1 /*
2 * CDDL HEADER START
3 *
4 * This file and its contents are supplied under the terms of the
5 * Common Development and Distribution License ("CDDL"), version 1.0.
6 * You may only use this file in accordance with the terms of version
7 * 1.0 of the CDDL.
8 *
9 * A full copy of the text of the CDDL should have accompanied this
10 * source. A copy of the CDDL is also available via the Internet at
11 * http://www.illumos.org/license/CDDL.
12 *
13 * CDDL HEADER END
14 */
15
16 /*
17 * Copyright (c) 2016, 2017 by Delphix. All rights reserved.
18 */
19
20 /*
21 * ZFS Channel Programs (ZCP)
22 *
23 * The ZCP interface allows various ZFS commands and operations ZFS
24 * administrative operations (e.g. creating and destroying snapshots, typically
25 * performed via an ioctl to /dev/zfs by the zfs(1M) command and
26 * libzfs/libzfs_core) to be run * programmatically as a Lua script. A ZCP
27 * script is run as a dsl_sync_task and fully executed during one transaction
28 * group sync. This ensures that no other changes can be written concurrently
29 * with a running Lua script. Combining multiple calls to the exposed ZFS
30 * functions into one script gives a number of benefits:
31 *
32 * 1. Atomicity. For some compound or iterative operations, it's useful to be
33 * able to guarantee that the state of a pool has not changed between calls to
34 * ZFS.
35 *
36 * 2. Performance. If a large number of changes need to be made (e.g. deleting
37 * many filesystems), there can be a significant performance penalty as a
38 * result of the need to wait for a transaction group sync to pass for every
39 * single operation. When expressed as a single ZCP script, all these changes
40 * can be performed at once in one txg sync.
41 *
42 * A modified version of the Lua 5.2 interpreter is used to run channel program
43 * scripts. The Lua 5.2 manual can be found at:
44 *
45 * http://www.lua.org/manual/5.2/
46 *
47 * If being run by a user (via an ioctl syscall), executing a ZCP script
48 * requires root privileges in the global zone.
49 *
50 * Scripts are passed to zcp_eval() as a string, then run in a synctask by
51 * zcp_eval_sync(). Arguments can be passed into the Lua script as an nvlist,
52 * which will be converted to a Lua table. Similarly, values returned from
53 * a ZCP script will be converted to an nvlist. See zcp_lua_to_nvlist_impl()
54 * for details on exact allowed types and conversion.
55 *
56 * ZFS functionality is exposed to a ZCP script as a library of function calls.
57 * These calls are sorted into submodules, such as zfs.list and zfs.sync, for
58 * iterators and synctasks, respectively. Each of these submodules resides in
59 * its own source file, with a zcp_*_info structure describing each library
60 * call in the submodule.
61 *
62 * Error handling in ZCP scripts is handled by a number of different methods
63 * based on severity:
64 *
65 * 1. Memory and time limits are in place to prevent a channel program from
66 * consuming excessive system or running forever. If one of these limits is
67 * hit, the channel program will be stopped immediately and return from
68 * zcp_eval() with an error code. No attempt will be made to roll back or undo
69 * any changes made by the channel program before the error occured.
70 * Consumers invoking zcp_eval() from elsewhere in the kernel may pass a time
71 * limit of 0, disabling the time limit.
72 *
73 * 2. Internal Lua errors can occur as a result of a syntax error, calling a
74 * library function with incorrect arguments, invoking the error() function,
75 * failing an assert(), or other runtime errors. In these cases the channel
76 * program will stop executing and return from zcp_eval() with an error code.
77 * In place of a return value, an error message will also be returned in the
78 * 'result' nvlist containing information about the error. No attempt will be
79 * made to roll back or undo any changes made by the channel program before the
80 * error occured.
81 *
82 * 3. If an error occurs inside a ZFS library call which returns an error code,
83 * the error is returned to the Lua script to be handled as desired.
84 *
85 * In the first two cases, Lua's error-throwing mechanism is used, which
86 * longjumps out of the script execution with luaL_error() and returns with the
87 * error.
88 *
89 * See zfs-program(1M) for more information on high level usage.
90 */
91
92 #include "lua.h"
93 #include "lualib.h"
94 #include "lauxlib.h"
95
96 #include <sys/dsl_prop.h>
97 #include <sys/dsl_synctask.h>
98 #include <sys/dsl_dataset.h>
99 #include <sys/zcp.h>
100 #include <sys/zcp_iter.h>
101 #include <sys/zcp_prop.h>
102 #include <sys/zcp_global.h>
103 #include <util/sscanf.h>
104
105 #define ZCP_NVLIST_MAX_DEPTH 20
106
107 uint64_t zfs_lua_check_instrlimit_interval = 100;
108 uint64_t zfs_lua_max_instrlimit = ZCP_MAX_INSTRLIMIT;
109 uint64_t zfs_lua_max_memlimit = ZCP_MAX_MEMLIMIT;
110
111 /*
112 * Forward declarations for mutually recursive functions
113 */
114 static int zcp_nvpair_value_to_lua(lua_State *, nvpair_t *, char *, int);
115 static int zcp_lua_to_nvlist_impl(lua_State *, int, nvlist_t *, const char *,
116 int);
117
118 /*
119 * The outer-most error callback handler for use with lua_pcall(). On
120 * error Lua will call this callback with a single argument that
121 * represents the error value. In most cases this will be a string
122 * containing an error message, but channel programs can use Lua's
123 * error() function to return arbitrary objects as errors. This callback
124 * returns (on the Lua stack) the original error object along with a traceback.
125 *
126 * Fatal Lua errors can occur while resources are held, so we also call any
127 * registered cleanup function here.
128 */
129 static int
130 zcp_error_handler(lua_State *state)
131 {
132 const char *msg;
133
134 zcp_cleanup(state);
135
136 VERIFY3U(1, ==, lua_gettop(state));
137 msg = lua_tostring(state, 1);
138 luaL_traceback(state, state, msg, 1);
139 return (1);
140 }
141
142 int
143 zcp_argerror(lua_State *state, int narg, const char *msg, ...)
144 {
145 va_list alist;
146
147 va_start(alist, msg);
148 const char *buf = lua_pushvfstring(state, msg, alist);
149 va_end(alist);
150
151 return (luaL_argerror(state, narg, buf));
152 }
153
154 /*
155 * Install a new cleanup function, which will be invoked with the given
156 * opaque argument if a fatal error causes the Lua interpreter to longjump out
157 * of a function call.
158 *
159 * If an error occurs, the cleanup function will be invoked exactly once and
160 * then unreigstered.
161 *
162 * Returns the registered cleanup handler so the caller can deregister it
163 * if no error occurs.
