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 | 93 ++++++++++++++++++++++++++++++++++++--- 2 files changed, 94 insertions(+), 6 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index d8a330f..68fc640 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1593,6 +1593,13 @@ config USE_OF help Include support for flattened device tree machine descriptions. +config ARM_APPENDED_DTB + bool "Use appended device tree blob" if OF + default n + help + With this option, the boot code will look for a dtb bianry + appended to zImage. + # Compressed boot loader in ROM. Yes, we really want to ask about # TEXT and BSS so we preserve their values in the config files. config ZBOOT_ROM_TEXT diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index 200625c..ae9f8c6 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -210,6 +210,46 @@ restart: adr r0, LC0 */ mov r10, r6 #endif +#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 r12, [r6, #0] + ldr r1, =0xedfe0dd0 @ sig is 0xdoodfeed big endian + cmp r12, r1 + bne dtb_check_done + + /* Get the dtb's size */ + ldr r12, [r6, #4] @ device tree size + + /* convert r12 (dtb size) to little endian */ + eor r1, r12, r12, ror #16 + bic r1, r1, #0x00ff0000 + mov r12, r12, ror #8 + eor r12, r12, r1, lsr #8 + + add r10, r10, r12 + add r6, r6, r12 + +dtb_check_done: + adr r1, LC0 + ldr r12, [r1, #28] @ restore r12 (GOT end) +#endif /* * Check to see if we will overwrite ourselves. @@ -223,8 +263,8 @@ restart: adr r0, LC0 */ cmp r4, r10 bhs wont_overwrite - add r10, r4, r9 - cmp r10, r5 + add r1, r4, r9 + cmp r1, r5 bls wont_overwrite /* @@ -272,8 +312,10 @@ wont_overwrite: * r12 = GOT end * sp = stack pointer */ - teq r0, #0 - beq not_relocated + adr r1, LC0 + ldr r6, [r1, #16] @ reload _edata value + + add r6, r6, r0 add r11, r11, r0 add r12, r12, r0 @@ -288,12 +330,34 @@ wont_overwrite: /* * Relocate all entries in the GOT table. + * Bump bss entries to past image end (r10) */ + sub r5, r10, r6 @ delta of image end and _edata + add r5, r5, #7 @ ... rounded up to a multiple + bic r5, r5, #7 @ ... of 8 bytes, so misaligned + @ ... GOT entry doesn't + @ ... overwrite end of image + 1: ldr r1, [r11, #0] @ relocate entries in the GOT add r1, r1, r0 @ table. This fixes up the + cmp r1, r2 + movcc r9, #0 @ r9 = entry < bss_start ? 0 : + movcs r9, #1 @ 1; + cmp r1, r3 + movcs r9, #0 @ r9 = entry >= end ? 0 : t1; + cmp r9, #0 + addne r1, r5 @ entry += r9 ? bss delta : 0; str r1, [r11], #4 @ C references. cmp r11, r12 blo 1b + + /* bump our bss registers too */ + add r2, r2, r5 + add r3, r3, r5 + + /* bump the stack pinter, if at or above _edata */ + cmp sp, r6 + addcs sp, sp, r5 #else /* @@ -309,7 +373,7 @@ wont_overwrite: blo 1b #endif -not_relocated: mov r0, #0 + mov r0, #0 1: str r0, [r2], #4 @ clear bss str r0, [r2], #4 str r0, [r2], #4 @@ -317,8 +381,25 @@ not_relocated: mov r0, #0 cmp r2, r3 blo 1b +#ifdef CONFIG_ARM_APPENDED_DTB +/* + * The C runtime environment should now be set up sufficiently. + * r4 = kernel execution address + * r6 = _edata + * r7 = architecture ID + * r8 = atags pointer + * + * if there is a device tree (dtb) appended to zImage, set up to use this dtb. + */ + ldr r0, [r6, #0] + ldr r1, =0xedfe0dd0 @ sig is 0xdoodfeed big endian + cmp r0, r1 + bne keep_atags + + mov r8, r6 @ use the appended device tree +keep_atags: +#endif /* - * The C runtime environment should now be setup sufficiently. * Set up some pointers, and start decompressing. * r4 = kernel execution address * r7 = architecture ID _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
