core/iwasm: Support mapped file system access on non-libuv WASI (#2628)

This patch enables mapping host directories to guest directories by parsing
the `map_dir_list` argument in API `wasm_runtime_init_wasi` for libc-wasi. It
follows the format `<guest-path>::<host-path>`.

It also adds argument `--map-dir=<guest::host>` argument for `iwasm`
common line tool, and allows to add multiple mappings:
```bash
iwasm --map-dir=<guest-path1::host-path1> --map-dir=<guest-path2::host-path2> ...
```

core/iwasm/common/wasm_runtime_common.c

@@ -3012,8 +3012,82 @@ wasm_runtime_init_wasi(WASMModuleInstanceCommon *module_inst,
             goto fail;
         }
 
-        fd_table_insert_existing(curfds, wasm_fd, raw_fd);
+        if (!fd_table_insert_existing(curfds, wasm_fd, raw_fd)
-        fd_prestats_insert(prestats, dir_list[i], wasm_fd);
+            || !fd_prestats_insert(prestats, dir_list[i], wasm_fd)) {
+            if (error_buf)
+                snprintf(
+                    error_buf, error_buf_size,
+                    "error while pre-opening directory %s: insertion failed\n",
+                    dir_list[i]);
+            goto fail;
+        }
+    }
+
+    for (i = 0; i < map_dir_count; i++, wasm_fd++) {
+        char mapping_copy_buf[256];
+        char *mapping_copy = mapping_copy_buf;
+        char *map_mapped = NULL, *map_host = NULL;
+        const unsigned long max_len = strlen(map_dir_list[i]) * 2 + 3;
+
+        /* Allocation limit for runtime environments with reduced stack size */
+        if (max_len > 256) {
+            if (!(mapping_copy = wasm_runtime_malloc(max_len))) {
+                snprintf(error_buf, error_buf_size,
+                         "error while allocating for directory mapping\n");
+                goto fail;
+            }
+        }
+
+        strncpy(mapping_copy, map_dir_list[i], strlen(map_dir_list[i]) + 1);
+        map_mapped = strtok(mapping_copy, "::");
+        map_host = strtok(NULL, "::");
+
+        if (!map_mapped || !map_host) {
+            if (error_buf)
+                snprintf(error_buf, error_buf_size,
+                         "error while pre-opening mapped directory: "
+                         "invalid map\n");
+            if (mapping_copy != mapping_copy_buf)
+                wasm_runtime_free(mapping_copy);
+            goto fail;
+        }
+
+        path = realpath(map_host, resolved_path);
+        if (!path) {
+            if (error_buf)
+                snprintf(error_buf, error_buf_size,
+                         "error while pre-opening mapped directory %s: %d\n",
+                         map_host, errno);
+            if (mapping_copy != mapping_copy_buf)
+                wasm_runtime_free(mapping_copy);
+            goto fail;
+        }
+
+        raw_fd = open(path, O_RDONLY | O_DIRECTORY, 0);
+        if (raw_fd == -1) {
+            if (error_buf)
+                snprintf(error_buf, error_buf_size,
+                         "error while pre-opening mapped directory %s: %d\n",
+                         map_host, errno);
+            if (mapping_copy != mapping_copy_buf)
+                wasm_runtime_free(mapping_copy);
+            goto fail;
+        }
+
+        if (!fd_table_insert_existing(curfds, wasm_fd, raw_fd)
+            || !fd_prestats_insert(prestats, map_mapped, wasm_fd)) {
+            if (error_buf)
+                snprintf(error_buf, error_buf_size,
+                         "error while pre-opening mapped directory %s: "
+                         "insertion failed\n",
+                         dir_list[i]);
+            if (mapping_copy != mapping_copy_buf)
+                wasm_runtime_free(mapping_copy);
+            goto fail;
+        }
+
+        if (mapping_copy != mapping_copy_buf)
+            wasm_runtime_free(mapping_copy);
     }
 
     /* addr_pool(textual) -> apool */

core/iwasm/include/wasm_export.h

@@ -423,6 +423,7 @@ wasm_runtime_get_module_hash(wasm_module_t module);
  * @param dir_list      The list of directories to preopen. (real path)
  * @param dir_count     The number of elements in dir_list.
  * @param map_dir_list  The list of directories to preopen. (mapped path)
+ *                      Format for each map entry: <guest-path>::<host-path>
  * @param map_dir_count The number of elements in map_dir_list.
  *                      If map_dir_count is smaller than dir_count,
  *                      mapped path is assumed to be same as the

product-mini/platforms/posix/main.c

@@ -75,6 +75,9 @@ print_help()
     printf("  --dir=<dir>              Grant wasi access to the given host directories\n");
     printf("                           to the program, for example:\n");
     printf("                             --dir=<dir1> --dir=<dir2>\n");
+    printf("  --map-dir=<guest::host>  Grant wasi access to the given host directories\n");
+    printf("                           to the program at a specific guest path, for example:\n");
+    printf("                             --map-dir=<guest-path1::host-path1> --map-dir=<guest-path2::host-path2>\n");
     printf("  --addr-pool=<addrs>      Grant wasi access to the given network addresses in\n");
     printf("                           CIRD notation to the program, seperated with ',',\n");
     printf("                           for example:\n");
@@ -573,6 +576,8 @@ main(int argc, char *argv[])
 #if WASM_ENABLE_LIBC_WASI != 0
     const char *dir_list[8] = { NULL };
     uint32 dir_list_size = 0;
+    const char *map_dir_list[8] = { NULL };
+    uint32 map_dir_list_size = 0;
     const char *env_list[8] = { NULL };
     uint32 env_list_size = 0;
     const char *addr_pool[8] = { NULL };
@@ -711,6 +716,16 @@ main(int argc, char *argv[])
             }
             dir_list[dir_list_size++] = argv[0] + 6;
         }
+        else if (!strncmp(argv[0], "--map-dir=", 10)) {
+            if (argv[0][10] == '\0')
+                return print_help();
+            if (map_dir_list_size >= sizeof(map_dir_list) / sizeof(char *)) {
+                printf("Only allow max map dir number %d\n",
+                       (int)(sizeof(map_dir_list) / sizeof(char *)));
+                return 1;
+            }
+            map_dir_list[map_dir_list_size++] = argv[0] + 10;
+        }
         else if (!strncmp(argv[0], "--env=", 6)) {
             char *tmp_env;
 
@@ -920,8 +935,9 @@ main(int argc, char *argv[])
     }
 
 #if WASM_ENABLE_LIBC_WASI != 0
-    wasm_runtime_set_wasi_args(wasm_module, dir_list, dir_list_size, NULL, 0,
+    wasm_runtime_set_wasi_args(wasm_module, dir_list, dir_list_size,
-                               env_list, env_list_size, argv, argc);
+                               map_dir_list, map_dir_list_size, env_list,
+                               env_list_size, argv, argc);
 
     wasm_runtime_set_wasi_addr_pool(wasm_module, addr_pool, addr_pool_size);
     wasm_runtime_set_wasi_ns_lookup_pool(wasm_module, ns_lookup_pool,