlinks (not what a symlink points to) | //! | 89 | readlink | path, path_len, buf, len | a symlink's target; returns its length (cut to `len`, no NUL) | //! | 109 | setpgid | pid, pgid | 0 = myself / a new group | //! | 110 | getppid | | 0 if started by the kernel or orphaned | //! | 111 | getpgrp | | | //! | 121 | getpgid | pid | | //! | 217 | getdents64 | fd, buf, len | Linux `struct linux_dirent64` records | //! | 228 | clock_gettime | clock, *timespec | CLOCK_REALTIME/MONOTONIC both = time since boot (we have no RTC driver) | //! | 231 | exit_group | code | = exit (one thread per process) | //! | 292 | dup3 | old, new, flags | flags: O_CLOEXEC | //! | 293 | pipe2 | *[u32; 2], flags | flags: O_CLOEXEC | //! | 318 | getrandom | buf, len, flags | random bytes (virtio-rng); up to 64 KiB per call; flags ignored | //! | 500 | spawn | path, path_len, argv, argv_len, *SpawnOptions | ours: new process running a program (fork+exec in one step, like posix_spawn) | //! | 501 | mounts | buf, len | ours: "path fstype\n" per mount (Linux: read /proc/mounts) | //! | 502 | sysinfo | *SysInfo | ours: CPUs, threads, memory, per-CPU busy time (Linux: /proc/stat etc.) | //! | 503 | resolve | name, name_len, *[[u8; 4]], max | ours: DNS lookup (A records), returns the count. Linux does DNS in libc | //! | 504 | netinfo | *NetInfo | ours: MAC, IP, gateway, DNS, packet counters (Linux: netlink/ioctls) | //! | 505 | trace_me | on | ours: print my syscalls from now on (survives execve; `run --trace`) | //! //! spawn's `argv` is all arguments separated by NUL bytes ("ls\0-l\0/bin"); //! empty means just [program name]. `SpawnOptions` (or a null pointer for //! the defaults) picks the child's stdin/stdout/stderr from the caller's fds //! (-1 = same as mine) and flags (SPAWN_TRACE = print its syscalls). //! //! The framebuffer ioctls (on an fd of /dev/fb0; numbers in Linux's 'F' //! range, but the structs are our own -- Linux's fb_var_screeninfo has 40 //! fields): //! //! FB_GET_INFO 0x4600 *FbInfo {width, height, stride_bytes, bpp} (u32s) //! FB_FLUSH 0x46f0 *[x, y, w, h] or 0 = what `write` changed: show it //! FB_FILL 0x46f1 *[x, y, w, h, 0x00RRGGBB]: fill (not flushed) //! FB_SET_CONSOLE 0x46f2 *[x, y, w, h] or 0 = full screen: move the text //! console there; returns columns << 16 | rows //! //! What happens on `syscall` (the CPU does steps 1-3 in one instruction): //! 1. rcx = user RIP (next instruction), r11 = user RFLAGS //! 2. RFLAGS &= !SFMASK (we mask IF -> interrupts off) //! 3. CS/SS = kernel selectors from STAR, RIP = LSTAR (`syscall_entry`), CPL = 0 //! ...but RSP is still the *user* stack! The CPU doesn't switch stacks for //! `syscall` (unlike interrupts, which use TSS.RSP0). So `syscall_entry` //! must do it first: stash the user RSP, load this thread's kernel stack, //! save all registers as a `TrapFrame` (trap.rs), re-enable interrupts and //! call `syscall_dispatch` in Rust. The way back is trap.rs's common exit, //! `iretq` (stage 13 used the faster `sysretq`, but that can't restore //! rcx/r11, which a signal handler's return needs). //! //! **Several CPUs.** The "kernel stack of the running thread" differs per //! CPU, but at the entry we have no free register to compute which CPU we //! are on. The trick every x86_64 kernel uses: the GS segment base. Each CPU //! keeps a pointer to its own `smp::PerCpu` block in the KERNEL_GS_BASE MSR; //! `swapgs` swaps that with the (user's) GS base, so for a few instructions //! `gs:[0]` is *this CPU's* kernel stack and `gs:[8]` a scratch slot. We //! swap back right after switching stacks, so the thread can be moved to //! another CPU later without any GS confusion. //! //! Why not `int 0x80`? It also works (and is simpler: the CPU switches stacks //! via TSS.RSP0 for us), but `syscall` is what Linux and every modern x86_64 //! OS use, and it's faster. use crate::errno::Errno; use crate::fs::file::{InodeFile, Stat}; use crate::fs::{self, InodeKind}; use crate::trap::TrapFrame; use crate::{memory, process, signal, thread}; use alloc::{string::String, sync::Arc, vec::Vec}; use core::arch::global_asm; use core::sync::atomic::Ordering; pub const SYS_READ: u64 = 0; pub const SYS_WRITE: u64 = 1; pub const SYS_OPEN: u64 = 2; pub const SYS_CLOSE: u64 = 3; pub const SYS_STAT: u64 = 4; pub const SYS_FSTAT: u64 = 5; pub const SYS_LSEEK: u64 = 8; pub const SYS_IOCTL: u64 = 16; pub const SYS_PIPE: u64 = 22; pub const SYS_SCHED_YIELD: u64 = 24; pub const SYS_SLEEP_MS: u64 = 35; pub const SYS_GETPID: u64 = 39; pub const SYS_EXIT: u64 = 60; pub const SYS_UNAME: u64 = 63; pub const SYS_GETCWD: u64 = 79; pub const SYS_CHDIR: u64 = 80; pub const SYS_MKDIR: u64 = 83; pub const SYS_RMDIR: u64 = 84; pub const SYS_UNLINK: u64 = 87; pub const SYS_READLINK: u64 = 89; pub const SYS_SOCKET: u64 = 41; pub const SYS_CONNECT: u64 = 42; pub const SYS_ACCEPT: u64 = 43; pub const SYS_SENDTO: u64 = 44; pub const SYS_RECVFROM: u64 = 45; pub const SYS_BIND: