include/linux/ihex.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Compact binary representation of ihex records. Some devices need their
 * firmware loaded in strange orders rather than a single big blob, but
 * actually parsing ihex-as-text within the kernel seems silly. Thus,...
 */

#ifndef __LINUX_IHEX_H__
#define __LINUX_IHEX_H__

#include <linux/types.h>
#include <linux/firmware.h>
#include <linux/device.h>

/* Intel HEX files actually limit the length to 256 bytes, but we have
   drivers which would benefit from using separate records which are
   longer than that, so we extend to 16 bits of length */
struct ihex_binrec {
	__be32 addr;
	__be16 len;
	uint8_t data[0];
} __attribute__((packed));

/* Find the next record, taking into account the 4-byte alignment */
static inline const struct ihex_binrec *
__ihex_next_binrec(const struct ihex_binrec *rec)
{
	int next = ((be16_to_cpu(rec->len) + 5) & ~3) - 2;
	rec = (void *)&rec->data[next];

	return rec;
}

static inline const struct ihex_binrec *
ihex_next_binrec(const struct ihex_binrec *rec)
{
	rec = __ihex_next_binrec(rec);

	return be16_to_cpu(rec->len) ? rec : NULL;
}

/* Check that ihex_next_binrec() won't take us off the end of the image... */
static inline int ihex_validate_fw(const struct firmware *fw)
{
	const struct ihex_binrec *end, *rec;

	rec = (const void *)fw->data;
	end = (const void *)&fw->data[fw->size - sizeof(*end)];

	for (; rec <= end; rec = __ihex_next_binrec(rec)) {
		/* Zero length marks end of records */
		if (!be16_to_cpu(rec->len))
			return 0;
	}
	return -EINVAL;
}

/* Request firmware and validate it so that we can trust we won't
 * run off the end while reading records... */
static inline int request_ihex_firmware(const struct firmware **fw,
					const char *fw_name,
					struct device *dev)
{
	const struct firmware *lfw;
	int ret;

	ret = request_firmware(&lfw, fw_name, dev);
	if (ret)
		return ret;
	ret = ihex_validate_fw(lfw);
	if (ret) {
		dev_err(dev, "Firmware \"%s\" not valid IHEX records\n",
			fw_name);
		release_firmware(lfw);
		return ret;
	}
	*fw = lfw;
	return 0;
}
#endif /* __LINUX_IHEX_H__ */