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// 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;
/*
* We ignore the following return values and always register.
* These init() routines are designed so that their failed state is
* always manageable by the corresponding exit() calls.
*/
rb_hardconfig_init(rb_kobj);
rb_softconfig_init(rb_kobj);
return 0;
}
static void __exit routerboot_exit(void)
{
rb_softconfig_exit();
rb_hardconfig_exit();
kobject_put(rb_kobj); // recursive afaict
}
/* Common routines */
ssize_t routerboot_tag_show_string(const u8 *pld, u16 pld_len, char *buf)
{
return scnprintf(buf, pld_len+1, "%s\n", pld);
}
ssize_t routerboot_tag_show_u32s(const u8 *pld, u16 pld_len, char *buf)
{
char *out = buf;
u32 data; // cpu-endian
/* Caller ensures pld_len > 0 */
if (pld_len % sizeof(data))
return -EINVAL;
data = *(u32 *)pld;
do {
out += sprintf(out, "0x%08x\n", data);
data++;
} while ((pld_len -= sizeof(data)));
return out - buf;
}
module_init(routerboot_init);
module_exit(routerboot_exit);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("MikroTik RouterBoot sysfs support");
MODULE_AUTHOR("Thibaut VARENE");
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