// SPDX-License-Identifier: GPL-2.0-or-later
/*
   Simple utility to make a single-image install kernel with initial ramdisk
   for Sparc tftpbooting without need to set up nfs.

   Copyright (C) 1996,1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
   Pete Zaitcev <zaitcev@yahoo.com> endian fixes for cross-compiles, 2000.
   Copyright (C) 2011 Sam Ravnborg <sam@ravnborg.org>

 */

#include <dirent.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>

#include <sys/types.h>
#include <sys/stat.h>

/*
 * Note: run this on an a.out kernel (use elftoaout for it),
 * as PROM looks for a.out image only.
 */

#define AOUT_TEXT_OFFSET   32

static int is64bit = 0;

/* align to power-of-two size */
static int align(int n)
{
        if (is64bit)
                return (n + 0x1fff) & ~0x1fff;
        else
                return (n + 0xfff) & ~0xfff;
}

/* read two bytes as big endian */
static unsigned short ld2(char *p)
{
        return (p[0] << 8) | p[1];
}

/* save 4 bytes as big endian */
static void st4(char *p, unsigned int x)
{
        p[0] = x >> 24;
        p[1] = x >> 16;
        p[2] = x >> 8;
        p[3] = x;
}

static void die(const char *str)
{
        perror(str);
        exit(1);
}

static void usage(void)
{
        /* fs_img.gz is an image of initial ramdisk. */
        fprintf(stderr, "Usage: piggyback bits vmlinux.aout System.map fs_img.gz\n");
        fprintf(stderr, "\tKernel image will be modified in place.\n");
        exit(1);
}

static int start_line(const char *line)
{
        if (strcmp(line + 10, " _start\n") == 0)
                return 1;
        else if (strcmp(line + 18, " _start\n") == 0)
                return 1;
        return 0;
}

static int end_line(const char *line)
{
        if (strcmp(line + 10, " _end\n") == 0)
                return 1;
        else if (strcmp (line + 18, " _end\n") == 0)
                return 1;
        return 0;
}

/*
 * Find address for start and end in System.map.
 * The file looks like this:
 * f0004000 ... _start
 * f0379f79 ... _end
 * 1234567890123456
 * ^coloumn 1
 * There is support for 64 bit addresses too.
 *
 * Return 0 if either start or end is not found
 */
static int get_start_end(const char *filename, unsigned int *start,
                                               unsigned int *end)
{
        FILE *map;
        char buffer[1024];

        *start = 0;
        *end = 0;
        map = fopen(filename, "r");
        if (!map)
                die(filename);
        while (fgets(buffer, 1024, map)) {
                if (start_line(buffer))
                        *start = strtoul(buffer, NULL, 16);
                else if (end_line(buffer))
                        *end = strtoul(buffer, NULL, 16);
        }
        fclose (map);

        if (*start == 0 || *end == 0)
                return 0;

        return 1;
}

#define LOOKBACK (128 * 4)
#define BUFSIZE 1024
/*
 * Find the HdrS entry from head_32/head_64.
 * We check if it is at the beginning of the file (sparc64 case)
 * and if not we search for it.
 * When we search do so in steps of 4 as HdrS is on a 4-byte aligned
 * address (it is on same alignment as sparc instructions)
 * Return the offset to the HdrS entry (as off_t)
 */
static off_t get_hdrs_offset(int kernelfd, const char *filename)
{
        char buffer[BUFSIZE];
        off_t offset;
        int i;

        if (lseek(kernelfd, 0, SEEK_SET) < 0)
                die("lseek");
        if (read(kernelfd, buffer, BUFSIZE) != BUFSIZE)
                die(filename);

