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 <[email protected]> --- arch/arm/Kconfig | 7 ++++ arch/arm/boot/compressed/head.S | 78 ++++++++++++++++++++++++++++++++++++++- 2 files changed, 82 insertions(+), 3 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 92bae09..3556aea 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1651,6 +1651,13 @@ config ZBOOT_ROM Say Y here if you intend to execute your compressed kernel image (zImage) directly from ROM or flash. If unsure, say N. +config ARM_APPENDED_DTB + bool "Use appended device tree blob" + depends on OF && !ZBOOT_ROM + help + With this option, the boot code will look for a device tree binary + (dtb) appended to zImage. + config CMDLINE string "Default kernel command string" default "" diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index 200625c..4f8bd65 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -211,6 +211,61 @@ restart: adr r0, LC0 mov r10, r6 #endif + mov lr, #0 @ init lr (dtb size) to 0 +#ifdef CONFIG_ARM_APPENDED_DTB +/* + * r0 = delta + * r2 = BSS start + * r3 = BSS end + * r4 = final kernel address + * r5 = start of this image + * 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 + * + * 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 + mov lr, #0 @ dtb not found, it's size is 0 + bne dtb_check_done + + mov r8, r6 @ use the appended device tree + + /* Get the dtb's size */ + ldr lr, [r6, #4] + +#ifndef __ARMEB__ + /* convert lr (dtb size) to little endian */ + eor r1, lr, lr, ror #16 + bic r1, r1, #0x00ff0000 + mov lr, lr, ror #8 + eor lr, lr, r1, lsr #8 +#endif + /* + * dtb size rounded up to a multiple of 8 bytes so a + * misaligned GOT entry doesn't cause the end of the + * dtb binary to be overwritten. + */ + add lr, lr, #7 + bic lr, lr, #7 + + add r10, r10, lr + add r6, r6, lr +dtb_check_done: +#endif + /* * Check to see if we will overwrite ourselves. * r4 = final kernel address @@ -271,8 +326,9 @@ wont_overwrite: * r11 = GOT start * r12 = GOT end * sp = stack pointer + * lr = appended dtb size (0 if not present) */ - teq r0, #0 + orrs r1, r0, lr beq not_relocated add r11, r11, r0 add r12, r12, r0 @@ -288,12 +344,28 @@ 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, lr @ entry += dtb size + str r1, [r11], #4 @ next entry cmp r11, r12 blo 1b + + /* bump our bss registers too */ + add r2, r2, lr + add r3, r3, lr + + /* + * bump the stack pinter + * + * If the linker script changes so the stack is not after + * the bss section, this code will be wrong. + */ + add sp, sp, lr #else /* _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