u64 = 49; pub const SYS_LISTEN: u64 = 50; pub const SYS_SETSOCKOPT: u64 = 54; pub const SYS_GETDENTS64: u64 = 217; pub const SYS_GETRANDOM: u64 = 318; pub const SYS_CLOCK_GETTIME: u64 = 228; pub const SYS_SPAWN: u64 = 500; pub const SYS_MOUNTS: u64 = 501; pub const SYS_SYSINFO: u64 = 502; pub const SYS_RESOLVE: u64 = 503; pub const SYS_NETINFO: u64 = 504; pub const SYS_MMAP: u64 = 9; pub const SYS_MPROTECT: u64 = 10; pub const SYS_MUNMAP: u64 = 11; pub const SYS_BRK: u64 = 12; pub const SYS_RT_SIGACTION: u64 = 13; pub const SYS_RT_SIGPROCMASK: u64 = 14; pub const SYS_RT_SIGRETURN: u64 = 15; pub const SYS_DUP: u64 = 32; pub const SYS_DUP2: u64 = 33; pub const SYS_PAUSE: u64 = 34; pub const SYS_CLONE: u64 = 56; pub const SYS_FORK: u64 = 57; pub const SYS_VFORK: u64 = 58; pub const SYS_EXECVE: u64 = 59; pub const SYS_WAIT4: u64 = 61; pub const SYS_KILL: u64 = 62; pub const SYS_FCNTL: u64 = 72; pub const SYS_SETPGID: u64 = 109; pub const SYS_GETPPID: u64 = 110; pub const SYS_GETPGRP: u64 = 111; pub const SYS_GETPGID: u64 = 121; pub const SYS_EXIT_GROUP: u64 = 231; pub const SYS_DUP3: u64 = 292; pub const SYS_PIPE2: u64 = 293; pub const SYS_TRACE_ME: u64 = 505; // Socket constants (Linux's values). pub const AF_INET: u64 = 2; pub const SOCK_STREAM: u64 = 1; pub const SOCK_DGRAM: u64 = 2; pub const IPPROTO_ICMP: u64 = 1; pub const SOL_SOCKET: u64 = 1; pub const SO_RCVTIMEO: u64 = 20; pub const O_CREAT: u64 = 0o100; pub const O_TRUNC: u64 = 0o1000; pub const O_APPEND: u64 = 0o2000; pub const O_NONBLOCK: u64 = 0o4000; pub const O_CLOEXEC: u64 = 0o2000000; /// fcntl commands. pub const F_DUPFD: u64 = 0; pub const F_GETFD: u64 = 1; pub const F_SETFD: u64 = 2; pub const F_GETFL: u64 = 3; pub const F_SETFL: u64 = 4; pub const F_DUPFD_CLOEXEC: u64 = 1030; pub const FD_CLOEXEC: u64 = 1; /// Terminal ioctls (Linux's numbers). pub const TIOCGPGRP: u64 = 0x540F; pub const TIOCSPGRP: u64 = 0x5410; pub const TIOCGWINSZ: u64 = 0x5413; /// mmap flags. pub const MAP_SHARED: u64 = 0x01; pub const MAP_PRIVATE: u64 = 0x02; pub const MAP_FIXED: u64 = 0x10; pub const MAP_ANONYMOUS: u64 = 0x20; /// clone flags we understand. pub const CLONE_VFORK: u64 = 0x4000; /// ioctl request (ours): arg 1 = raw mode, 0 = cooked; returns the old mode. pub const TTY_SET_RAW: u64 = 1; pub const SPAWN_TRACE: u64 = 1; /// Framebuffer ioctls (see the table at the top). pub const FB_GET_INFO: u64 = 0x4600; pub const FB_FLUSH: u64 = 0x46f0; pub const FB_FILL: u64 = 0x46f1; pub const FB_SET_CONSOLE: u64 = 0x46f2; /// Name of a syscall number (for tracing). pub fn name(nr: u64) -> &'static str { match nr { SYS_READ => "read", SYS_WRITE => "write", SYS_OPEN => "open", SYS_CLOSE => "close", SYS_STAT => "stat", SYS_FSTAT => "fstat", SYS_LSEEK => "lseek", SYS_IOCTL => "ioctl", SYS_PIPE => "pipe", SYS_SCHED_YIELD => "sched_yield", SYS_SLEEP_MS => "sleep_ms", SYS_GETPID => "getpid", SYS_EXIT => "exit", SYS_WAIT4 => "wait4", SYS_MMAP => "mmap", SYS_MPROTECT => "mprotect", SYS_MUNMAP => "munmap", SYS_BRK => "brk", SYS_RT_SIGACTION => "rt_sigaction", SYS_RT_SIGPROCMASK => "rt_sigprocmask", SYS_RT_SIGRETURN => "rt_sigreturn", SYS_DUP => "dup", SYS_DUP2 => "dup2", SYS_DUP3 => "dup3", SYS_PAUSE => "pause", SYS_CLONE => "clone", SYS_FORK => "fork", SYS_VFORK => "vfork", SYS_EXECVE => "execve", SYS_KILL => "kill", SYS_FCNTL => "fcntl", SYS_SETPGID => "setpgid", SYS_GETPPID => "getppid", SYS_GETPGRP => "getpgrp", SYS_GETPGID => "getpgid", SYS_EXIT_GROUP => "exit_group", SYS_PIPE2 => "pipe2", SYS_TRACE_ME => "trace_me", SYS_UNAME => "uname", SYS_GETCWD => "getcwd", SYS_CHDIR => "chdir", SYS_MKDIR => "mkdir", SYS_RMDIR => "rmdir", SYS_UNLINK => "unlink", SYS_READLINK => "readlink", SYS_GETDENTS64 => "getdents64", SYS_GETRANDOM => "getrandom", SYS_SPAWN => "spawn", SYS_MOUNTS => "mounts", SYS_SYSINFO => "sysinfo", SYS_SOCKET => "socket", SYS_CONNECT => "connect", SYS_ACCEPT => "accept", SYS_SENDTO => "sendto", SYS_RECVFROM => "recvfrom", SYS_BIND => "bind", SYS_LISTEN => "listen", SYS_SETSOCKOPT => "setsockopt", SYS_CLOCK_GETTIME => "clock_gettime", SYS_RESOLVE => "resolve", SYS_NETINFO => "netinfo", _ => "?", } } /// spawn's options, as laid out in user memory. #[repr(C)] #[derive(Clone, Copy)] pub struct SpawnOptions { pub stdin: i64, // caller's fd to use as the child's fd 0; -1 = caller's fd 0 pub stdout: i64, pub stderr: i64, pub flags: u64, } /// Called by the scheduler when switching threads: the kernel stack that /// `syscall` on this CPU should use from now on. pub fn set_kernel_stack(stack_top: u64) { crate::smp::this_cpu().syscall_kernel_rsp.store(stack_top, Ordering::Relaxed); } /// Program the MSRs that make `syscall` work (on the calling CPU; every CPU /// runs this once). pub fn init() { use x86_64::VirtAddr; use x86_64::registers::model_specific::{Efer, EferFlags, KernelGsBase, LStar, SFMask, Star}; use x86_64::registers::rflags::RFlags; let s = crate::gdt::selectors(); unsafe { // EFER.SCE: enable the