fs: improve ioctl implementation

lib/fs.c

@@ -62,7 +62,17 @@
 #include <fcntl.h>
 
 #if defined(__linux__)
+#define HAS_IOCTL
+#endif
+
+#ifdef HAS_IOCTL
 #include <sys/ioctl.h>
+
+#define IOC_DIR_NONE	(_IOC_NONE)
+#define IOC_DIR_READ	(_IOC_READ)
+#define IOC_DIR_WRITE	(_IOC_WRITE)
+#define IOC_DIR_RW		(_IOC_READ | _IOC_WRITE)
+
 #endif
 
 #include "ucode/module.h"
@@ -937,50 +947,50 @@ uc_fs_fileno(uc_vm_t *vm, size_t nargs)
 	return uc_fs_fileno_common(vm, nargs, "fs.file");
 }
 
-#if defined(__linux__)
+#ifdef HAS_IOCTL
 
 /**
  * Performs an ioctl operation on the file.
- * 
+ *
  * The direction parameter specifies who is reading and writing,
  * from the user's point of view. It can be one of the following values:
- * 
- * | Direction | Description                                                                             |
- * |-----------|-----------------------------------------------------------------------------------------|
- * | 0         | NONE - neither userspace nor kernel is writing, ioctl is executed without passing data. |
- * | 1         | WRITE - userspace is writing and kernel is reading.                                     |
- * | 2         | READ - kernel is writing and userspace is reading.                                      |
- * | 3         | READ+WRITE - userspace is writing and kernel is writing back into the data structure.   |
- * 
+ *
+ * | Direction      | Description                                                                       |
+ * |----------------|-----------------------------------------------------------------------------------|
+ * | IOC_DIR_NONE   | neither userspace nor kernel is writing, ioctl is executed without passing data.  |
+ * | IOC_DIR_WRITE  | userspace is writing and kernel is reading.                                       |
+ * | IOC_DIR_READ   | kernel is writing and userspace is reading.                                       |
+ * | IOC_DIR_RW     | userspace is writing and kernel is writing back into the data structure.          |
+ *
  * The size parameter has a different purpose depending on the direction parameter:
- * - direction = 0 -> the size parameter is not used
- * - direction = 1 -> size must be the length (in bytes) of argp
- * - direction = 2 -> expected length (in bytes) of the data returned by kernel
- * - direction = 3 -> size is the length (in bytes) of argp, and the length of the data returned by kernel.
- * 
- * The argp parameter should be the data to be written for direction '1' and '3', otherwise null.
- * 
- * Returns the result of the ioctl operation; for direction '2' and '3' this is a string containing
+ * - IOC_DIR_NONE  -> the size parameter is not used
+ * - IOC_DIR_WRITE -> size must be the length (in bytes) of argp
+ * - IOC_DIR_READ  -> expected length (in bytes) of the data returned by kernel
+ * - IOC_DIR_RW    -> size is the length (in bytes) of argp, and the length of the data returned by kernel.
+ *
+ * The argp parameter should be the data to be written for IOC_DIR_WRITE and IOC_DIR_RW, otherwise null.
+ *
+ * Returns the result of the ioctl operation; for IOC_DIR_READ and IOC_DIR_RW this is a string containing
  * the data, otherwise a number as return code.
  * In case of an error, null is returned and the error code is available via last_error.
- * 
+ *
  * @function module:fs.file#ioctl
- * 
+ *
  * @param {number} direction
- * The direction of the ioctl operation.
- * 
+ * The direction of the ioctl operation. Use constants IOC_DIR_*.
+ *
  * @param {number} type
  * ioctl type (see https://www.kernel.org/doc/html/latest/userspace-api/ioctl/ioctl-number.html)
- * 
+ *
  * @param {number} num
  * ioctl sequence number.
- * 
+ *
  * @param {number} size
  * The size of the ioctl operation payload.
- * 
+ *
  * @param {?string} payload
  * The ioctl payload.
- * 
+ *
  * @returns {?number|?string}
  */
 static uc_value_t *
@@ -992,12 +1002,12 @@ uc_fs_ioctl(uc_vm_t *vm, size_t nargs)
 	uc_value_t *num = uc_fn_arg(2);
 	uc_value_t *size = uc_fn_arg(3);
 	uc_value_t *payload = uc_fn_arg(4);
+	uc_string_t *mem = NULL;
 	char *buf = NULL;
 	unsigned long req = 0;
 	unsigned int dir, ty, nr;
 	size_t sz;
 	int fd, ret;
-	bool freebuf = false;
 
 	if (!fp)
 		err_return(EBADF);
@@ -1016,48 +1026,52 @@ uc_fs_ioctl(uc_vm_t *vm, size_t nargs)
 	nr = ucv_uint64_get(num);
 
 	switch (dir) {
-	case 0: /* ioctl w/o read and write */
-		req = _IOC(_IOC_NONE, ty, nr, 0);
+	case IOC_DIR_NONE:
+		sz = 0;
 		break;
-	case 1: /* ioctl write */
+	case IOC_DIR_WRITE:
 		if (ucv_type(payload) != UC_STRING)
 			err_return(EINVAL);
 
-		req = _IOC(_IOC_WRITE, ty, nr, sz);
 		buf = ucv_string_get(payload);
 		break;
-	case 2: /* ioctl read */
-		req = _IOC(_IOC_READ, ty, nr, sz);
-		buf = xalloc(sz);
-		if (!buf)
+	case IOC_DIR_READ:
+		mem = xalloc(sizeof(uc_string_t) + sz + 1);
+		if (!mem)
 			err_return(ENOMEM);
 
-		freebuf = true;
+		mem->header.type = UC_STRING;
+		mem->header.refcount = 1;
+		mem->length = sz;
+		buf = mem->str;
+
 		break;
-	case 3: /* ioctl read+write */
-		req = _IOC((_IOC_READ|_IOC_WRITE), ty, nr, sz);
-		buf = ucv_string_get(payload);
+	case IOC_DIR_RW:
+		if (ucv_type(payload) != UC_STRING)
+			err_return(EINVAL);
+
+		mem = (uc_string_t *)payload;
+		buf = mem->str;
+		sz = mem->length;
+
 		break;
 	default: err_return(EINVAL);
 	}
 
+	req = _IOC(dir, ty, nr, sz);
 	ret = ioctl(fd, req, buf);
 	if (ret < 0) {
-		if (freebuf)
-			free(buf);
+		if (dir == IOC_DIR_READ)
+			free(mem);
 
 		err_return(errno);
 	}
 
-	if (dir >= 2) {
-		payload = ucv_string_new_length(buf, sz);
-		if (freebuf)
-			free(buf);
+	if (mem) {
+		return &mem->header;
 	} else {
-		payload = ucv_uint64_new(ret);
+		return ucv_uint64_new(ret);
 	}
-
-	return payload;
 }
 
 #endif
@@ -2880,4 +2894,12 @@ void uc_module_init(uc_vm_t *vm, uc_value_t *scope)
 	ucv_object_add(scope, "stdin", uc_resource_new(file_type, stdin));
 	ucv_object_add(scope, "stdout", uc_resource_new(file_type, stdout));
 	ucv_object_add(scope, "stderr", uc_resource_new(file_type, stderr));
+
+#ifdef HAS_IOCTL
+#define ADD_CONST(x) ucv_object_add(scope, #x, ucv_int64_new(x))
+	ADD_CONST(IOC_DIR_NONE);
+	ADD_CONST(IOC_DIR_READ);
+	ADD_CONST(IOC_DIR_WRITE);
+	ADD_CONST(IOC_DIR_RW);
+#endif
 }