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// SPDX-License-Identifier: GPL-2.0-only
/*
* mkbrncmdline.c - partially based on OpenWrt's wndr3700.c
*
* Copyright (C) 2011 Tobias Diedrich <ranma+openwrt@tdiedrich.de>
*/
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <string.h>
#include <netinet/in.h>
#include <inttypes.h>
static void usage(const char *) __attribute__ (( __noreturn__ ));
static void usage(const char *mess)
{
fprintf(stderr, "Error: %s\n", mess);
fprintf(stderr, "Usage: mkbrncmdline -i input_file -o output_file [-a loadaddress] arg1 [argx ...]\n");
fprintf(stderr, "\n");
exit(1);
}
static char *input_file = NULL;
static char *output_file = NULL;
static unsigned loadaddr = 0x80002000;
static void parseopts(int *argc, char ***argv)
{
char *endptr;
int res;
while ((res = getopt(*argc, *argv, "a:i:o:")) != -1) {
switch (res) {
default:
usage("Unknown option");
break;
case 'a':
loadaddr = strtoul(optarg, &endptr, 0);
if (endptr == optarg || *endptr != 0)
usage("loadaddress must be a decimal or hexadecimal 32-bit value");
break;
case 'i':
input_file = optarg;
break;
case 'o':
output_file = optarg;
break;
}
}
*argc -= optind;
*argv += optind;
}
static void emitload(int outfd, int reg, unsigned value)
{
char buf[8] = {
0x3c, 0x04 + reg,
value >> 24, value >> 16,
0x34, 0x84 + reg + (reg << 5),
value >> 8, value,
};
if (write(outfd, buf, sizeof(buf)) != sizeof(buf)) {
fprintf(stderr, "write: %s\n", strerror(errno));
exit(1);
}
}
int main(int argc, char **argv)
{
int outfd;
int i;
int fd;
size_t len, skip, buf_len;
unsigned cmdline_addr;
unsigned s_ofs;
char *buf;
parseopts(&argc, &argv);
if (argc < 1)
usage("must specify at least one kernel cmdline argument");
if (input_file == NULL || output_file == NULL)
usage("must specify input and output file");
if ((outfd = open(output_file, O_WRONLY|O_CREAT|O_TRUNC, 0644)) == -1)
{
fprintf(stderr, "Error opening '%s' for writing: %s\n", output_file, strerror(errno));
exit(1);
}
// mmap input_file
if ((fd = open(input_file, O_RDONLY)) < 0
|| (len = lseek(fd, 0, SEEK_END)) < 0
|| (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1)
|| close(fd) < 0)
{
fprintf(stderr, "Error mapping file '%s': %s\n", input_file, strerror(errno));
exit(1);
}
cmdline_addr = loadaddr + len;
// Kernel args are passed in registers a0,a1,a2 and a3
emitload(outfd, 0, 0); /* a0 = 0 */
emitload(outfd, 1, 0); /* a1 = 0 */
emitload(outfd, 2, cmdline_addr); /* a2 = &cmdline */
emitload(outfd, 3, 0); /* a3 = 0 */
skip = lseek(outfd, 0, SEEK_END);
// write the kernel
if (write(outfd, input_file + skip, len - skip) != len -skip) {
fprintf(stderr, "write: %s\n", strerror(errno));
exit(1);
}
// write cmdline structure
buf_len = (argc + 1) * 4;
for (i=0; i<argc; i++) {
buf_len += strlen(argv[i]) + 1;
}
buf = malloc(buf_len + 16);
if (!buf) {
fprintf(stderr, "Could not allocate memory for cmdline buffer\n");
exit(1);
}
memset(buf, 0, buf_len);
s_ofs = 4 * (argc + 1);
for (i=0; i<argc; i++) {
unsigned s_ptr = cmdline_addr + s_ofs;
buf[i * 4 + 0] = s_ptr >> 24;
buf[i * 4 + 1] = s_ptr >> 16;
buf[i * 4 + 2] = s_ptr >> 8;
buf[i * 4 + 3] = s_ptr >> 0;
memcpy(&buf[s_ofs], argv[i], strlen(argv[i]));
s_ofs += strlen(argv[i]) + 1;
}
if (write(outfd, buf, buf_len) != buf_len) {
fprintf(stderr, "write: %s\n", strerror(errno));
exit(1);
}
munmap(input_file, len);
close(outfd);
free(buf);
return 0;
}
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