syscall/sysret instructions at all. Efer::update(|flags| flags.insert(EferFlags::SYSTEM_CALL_EXTENSIONS)); } // STAR: which segments syscall/sysret load (see gdt.rs for the layout rule). Star::write(s.user_code, s.user_data, s.kernel_code, s.kernel_data) .expect("GDT layout doesn't fit syscall/sysret"); // LSTAR: where `syscall` jumps to. LStar::write(VirtAddr::new(syscall_entry as *const () as u64)); // SFMASK: RFLAGS bits to clear on entry. IF: no interrupts until we're on // the kernel stack. DF: Rust expects the direction flag clear. TF: no // single-stepping into the kernel. SFMask::write(RFlags::INTERRUPT_FLAG | RFlags::DIRECTION_FLAG | RFlags::TRAP_FLAG); // KERNEL_GS_BASE: this CPU's PerCpu block, for `swapgs` in the entry. KernelGsBase::write(VirtAddr::from_ptr(crate::smp::this_cpu())); } unsafe extern "C" { fn syscall_entry(); } global_asm!( ".global syscall_entry", "syscall_entry:", // Interrupts are off (SFMASK). Switch to this thread's kernel stack, // found in this CPU's PerCpu block (gs:[0]; gs:[8] is scratch). " swapgs", " mov gs:[8], rsp", " mov rsp, gs:[0]", // Build a TrapFrame (trap.rs), the same layout an interrupt makes: " push 0", // ss (filled in by syscall_dispatch) " push qword ptr gs:[8]", // user rsp " swapgs", // GS back to normal right away " push r11", // user rflags (saved there by `syscall`) " push 0", // cs (filled in by syscall_dispatch) " push rcx", // user rip (saved there by `syscall`) " push rax", // `error` slot: the syscall number " push 0x100", // `vector`: TRAP_SYSCALL " push rax", " push rbx", " push rcx", " push rdx", " push rsi", " push rdi", " push rbp", " push r8", " push r9", " push r10", " push r11", " push r12", " push r13", " push r14", " push r15", " mov rdi, rsp", // syscall_dispatch(&mut TrapFrame) " sti", // we're on our own stack now: preemption is fine " call {dispatch}", // Back to user mode with `iretq` through the common exit (which // restores every register from the frame). Not `sysretq`: fork, execve, // signals and rt_sigreturn may have changed *any* register, and // sysret can't set rcx and r11. " jmp {ret}", dispatch = sym syscall_dispatch, ret = sym crate::trap::trap_return, ); /// Rust side of every system call. Arguments are in the saved registers /// (rdi, rsi, rdx, r10, r8, r9 = a1..a6), the number in `error` (= rax at /// entry); the result goes into the saved rax. extern "C" fn syscall_dispatch(frame: &mut TrapFrame) { let sel = crate::gdt::selectors(); frame.cs = sel.user_code.0 as u64; frame.ss = sel.user_data.0 as u64; let nr = frame.error; let (a1, a2, a3, a4, a5) = (frame.rdi, frame.rsi, frame.rdx, frame.r10, frame.r8); let process = thread::current_process(); let trace = process.as_ref().is_some_and(|p| p.tracing()); if trace && (nr == SYS_EXIT || nr == SYS_EXIT_GROUP) { crate::kprintln!("[trace {}] exit({})", process.as_ref().unwrap().pid, a1 as i64); } drop(process); // don't hold an Arc while blocking/exiting // A successful execve throws away the memory its path lived in, so the // trace line for it is made before the call. let exec_line = (trace && nr == SYS_EXECVE).then(|| trace_line(nr, [a1, a2, a3, a4], 0)); if nr == SYS_RT_SIGRETURN { // Restores *all* registers (rax included) from the signal frame. signal::sys_rt_sigreturn(frame); signal::deliver(frame); // signals unblocked by the restored mask return; } let result = match nr { SYS_READ => sys_read(a1, a2, a3), SYS_WRITE => sys_write(a1, a2, a3), SYS_OPEN => sys_open(a1, a2, a3), SYS_CLOSE => current().and_then(|p| p.close(a1)).map(|_| 0), SYS_STAT => sys_stat(a1, a2, a3), SYS_FSTAT => sys_fstat(a1, a2), SYS_LSEEK => current().and_then(|p| p.file(a1)).and_then(|f| f.seek(a2 as i64, a3)), SYS_MMAP => current().and_then(|p| sys_mmap(&p, a1, a2, a3, a4, a5, frame.r9)), SYS_MPROTECT => current().and_then(|p| sys_mprotect(&p, a1, a2, a3)), SYS_MUNMAP => current().and_then(|p| sys_munmap(&p, a1, a2)), SYS_BRK => current().map(|p| p.mm.lock().set_brk(a1)), SYS_RT_SIGACTION => sys_rt_sigaction(a1, a2, a3, a4), SYS_RT_SIGPROCMASK => sys_rt_sigprocmask(a1, a2, a3, a4), SYS_IOCTL => sys_ioctl(a1, a2, a3), SYS_PIPE => sys_pipe2(a1, 0), SYS_PIPE2 => sys_pipe2(a1, a2), SYS_SCHED_YIELD => { thread::yield_now(); Ok(0) } SYS_DUP => current().and_then(|p| p.file(a1).and_then(|f| p.add_file(f))), SYS_DUP2 => current().and_then(|p| if a1 == a2 { p.file(a1).map(|_| a1) } else { p.dup_to(a1, a2, false) }), SYS_DUP3 => sys_dup3(a1, a2, a3), SYS_PAUSE => Err(thread::pause()), SYS_SLEEP_MS => { // The PIT fires ~18.2 times a second: 1 tick = ~55 ms. Round up. thread::sleep_ticks_intr(a1.div_ceil(55)).map(|_| 0) } SYS_GETPID => current().map(|p| p.pid), SYS_CLONE => sys_clone(frame, a1, a2), SYS_FORK => current().and_then(|p| process::fork(&p, frame, 0, false)), SYS_VFORK => current().and_then(|p| process::fork(&p, frame, 0, true)), SYS_EXECVE => sys_execve(frame, a1, a2, a3), SYS_EXIT | SYS_EXIT_GROUP => process::exit_current(process::ExitStatus::Exited(a1 