/*
 * Copyright (C) 2012 Samsung Electronics
 *
 * SPDX-License-Identifier:     GPL-2.0+
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <compiler.h>

#define CHECKSUM_OFFSET         (14*1024-4)
#define FILE_PERM               (S_IRUSR | S_IWUSR | S_IRGRP \
                                | S_IWGRP | S_IROTH | S_IWOTH)
/*
 * Requirement for the fixed size SPL header:
 * IROM code reads first (CHECKSUM_OFFSET + 4) bytes from boot device. It then
 * calculates the checksum of CHECKSUM_OFFSET bytes and compares with data at
 * CHECKSUM_OFFSET location.
 *
 * Requirement for the variable size SPL header:

 * IROM code reads the below header to find out the size of the blob (total
 * size, header size included) and its checksum. Then it reads the rest of the
 * blob [i.e size - sizeof(struct var_size_header) bytes], calculates the
 * checksum and compares it with value read from the header.
 */
struct var_size_header {
        uint32_t spl_size;
        uint32_t spl_checksum;
        uint32_t reserved[2];
};

static const char *prog_name;

static void write_to_file(int ofd, void *buffer, int size)
{
        if (write(ofd, buffer, size) == size)
                return;

        fprintf(stderr, "%s: Failed to write to output file: %s\n",
                prog_name, strerror(errno));
        exit(EXIT_FAILURE);
}

/*
 * The argv is expected to include one optional parameter and two filenames:
 * [--vs] IN OUT
 *
 * --vs - turns on the variable size SPL mode
 * IN  - the u-boot SPL binary, usually u-boot-spl.bin
 * OUT - the prepared SPL blob, usually ${BOARD}-spl.bin
 *
 * This utility first reads the "u-boot-spl.bin" into a buffer. In case of
 * fixed size SPL the buffer size is exactly CHECKSUM_OFFSET (such that
 * smaller u-boot-spl.bin gets padded with 0xff bytes, the larger than limit
 * u-boot-spl.bin causes an error). For variable size SPL the buffer size is
 * eqaul to size of the IN file.
 *
 * Then it calculates checksum of the buffer by just summing up all bytes.
 * Then
 *
 * - for fixed size SPL the buffer is written into the output file and the
 *   checksum is appended to the file in little endian format, which results
 *   in checksum added exactly at CHECKSUM_OFFSET.
 *
 * - for variable size SPL the checksum and file size are stored in the
 *   var_size_header structure (again, in little endian format) and the
 *   structure is written into the output file. Then the buffer is written
 *   into the output file.
 */
int main(int argc, char **argv)
{
        unsigned char *buffer;
        int i, ifd, ofd;
        uint32_t checksum = 0;
        off_t   len;
        int     var_size_flag, read_size, count;
        struct stat stat;
        const int if_index = argc - 2; /* Input file name index in argv. */
        const int of_index = argc - 1; /* Output file name index in argv. */

        /* Strip path off the program name. */
        prog_name = strrchr(argv[0], '/');
        if (prog_name)
                prog_name++;
        else
                prog_name = argv[0];

        if ((argc < 3) ||
            (argc > 4) ||
            ((argc == 4) && strcmp(argv[1], "--vs"))) {
                fprintf(stderr, "Usage: %s [--vs] <infile> <outfile>\n",
                        prog_name);
                exit(EXIT_FAILURE);
        }

        /* four args mean variable size SPL wrapper is required */
        var_size_flag = (argc == 4);

        ifd = open(argv[if_index], O_RDONLY);
        if (ifd < 0) {
                fprintf(stderr, "%s: Can't open %s: %s\n",
                        prog_name, argv[if_index], strerror(errno));
                exit(EXIT_FAILURE);
        }

        ofd = open(argv[of_index], O_WRONLY | O_CREAT | O_TRUNC, FILE_PERM);
        if (ifd < 0) {
                fprintf(stderr, "%s: Can't open %s: %s\n",
                        prog_name, argv[of_index], strerror(errno));
                exit(EXIT_FAILURE);
        }

        if (fstat(ifd, &stat)) {
                fprintf(stderr, "%s: Unable to get size of %s: %s\n",
                        prog_name, argv[if_index], strerror(errno));
                exit(EXIT_FAILURE);
        }

        len = stat.st_size;

        if (var_size_flag) {
                read_size = len;
                count = len;
        } else {
                if (len > CHECKSUM_OFFSET) {
                        fprintf(stderr,
                                "%s: %s is too big (exceeds %d bytes)\n",
                                prog_name, argv[if_index], CHECKSUM_OFFSET);
                        exit(EXIT_FAILURE);
                }
                count = CHECKSUM_OFFSET;
                read_size = len;
        }

        buffer = malloc(count);
        if (!buffer) {
                fprintf(stderr,
                        "%s: Failed to allocate %d bytes to store %s\n",
                        prog_name, count, argv[if_index]);
                exit(EXIT_FAILURE);
        }

        if (read(ifd, buffer, read_size) != read_size) {
                fprintf(stderr, "%s: Can't read %s: %s\n",
                        prog_name, argv[if_index], strerror(errno));
                exit(EXIT_FAILURE);
        }

        /* Pad if needed with 0xff to make flashing faster. */
        if (read_size < count)
                memset((char *)buffer + read_size, 0xff, count - read_size);

        for (i = 0, checksum = 0; i < count; i++)
                checksum += buffer[i];
        checksum = cpu_to_le32(checksum);

        if (var_size_flag) {
                /* Prepare and write out the variable size SPL header. */
                struct var_size_header vsh;
                uint32_t spl_size;

                memset(&vsh, 0, sizeof(vsh));
                memcpy(&vsh.spl_checksum, &checksum, sizeof(checksum));

                spl_size = cpu_to_le32(count + sizeof(struct var_size_header));
                memcpy(&vsh.spl_size, &spl_size, sizeof(spl_size));
                write_to_file(ofd, &vsh, sizeof(vsh));
        }

        write_to_file(ofd, buffer, count);

        /* For fixed size SPL checksum is appended in the end. */
        if (!var_size_flag)
                write_to_file(ofd, &checksum, sizeof(checksum));

        close(ifd);
        close(ofd);
        free(buffer);

        return EXIT_SUCCESS;
}