cpython/Python/emscripten_syscalls.c at main · StanFromIreland/cpython · GitHub

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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();

}

EM_JS(int, __syscall_umask_js, (int mask), {

// If we're in node and we can, call native process.umask()

if (ENVIRONMENT_IS_NODE) {

try {

return process.umask(mask);

} catch(e) {

// oops...

// NodeJS docs: "In Worker threads, process.umask(mask) will throw an exception."

// umask docs: "This system call always succeeds"

return 0;

}

// Fall back to the stub case of returning 0.

return 0;

})

int __syscall_umask(int mask) {

return __syscall_umask_js(mask);

}

#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;

};

})

__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"];

}

})();

};

);

// 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"];

}

})();

});

// 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);

}

cpython/Python/emscripten_syscalls.c at main · StanFromIreland/cpython · GitHub

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