as i32 as i64)), SYS_WAIT4 => sys_wait4(a1 as i32 as i64, a2, a3), SYS_KILL => current().and_then(|p| signal::sys_kill(&p, a1 as i32 as i64, a2)), SYS_UNAME => sys_uname(a1), SYS_FCNTL => sys_fcntl(a1, a2, a3), SYS_GETCWD => sys_getcwd(a1, a2), SYS_CHDIR => sys_chdir(a1, a2), SYS_MKDIR => user_path(a1, a2).and_then(|p| fs::create(&p, InodeKind::Directory)).map(|_| 0), SYS_RMDIR => user_path(a1, a2).and_then(|p| fs::remove(&p, true)).map(|_| 0), SYS_UNLINK => user_path(a1, a2).and_then(|p| fs::remove(&p, false)).map(|_| 0), SYS_READLINK => sys_readlink(a1, a2, a3, a4), SYS_SETPGID => current().and_then(|p| process::setpgid(&p, a1, a2)).map(|_| 0), SYS_GETPPID => current().map(|p| if p.parent() == process::ORPHAN { 0 } else { p.parent() }), SYS_GETPGRP => current().map(|p| p.pgid()), SYS_GETPGID => current().and_then(|p| if a1 == 0 { Ok(p.pgid()) } else { process::get(a1).map(|t| t.pgid()).ok_or(Errno::ESRCH) }), SYS_GETDENTS64 => sys_getdents64(a1, a2, a3), SYS_SPAWN => sys_spawn(a1, a2, a3, a4, a5), SYS_MOUNTS => sys_mounts(a1, a2), SYS_SYSINFO => sys_sysinfo(a1), SYS_SOCKET => sys_socket(a1, a2, a3), SYS_CONNECT => with_socket(a1, |s| s.connect(read_sockaddr(a2)?)).map(|_| 0), SYS_ACCEPT => sys_accept(a1, a2, a3), SYS_SENDTO => sys_sendto(a1, a2, a3, a5), SYS_RECVFROM => sys_recvfrom(a1, a2, a3, a5), SYS_BIND => with_socket(a1, |s| s.bind(read_sockaddr(a2)?.1)).map(|_| 0), SYS_LISTEN => with_socket(a1, |s| s.listen(a2 as usize)).map(|_| 0), SYS_SETSOCKOPT => sys_setsockopt(a1, a2, a3, a4, a5), SYS_CLOCK_GETTIME => sys_clock_gettime(a2), SYS_RESOLVE => sys_resolve(a1, a2, a3, a4), SYS_NETINFO => copy_to_user(a1, &crate::net::info()).map(|_| 0), SYS_GETRANDOM => sys_getrandom(a1, a2), SYS_TRACE_ME => current().map(|p| p.trace.store(a1 != 0, Ordering::Relaxed)).map(|_| 0), _ => Err(Errno::ENOSYS), }; let ret = match result { Ok(value) => value as i64, Err(errno) => -(errno as i64), }; // execve: success means "the new program starts with these registers" // (rax = 0 there anyway); the frame was replaced, so don't touch it. if !(nr == SYS_EXECVE && ret == 0) { frame.rax = ret as u64; } if trace { let pid = current().map(|p| p.pid).unwrap_or(0); match exec_line { Some(line) if ret == 0 => crate::kprintln!("[trace {}] {}", pid, line), _ => crate::kprintln!("[trace {}] {}", pid, trace_line(nr, [a1, a2, a3, a4], ret)), } } // A signal may have arrived meanwhile (or the call was interrupted by // one): act on it before returning to the program. signal::deliver(frame); } /// One syscall in strace style: `open("/mnt/disk0/readme.txt", 0) = 3`. /// Strings and buffers are read back from user memory (after the call, so /// `read` shows what it got), shortened to 40 bytes. fn trace_line(nr: u64, a: [u64; 4], ret: i64) -> String { use alloc::format; let text = |ptr: u64, len: u64| -> String { let Ok(bytes) = user_slice(ptr, len.min(40)) else { return String::from("") }; let mut s = String::from("\""); for &b in bytes { match b { b'\n' => s.push_str("\\n"), b'"' => s.push_str("\\\""), 0x20..=0x7e => s.push(b as char), _ => s.push_str(&format!("\\x{:02x}", b)), } } s.push('"'); if len > 40 { s.push_str("..."); } s }; let cstr = |ptr: u64| -> String { match user_cstr(ptr, 4096) { Ok(bytes) => format!("\"{}\"", String::from_utf8_lossy(&bytes)), Err(_) => String::from(""), } }; let args = match nr { SYS_READ => format!("{}, {}, {}", a[0], if ret > 0 { text(a[1], ret as u64) } else { String::from("\"\"") }, a[2]), SYS_WRITE => format!("{}, {}, {}", a[0], text(a[1], a[2]), a[2]), SYS_OPEN => format!("{}, {:#o}", text(a[0], a[1]), a[2]), SYS_STAT => format!("{}, {:#x}", text(a[0], a[1]), a[2]), SYS_READLINK => format!("{}, {:#x}, {}", text(a[0], a[1]), a[2], a[3]), SYS_CHDIR | SYS_MKDIR | SYS_RMDIR | SYS_UNLINK => text(a[0], a[1]), SYS_SPAWN => format!("{}, {}", text(a[0], a[1]), text(a[2], a[3])), SYS_SCHED_YIELD | SYS_GETPID => String::new(), SYS_CLOSE | SYS_SLEEP_MS | SYS_EXIT | SYS_EXIT_GROUP | SYS_DUP => format!("{}", a[0] as i64), SYS_PIPE | SYS_UNAME => format!("{:#x}", a[0]), SYS_FSTAT | SYS_GETCWD | SYS_MOUNTS => format!("{}, {:#x}", a[0], a[1]), SYS_WAIT4 => format!("{}, {:#x}, {}", a[0] as i32, a[1], a[2]), SYS_KILL => format!("{}, {}", a[0] as i32, a[1]), SYS_FORK | SYS_VFORK | SYS_GETPPID | SYS_GETPGRP | SYS_PAUSE => String::new(), SYS_EXECVE => format!("{}, ...", cstr(a[0])), SYS_MMAP => format!("{:#x}, {}, {}, {:#x}", a[0], a[1], a[2], a[3]), _ => format!("{}, {:#x}, {:#x}", a[0], a[1], a[2]), }; match Errno::from_ret(ret) { Some(e) if ret < 0 => format!("{}({}) = {} {:?}", name(nr), args, ret, e), _ => format!