164 */
165 zcp_cleanup_handler_t *
166 zcp_register_cleanup(lua_State *state, zcp_cleanup_t cleanfunc, void *cleanarg)
167 {
168 zcp_run_info_t *ri = zcp_run_info(state);
169
170 zcp_cleanup_handler_t *zch = kmem_alloc(sizeof (*zch), KM_SLEEP);
171 zch->zch_cleanup_func = cleanfunc;
172 zch->zch_cleanup_arg = cleanarg;
173 list_insert_head(&ri->zri_cleanup_handlers, zch);
174
175 return (zch);
176 }
177
178 void
179 zcp_deregister_cleanup(lua_State *state, zcp_cleanup_handler_t *zch)
180 {
181 zcp_run_info_t *ri = zcp_run_info(state);
182 list_remove(&ri->zri_cleanup_handlers, zch);
183 kmem_free(zch, sizeof (*zch));
184 }
185
186 /*
187 * Execute the currently registered cleanup handlers then free them and
188 * destroy the handler list.
189 */
190 void
191 zcp_cleanup(lua_State *state)
192 {
193 zcp_run_info_t *ri = zcp_run_info(state);
194
195 for (zcp_cleanup_handler_t *zch =
196 list_remove_head(&ri->zri_cleanup_handlers); zch != NULL;
197 zch = list_remove_head(&ri->zri_cleanup_handlers)) {
198 zch->zch_cleanup_func(zch->zch_cleanup_arg);
199 kmem_free(zch, sizeof (*zch));
200 }
201 }
202
203 /*
204 * Convert the lua table at the given index on the Lua stack to an nvlist
205 * and return it.
206 *
207 * If the table can not be converted for any reason, NULL is returned and
208 * an error message is pushed onto the Lua stack.
209 */
210 static nvlist_t *
211 zcp_table_to_nvlist(lua_State *state, int index, int depth)
212 {
213 nvlist_t *nvl;
214 /*
215 * Converting a Lua table to an nvlist with key uniqueness checking is
216 * O(n^2) in the number of keys in the nvlist, which can take a long
217 * time when we return a large table from a channel program.
218 * Furthermore, Lua's table interface *almost* guarantees unique keys
219 * on its own (details below). Therefore, we don't use fnvlist_alloc()
220 * here to avoid the built-in uniqueness checking.
221 *
222 * The *almost* is because it's possible to have key collisions between
223 * e.g. the string "1" and the number 1, or the string "true" and the
224 * boolean true, so we explicitly check that when we're looking at a
225 * key which is an integer / boolean or a string that can be parsed as
226 * one of those types. In the worst case this could still devolve into
227 * O(n^2), so we only start doing these checks on boolean/integer keys
228 * once we've seen a string key which fits this weird usage pattern.
229 *
230 * Ultimately, we still want callers to know that the keys in this
231 * nvlist are unique, so before we return this we set the nvlist's
232 * flags to reflect that.
233 */
234 VERIFY0(nvlist_alloc(&nvl, 0, KM_SLEEP));
235
236 /*
237 * Push an empty stack slot where lua_next() will store each
238 * table key.
239 */
240 lua_pushnil(state);
241 boolean_t saw_str_could_collide = B_FALSE;
242 while (lua_next(state, index) != 0) {
243 /*
244 * The next key-value pair from the table at index is
245 * now on the stack, with the key at stack slot -2 and
246 * the value at slot -1.
247 */
248 int err = 0;
249 char buf[32];
250 const char *key = NULL;
251 boolean_t key_could_collide = B_FALSE;
252
253 switch (lua_type(state, -2)) {
254 case LUA_TSTRING:
255 key = lua_tostring(state, -2);
256
257 /* check if this could collide with a number or bool */
258 long long tmp;
259 int parselen;
260 if ((sscanf(key, "%lld%n", &tmp, &parselen) > 0 &&
261 parselen == strlen(key)) ||
262 strcmp(key, "true") == 0 ||
263 strcmp(key, "false") == 0) {
264 key_could_collide = B_TRUE;
265 saw_str_could_collide = B_TRUE;
266 }
267 break;
268 case LUA_TBOOLEAN:
269 key = (lua_toboolean(state, -2) == B_TRUE ?
270 "true" : "false");
271 if (saw_str_could_collide) {
272 key_could_collide = B_TRUE;
273 }
274 break;
275 case LUA_TNUMBER:
276 VERIFY3U(sizeof (buf), >,
277 snprintf(buf, sizeof (buf), "%lld",
278 (longlong_t)lua_tonumber(state, -2)));
279 key = buf;
280 if (saw_str_could_collide) {
281 key_could_collide = B_TRUE;
282 }
283 break;
284 default:
285 fnvlist_free(nvl);
286 (void) lua_pushfstring(state, "Invalid key "
287 "type '%s' in table",
288 lua_typename(state, lua_type(state, -2)));
289 return (NULL);
290 }
291 /*
292 * Check for type-mismatched key collisions, and throw an error.
293 */
294 if (key_could_collide && nvlist_exists(nvl, key)) {
295 fnvlist_free(nvl);
296 (void) lua_pushfstring(state, "Collision of "
297 "key '%s' in table", key);
298 return (NULL);
299 }
300 /*
301 * Recursively convert the table value and insert into
302 * the new nvlist with the parsed key. To prevent
303 * stack overflow on circular or heavily nested tables,
304 * we track the current nvlist depth.
305 */
306 if (depth >= ZCP_NVLIST_MAX_DEPTH) {
307 fnvlist_free(nvl);
308 (void) lua_pushfstring(state, "Maximum table "
309 "depth (%d) exceeded for table",
310 ZCP_NVLIST_MAX_DEPTH);
311 return (NULL);
312 }
313 err = zcp_lua_to_nvlist_impl(state, -1, nvl, key,
314 depth + 1);
315 if (err != 0) {
316 fnvlist_free(nvl);
317 /*
318 * Error message has been pushed to the lua
319 * stack by the recursive call.
320 */
321 return (NULL);
322 }
323 /*
324 * Pop the value pushed by lua_next().
325 */
326 lua_pop(state, 1);
327 }
328
329 /*
330 * Mark the nvlist as having unique keys. This is a little ugly, but we
331 * ensured above that there are no duplicate keys in the nvlist.
332 */
333 nvl->nvl_nvflag |= NV_UNIQUE_NAME;
334
335 return (nvl);
336 }
337
338 /*
339 * Convert a value from the given index into the lua stack to an nvpair, adding
340 * it to an nvlist with the given key.
341 *
342 * Values are converted as follows:
343 *
344 * string -> string
345 * number -> int64
346 * boolean -> boolean
347 * nil -> boolean (no value)
348 *
349 * Lua tables are converted to nvlists and then inserted. The table's keys
350 * are converted to strings then used as keys in the nvlist to store each table
351 * element. Keys are converted as follows:
352 *
353 * string -> no change
354 * number -> "%lld"
355 * boolean -> "true" | "false"
356 * nil -> error
357 *
358 * In the case of a key collision, an error is thrown.
359 *
360 * If an error is encountered, a nonzero error code is returned, and an error
361 * string will be pushed onto the Lua stack.
