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Copy pathemscripten_syscalls.c
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334 lines (307 loc) · 12.3 KB
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#include "emscripten.h"
#include "stdio.h"
// All system calls: return nonnegative number on success, return -errno on
// failure. Negative results get stored back into errno here:
// https://github.com/emscripten-core/emscripten/blob/main/system/lib/libc/musl/src/internal/syscall_ret.c#L7
// If we're running in node, report the UID of the user in the native system as
// the UID of the user. Since the nodefs will report the uid correctly, if we
// don't make getuid report it correctly too we'll see some permission errors.
// Normally __syscall_getuid32 is a stub that always returns 0 but it is
// defined with weak linkage so we can override it.
EM_JS(int, __syscall_getuid32_js, (void), {
// If we're in node and we can, report the native uid
if (ENVIRONMENT_IS_NODE) {
return process.getuid();
}
// Fall back to the stub case of returning 0.
return 0;
})
int __syscall_getuid32(void) {
return __syscall_getuid32_js();
}
// Emscripten's syscall layer tracks the umask in SYSCALLS.currentUmask and
// applies it itself when creating files and directories. We mount the real
// filesystem via NODEFS, which applies proces.umask() to everything as well. To
// avoid masking the mode twice, read and zero out process umask at startup,
// and store it as emscripten's umask.
EM_JS(void, __syscall_init_umask_js, (void), {
if (ENVIRONMENT_IS_NODE) {
try {
// process.umask(0) returns the previous umask and sets it to 0.
SYSCALLS.currentUmask = process.umask(0);
} catch (e) {
// NodeJS docs: "In Worker threads, process.umask(mask) will throw an
// exception." In that case just keep emscripten's default umask.
}
}
})
EM_JS_DEPS(__syscall_init_umask, "$SYSCALLS");
__attribute__((constructor)) void __syscall_init_umask(void) {
__syscall_init_umask_js();
}
#include <wasi/api.h>
#include <errno.h>
#include <fcntl.h>
// Variant of EM_JS that does C preprocessor substitution on the body
#define EM_JS_MACROS(ret, func_name, args, body...) \
EM_JS(ret, func_name, args, body)
EM_JS_MACROS(void, _emscripten_promising_main_js, (void), {
// Define FS.createAsyncInputDevice(), This is quite similar to
// FS.createDevice() defined here:
// https://github.com/emscripten-core/emscripten/blob/4.0.11/src/lib/libfs.js?plain=1#L1642
// but instead of returning one byte at a time, the input() function should
// return a Uint8Array. This makes the handler code simpler, the
// `createAsyncInputDevice` simpler, and everything faster.
FS.createAsyncInputDevice = function(parent, name, input) {
parent = typeof parent == 'string' ? parent : FS.getPath(parent);
var path = PATH.join2(parent, name);
var mode = FS_getMode(true, false);
FS.createDevice.major ||= 64;
var dev = FS.makedev(FS.createDevice.major++, 0);
async function getDataBuf() {
var buf;
try {
buf = await input();
} catch (e) {
throw new FS.ErrnoError(EIO);
}
if (!buf?.byteLength) {
throw new FS.ErrnoError(EAGAIN);
}
ops._dataBuf = buf;
}
var ops = {
_dataBuf: new Uint8Array(0),
open(stream) {
stream.seekable = false;
},
async readAsync(stream, buffer, offset, length, pos /* ignored */) {
buffer = buffer.subarray(offset, offset + length);
if (!ops._dataBuf.byteLength) {
await getDataBuf();
}
var toRead = Math.min(ops._dataBuf.byteLength, buffer.byteLength);
buffer.subarray(0, toRead).set(ops._dataBuf);
buffer = buffer.subarray(toRead);
ops._dataBuf = ops._dataBuf.subarray(toRead);
if (toRead) {
stream.node.atime = Date.now();
}
return toRead;
},
};
FS.registerDevice(dev, ops);
return FS.mkdev(path, mode, dev);
};
if (!WebAssembly.promising) {
// No stack switching support =(
return;
}
const origResolveGlobalSymbol = resolveGlobalSymbol;
if (ENVIRONMENT_IS_NODE && !Module.onExit) {
Module.onExit = (code) => process.exit(code);
}
// * wrap the main symbol with WebAssembly.promising,
// * call exit_with_live_runtime() to prevent emscripten from shutting down
// the runtime before the promise resolves,
// * call onExit / process.exit ourselves, since exit_with_live_runtime()
// prevented Emscripten from calling it normally.