        if (buffer[40] == 'H' && buffer[41] == 'd' &&
            buffer[42] == 'r' && buffer[43] == 'S') {
                return 40;
        } else {
                /*  Find the gokernel label */
                /* Decode offset from branch instruction */
                offset = ld2(buffer + AOUT_TEXT_OFFSET + 2) << 2;
                /* Go back 512 bytes so we do not miss HdrS */
                offset -= LOOKBACK;
                /* skip a.out header */
                offset += AOUT_TEXT_OFFSET;
                if (offset < 0) {
                        errno = -EINVAL;
                        die("Calculated a negative offset, probably elftoaout generated an invalid image. Did you use a recent elftoaout ?");
                }
                if (lseek(kernelfd, offset, SEEK_SET) < 0)
                        die("lseek");
                if (read(kernelfd, buffer, BUFSIZE) != BUFSIZE)
                        die(filename);

                for (i = 0; i < LOOKBACK; i += 4) {
                        if (buffer[i + 0] == 'H' && buffer[i + 1] == 'd' &&
                            buffer[i + 2] == 'r' && buffer[i + 3] == 'S') {
                                return offset + i;
                        }
                }
        }
        fprintf (stderr, "Couldn't find headers signature in %s\n", filename);
        exit(1);
}

int main(int argc,char **argv)
{
        static char aout_magic[] = { 0x01, 0x03, 0x01, 0x07 };
        char buffer[1024];
        unsigned int i, start, end;
        off_t offset;
        struct stat s;
        int image, tail;

        if (argc != 5)
                usage();
        if (strcmp(argv[1], "64") == 0)
                is64bit = 1;
        if (stat (argv[4], &s) < 0)
                die(argv[4]);

        if (!get_start_end(argv[3], &start, &end)) {
                fprintf(stderr, "Could not determine start and end from %s\n",
                        argv[3]);
                exit(1);
        }
        if ((image = open(argv[2], O_RDWR)) < 0)
                die(argv[2]);
        if (read(image, buffer, 512) != 512)
                die(argv[2]);
        if (memcmp(buffer, aout_magic, 4) != 0) {
                fprintf (stderr, "Not a.out. Don't blame me.\n");
                exit(1);
        }
        /*
         * We need to fill in values for
         * sparc_ramdisk_image + sparc_ramdisk_size
         * To locate these symbols search for the "HdrS" text which appear
         * in the image a little before the gokernel symbol.
         * See definition of these in init_32.S
         */

        offset = get_hdrs_offset(image, argv[2]);
        /* skip HdrS + LINUX_VERSION_CODE + HdrS version */
        offset += 10;

        if (lseek(image, offset, 0) < 0)
                die("lseek");

        /*
         * root_flags = 0
         * root_dev = 1 (RAMDISK_MAJOR)
         * ram_flags = 0
         * sparc_ramdisk_image = "PAGE aligned address after _end")
         * sparc_ramdisk_size = size of image
         */
        st4(buffer, 0);
        st4(buffer + 4, 0x01000000);
        st4(buffer + 8, align(end + 32));
        st4(buffer + 12, s.st_size);

        if (write(image, buffer + 2, 14) != 14)
                die(argv[2]);

        /* For sparc64 update a_text and clear a_data + a_bss */
        if (is64bit)
        {
                if (lseek(image, 4, 0) < 0)
                        die("lseek");
                /* a_text */
                st4(buffer, align(end + 32 + 8191) - (start & ~0x3fffffUL) +
                            s.st_size);
                /* a_data */
                st4(buffer + 4, 0);
                /* a_bss */
                st4(buffer + 8, 0);
                if (write(image, buffer, 12) != 12)
                        die(argv[2]);
        }

        /* seek page aligned boundary in the image file and add boot image */
        if (lseek(image, AOUT_TEXT_OFFSET - start + align(end + 32), 0) < 0)
                die("lseek");
        if ((tail = open(argv[4], O_RDONLY)) < 0)
                die(argv[4]);
        while ((i = read(tail, buffer, 1024)) > 0)
                if (write(image, buffer, i) != i)
                        die(argv[2]);
        if (close(image) < 0)
                die("close");
        if (close(tail) < 0)
                die("close");
        return 0;
}