362 */
363 static int
364 zcp_lua_to_nvlist_impl(lua_State *state, int index, nvlist_t *nvl,
365 const char *key, int depth)
366 {
367 /*
368 * Verify that we have enough remaining space in the lua stack to parse
369 * a key-value pair and push an error.
370 */
371 if (!lua_checkstack(state, 3)) {
372 (void) lua_pushstring(state, "Lua stack overflow");
373 return (1);
374 }
375
376 index = lua_absindex(state, index);
377
378 switch (lua_type(state, index)) {
379 case LUA_TNIL:
380 fnvlist_add_boolean(nvl, key);
381 break;
382 case LUA_TBOOLEAN:
383 fnvlist_add_boolean_value(nvl, key,
384 lua_toboolean(state, index));
385 break;
386 case LUA_TNUMBER:
387 fnvlist_add_int64(nvl, key, lua_tonumber(state, index));
388 break;
389 case LUA_TSTRING:
390 fnvlist_add_string(nvl, key, lua_tostring(state, index));
391 break;
392 case LUA_TTABLE: {
393 nvlist_t *value_nvl = zcp_table_to_nvlist(state, index, depth);
394 if (value_nvl == NULL)
395 return (EINVAL);
396
397 fnvlist_add_nvlist(nvl, key, value_nvl);
398 fnvlist_free(value_nvl);
399 break;
400 }
401 default:
402 (void) lua_pushfstring(state,
403 "Invalid value type '%s' for key '%s'",
404 lua_typename(state, lua_type(state, index)), key);
405 return (EINVAL);
406 }
407
408 return (0);
409 }
410
411 /*
412 * Convert a lua value to an nvpair, adding it to an nvlist with the given key.
413 */
414 static void
415 zcp_lua_to_nvlist(lua_State *state, int index, nvlist_t *nvl, const char *key)
416 {
417 /*
418 * On error, zcp_lua_to_nvlist_impl pushes an error string onto the Lua
419 * stack before returning with a nonzero error code. If an error is
420 * returned, throw a fatal lua error with the given string.
421 */
422 if (zcp_lua_to_nvlist_impl(state, index, nvl, key, 0) != 0)
423 (void) lua_error(state);
424 }
425
426 static int
427 zcp_lua_to_nvlist_helper(lua_State *state)
428 {
429 nvlist_t *nv = (nvlist_t *)lua_touserdata(state, 2);
430 const char *key = (const char *)lua_touserdata(state, 1);
431 zcp_lua_to_nvlist(state, 3, nv, key);
432 return (0);
433 }
434
435 static void
436 zcp_convert_return_values(lua_State *state, nvlist_t *nvl,
437 const char *key, int *result)
438 {
439 int err;
440 VERIFY3U(1, ==, lua_gettop(state));
441 lua_pushcfunction(state, zcp_lua_to_nvlist_helper);
442 lua_pushlightuserdata(state, (char *)key);
443 lua_pushlightuserdata(state, nvl);
444 lua_pushvalue(state, 1);
445 lua_remove(state, 1);
446 err = lua_pcall(state, 3, 0, 0); /* zcp_lua_to_nvlist_helper */
447 if (err != 0) {
448 zcp_lua_to_nvlist(state, 1, nvl, ZCP_RET_ERROR);
449 *result = SET_ERROR(ECHRNG);
450 }
451 }
452
453 /*
454 * Push a Lua table representing nvl onto the stack. If it can't be
455 * converted, return EINVAL, fill in errbuf, and push nothing. errbuf may
456 * be specified as NULL, in which case no error string will be output.
457 *
458 * Most nvlists are converted as simple key->value Lua tables, but we make
459 * an exception for the case where all nvlist entries are BOOLEANs (a string
460 * key without a value). In Lua, a table key pointing to a value of Nil
461 * (no value) is equivalent to the key not existing, so a BOOLEAN nvlist
462 * entry can't be directly converted to a Lua table entry. Nvlists of entirely
463 * BOOLEAN entries are frequently used to pass around lists of datasets, so for
464 * convenience we check for this case, and convert it to a simple Lua array of
465 * strings.
466 */
467 int
468 zcp_nvlist_to_lua(lua_State *state, nvlist_t *nvl,
469 char *errbuf, int errbuf_len)
470 {
471 nvpair_t *pair;
472 lua_newtable(state);
473 boolean_t has_values = B_FALSE;
474 /*
475 * If the list doesn't have any values, just convert it to a string
476 * array.
477 */
478 for (pair = nvlist_next_nvpair(nvl, NULL);
479 pair != NULL; pair = nvlist_next_nvpair(nvl, pair)) {
480 if (nvpair_type(pair) != DATA_TYPE_BOOLEAN) {
481 has_values = B_TRUE;
482 break;
483 }
484 }
485 if (!has_values) {
486 int i = 1;
487 for (pair = nvlist_next_nvpair(nvl, NULL);
488 pair != NULL; pair = nvlist_next_nvpair(nvl, pair)) {
489 (void) lua_pushinteger(state, i);
490 (void) lua_pushstring(state, nvpair_name(pair));
491 (void) lua_settable(state, -3);
492 i++;
493 }
494 } else {
495 for (pair = nvlist_next_nvpair(nvl, NULL);
496 pair != NULL; pair = nvlist_next_nvpair(nvl, pair)) {
497 int err = zcp_nvpair_value_to_lua(state, pair,
498 errbuf, errbuf_len);
499 if (err != 0) {
500 lua_pop(state, 1);
501 return (err);
502 }
503 (void) lua_setfield(state, -2, nvpair_name(pair));
504 }
505 }
506 return (0);
507 }
508
509 /*
510 * Push a Lua object representing the value of "pair" onto the stack.
511 *
512 * Only understands boolean_value, string, int64, nvlist,
513 * string_array, and int64_array type values. For other
514 * types, returns EINVAL, fills in errbuf, and pushes nothing.
