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: 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
Nicolas Pitre
parent
72bf0bce41
commit
e2a6a3aafa
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@ -1781,6 +1781,26 @@ config ZBOOT_ROM_SH_MOBILE_SDHI
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endchoice
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config ARM_APPENDED_DTB
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bool "Use appended device tree blob to zImage (EXPERIMENTAL)"
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depends on OF && !ZBOOT_ROM && EXPERIMENTAL
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help
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With this option, the boot code will look for a device tree binary
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(DTB) appended to zImage
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(e.g. cat zImage <filename>.dtb > zImage_w_dtb).
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This is meant as a backward compatibility convenience for those
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systems with a bootloader that can't be upgraded to accommodate
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the documented boot protocol using a device tree.
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Beware that there is very little in terms of protection against
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this option being confused by leftover garbage in memory that might
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look like a DTB header after a reboot if no actual DTB is appended
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to zImage. Do not leave this option active in a production kernel
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if you don't intend to always append a DTB. Proper passing of the
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location into r2 of a bootloader provided DTB is always preferable
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to this option.
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config CMDLINE
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string "Default kernel command string"
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default ""
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@ -216,6 +216,59 @@ restart: adr r0, LC0
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mov r10, r6
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#endif
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mov r5, #0 @ init dtb size to 0
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#ifdef CONFIG_ARM_APPENDED_DTB
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/*
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* r0 = delta
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* r2 = BSS start
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* r3 = BSS end
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* r4 = final kernel address
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* r5 = appended dtb size (still unknown)
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* r6 = _edata
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* r7 = architecture ID
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* r8 = atags/device tree pointer
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* r9 = size of decompressed image
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* r10 = end of this image, including bss/stack/malloc space if non XIP
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* r11 = GOT start
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* r12 = GOT end
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* sp = stack pointer
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*
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* if there are device trees (dtb) appended to zImage, advance r10 so that the
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* dtb data will get relocated along with the kernel if necessary.
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*/
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ldr lr, [r6, #0]
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#ifndef __ARMEB__
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ldr r1, =0xedfe0dd0 @ sig is 0xd00dfeed big endian
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#else
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ldr r1, =0xd00dfeed
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#endif
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cmp lr, r1
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bne dtb_check_done @ not found
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mov r8, r6 @ use the appended device tree
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/* Get the dtb's size */
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ldr r5, [r6, #4]
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#ifndef __ARMEB__
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/* convert r5 (dtb size) to little endian */
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eor r1, r5, r5, ror #16
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bic r1, r1, #0x00ff0000
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mov r5, r5, ror #8
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eor r5, r5, r1, lsr #8
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#endif
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/* preserve 64-bit alignment */
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add r5, r5, #7
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bic r5, r5, #7
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/* relocate some pointers past the appended dtb */
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add r6, r6, r5
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add r10, r10, r5
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add sp, sp, r5
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dtb_check_done:
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#endif
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/*
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* Check to see if we will overwrite ourselves.
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* r4 = final kernel address
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@ -285,14 +338,16 @@ wont_overwrite:
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* r2 = BSS start
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* r3 = BSS end
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* r4 = kernel execution address
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* r5 = appended dtb size (0 if not present)
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* r7 = architecture ID
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* r8 = atags pointer
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* r11 = GOT start
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* r12 = GOT end
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* sp = stack pointer
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*/
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teq r0, #0
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orrs r1, r0, r5
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beq not_relocated
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add r11, r11, r0
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add r12, r12, r0
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@ -307,12 +362,21 @@ wont_overwrite:
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/*
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* Relocate all entries in the GOT table.
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* Bump bss entries to _edata + dtb size
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*/
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1: ldr r1, [r11, #0] @ relocate entries in the GOT
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add r1, r1, r0 @ table. This fixes up the
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str r1, [r11], #4 @ C references.
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add r1, r1, r0 @ This fixes up C references
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cmp r1, r2 @ if entry >= bss_start &&
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cmphs r3, r1 @ bss_end > entry
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addhi r1, r1, r5 @ entry += dtb size
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str r1, [r11], #4 @ next entry
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cmp r11, r12
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blo 1b
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/* bump our bss pointers too */
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add r2, r2, r5
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add r3, r3, r5
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#else
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/*
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