("{}({}) = {}", name(nr), args, ret), } } fn current() -> Result, Errno> { thread::current_process().ok_or(Errno::EINVAL) } /// Turn a user pointer + length into a slice, after checking that the user /// may really access that memory. Never trust pointers from user space! pub fn user_slice(ptr: u64, len: u64) -> Result<&'static [u8], Errno> { if len == 0 { return Ok(&[]); // nothing to access, so any pointer is fine (like Linux) } if !crate::mm::user_access_ok(ptr, len, false) { return Err(Errno::EFAULT); } Ok(unsafe { core::slice::from_raw_parts(ptr as *const u8, len as usize) }) } /// Like `user_slice`, but the user must be allowed to *write* the memory. pub fn user_slice_mut(ptr: u64, len: u64) -> Result<&'static mut [u8], Errno> { if len == 0 { return Ok(&mut []); } if !crate::mm::user_access_ok(ptr, len, true) { return Err(Errno::EFAULT); } Ok(unsafe { core::slice::from_raw_parts_mut(ptr as *mut u8, len as usize) }) } fn sys_read(fd: u64, buf: u64, len: u64) -> Result { let file = current()?.file(fd)?; // clone the Arc: no lock held while we block let buf = user_slice_mut(buf, len)?; file.read(buf).map(|n| n as u64) } fn sys_write(fd: u64, buf: u64, len: u64) -> Result { let process = current()?; let file = process.file(fd)?; let buf = user_slice(buf, len)?; let result = file.write(buf).map(|n| n as u64); if result == Err(Errno::EPIPE) { // Nobody will ever read this: SIGPIPE, which by default ends the // writer. That's how `yes | head -1` stops `yes`. signal::send(&process, signal::SIGPIPE, signal::SigInfo::from_pid(signal::SIGPIPE, 0)); } result } /// Read a path argument and make it absolute (relative to the cwd). fn user_path(ptr: u64, len: u64) -> Result { if len > 4096 { return Err(Errno::ENAMETOOLONG); } let path = core::str::from_utf8(user_slice(ptr, len)?).map_err(|_| Errno::EINVAL)?; current()?.resolve(path) } /// Copy a plain-data struct out to user memory. fn copy_to_user(ptr: u64, value: &T) -> Result<(), Errno> { let size = core::mem::size_of::(); let dst = user_slice_mut(ptr, size as u64)?; let src = unsafe { core::slice::from_raw_parts(value as *const T as *const u8, size) }; dst.copy_from_slice(src); Ok(()) } /// Copy `N` u32s in from user memory (ioctl arguments). fn read_user_u32s(ptr: u64) -> Result<[u32; N], Errno> { let src = user_slice(ptr, 4 * N as u64)?; let mut out = [0u32; N]; for (i, word) in out.iter_mut().enumerate() { *word = u32::from_le_bytes(src[4 * i..4 * i + 4].try_into().unwrap()); } Ok(out) } fn sys_open(path_ptr: u64, path_len: u64, flags: u64) -> Result { let path = user_path(path_ptr, path_len)?; let inode = match fs::lookup(&path) { Err(Errno::ENOENT) if flags & O_CREAT != 0 => fs::create(&path, InodeKind::File)?, other => other?, }; // Device files (/dev/...) come with their own File. let cloexec = flags & O_CLOEXEC != 0; if let Some(device) = inode.open_device() { return current()?.add_file_with(device, 0, cloexec); } if flags & O_TRUNC != 0 && inode.kind() == InodeKind::File { inode.truncate()?; } let file = if flags & O_APPEND != 0 { InodeFile::open_append(inode)? } else { InodeFile::open(inode)? }; current()?.add_file_with(Arc::new(file), 0, cloexec) } fn sys_stat(path_ptr: u64, path_len: u64, stat_ptr: u64) -> Result { let inode = fs::lookup(&user_path(path_ptr, path_len)?)?; copy_to_user(stat_ptr, &Stat::of(&*inode))?; Ok(0) } fn sys_fstat(fd: u64, stat_ptr: u64) -> Result { let stat = current()?.file(fd)?.stat()?; copy_to_user(stat_ptr, &stat)?; Ok(0) } fn sys_pipe2(fds_ptr: u64, flags: u64) -> Result { if flags & !O_CLOEXEC != 0 { return Err(Errno::EINVAL); // O_NONBLOCK, O_DIRECT: not supported } let cloexec = flags & O_CLOEXEC != 0; user_slice_mut(fds_ptr, 8)?; // check before creating anything let process = current()?; let (reader, writer) = fs::pipe::new(); let read_fd = process.add_file_with(Arc::new(reader), 0, cloexec)?; let write_fd = match process.add_file_with(Arc::new(writer), 0, cloexec) { Ok(fd) => fd, Err(e) => { process.close(read_fd)?; return Err(e); } }; copy_to_user(fds_ptr, &[read_fd as u32, write_fd as u32])?; Ok(0) } fn sys_dup3(old: u64, new: u64, flags: u64) -> Result { if old == new || flags & !O_CLOEXEC != 0 { return Err(Errno::EINVAL); } current()?.dup_to(old, new, flags & O_CLOEXEC != 0) } /// fcntl: just the fd flags (close-on-exec) and duplication. Status flags: /// everything is blocking, read/write (O_NONBLOCK isn't supported yet). fn sys_fcntl(fd: u64, cmd: u64, arg: u64) -> Result { let p = current()?; let file = p.file(fd)?; match cmd { F_DUPFD | F_DUPFD_CLOEXEC if arg as usize >= process::MAX_FDS => Err(Errno::EINVAL), F_DUPFD => p.add_file_with(file, arg as usize, false), F_DUPFD_CLOEXEC => p.add_file_with(file, arg as usize, true), F_GETFD => p.cloexec(fd).map(|on| if on { FD_CLOEXEC } else { 0 }), F_SETFD => p.set_cloexec(fd, arg & FD_CLOEXEC != 0).map(|_| 0), F_GETFL => Ok(2), // O_RDWR F_SETFL if arg & O_NONBLOCK != 0 => Err(Errno::EINVAL), F_SETFL => Ok(0), _ => Err(Errno::EINVAL), } } fn sys_getcwd(buf: u64, len: u64) -> Result { let cwd = current()?.cwd.lock().clone(); if (len as usize) < cwd.len() { return Err(Errno::ERANGE); } user_slice_mut(buf, cwd.len() as u64)?.copy_from_slice(cwd.as_bytes()); Ok(cwd.len() as u64) } fn sys_chdir(path_ptr: u64, path_len: u64) -> Result { let path = user_path(path_ptr, path_len)?; if fs::lookup(&path)?.kind() != InodeKind::Directory { return Err(Errno::ENOTDIR); } *current()?.cwd.lock() = path; Ok(0) } fn sys_readlink(path_ptr: u64, path_len: u64, buf: u64, len: u64) -> Result { let target = fs::readlink(&user_path(path_ptr, path_len)?)