cpython/Python/emscripten_syscalls.c at main · All-Blockchains/cpython · GitHub

History

326 lines (302 loc) · 12.1 KB

Raw

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

#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;

};

})

__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 · All-Blockchains/cpython · GitHub

Uh oh!

Expand file tree

Breadcrumbs

emscripten_syscalls.c

Latest commit

History

Breadcrumbs

emscripten_syscalls.c

File metadata and controls