resolveGlobalSymbol = function (name, direct = false) {
const orig = origResolveGlobalSymbol(name, direct);
if (name === "main") {
const main = WebAssembly.promising(orig.sym);
orig.sym = (...args) => {
(async () => {
const ret = await main(...args);
Module.onExit?.(ret);
})();
_emscripten_exit_with_live_runtime();
};
}
return orig;
};
})
EM_JS_DEPS(_emscripten_promising_main,
"$FS,$PATH,$FS_getMode,$resolveGlobalSymbol,"
"emscripten_exit_with_live_runtime");
__attribute__((constructor)) void _emscripten_promising_main(void) {
_emscripten_promising_main_js();
}
#define IOVEC_T_BUF_OFFSET 0
#define IOVEC_T_BUF_LEN_OFFSET 4
#define IOVEC_T_SIZE 8
_Static_assert(offsetof(__wasi_iovec_t, buf) == IOVEC_T_BUF_OFFSET,
"Unexpected __wasi_iovec_t layout");
_Static_assert(offsetof(__wasi_iovec_t, buf_len) == IOVEC_T_BUF_LEN_OFFSET,
"Unexpected __wasi_iovec_t layout");
_Static_assert(sizeof(__wasi_iovec_t) == IOVEC_T_SIZE,
"Unexpected __wasi_iovec_t layout");
// If the stream has a readAsync handler, read to buffer defined in iovs, write
// number of bytes read to *nread, and return a promise that resolves to the
// errno. Otherwise, return null.
EM_JS_MACROS(__externref_t, __maybe_fd_read_async, (
__wasi_fd_t fd,
const __wasi_iovec_t *iovs,
size_t iovcnt,
__wasi_size_t *nread
), {
if (!WebAssembly.promising) {
return null;
}
var stream;
try {
stream = SYSCALLS.getStreamFromFD(fd);
} catch (e) {
// If the fd was already closed or never existed, getStreamFromFD()
// raises. We'll let fd_read_orig() handle setting errno.
return null;
}
if (!stream.stream_ops.readAsync) {
// Not an async device. Fall back to __wasi_fd_read_orig().
return null;
}
return (async () => {
// This is the same as libwasi.js fd_read() and doReadv() except we use
// readAsync and we await it.
// https://github.com/emscripten-core/emscripten/blob/4.0.11/src/lib/libwasi.js?plain=1#L331
// https://github.com/emscripten-core/emscripten/blob/4.0.11/src/lib/libwasi.js?plain=1#L197
try {
var ret = 0;
for (var i = 0; i < iovcnt; i++) {
var ptr = HEAP32[(iovs + IOVEC_T_BUF_OFFSET)/4];
var len = HEAP32[(iovs + IOVEC_T_BUF_LEN_OFFSET)/4];
iovs += IOVEC_T_SIZE;
var curr = await stream.stream_ops.readAsync(stream, HEAP8, ptr, len);
if (curr < 0) return -1;
ret += curr;
if (curr < len) break; // nothing more to read
}
HEAP32[nread/4] = ret;
return 0;
} catch (e) {
if (e.name !== 'ErrnoError') {
throw e;
}
return e["errno"];
}
})();
};
);
EM_JS_DEPS(__maybe_fd_read_async, "$SYSCALLS");
// Bind original fd_read syscall to __wasi_fd_read_orig().
__wasi_errno_t __wasi_fd_read_orig(__wasi_fd_t fd, const __wasi_iovec_t *iovs,
size_t iovs_len, __wasi_size_t *nread)
__attribute__((__import_module__("wasi_snapshot_preview1"),
__import_name__("fd_read"), __warn_unused_result__));
// Take a promise that resolves to __wasi_errno_t and suspend until it resolves,
// get the output.
