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Commit 9c239053 authored by Sam Ravnborg's avatar Sam Ravnborg Committed by David S. Miller
Browse files

sparc: additional comments to piggyback_32.c 



While reverse engineering the functionality of piggyback
I missed that the code was actually commented.
So I added a few comments.

Signed-off-by: default avatarSam Ravnborg <sam@ravnborg.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b2a39b0d

arch/sparc/boot/piggyback_32.c

+21 −2
Original line number Diff line number Diff line
@@ -36,6 +36,8 @@ 
 * as PROM looks for a.out image only.

 */



#define AOUT_TEXT_OFFSET   32



/* read two bytes as big endian */

static unsigned short ld2(char *p)

{
@@ -154,12 +156,20 @@ int main(int argc,char **argv) 
			die(argv[1]);

		j = 0;

	} else if (memcmp(buffer, aout_magic, 4) == 0) {

		i = j = 32;

		i = j = AOUT_TEXT_OFFSET;

	} else {

		fprintf (stderr, "Not ELF nor a.out. Don't blame me.\n");

		exit(1);

	}

	k = i;

	/*

	 * 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

	 */



	/*  Find the gokernel label */

	i += (ld2(buffer + j + 2) << 2) - 512;

	if (lseek(image, i, 0) < 0)

		die("lseek");
@@ -177,6 +187,13 @@ int main(int argc,char **argv) 
	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, (end + 32 + 4095) & ~4095);
@@ -184,6 +201,8 @@ int main(int argc,char **argv) 


	if (write(image, buffer + 2, 14) != 14)

		die(argv[1]);



	/* seek page aligned boundary in the image file and add boot image */

	if (lseek(image, k - start + ((end + 32 + 4095) & ~4095), 0) < 0)

		die("lseek");

	if ((tail = open(argv[3],O_RDONLY)) < 0)