515 */
516 static int
517 zcp_nvpair_value_to_lua(lua_State *state, nvpair_t *pair,
518 char *errbuf, int errbuf_len)
519 {
520 int err = 0;
521
522 if (pair == NULL) {
523 lua_pushnil(state);
524 return (0);
525 }
526
527 switch (nvpair_type(pair)) {
528 case DATA_TYPE_BOOLEAN_VALUE:
529 (void) lua_pushboolean(state,
530 fnvpair_value_boolean_value(pair));
531 break;
532 case DATA_TYPE_STRING:
533 (void) lua_pushstring(state, fnvpair_value_string(pair));
534 break;
535 case DATA_TYPE_INT64:
536 (void) lua_pushinteger(state, fnvpair_value_int64(pair));
537 break;
538 case DATA_TYPE_NVLIST:
539 err = zcp_nvlist_to_lua(state,
540 fnvpair_value_nvlist(pair), errbuf, errbuf_len);
541 break;
542 case DATA_TYPE_STRING_ARRAY: {
543 char **strarr;
544 uint_t nelem;
545 (void) nvpair_value_string_array(pair, &strarr, &nelem);
546 lua_newtable(state);
547 for (int i = 0; i < nelem; i++) {
548 (void) lua_pushinteger(state, i + 1);
549 (void) lua_pushstring(state, strarr[i]);
550 (void) lua_settable(state, -3);
551 }
552 break;
553 }
554 case DATA_TYPE_UINT64_ARRAY: {
555 uint64_t *intarr;
556 uint_t nelem;
557 (void) nvpair_value_uint64_array(pair, &intarr, &nelem);
558 lua_newtable(state);
559 for (int i = 0; i < nelem; i++) {
560 (void) lua_pushinteger(state, i + 1);
561 (void) lua_pushinteger(state, intarr[i]);
562 (void) lua_settable(state, -3);
563 }
564 break;
565 }
566 case DATA_TYPE_INT64_ARRAY: {
567 int64_t *intarr;
568 uint_t nelem;
569 (void) nvpair_value_int64_array(pair, &intarr, &nelem);
570 lua_newtable(state);
571 for (int i = 0; i < nelem; i++) {
572 (void) lua_pushinteger(state, i + 1);
573 (void) lua_pushinteger(state, intarr[i]);
574 (void) lua_settable(state, -3);
575 }
576 break;
577 }
578 default: {
579 if (errbuf != NULL) {
580 (void) snprintf(errbuf, errbuf_len,
581 "Unhandled nvpair type %d for key '%s'",
582 nvpair_type(pair), nvpair_name(pair));
583 }
584 return (EINVAL);
585 }
586 }
587 return (err);
588 }
589
590 int
591 zcp_dataset_hold_error(lua_State *state, dsl_pool_t *dp, const char *dsname,
592 int error)
593 {
594 if (error == ENOENT) {
595 (void) zcp_argerror(state, 1, "no such dataset '%s'", dsname);
596 return (0); /* not reached; zcp_argerror will longjmp */
597 } else if (error == EXDEV) {
598 (void) zcp_argerror(state, 1,
599 "dataset '%s' is not in the target pool '%s'",
600 dsname, spa_name(dp->dp_spa));
601 return (0); /* not reached; zcp_argerror will longjmp */
602 } else if (error == EIO) {
603 (void) luaL_error(state,
604 "I/O error while accessing dataset '%s'", dsname);
605 return (0); /* not reached; luaL_error will longjmp */
606 } else if (error != 0) {
607 (void) luaL_error(state,
608 "unexpected error %d while accessing dataset '%s'",
609 error, dsname);
610 return (0); /* not reached; luaL_error will longjmp */
611 }
612 return (0);
613 }
614
615 /*
616 * Note: will longjmp (via lua_error()) on error.
617 * Assumes that the dsname is argument #1 (for error reporting purposes).
618 */
619 dsl_dataset_t *
620 zcp_dataset_hold(lua_State *state, dsl_pool_t *dp, const char *dsname,
621 void *tag)
622 {
623 dsl_dataset_t *ds;
624 int error = dsl_dataset_hold(dp, dsname, tag, &ds);
625 (void) zcp_dataset_hold_error(state, dp, dsname, error);
626 return (ds);
627 }
628
629 static int zcp_debug(lua_State *);
630 static zcp_lib_info_t zcp_debug_info = {
631 .name = "debug",
632 .func = zcp_debug,
633 .pargs = {
634 { .za_name = "debug string", .za_lua_type = LUA_TSTRING},
635 {NULL, 0}
636 },
637 .kwargs = {
638 {NULL, 0}
639 }
640 };
641
642 static int
643 zcp_debug(lua_State *state)
644 {
645 const char *dbgstring;
646 zcp_run_info_t *ri = zcp_run_info(state);
647 zcp_lib_info_t *libinfo = &zcp_debug_info;
648
649 zcp_parse_args(state, libinfo->name, libinfo->pargs, libinfo->kwargs);
650
651 dbgstring = lua_tostring(state, 1);
652
653 zfs_dbgmsg("txg %lld ZCP: %s", ri->zri_tx->tx_txg, dbgstring);
654
655 return (0);
656 }
657
658 static int zcp_exists(lua_State *);
659 static zcp_lib_info_t zcp_exists_info = {
660 .name = "exists",
661 .func = zcp_exists,
662 .pargs = {
663 { .za_name = "dataset", .za_lua_type = LUA_TSTRING},
664 {NULL, 0}
665 },
666 .kwargs = {
667 {NULL, 0}
668 }
669 };
670
671 static int
672 zcp_exists(lua_State *state)
673 {
674 zcp_run_info_t *ri = zcp_run_info(state);
675 dsl_pool_t *dp = ri->zri_pool;
676 zcp_lib_info_t *libinfo = &zcp_exists_info;
677
678 zcp_parse_args(state, libinfo->name, libinfo->pargs, libinfo->kwargs);
679
680 const char *dsname = lua_tostring(state, 1);
681
682 dsl_dataset_t *ds;
683 int error = dsl_dataset_hold(dp, dsname, FTAG, &ds);
684 if (error == 0) {
685 dsl_dataset_rele(ds, FTAG);
686 lua_pushboolean(state, B_TRUE);
687 } else if (error == ENOENT) {
688 lua_pushboolean(state, B_FALSE);
689 } else if (error == EXDEV) {
690 return (luaL_error(state, "dataset '%s' is not in the "
691 "target pool", dsname));
692 } else if (error == EIO) {
693 return (luaL_error(state, "I/O error opening dataset '%s'",
694 dsname));
695 } else if (error != 0) {
696 return (luaL_error(state, "unexpected error %d", error));
697 }
698
699 return (1);
700 }
701
702 /*
703 * Allocate/realloc/free a buffer for the lua interpreter.
704 *
705 * When nsize is 0, behaves as free() and returns NULL.
706 *
707 * If ptr is NULL, behaves as malloc() and returns an allocated buffer of size
708 * at least nsize.
709 *
710 * Otherwise, behaves as realloc(), changing the allocation from osize to nsize.
711 * Shrinking the buffer size never fails.
712 *
713 * The original allocated buffer size is stored as a uint64 at the beginning of
714 * the buffer to avoid actually reallocating when shrinking a buffer, since lua
715 * requires that this operation never fail.
716 */
717 static void *
718 zcp_lua_alloc(void *ud, void *ptr, size_t osize, size_t nsize)
719 {
720 zcp_alloc_arg_t *allocargs = ud;
721 int flags = (allocargs->aa_must_succeed) ?