?; let n = target.len().min(len as usize); user_slice_mut(buf, n as u64)?.copy_from_slice(&target.as_bytes()[..n]); Ok(n as u64) } fn sys_getdents64(fd: u64, buf: u64, len: u64) -> Result { let file = current()?.file(fd)?; file.getdents(user_slice_mut(buf, len)?).map(|n| n as u64) } fn sys_spawn(path_ptr: u64, path_len: u64, argv_ptr: u64, argv_len: u64, opts_ptr: u64) -> Result { let parent = current()?; let path = user_path(path_ptr, path_len)?; if argv_len as usize > process::MAX_ARGS_SIZE { return Err(Errno::E2BIG); } let blob = core::str::from_utf8(user_slice(argv_ptr, argv_len)?).map_err(|_| Errno::EINVAL)?; let mut args: Vec = blob.split('\0').filter(|a| !a.is_empty()).map(String::from).collect(); if args.is_empty() { args.push(String::from(path.rsplit('/').next().unwrap_or(""))); } let opts = if opts_ptr == 0 { SpawnOptions { stdin: -1, stdout: -1, stderr: -1, flags: 0 } } else { let bytes = user_slice(opts_ptr, core::mem::size_of::() as u64)?; unsafe { core::ptr::read_unaligned(bytes.as_ptr() as *const SpawnOptions) } }; // Child fd n = the caller's fd chosen in the options (-1: the caller's fd n). let pick = |n: u64, choice: i64| parent.file(if choice < 0 { n } else { choice as u64 }); let stdio = [pick(0, opts.stdin)?, pick(1, opts.stdout)?, pick(2, opts.stderr)?]; let spawn = process::SpawnArgs { args, env: parent.env(), stdio, cwd: parent.cwd.lock().clone(), parent: parent.pid, pgid: parent.pgid(), // same process group, like fork trace: opts.flags & SPAWN_TRACE != 0, }; drop(parent); process::spawn_path(&path, spawn).map(|child| child.pid) } fn sys_ioctl(fd: u64, request: u64, arg: u64) -> Result { let process = current()?; let file = process.file(fd)?; if let Some(fb) = file.as_framebuffer() { return fb_ioctl(fb, request, arg); } if file.stat()?.kind != crate::fs::file::KIND_CONSOLE { return Err(Errno::ENOTTY); } match request { TTY_SET_RAW => Ok(crate::tty::set_raw(arg != 0, process.pid) as u64), // Which process group is in the foreground (gets Ctrl+C)? TIOCGPGRP => copy_to_user(arg, &(crate::tty::foreground() as u32)).map(|_| 0), TIOCSPGRP => { let pgid = read_user_u32s::<1>(arg)?[0] as u64; if process::group_members(pgid).is_empty() { return Err(Errno::ESRCH); } crate::tty::set_foreground(pgid); Ok(0) } TIOCGWINSZ => { let (cols, rows) = crate::vga_buffer::size(); copy_to_user(arg, &[rows as u16, cols as u16, 0, 0]).map(|_| 0) } _ => Err(Errno::EINVAL), } } /// The /dev/fb0 ioctls (table at the top of this file). fn fb_ioctl(fb: &crate::dev::Framebuffer, request: u64, arg: u64) -> Result { let info = fb.info; match request { FB_GET_INFO => { copy_to_user(arg, &[info.width, info.height, info.stride * 4, 32u32])?; Ok(0) } FB_FLUSH if arg == 0 => fb.flush().then_some(0).ok_or(Errno::EIO), FB_FLUSH => { let [x, y, w, h] = read_user_u32s::<4>(arg)?; crate::virtio::gpu::flush(x, y, w, h).then_some(0).ok_or(Errno::EIO) } FB_FILL => { let [x, y, w, h, color] = read_user_u32s::<5>(arg)?; fb.fill(x, y, w, h, color); Ok(0) } FB_SET_CONSOLE => { let [x, y, w, h] = if arg == 0 { [0; 4] } else { read_user_u32s::<4>(arg)? }; let (cols, rows) = crate::vga_buffer::set_viewport(crate::fbcon::Rect { x, y, w, h }).ok_or(Errno::ENODEV)?; Ok((cols as u64) << 16 | rows as u64) } _ => Err(Errno::EINVAL), } } /// getrandom(buf, len, flags): Linux 318. We always have "enough entropy" /// (the host's), so the flags (GRND_NONBLOCK, GRND_RANDOM) change nothing. fn sys_getrandom(buf: u64, len: u64) -> Result { let buf = user_slice_mut(buf, len.min(65536))?; crate::virtio::rng::fill(buf); Ok(buf.len() as u64) } /// Linux's `struct utsname`: six NUL-terminated strings of 65 bytes each. fn sys_uname(buf: u64) -> Result { let fields = [ "Rustbelt", // sysname (`uname -s`) "qemu", // nodename (hostname) env!("CARGO_PKG_VERSION"), // release (`uname -r`) "stage 14: processes", // version "x86_64", // machine "(none)", // domainname ]; let out = user_slice_mut(buf, 6 * 65)?; out.fill(0); for (i, field) in fields.iter().enumerate() { out[i * 65..i * 65 + field.len()].copy_from_slice(field.as_bytes()); } Ok(0) } /// What `sysinfo` fills in (ours; the user side is in user/ulib.rs). #[repr(C)] #[derive(Default)] pub struct SysInfo { pub cpus: u64, pub this_cpu: u64, pub threads: u64, pub processes: u64, pub frames_in_use: u64, pub uptime_ticks: u64, /// Per CPU: local-timer ticks so far, and how many found it busy /// (running something other than its idle thread). pub ticks: [u64; 16], pub busy_ticks: [u64; 16], } fn sys_sysinfo(buf: u64) -> Result { let out = user_slice_mut(buf, core::mem::size_of::() as u64)?; let mut info = SysInfo { cpus: crate::smp::cpu_count() as u64, this_cpu: