#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <inttypes.h>
#include <string.h>

static off_t find_gfxboot(const char *string,
			  uint8_t *data, off_t offset, off_t size)
{
	size_t len = strlen(string);

	for (; offset <= (size - len); offset++) {
		if (memcmp(&data[offset], string, len) == 0)
			return offset;
	}

	return size;
}

static void print_gfxboot_addr(const char *string, uint8_t *addr, off_t size)
{
	off_t offset;

	offset = 0;
	while (offset < size) {
		offset = find_gfxboot(string, addr, offset, size);
		if (offset < size) {
			printf("GFXBOOT string found at: 0x%" PRIx64 "\n",
				offset);
			offset++;
		}
	}
}

int main(int argc, char **argv)
{
	int fd;
	uint8_t *addr;
	struct stat stbuf;
	const char *string = "GFXBOOT bootlogo";
	off_t patch_address = 0;

	if (argc != 2) {
		printf("Usage: %s ISO\n", argv[0]);
		return 1;
	}

	fd = open(argv[1], O_RDWR);
	if (fd == -1) {
		fprintf(stderr, "open failed: %m\n");
		return 1;
	}

	if (fstat(fd, &stbuf) == -1) {
		fprintf(stderr, "fstat failed: %m\n");
		return 1;
	}

	addr = mmap(NULL, stbuf.st_size, PROT_READ | PROT_WRITE,
		    MAP_SHARED, fd, 0);
	if (addr == MAP_FAILED) {
		fprintf(stderr, "mmap failed: %m\n");
		return 1;
	}

	if (patch_address) {
		size_t len = strlen(string);

		if ((patch_address + len) > stbuf.st_size) {
			fprintf(stderr, "Patch address is invalid\n");
			return 1;
		}
		if (memcmp(&addr[patch_address], string, len) != 0) {
			fprintf(stderr,
				"GFXBOOT string not found at patch address\n");
			return 1;
		}

		memset(&addr[patch_address], ' ', len);
	} else
		print_gfxboot_addr(string, addr, stbuf.st_size);

	munmap(addr, stbuf.st_size);

	close(fd);

	return 0;
}