722 KM_SLEEP : (KM_NOSLEEP | KM_NORMALPRI);
723
724 if (nsize == 0) {
725 if (ptr != NULL) {
726 int64_t *allocbuf = (int64_t *)ptr - 1;
727 int64_t allocsize = *allocbuf;
728 ASSERT3S(allocsize, >, 0);
729 ASSERT3S(allocargs->aa_alloc_remaining + allocsize, <=,
730 allocargs->aa_alloc_limit);
731 allocargs->aa_alloc_remaining += allocsize;
732 kmem_free(allocbuf, allocsize);
733 }
734 return (NULL);
735 } else if (ptr == NULL) {
736 int64_t *allocbuf;
737 int64_t allocsize = nsize + sizeof (int64_t);
738
739 if (!allocargs->aa_must_succeed &&
740 (allocsize <= 0 ||
741 allocsize > allocargs->aa_alloc_remaining)) {
742 return (NULL);
743 }
744
745 allocbuf = kmem_alloc(allocsize, flags);
746 if (allocbuf == NULL) {
747 return (NULL);
748 }
749 allocargs->aa_alloc_remaining -= allocsize;
750
751 *allocbuf = allocsize;
752 return (allocbuf + 1);
753 } else if (nsize <= osize) {
754 /*
755 * If shrinking the buffer, lua requires that the reallocation
756 * never fail.
757 */
758 return (ptr);
759 } else {
760 ASSERT3U(nsize, >, osize);
761
762 uint64_t *luabuf = zcp_lua_alloc(ud, NULL, 0, nsize);
763 if (luabuf == NULL) {
764 return (NULL);
765 }
766 (void) memcpy(luabuf, ptr, osize);
767 VERIFY3P(zcp_lua_alloc(ud, ptr, osize, 0), ==, NULL);
768 return (luabuf);
769 }
770 }
771
772 /* ARGSUSED */
773 static void
774 zcp_lua_counthook(lua_State *state, lua_Debug *ar)
775 {
776 lua_getfield(state, LUA_REGISTRYINDEX, ZCP_RUN_INFO_KEY);
777 zcp_run_info_t *ri = lua_touserdata(state, -1);
778
779 /*
780 * Check if we were canceled while waiting for the
781 * txg to sync or from our open context thread
782 */
783 if (ri->zri_canceled ||
784 (!ri->zri_sync && issig(JUSTLOOKING) && issig(FORREAL))) {
785 ri->zri_canceled = B_TRUE;
786 (void) lua_pushstring(state, "Channel program was canceled.");
787 (void) lua_error(state);
788 }
789
790 /*
791 * Check how many instructions the channel program has
792 * executed so far, and compare against the limit.
793 */
794 ri->zri_curinstrs += zfs_lua_check_instrlimit_interval;
795 if (ri->zri_maxinstrs != 0 && ri->zri_curinstrs > ri->zri_maxinstrs) {
796 ri->zri_timed_out = B_TRUE;
797 (void) lua_pushstring(state,
798 "Channel program timed out.");
799 (void) lua_error(state);
800 }
801 }
802
803 static int
804 zcp_panic_cb(lua_State *state)
805 {
806 panic("unprotected error in call to Lua API (%s)\n",
807 lua_tostring(state, -1));
808 return (0);
809 }
810
811 static void
812 zcp_eval_impl(dmu_tx_t *tx, zcp_run_info_t *ri)
813 {
814 int err;
815 lua_State *state = ri->zri_state;
816
817 VERIFY3U(3, ==, lua_gettop(state));
818
819 /* finish initializing our runtime state */
820 ri->zri_pool = dmu_tx_pool(tx);
821 ri->zri_tx = tx;
822 list_create(&ri->zri_cleanup_handlers, sizeof (zcp_cleanup_handler_t),
823 offsetof(zcp_cleanup_handler_t, zch_node));
824
825 /*
826 * Store the zcp_run_info_t struct for this run in the Lua registry.
827 * Registry entries are not directly accessible by the Lua scripts but
828 * can be accessed by our callbacks.
829 */
830 lua_pushlightuserdata(state, ri);
831 lua_setfield(state, LUA_REGISTRYINDEX, ZCP_RUN_INFO_KEY);
832 VERIFY3U(3, ==, lua_gettop(state));
833
834 /*
835 * Tell the Lua interpreter to call our handler every count
836 * instructions. Channel programs that execute too many instructions
837 * should die with ETIME.
838 */
839 (void) lua_sethook(state, zcp_lua_counthook, LUA_MASKCOUNT,
840 zfs_lua_check_instrlimit_interval);
841
842 /*
843 * Tell the Lua memory allocator to stop using KM_SLEEP before handing
844 * off control to the channel program. Channel programs that use too
845 * much memory should die with ENOSPC.
846 */
847 ri->zri_allocargs->aa_must_succeed = B_FALSE;
848
849 /*
850 * Call the Lua function that open-context passed us. This pops the
851 * function and its input from the stack and pushes any return
852 * or error values.
853 */
854 err = lua_pcall(state, 1, LUA_MULTRET, 1);
855
856 /*
857 * Let Lua use KM_SLEEP while we interpret the return values.
858 */
859 ri->zri_allocargs->aa_must_succeed = B_TRUE;
860
861 /*
862 * Remove the error handler callback from the stack. At this point,
863 * there shouldn't be any cleanup handler registered in the handler
864 * list (zri_cleanup_handlers), regardless of whether it ran or not.
865 */
866 list_destroy(&ri->zri_cleanup_handlers);
867 lua_remove(state, 1);
868
869 switch (err) {
870 case LUA_OK: {
871 /*
872 * Lua supports returning multiple values in a single return
873 * statement. Return values will have been pushed onto the
874 * stack:
875 * 1: Return value 1
876 * 2: Return value 2
877 * 3: etc...
878 * To simplify the process of retrieving a return value from a
879 * channel program, we disallow returning more than one value
880 * to ZFS from the Lua script, yielding a singleton return
881 * nvlist of the form { "return": Return value 1 }.
882 */
883 int return_count = lua_gettop(state);
884
885 if (return_count == 1) {
886 ri->zri_result = 0;
887 zcp_convert_return_values(state, ri->zri_outnvl,
888 ZCP_RET_RETURN, &ri->zri_result);
889 } else if (return_count > 1) {
890 ri->zri_result = SET_ERROR(ECHRNG);
891 lua_settop(state, 0);
892 (void) lua_pushfstring(state, "Multiple return "
893 "values not supported");
894 zcp_convert_return_values(state, ri->zri_outnvl,
895 ZCP_RET_ERROR, &ri->zri_result);
896 }
897 break;
898 }
899 case LUA_ERRRUN:
900 case LUA_ERRGCMM: {
901 /*
902 * The channel program encountered a fatal error within the
903 * script, such as failing an assertion, or calling a function
904 * with incompatible arguments. The error value and the
905 * traceback generated by zcp_error_handler() should be on the
906 * stack.
