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Commit e2a6a3aa authored by John Bonesio's avatar John Bonesio Committed by Nicolas Pitre
Browse files

ARM: zImage: Allow the appending of a device tree binary 



This patch provides the ability to boot using a device tree that is appended
to the raw binary zImage (e.g. cat zImage <filename>.dtb > zImage_w_dtb).

Signed-off-by: default avatarJohn Bonesio <bones@secretlab.ca>
[nico: ported to latest zImage changes plus additional cleanups/improvements]
Signed-off-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: default avatarGrant Likely <grant.likely@secretlab.ca>
Acked-by: default avatarTony Lindgren <tony@atomide.com>
Tested-by: default avatarShawn Guo <shawn.guo@linaro.org>
Tested-by: default avatarDave Martin <dave.martin@linaro.org>
Tested-by: default avatarThomas Abraham <thomas.abraham@linaro.org>
parent 72bf0bce

arch/arm/Kconfig

+20 −0
Original line number Diff line number Diff line
@@ -1781,6 +1781,26 @@ config ZBOOT_ROM_SH_MOBILE_SDHI 


endchoice



config ARM_APPENDED_DTB

	bool "Use appended device tree blob to zImage (EXPERIMENTAL)"

	depends on OF && !ZBOOT_ROM && EXPERIMENTAL

	help

	  With this option, the boot code will look for a device tree binary

	  (DTB) appended to zImage

	  (e.g. cat zImage <filename>.dtb > zImage_w_dtb).



	  This is meant as a backward compatibility convenience for those

	  systems with a bootloader that can't be upgraded to accommodate

	  the documented boot protocol using a device tree.



	  Beware that there is very little in terms of protection against

	  this option being confused by leftover garbage in memory that might

	  look like a DTB header after a reboot if no actual DTB is appended

	  to zImage.  Do not leave this option active in a production kernel

	  if you don't intend to always append a DTB.  Proper passing of the

	  location into r2 of a bootloader provided DTB is always preferable

	  to this option.



config CMDLINE

	string "Default kernel command string"

	default ""

arch/arm/boot/compressed/head.S

+67 −3
Original line number Diff line number Diff line
@@ -216,6 +216,59 @@ restart: adr r0, LC0 
		mov	r10, r6

#endif



		mov	r5, #0			@ init dtb size to 0

#ifdef CONFIG_ARM_APPENDED_DTB

/*

 *   r0  = delta

 *   r2  = BSS start

 *   r3  = BSS end

 *   r4  = final kernel address

 *   r5  = appended dtb size (still unknown)

 *   r6  = _edata

 *   r7  = architecture ID

 *   r8  = atags/device tree pointer

 *   r9  = size of decompressed image

 *   r10 = end of this image, including  bss/stack/malloc space if non XIP

 *   r11 = GOT start

 *   r12 = GOT end

 *   sp  = stack pointer

 *

 * if there are device trees (dtb) appended to zImage, advance r10 so that the

 * dtb data will get relocated along with the kernel if necessary.

 */



		ldr	lr, [r6, #0]

#ifndef __ARMEB__

		ldr	r1, =0xedfe0dd0		@ sig is 0xd00dfeed big endian

#else

		ldr	r1, =0xd00dfeed

#endif

		cmp	lr, r1

		bne	dtb_check_done		@ not found



		mov	r8, r6			@ use the appended device tree



		/* Get the dtb's size */

		ldr	r5, [r6, #4]

#ifndef __ARMEB__

		/* convert r5 (dtb size) to little endian */

		eor	r1, r5, r5, ror #16

		bic	r1, r1, #0x00ff0000

		mov	r5, r5, ror #8

		eor	r5, r5, r1, lsr #8

#endif



		/* preserve 64-bit alignment */

		add	r5, r5, #7

		bic	r5, r5, #7



		/* relocate some pointers past the appended dtb */

		add	r6, r6, r5

		add	r10, r10, r5

		add	sp, sp, r5

dtb_check_done:

#endif



/*

 * Check to see if we will overwrite ourselves.

 *   r4  = final kernel address
@@ -285,14 +338,16 @@ wont_overwrite: 
 *   r2  = BSS start

 *   r3  = BSS end

 *   r4  = kernel execution address

 *   r5  = appended dtb size (0 if not present)

 *   r7  = architecture ID

 *   r8  = atags pointer

 *   r11 = GOT start

 *   r12 = GOT end

 *   sp  = stack pointer

 */

		teq	r0, #0

		orrs	r1, r0, r5

		beq	not_relocated



		add	r11, r11, r0

		add	r12, r12, r0
@@ -307,12 +362,21 @@ wont_overwrite: 


		/*

		 * Relocate all entries in the GOT table.

		 * Bump bss entries to _edata + dtb size

		 */

1:		ldr	r1, [r11, #0]		@ relocate entries in the GOT

		add	r1, r1, r0		@ table.  This fixes up the

		str	r1, [r11], #4		@ C references.

		add	r1, r1, r0		@ This fixes up C references

		cmp	r1, r2			@ if entry >= bss_start &&

		cmphs	r3, r1			@       bss_end > entry

		addhi	r1, r1, r5		@    entry += dtb size

		str	r1, [r11], #4		@ next entry

		cmp	r11, r12

		blo	1b



		/* bump our bss pointers too */

		add	r2, r2, r5

		add	r3, r3, r5



#else



		/*