crate::smp::cpu_id() as u64, threads: thread::thread_count() as u64, processes: process::count() as u64, frames_in_use: memory::frames_in_use() as u64, uptime_ticks: crate::interrupts::ticks(), ..Default::default() }; for cpu in 0..info.cpus as usize { (info.ticks[cpu], info.busy_ticks[cpu]) = thread::cpu_ticks(cpu); } let bytes = unsafe { core::slice::from_raw_parts(&info as *const SysInfo as *const u8, core::mem::size_of::()) }; out.copy_from_slice(bytes); Ok(0) } /// The mount table as text, one "path fstype" line per mount. fn sys_mounts(buf: u64, len: u64) -> Result { let mut text = String::new(); for (path, fs_type) in fs::mounts() { text.push_str(&path); text.push(' '); text.push_str(fs_type); text.push('\n'); } if (len as usize) < text.len() { return Err(Errno::ERANGE); } user_slice_mut(buf, text.len() as u64)?.copy_from_slice(text.as_bytes()); Ok(text.len() as u64) } // --- Networking (net/socket.rs does the real work) ----------------------------- /// Linux's `struct sockaddr_in`: family, port and address in network byte /// order (big-endian), 8 bytes of padding. #[repr(C)] #[derive(Clone, Copy, Default)] pub struct SockAddrIn { pub family: u16, pub port_be: u16, pub addr: [u8; 4], pub zero: [u8; 8], } fn read_sockaddr(ptr: u64) -> Result { let bytes = user_slice(ptr, 16)?; let family = u16::from_ne_bytes([bytes[0], bytes[1]]); if family as u64 != AF_INET { return Err(Errno::EAFNOSUPPORT); } Ok(([bytes[4], bytes[5], bytes[6], bytes[7]], u16::from_be_bytes([bytes[2], bytes[3]]))) } fn write_sockaddr(ptr: u64, (addr, port): crate::net::socket::Addr) -> Result<(), Errno> { if ptr == 0 { return Ok(()); // caller doesn't want it } copy_to_user(ptr, &SockAddrIn { family: AF_INET as u16, port_be: port.to_be(), addr, zero: [0; 8] }) } /// Run `f` on the socket behind `fd` (ENOTSOCK if it's another kind of /// file). We hold our own Arc to it, so the fd may be closed meanwhile. fn with_socket(fd: u64, f: impl FnOnce(&crate::net::socket::Socket) -> Result) -> Result { let file = current()?.file(fd)?; f(file.as_socket().ok_or(Errno::ENOTSOCK)?) } fn sys_socket(domain: u64, ty: u64, protocol: u64) -> Result { use crate::net::socket::{Kind, Socket}; if domain != AF_INET { return Err(Errno::EAFNOSUPPORT); } let kind = match (ty & 0xf, protocol) { (SOCK_STREAM, 0 | 6) => Kind::Tcp, (SOCK_DGRAM, 0 | 17) => Kind::Udp, (SOCK_DGRAM, IPPROTO_ICMP) => Kind::Icmp, _ => return Err(Errno::EPROTONOSUPPORT), }; current()?.add_file(Arc::new(Socket::new(kind)?)) } fn sys_accept(fd: u64, addr_ptr: u64, len_ptr: u64) -> Result { let (socket, peer) = with_socket(fd, |s| s.accept())?; let new_fd = current()?.add_file(Arc::new(socket))?; write_sockaddr(addr_ptr, peer)?; if len_ptr != 0 { copy_to_user(len_ptr, &16u32)?; } Ok(new_fd) } fn sys_sendto(fd: u64, buf: u64, len: u64, addr_ptr: u64) -> Result { let to = if addr_ptr == 0 { None } else { Some(read_sockaddr(addr_ptr)?) }; with_socket(fd, |s| s.send(user_slice(buf, len)?, to)).map(|n| n as u64) } fn sys_recvfrom(fd: u64, buf: u64, len: u64, addr_ptr: u64) -> Result { let (n, from) = with_socket(fd, |s| s.recv(user_slice_mut(buf, len)?))?; if let Some(from) = from { write_sockaddr(addr_ptr, from)?; } Ok(n as u64) } /// Only SO_RCVTIMEO: `struct timeval {i64 seconds, i64 microseconds}`; /// zero means "block forever", like Linux. fn sys_setsockopt(fd: u64, level: u64, name: u64, value: u64, len: u64) -> Result { if level != SOL_SOCKET || name != SO_RCVTIMEO || len < 16 { return Err(Errno::EOPNOTSUPP); } let tv = user_slice(value, 16)?; let secs = u64::from_ne_bytes(tv[..8].try_into().unwrap()); let usecs = u64::from_ne_bytes(tv[8..16].try_into().unwrap()); let total = secs.saturating_mul(1_000_000).saturating_add(usecs); with_socket(fd, |s| Ok(s.set_recv_timeout(if total == 0 { None } else { Some(total) })))?; Ok(0) } /// `struct timespec {i64 seconds, i64 nanoseconds}` since boot. fn sys_clock_gettime(ts_ptr: u64) -> Result { let us = crate::time::now_us(); copy_to_user(ts_ptr, &[us / 1_000_000, (us % 1_000_000) * 1000])?; Ok(0) } fn sys_resolve(name_ptr: u64, name_len: u64, out: u64, max: u64) -> Result { if name_len > 253 { return Err(Errno::ENAMETOOLONG); } let name = core::str::from_utf8(user_slice(name_ptr, name_len)?).map_err(|_| Errno::EINVAL)?; let addrs = crate::net::resolve(name, 5_000_000)?; let n = addrs.len().min(max as usize); let dst = user_slice_mut(out, 4 * n as u64)?; for (i, a) in addrs.iter().take(n).enumerate() { dst[4 * i..4 * i + 4].copy_from_slice(a); } Ok(n as u64) } // --- Processes, memory, signals (stage 14) -------------------------------------- /// A NUL-terminated string from user memory (at most `max` bytes). pub fn user_cstr(ptr: u64, max: usize) -> Result, Errno> { let mut out = Vec::new(); // Page by page: the string may end right before an unmapped page. let mut addr = ptr; loop { let chunk = (4096 - addr % 4096).min((max + 1 - out.len()) as u64); let bytes = user_slice(addr, chunk)?; if let