907 */
908 VERIFY3U(1, ==, lua_gettop(state));
909 if (ri->zri_timed_out) {
910 ri->zri_result = SET_ERROR(ETIME);
911 } else if (ri->zri_canceled) {
912 ri->zri_result = SET_ERROR(EINTR);
913 } else {
914 ri->zri_result = SET_ERROR(ECHRNG);
915 }
916
917 zcp_convert_return_values(state, ri->zri_outnvl,
918 ZCP_RET_ERROR, &ri->zri_result);
919 break;
920 }
921 case LUA_ERRERR: {
922 /*
923 * The channel program encountered a fatal error within the
924 * script, and we encountered another error while trying to
925 * compute the traceback in zcp_error_handler(). We can only
926 * return the error message.
927 */
928 VERIFY3U(1, ==, lua_gettop(state));
929 if (ri->zri_timed_out) {
930 ri->zri_result = SET_ERROR(ETIME);
931 } else if (ri->zri_canceled) {
932 ri->zri_result = SET_ERROR(EINTR);
933 } else {
934 ri->zri_result = SET_ERROR(ECHRNG);
935 }
936
937 zcp_convert_return_values(state, ri->zri_outnvl,
938 ZCP_RET_ERROR, &ri->zri_result);
939 break;
940 }
941 case LUA_ERRMEM:
942 /*
943 * Lua ran out of memory while running the channel program.
944 * There's not much we can do.
945 */
946 ri->zri_result = SET_ERROR(ENOSPC);
947 break;
948 default:
949 VERIFY0(err);
950 }
951 }
952
953 static void
954 zcp_pool_error(zcp_run_info_t *ri, const char *poolname)
955 {
956 ri->zri_result = SET_ERROR(ECHRNG);
957 lua_settop(ri->zri_state, 0);
958 (void) lua_pushfstring(ri->zri_state, "Could not open pool: %s",
959 poolname);
960 zcp_convert_return_values(ri->zri_state, ri->zri_outnvl,
961 ZCP_RET_ERROR, &ri->zri_result);
962
963 }
964
965 /*
966 * This callback is called when txg_wait_synced_sig encountered a signal.
967 * The txg_wait_synced_sig will continue to wait for the txg to complete
968 * after calling this callback.
969 */
970 /* ARGSUSED */
971 static void
972 zcp_eval_sig(void *arg, dmu_tx_t *tx)
973 {
974 zcp_run_info_t *ri = arg;
975
976 ri->zri_canceled = B_TRUE;
977 }
978
979 static void
980 zcp_eval_sync(void *arg, dmu_tx_t *tx)
981 {
982 zcp_run_info_t *ri = arg;
983
984 /*
985 * Open context should have setup the stack to contain:
986 * 1: Error handler callback
987 * 2: Script to run (converted to a Lua function)
988 * 3: nvlist input to function (converted to Lua table or nil)
989 */
990 VERIFY3U(3, ==, lua_gettop(ri->zri_state));
991
992 zcp_eval_impl(tx, ri);
993 }
994
995 static void
996 zcp_eval_open(zcp_run_info_t *ri, const char *poolname)
997 {
998 int error;
999 dsl_pool_t *dp;
1000 dmu_tx_t *tx;
1001
1002 /*
1003 * See comment from the same assertion in zcp_eval_sync().
1004 */
1005 VERIFY3U(3, ==, lua_gettop(ri->zri_state));
1006
1007 error = dsl_pool_hold(poolname, FTAG, &dp);
1008 if (error != 0) {
1009 zcp_pool_error(ri, poolname);
1010 return;
1011 }
1012
1013 /*
1014 * As we are running in open-context, we have no transaction associated
1015 * with the channel program. At the same time, functions from the
1016 * zfs.check submodule need to be associated with a transaction as
1017 * they are basically dry-runs of their counterparts in the zfs.sync
1018 * submodule. These functions should be able to run in open-context.
1019 * Therefore we create a new transaction that we later abort once
1020 * the channel program has been evaluated.
1021 */
1022 tx = dmu_tx_create_dd(dp->dp_mos_dir);
1023
1024 zcp_eval_impl(tx, ri);
1025
1026 dmu_tx_abort(tx);
1027
1028 dsl_pool_rele(dp, FTAG);
1029 }
1030
1031 int
1032 zcp_eval(const char *poolname, const char *program, boolean_t sync,
1033 uint64_t instrlimit, uint64_t memlimit, nvpair_t *nvarg, nvlist_t *outnvl)
1034 {
1035 int err;
1036 lua_State *state;
1037 zcp_run_info_t runinfo;
1038
1039 if (instrlimit > zfs_lua_max_instrlimit)
1040 return (SET_ERROR(EINVAL));
1041 if (memlimit == 0 || memlimit > zfs_lua_max_memlimit)
1042 return (SET_ERROR(EINVAL));
1043
1044 zcp_alloc_arg_t allocargs = {
1045 .aa_must_succeed = B_TRUE,
1046 .aa_alloc_remaining = (int64_t)memlimit,
1047 .aa_alloc_limit = (int64_t)memlimit,
1048 };
1049
1050 /*
1051 * Creates a Lua state with a memory allocator that uses KM_SLEEP.
1052 * This should never fail.
1053 */
1054 state = lua_newstate(zcp_lua_alloc, &allocargs);
1055 VERIFY(state != NULL);
1056 (void) lua_atpanic(state, zcp_panic_cb);
1057
1058 /*
1059 * Load core Lua libraries we want access to.
1060 */
1061 VERIFY3U(1, ==, luaopen_base(state));
1062 lua_pop(state, 1);
1063 VERIFY3U(1, ==, luaopen_coroutine(state));
1064 lua_setglobal(state, LUA_COLIBNAME);
1065 VERIFY0(lua_gettop(state));
1066 VERIFY3U(1, ==, luaopen_string(state));
1067 lua_setglobal(state, LUA_STRLIBNAME);
1068 VERIFY0(lua_gettop(state));
1069 VERIFY3U(1, ==, luaopen_table(state));
1070 lua_setglobal(state, LUA_TABLIBNAME);
1071 VERIFY0(lua_gettop(state));
1072
1073 /*
1074 * Load globally visible variables such as errno aliases.
1075 */
1076 zcp_load_globals(state);
1077 VERIFY0(lua_gettop(state));
1078
1079 /*
1080 * Load ZFS-specific modules.
1081 */
1082 lua_newtable(state);
1083 VERIFY3U(1, ==, zcp_load_list_lib(state));
1084 lua_setfield(state, -2, "list");
1085 VERIFY3U(1, ==, zcp_load_synctask_lib(state, B_FALSE));
1086 lua_setfield(state, -2, "check");
1087 VERIFY3U(1, ==, zcp_load_synctask_lib(state, B_TRUE));
1088 lua_setfield(state, -2, "sync");
1089 VERIFY3U(1, ==, zcp_load_get_lib(state));
1090 lua_pushcclosure(state, zcp_debug_info.func, 0);
1091 lua_setfield(state, -2, zcp_debug_info.name);
1092 lua_pushcclosure(state, zcp_exists_info.func, 0);
1093 lua_setfield(state, -2, zcp_exists_info.name);
1094 lua_setglobal(state, "zfs");
1095 VERIFY0(lua_gettop(state));
1096
1097 /*
1098 * Push the error-callback that calculates Lua stack traces on
1099 * unexpected failures.
