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

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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: John Bonesio <bones@secretlab.ca>
[nico: ported to latest zImage changes plus additional cleanups/improvements]
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Dave Martin <dave.martin@linaro.org>
Tested-by: Thomas Abraham <thomas.abraham@linaro.org>
This commit is contained in:
John Bonesio 2011-05-27 18:45:50 -04:00 committed by Nicolas Pitre
parent 72bf0bce41
commit e2a6a3aafa
2 changed files with 87 additions and 3 deletions
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20
arch/arm/Kconfig
View File

@ -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 ""

70
arch/arm/boot/compressed/head.S
View File

@ -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
/*