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Commit d35ce356 authored by Andrew Boie's avatar Andrew Boie
Browse files

mkbootimg: support longer kernel command lines 



We can't simply increase the value of BOOT_ARGS_SIZE since that
would break past binary compatibility; the offset of 'id' would
change. This can cause serious problems with incremental OTA updates.

Instead, define a supplemental field which stores command line
information beyond the first 512 bytes. A value of 1024 was chosen
to keep the total size of struct boot_img_hdr under the smallest
page size of 2048 bytes.

Even if the extra_cmdline field is used, the original cmdline
field is still always NULL-terminated to avoid issues with older
bootloaders that haven't been updated.

Change-Id: I887e6f1db351a5b71a61e3a03363cf8856123d74
Signed-off-by: default avatarAndrew Boie <andrew.p.boie@intel.com>
parent 2e63e71f

mkbootimg/bootimg.h

+6 −1
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ typedef struct boot_img_hdr boot_img_hdr; 
#define BOOT_MAGIC_SIZE 8

#define BOOT_NAME_SIZE 16

#define BOOT_ARGS_SIZE 512

#define BOOT_EXTRA_ARGS_SIZE 1024



struct boot_img_hdr

{
@@ -47,6 +48,10 @@ struct boot_img_hdr 
    unsigned char cmdline[BOOT_ARGS_SIZE];



    unsigned id[8]; /* timestamp / checksum / sha1 / etc */



    /* Supplemental command line data; kept here to maintain

     * binary compatibility with older versions of mkbootimg */

    unsigned char extra_cmdline[BOOT_EXTRA_ARGS_SIZE];

};



/*

mkbootimg/mkbootimg.c

+11 −2
Original line number Diff line number Diff line
@@ -114,6 +114,7 @@ int main(int argc, char **argv) 
    unsigned ramdisk_offset = 0x01000000;

    unsigned second_offset  = 0x00f00000;

    unsigned tags_offset    = 0x00000100;

    size_t cmdlen;



    argc--;

    argv++;
@@ -192,11 +193,19 @@ int main(int argc, char **argv) 


    memcpy(hdr.magic, BOOT_MAGIC, BOOT_MAGIC_SIZE);



    if(strlen(cmdline) > (BOOT_ARGS_SIZE - 1)) {

    cmdlen = strlen(cmdline);

    if(cmdlen > (BOOT_ARGS_SIZE + BOOT_EXTRA_ARGS_SIZE - 2)) {

        fprintf(stderr,"error: kernel commandline too large\n");

        return 1;

    }

    strcpy((char*)hdr.cmdline, cmdline);

    /* Even if we need to use the supplemental field, ensure we

     * are still NULL-terminated */

    strncpy((char *)hdr.cmdline, cmdline, BOOT_ARGS_SIZE - 1);

    hdr.cmdline[BOOT_ARGS_SIZE - 1] = '\0';

    if (cmdlen >= (BOOT_ARGS_SIZE - 1)) {

        cmdline += (BOOT_ARGS_SIZE - 1);

        strncpy((char *)hdr.extra_cmdline, cmdline, BOOT_EXTRA_ARGS_SIZE);

    }



    kernel_data = load_file(kernel_fn, &hdr.kernel_size);

    if(kernel_data == 0) {