1100 */
1101 lua_pushcfunction(state, zcp_error_handler);
1102 VERIFY3U(1, ==, lua_gettop(state));
1103
1104 /*
1105 * Load the actual script as a function onto the stack as text ("t").
1106 * The only valid error condition is a syntax error in the script.
1107 * ERRMEM should not be possible because our allocator is using
1108 * KM_SLEEP. ERRGCMM should not be possible because we have not added
1109 * any objects with __gc metamethods to the interpreter that could
1110 * fail.
1111 */
1112 err = luaL_loadbufferx(state, program, strlen(program),
1113 "channel program", "t");
1114 if (err == LUA_ERRSYNTAX) {
1115 fnvlist_add_string(outnvl, ZCP_RET_ERROR,
1116 lua_tostring(state, -1));
1117 lua_close(state);
1118 return (SET_ERROR(EINVAL));
1119 }
1120 VERIFY0(err);
1121 VERIFY3U(2, ==, lua_gettop(state));
1122
1123 /*
1124 * Convert the input nvlist to a Lua object and put it on top of the
1125 * stack.
1126 */
1127 char errmsg[128];
1128 err = zcp_nvpair_value_to_lua(state, nvarg,
1129 errmsg, sizeof (errmsg));
1130 if (err != 0) {
1131 fnvlist_add_string(outnvl, ZCP_RET_ERROR, errmsg);
1132 lua_close(state);
1133 return (SET_ERROR(EINVAL));
1134 }
1135 VERIFY3U(3, ==, lua_gettop(state));
1136
1137 runinfo.zri_state = state;
1138 runinfo.zri_allocargs = &allocargs;
1139 runinfo.zri_outnvl = outnvl;
1140 runinfo.zri_result = 0;
1141 runinfo.zri_cred = CRED();
1142 runinfo.zri_timed_out = B_FALSE;
1143 runinfo.zri_canceled = B_FALSE;
1144 runinfo.zri_sync = sync;
1145 runinfo.zri_space_used = 0;
1146 runinfo.zri_curinstrs = 0;
1147 runinfo.zri_maxinstrs = instrlimit;
1148
1149 if (sync) {
1150 err = dsl_sync_task_sig(poolname, NULL, zcp_eval_sync,
1151 zcp_eval_sig, &runinfo, 0, ZFS_SPACE_CHECK_ZCP_EVAL);
1152 if (err != 0)
1153 zcp_pool_error(&runinfo, poolname);
1154 } else {
1155 zcp_eval_open(&runinfo, poolname);
1156 }
1157 lua_close(state);
1158
1159 return (runinfo.zri_result);
1160 }
1161
1162 /*
1163 * Retrieve metadata about the currently running channel program.
1164 */
1165 zcp_run_info_t *
1166 zcp_run_info(lua_State *state)
1167 {
1168 zcp_run_info_t *ri;
1169
1170 lua_getfield(state, LUA_REGISTRYINDEX, ZCP_RUN_INFO_KEY);
1171 ri = lua_touserdata(state, -1);
1172 lua_pop(state, 1);
1173 return (ri);
1174 }
1175
1176 /*
1177 * Argument Parsing
1178 * ================
1179 *
1180 * The Lua language allows methods to be called with any number
1181 * of arguments of any type. When calling back into ZFS we need to sanitize
1182 * arguments from channel programs to make sure unexpected arguments or
1183 * arguments of the wrong type result in clear error messages. To do this
1184 * in a uniform way all callbacks from channel programs should use the
1185 * zcp_parse_args() function to interpret inputs.
1186 *
1187 * Positional vs Keyword Arguments
1188 * ===============================
1189 *
1190 * Every callback function takes a fixed set of required positional arguments
1191 * and optional keyword arguments. For example, the destroy function takes
1192 * a single positional string argument (the name of the dataset to destroy)
1193 * and an optional "defer" keyword boolean argument. When calling lua functions
1194 * with parentheses, only positional arguments can be used:
1195 *
1196 * zfs.sync.snapshot("rpool@snap")
1197 *
1198 * To use keyword arguments functions should be called with a single argument
1199 * that is a lua table containing mappings of integer -> positional arguments
1200 * and string -> keyword arguments:
1201 *
1202 * zfs.sync.snapshot({1="rpool@snap", defer=true})
1203 *
1204 * The lua language allows curly braces to be used in place of parenthesis as
1205 * syntactic sugar for this calling convention:
1206 *
1207 * zfs.sync.snapshot{"rpool@snap", defer=true}
1208 */
1209
1210 /*
1211 * Throw an error and print the given arguments. If there are too many
1212 * arguments to fit in the output buffer, only the error format string is
1213 * output.
1214 */
1215 static void
1216 zcp_args_error(lua_State *state, const char *fname, const zcp_arg_t *pargs,
1217 const zcp_arg_t *kwargs, const char *fmt, ...)
1218 {
1219 int i;
1220 char errmsg[512];
1221 size_t len = sizeof (errmsg);
1222 size_t msglen = 0;
1223 va_list argp;
1224
1225 va_start(argp, fmt);
1226 VERIFY3U(len, >, vsnprintf(errmsg, len, fmt, argp));
1227 va_end(argp);
1228
1229 /*
1230 * Calculate the total length of the final string, including extra
1231 * formatting characters. If the argument dump would be too large,
1232 * only print the error string.