EM_JS(int, __block_for_int, (__externref_t p), {
return p;
}
if (WebAssembly.Suspending) {
__block_for_int = new WebAssembly.Suspending(__block_for_int);
}
)
// Replacement for fd_read syscall. Call __maybe_fd_read_async. If it returned
// null, delegate back to __wasi_fd_read_orig. Otherwise, use __block_for_int
// to get the result.
__wasi_errno_t __wasi_fd_read(__wasi_fd_t fd, const __wasi_iovec_t *iovs,
size_t iovs_len, __wasi_size_t *nread) {
__externref_t p = __maybe_fd_read_async(fd, iovs, iovs_len, nread);
if (__builtin_wasm_ref_is_null_extern(p)) {
return __wasi_fd_read_orig(fd, iovs, iovs_len, nread);
}
return __block_for_int(p);
}
#include <poll.h>
#define POLLFD_FD 0
#define POLLFD_EVENTS 4
#define POLLFD_REVENTS 6
#define POLLFD_SIZE 8
_Static_assert(offsetof(struct pollfd, fd) == 0, "Unepxected pollfd struct layout");
_Static_assert(offsetof(struct pollfd, events) == 4, "Unepxected pollfd struct layout");
_Static_assert(offsetof(struct pollfd, revents) == 6, "Unepxected pollfd struct layout");
_Static_assert(sizeof(struct pollfd) == 8, "Unepxected pollfd struct layout");
EM_JS_MACROS(__externref_t, __maybe_poll_async, (intptr_t fds, int nfds, int timeout), {
if (!WebAssembly.promising) {
return null;
}
return (async function() {
try {
var nonzero = 0;
var promises = [];
for (var i = 0; i < nfds; i++) {
var pollfd = fds + POLLFD_SIZE * i;
var fd = HEAP32[(pollfd + POLLFD_FD)/4];
var events = HEAP16[(pollfd + POLLFD_EVENTS)/2];
var mask = POLLNVAL;
var stream = FS.getStream(fd);
if (stream) {
mask = POLLIN | POLLOUT;
if (stream.stream_ops.pollAsync) {
promises.push(stream.stream_ops.pollAsync(stream, timeout).then((mask) => {
mask &= events | POLLERR | POLLHUP;
HEAP16[(pollfd + POLLFD_REVENTS)/2] = mask;
if (mask) {
nonzero ++;
}
}));
} else if (stream.stream_ops.poll) {
var mask = stream.stream_ops.poll(stream, timeout);
mask &= events | POLLERR | POLLHUP;
HEAP16[(pollfd + POLLFD_REVENTS)/2] = mask;
if (mask) {
nonzero ++;
}
}
}
}
await Promise.all(promises);
return nonzero;
} catch(e) {
if (e?.name !== "ErrnoError") throw e;
return -e["errno"];
}
})();
});
EM_JS_DEPS(__maybe_poll_async, "$FS");
// Bind original poll syscall to syscall_poll_orig().
int syscall_poll_orig(intptr_t fds, int nfds, int timeout)
__attribute__((__import_module__("env"),
__import_name__("__syscall_poll"), __warn_unused_result__));
int __syscall_poll(intptr_t fds, int nfds, int timeout) {
__externref_t p = __maybe_poll_async(fds, nfds, timeout);
if (__builtin_wasm_ref_is_null_extern(p)) {
return syscall_poll_orig(fds, nfds, timeout);
}
return __block_for_int(p);
}
#include <sys/ioctl.h>
int syscall_ioctl_orig(int fd, int request, void* varargs)
__attribute__((__import_module__("env"),
__import_name__("__syscall_ioctl"), __warn_unused_result__));
int __syscall_ioctl(int fd, int request, void* varargs) {
if (request == FIOCLEX || request == FIONCLEX) {
return 0;
}
if (request == FIONBIO) {
// Implement FIONBIO via fcntl.
// TODO: Upstream this.
int flags = fcntl(fd, F_GETFL, 0);
int nonblock = **((int**)varargs);
if (flags < 0) {
return -errno;
}
if (nonblock) {
flags |= O_NONBLOCK;
} else {
flags &= (~O_NONBLOCK);
}
int res = fcntl(fd, F_SETFL, flags);
if (res < 0) {
return -errno;
}
return res;
}
return syscall_ioctl_orig(fd, request, varargs);
}
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