[PATCH 1/4] ARM:boot:device tree: Allow the device tree binary to be appended to zImage
John Bonesio
bones at secretlab.ca
Tue Mar 1 10:33:27 EST 2011
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 at secretlab.ca>
---
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
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