1233 */
1234 msglen = strlen(errmsg);
1235 msglen += strlen(fname) + 4; /* : + {} + null terminator */
1236 for (i = 0; pargs[i].za_name != NULL; i++) {
1237 msglen += strlen(pargs[i].za_name);
1238 msglen += strlen(lua_typename(state, pargs[i].za_lua_type));
1239 if (pargs[i + 1].za_name != NULL || kwargs[0].za_name != NULL)
1240 msglen += 5; /* < + ( + )> + , */
1241 else
1242 msglen += 4; /* < + ( + )> */
1243 }
1244 for (i = 0; kwargs[i].za_name != NULL; i++) {
1245 msglen += strlen(kwargs[i].za_name);
1246 msglen += strlen(lua_typename(state, kwargs[i].za_lua_type));
1247 if (kwargs[i + 1].za_name != NULL)
1248 msglen += 4; /* =( + ) + , */
1249 else
1250 msglen += 3; /* =( + ) */
1251 }
1252
1253 if (msglen >= len)
1254 (void) luaL_error(state, errmsg);
1255
1256 VERIFY3U(len, >, strlcat(errmsg, ": ", len));
1257 VERIFY3U(len, >, strlcat(errmsg, fname, len));
1258 VERIFY3U(len, >, strlcat(errmsg, "{", len));
1259 for (i = 0; pargs[i].za_name != NULL; i++) {
1260 VERIFY3U(len, >, strlcat(errmsg, "<", len));
1261 VERIFY3U(len, >, strlcat(errmsg, pargs[i].za_name, len));
1262 VERIFY3U(len, >, strlcat(errmsg, "(", len));
1263 VERIFY3U(len, >, strlcat(errmsg,
1264 lua_typename(state, pargs[i].za_lua_type), len));
1265 VERIFY3U(len, >, strlcat(errmsg, ")>", len));
1266 if (pargs[i + 1].za_name != NULL || kwargs[0].za_name != NULL) {
1267 VERIFY3U(len, >, strlcat(errmsg, ", ", len));
1268 }
1269 }
1270 for (i = 0; kwargs[i].za_name != NULL; i++) {
1271 VERIFY3U(len, >, strlcat(errmsg, kwargs[i].za_name, len));
1272 VERIFY3U(len, >, strlcat(errmsg, "=(", len));
1273 VERIFY3U(len, >, strlcat(errmsg,
1274 lua_typename(state, kwargs[i].za_lua_type), len));
1275 VERIFY3U(len, >, strlcat(errmsg, ")", len));
1276 if (kwargs[i + 1].za_name != NULL) {
1277 VERIFY3U(len, >, strlcat(errmsg, ", ", len));
1278 }
1279 }
1280 VERIFY3U(len, >, strlcat(errmsg, "}", len));
1281
1282 (void) luaL_error(state, errmsg);
1283 panic("unreachable code");
1284 }
1285
1286 static void
1287 zcp_parse_table_args(lua_State *state, const char *fname,
1288 const zcp_arg_t *pargs, const zcp_arg_t *kwargs)
1289 {
1290 int i;
1291 int type;
1292
1293 for (i = 0; pargs[i].za_name != NULL; i++) {
1294 /*
1295 * Check the table for this positional argument, leaving it
1296 * on the top of the stack once we finish validating it.
1297 */
1298 lua_pushinteger(state, i + 1);
1299 lua_gettable(state, 1);
1300
1301 type = lua_type(state, -1);
1302 if (type == LUA_TNIL) {
1303 zcp_args_error(state, fname, pargs, kwargs,
1304 "too few arguments");
1305 panic("unreachable code");
1306 } else if (type != pargs[i].za_lua_type) {
1307 zcp_args_error(state, fname, pargs, kwargs,
1308 "arg %d wrong type (is '%s', expected '%s')",
1309 i + 1, lua_typename(state, type),
1310 lua_typename(state, pargs[i].za_lua_type));
1311 panic("unreachable code");
1312 }
1313
1314 /*
1315 * Remove the positional argument from the table.
1316 */
1317 lua_pushinteger(state, i + 1);
1318 lua_pushnil(state);
1319 lua_settable(state, 1);
1320 }
1321
1322 for (i = 0; kwargs[i].za_name != NULL; i++) {
1323 /*
1324 * Check the table for this keyword argument, which may be
1325 * nil if it was omitted. Leave the value on the top of
1326 * the stack after validating it.
1327 */
1328 lua_getfield(state, 1, kwargs[i].za_name);
1329
1330 type = lua_type(state, -1);
1331 if (type != LUA_TNIL && type != kwargs[i].za_lua_type) {
1332 zcp_args_error(state, fname, pargs, kwargs,
1333 "kwarg '%s' wrong type (is '%s', expected '%s')",
1334 kwargs[i].za_name, lua_typename(state, type),
1335 lua_typename(state, kwargs[i].za_lua_type));
1336 panic("unreachable code");
1337 }
1338
1339 /*
1340 * Remove the keyword argument from the table.
1341 */
1342 lua_pushnil(state);
1343 lua_setfield(state, 1, kwargs[i].za_name);
1344 }
1345
1346 /*
1347 * Any entries remaining in the table are invalid inputs, print
1348 * an error message based on what the entry is.
1349 */
1350 lua_pushnil(state);
1351 if (lua_next(state, 1)) {
1352 if (lua_isnumber(state, -2) && lua_tointeger(state, -2) > 0) {
1353 zcp_args_error(state, fname, pargs, kwargs,
1354 "too many positional arguments");
1355 } else if (lua_isstring(state, -2)) {
1356 zcp_args_error(state, fname, pargs, kwargs,
1357 "invalid kwarg '%s'", lua_tostring(state, -2));
1358 } else {
1359 zcp_args_error(state, fname, pargs, kwargs,
1360 "kwarg keys must be strings");
1361 }
1362 panic("unreachable code");
1363 }
1364
1365 lua_remove(state, 1);
1366 }
1367
1368 static void
1369 zcp_parse_pos_args(lua_State *state, const char *fname, const zcp_arg_t *pargs,
1370 const zcp_arg_t *kwargs)
1371 {
1372 int i;
1373 int type;
1374
1375 for (i = 0; pargs[i].za_name != NULL; i++) {
1376 type = lua_type(state, i + 1);
1377 if (type == LUA_TNONE) {
1378 zcp_args_error(state, fname, pargs, kwargs,
1379 "too few arguments");
1380 panic("unreachable code");
1381 } else if (type != pargs[i].za_lua_type) {
1382 zcp_args_error(state, fname, pargs, kwargs,
1383 "arg %d wrong type (is '%s', expected '%s')",
1384 i + 1, lua_typename(state, type),
1385 lua_typename(state, pargs[i].za_lua_type));
1386 panic("unreachable code");
1387 }
1388 }
1389 if (lua_gettop(state) != i) {
1390 zcp_args_error(state, fname, pargs, kwargs,
1391 "too many positional arguments");
1392 panic("unreachable code");
1393 }
1394
1395 for (i = 0; kwargs[i].za_name != NULL; i++) {
1396 lua_pushnil(state);
1397 }
1398 }
1399
1400 /*
1401 * Checks the current Lua stack against an expected set of positional and
1402 * keyword arguments. If the stack does not match the expected arguments
1403 * aborts the current channel program with a useful error message, otherwise
1404 * it re-arranges the stack so that it contains the positional arguments
1405 * followed by the keyword argument values in declaration order. Any missing
1406 * keyword argument will be represented by a nil value on the stack.
1407 *
1408 * If the stack contains exactly one argument of type LUA_TTABLE the curly
1409 * braces calling convention is assumed, otherwise the stack is parsed for
1410 * positional arguments only.
1411 *
1412 * This function should be used by every function callback. It should be called
1413 * before the callback manipulates the Lua stack as it assumes the stack
1414 * represents the function arguments.
1415 */
1416 void
1417 zcp_parse_args(lua_State *state, const char *fname, const zcp_arg_t *pargs,
1418 const zcp_arg_t *kwargs)
1419 {
1420 if (lua_gettop(state) == 1 && lua_istable(state, 1)) {
1421 zcp_parse_table_args(state, fname, pargs, kwargs);
1422 } else {
1423 zcp_parse_pos_args(state, fname, pargs, kwargs);
1424 }
1425 }