Initial commit

target/linux/generic/files/drivers/platform/mikrotik/routerboot.c

@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for MikroTik RouterBoot flash data. Common routines.
+ *
+ * Copyright (C) 2020 Thibaut VARÈNE <hacks+kernel@slashdirt.org>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ */
+
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/sysfs.h>
+
+#include "routerboot.h"
+
+static struct kobject *rb_kobj;
+
+/**
+ * routerboot_tag_find() - Locate a given tag in routerboot config data.
+ * @bufhead: the buffer to look into. Must start with a tag node.
+ * @buflen: size of bufhead
+ * @tag_id: the tag identifier to look for
+ * @pld_ofs: will be updated with tag payload offset in bufhead, if tag found
+ * @pld_len: will be updated with tag payload size, if tag found
+ *
+ * This incarnation of tag_find() does only that: it finds a specific routerboot
+ * tag node in the input buffer. Routerboot tag nodes are u32 values:
+ * - The low nibble is the tag identification number,
+ * - The high nibble is the tag payload length (node excluded) in bytes.
+ * The payload immediately follows the tag node. Tag nodes are 32bit-aligned.
+ * The returned pld_ofs will always be aligned. pld_len may not end on 32bit
+ * boundary (the only known case is when parsing ERD data).
+ * The nodes are cpu-endian on the flash media. The payload is cpu-endian when
+ * applicable. Tag nodes are not ordered (by ID) on flash.
+ *
+ * Return: 0 on success (tag found) or errno
+ */
+int routerboot_tag_find(const u8 *bufhead, const size_t buflen, const u16 tag_id,
+			u16 *pld_ofs, u16 *pld_len)
+{
+	const u32 *datum, *bufend;
+	u32 node;
+	u16 id, len;
+	int ret;
+
+	if (!bufhead || !tag_id)
+		return -EINVAL;
+
+	ret = -ENOENT;
+	datum = (const u32 *)bufhead;
+	bufend = (const u32 *)(bufhead + buflen);
+
+	while (datum < bufend) {
+		node = *datum++;
+
+		/* Tag list ends with null node */
+		if (!node)
+			break;
+
+		id = node & 0xFFFF;
+		len = node >> 16;
+
+		if (tag_id == id) {
+			if (datum >= bufend)
+				break;
+
+			if (pld_ofs)
+				*pld_ofs = (u16)((u8 *)datum - bufhead);
+			if (pld_len)
+				*pld_len = len;
+
+			ret = 0;
+			break;
+		}
+
+		/*
+		 * The only known situation where len may not end on 32bit
+		 * boundary is within ERD data. Since we're only extracting
+		 * one tag (the first and only one) from that data, we should
+		 * never need to forcefully ALIGN(). Do it anyway, this is not a
+		 * performance path.
+		 */
+		len = ALIGN(len, sizeof(*datum));
+		datum += len / sizeof(*datum);
+	}
+
+	return ret;
+}
+
+/**
+ * routerboot_rle_decode() - Simple RLE (MikroTik variant) decoding routine.
+ * @in: input buffer to decode
+ * @inlen: size of in
+ * @out: output buffer to write decoded data to
+ * @outlen: pointer to out size when function is called, will be updated with
+ * size of decoded output on return
+ *
+ * MikroTik's variant of RLE operates as follows, considering a signed run byte:
+ * - positive run => classic RLE
+ * - negative run => the next -<run> bytes must be copied verbatim
+ * The API is matched to the lzo1x routines for convenience.
+ *
+ * NB: The output buffer cannot overlap with the input buffer.
+ *
+ * Return: 0 on success or errno
+ */
+int routerboot_rle_decode(const u8 *in, size_t inlen, u8 *out, size_t *outlen)
+{
+	int ret, run, nbytes;	// use native types for speed
+	u8 byte;
+
+	if (!in || (inlen < 2) || !out)
+		return -EINVAL;
+
+	ret = -ENOSPC;
+	nbytes = 0;
+	while (inlen >= 2) {
+		run = *in++;
+		inlen--;
+
+		/* Verbatim copies */
+		if (run & 0x80) {
+			/* Invert run byte sign */
+			run = ~run & 0xFF;
+			run++;
+
+			if (run > inlen)
+				goto fail;
+
+			inlen -= run;
+
+			nbytes += run;
+			if (nbytes > *outlen)
+				goto fail;
+
+			/* Basic memcpy */
+			while (run-- > 0)
+				*out++ = *in++;
+		}
+		/* Stream of half-words RLE: <run><byte>. run == 0 is ignored */
+		else {
+			byte = *in++;
+			inlen--;
+
+			nbytes += run;
+			if (nbytes > *outlen)
+				goto fail;
+
+			while (run-- > 0)
+				*out++ = byte;
+		}
+	}
+
+	ret = 0;
+fail:
+	*outlen = nbytes;
+	return ret;
+}
+
+static int __init routerboot_init(void)
+{
+	rb_kobj = kobject_create_and_add("mikrotik", firmware_kobj);
+	if (!rb_kobj)
+		return -ENOMEM;
+
+	return rb_hardconfig_init(rb_kobj);
+}
+
+static void __exit routerboot_exit(void)
+{
+	rb_hardconfig_exit();
+	kobject_put(rb_kobj);	// recursive afaict
+}
+
+module_init(routerboot_init);
+module_exit(routerboot_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("MikroTik RouterBoot sysfs support");
+MODULE_AUTHOR("Thibaut VARENE");