Some(end) = bytes.iter().position(|&b| b == 0) { out.extend_from_slice(&bytes[..end]); return Ok(out); } out.extend_from_slice(bytes); if out.len() > max { return Err(Errno::ENAMETOOLONG); } addr += chunk; } } /// A NULL-terminated array of C strings (execve's argv and envp). fn user_cstr_array(ptr: u64) -> Result>, Errno> { let mut out = Vec::new(); if ptr == 0 { return Ok(out); // Linux allows NULL here (an empty list) } let mut total = 0; for i in 0.. { let p = u64::from_le_bytes(user_slice(ptr + 8 * i, 8)?.try_into().unwrap()); if p == 0 { break; } let s = user_cstr(p, process::MAX_ARGS_SIZE)?; total += s.len() + 1; if total > process::MAX_ARGS_SIZE { return Err(Errno::E2BIG); } out.push(s); } Ok(out) } fn sys_execve(frame: &mut TrapFrame, path: u64, argv: u64, envp: u64) -> Result { let p = current()?; let path = String::from_utf8(user_cstr(path, 4096)?).map_err(|_| Errno::EINVAL)?; let path = p.resolve(&path)?; let argv = user_cstr_array(argv)?; let envp = user_cstr_array(envp)?; process::execve(&p, frame, &path, &argv, &envp)?; Ok(0) } /// clone: only the fork-like uses (no threads yet): exit signal SIGCHLD /// (or 0) in the low byte, optionally CLONE_VFORK, optionally a new stack. fn sys_clone(frame: &TrapFrame, flags: u64, stack: u64) -> Result { let exit_signal = flags & 0xff; if flags & !(0xff | CLONE_VFORK) != 0 || (exit_signal != 0 && exit_signal != signal::SIGCHLD as u64) { return Err(Errno::ENOSYS); // CLONE_VM, CLONE_THREAD...: threads are future work } process::fork(¤t()?, frame, stack, flags & CLONE_VFORK != 0) } fn sys_wait4(pid: i64, status_ptr: u64, options: u64) -> Result { if status_ptr != 0 { user_slice_mut(status_ptr, 4)?; // check before reaping anything } let (pid, status) = process::wait4(&*current()?, pid, options)?; if status_ptr != 0 && pid != 0 { copy_to_user(status_ptr, &status)?; } Ok(pid) } fn sys_rt_sigaction(sig: u64, new_ptr: u64, old_ptr: u64, size: u64) -> Result { let new = if new_ptr == 0 { None } else { let bytes = user_slice(new_ptr, core::mem::size_of::() as u64)?; Some(unsafe { core::ptr::read_unaligned(bytes.as_ptr() as *const signal::SigAction) }) }; if old_ptr != 0 { user_slice_mut(old_ptr, 32)?; } let old = signal::sys_rt_sigaction(&*current()?, sig, new, size)?; if old_ptr != 0 { copy_to_user(old_ptr, &old)?; } Ok(0) } fn sys_rt_sigprocmask(how: u64, set_ptr: u64, old_ptr: u64, size: u64) -> Result { let set = if set_ptr == 0 { None } else { Some(u64::from_le_bytes(user_slice(set_ptr, 8)?.try_into().unwrap())) }; let old = signal::sys_rt_sigprocmask(&*current()?, how, set, size)?; if old_ptr != 0 { copy_to_user(old_ptr, &old)?; } Ok(0) } /// mmap(addr, len, prot, flags, fd, offset). The new region is empty: pages /// appear on first touch (demand paging, mm.rs). fn sys_mmap(p: &process::Process, addr: u64, len: u64, prot: u64, flags: u64, fd: u64, offset: u64) -> Result { use crate::mm::{Kind, Mm, Vma}; let len = len.checked_next_multiple_of(4096).ok_or(Errno::ENOMEM)?; let shared = match flags & (MAP_SHARED | MAP_PRIVATE) { MAP_SHARED => true, MAP_PRIVATE => false, _ => return Err(Errno::EINVAL), // exactly one of the two }; if len == 0 || prot & !7 != 0 || offset % 4096 != 0 { return Err(Errno::EINVAL); } let file = if flags & MAP_ANONYMOUS != 0 { None } else { // A file: only read-only sharing of its bytes is supported -- a // private copy of the file's pages (writes stay in this process). // MAP_SHARED of a file would need writes to reach the file (a page // cache), which we don't have. if shared { return Err(Errno::ENODEV); } let inode = p.file(fd)?.inode().ok_or(Errno::ENODEV)?; Some((inode, offset)) }; let mut mm = p.mm.lock(); let start = if flags & MAP_FIXED != 0 { if addr % 4096 != 0 || !Mm::range_ok(addr, addr.saturating_add(len)) { return Err(Errno::EINVAL); } mm.unmap(addr, addr + len); // MAP_FIXED replaces whatever was there addr } else { mm.find_free(len).ok_or(Errno::ENOMEM)? }; mm.insert(Vma { start, end: start + len, prot, shared, file, kind: Kind::Mmap }); if shared { // Shared memory gets its frames now, so a fork before the first // touch still shares them (mm.rs). if mm.populate(start, start + len).is_err() { mm.unmap(start, start + len); return Err(Errno::ENOMEM); } } Ok(start) } fn page_range(addr: u64, len: u64) -> Result<(u64, u64), Errno> { let end = addr.checked_add(len).ok_or(Errno::EINVAL)?.next_multiple_of(4096); if addr % 4096 != 0 || !crate::mm::Mm::range_ok(addr, end.max(addr + 1)) { return Err(Errno::EINVAL); } Ok((addr, end)) } fn sys_munmap(p: &process::Process, addr: u64, len: u64) -> Result { let (start, end) = page_range(addr, len)?; if len == 0 { return Err(Errno::EINVAL); } p.mm.lock().unmap(start, end); Ok(0) } fn sys_mprotect(p: &process::Process, addr: u64, len: u64, prot: u64) -> Result { if prot & !7 != 0 { return Err(Errno::EINVAL); } let (start, end) = page_range(addr, len)?; if start == end { return Ok(0); } p.mm.lock().protect(start, end, prot).map(|_| 0) }