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authorNicolas Pitre <nicolas.pitre@linaro.org>2011-06-12 01:07:33 -0400
committerNicolas Pitre <nico@fluxnic.net>2011-09-14 13:51:57 -0400
commit5ffb04f6690d71fab241b3562ebf52b893ac4ff1 (patch)
tree69897c130b7f3ff06d54d35eb3c92a8baea57119 /arch/arm/boot
parente2a6a3aafa9862c4a4b59f2a59b8f923d64a680e (diff)
ARM: zImage: make sure appended DTB doesn't get overwritten by kernel .bss
The appended DTB gets relocated with the decompressor code to get out of the way of the decompressed kernel. However the kernel's .bss section may be larger than the relocated code and data, and then the DTB gets overwritten. Let's make sure the relocation takes care of moving zImage far enough so no such conflict with .bss occurs. Thanks to Tony Lindgren <tony@atomide.com> for figuring out this issue. While at it, let's clean up the code a bit so that the wont_overwrite symbol is used while determining if a conflict exists, making the above change more precise as well as eliminating some ARM/THUMB alternates. Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org> 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>
Diffstat (limited to 'arch/arm/boot')
-rw-r--r--arch/arm/boot/compressed/Makefile3
-rw-r--r--arch/arm/boot/compressed/head.S19
2 files changed, 18 insertions, 4 deletions
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 0c74a6fab95..4867647b979 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -104,6 +104,9 @@ endif
ccflags-y := -fpic -fno-builtin
asflags-y := -Wa,-march=all
+# Supply kernel BSS size to the decompressor via a linker symbol.
+KBSS_SZ = $(shell size $(obj)/../../../../vmlinux | awk 'END{print $$3}')
+LDFLAGS_vmlinux = --defsym _kernel_bss_size=$(KBSS_SZ)
# Supply ZRELADDR to the decompressor via a linker symbol.
ifneq ($(CONFIG_AUTO_ZRELADDR),y)
LDFLAGS_vmlinux += --defsym zreladdr=$(ZRELADDR)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 3ce5738ddb9..ba5c552f8c6 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -248,6 +248,18 @@ restart: adr r0, LC0
mov r8, r6 @ use the appended device tree
+ /*
+ * Make sure that the DTB doesn't end up in the final
+ * kernel's .bss area. To do so, we adjust the decompressed
+ * kernel size to compensate if that .bss size is larger
+ * than the relocated code.
+ */
+ ldr r5, =_kernel_bss_size
+ adr r1, wont_overwrite
+ sub r1, r6, r1
+ subs r1, r5, r1
+ addhi r9, r9, r1
+
/* Get the dtb's size */
ldr r5, [r6, #4]
#ifndef __ARMEB__
@@ -276,15 +288,14 @@ dtb_check_done:
* r10 = end of this image, including bss/stack/malloc space if non XIP
* We basically want:
* r4 - 16k page directory >= r10 -> OK
- * r4 + image length <= current position (pc) -> OK
+ * r4 + image length <= address of wont_overwrite -> OK
*/
add r10, r10, #16384
cmp r4, r10
bhs wont_overwrite
add r10, r4, r9
- ARM( cmp r10, pc )
- THUMB( mov lr, pc )
- THUMB( cmp r10, lr )
+ adr r9, wont_overwrite
+ cmp r10, r9
bls wont_overwrite
/*