path: root/arch/arm64/Makefile
diff options
authorArd Biesheuvel <>2014-08-13 18:53:03 +0100
committerWill Deacon <>2014-08-19 19:26:09 +0100
commit4190312beb2acfb7bfb1bb971e24a759aa96b0e8 (patch)
tree8de244a8483bf476270dfea7b49585fd86494cdd /arch/arm64/Makefile
parent503e6636b6f96056210062be703356f4253b6db9 (diff)
arm64: align randomized TEXT_OFFSET on 4 kB boundary
When booting via UEFI, the kernel Image is loaded at a 4 kB boundary and the embedded EFI stub is executed in place. The EFI stub relocates the Image to reside TEXT_OFFSET bytes above a 2 MB boundary, and jumps into the kernel proper. In AArch64, PC relative symbol references are emitted using adrp/add or adrp/ldr pairs, where the offset into a 4 kB page is resolved using a separate :lo12: relocation. This implicitly assumes that the code will always be executed at the same relative offset with respect to a 4 kB boundary, or the references will point to the wrong address. This means we should link the kernel at a 4 kB aligned base address in order to remain compatible with the base address the UEFI loader uses when doing the initial load of Image. So update the code that generates TEXT_OFFSET to choose a multiple of 4 kB. At the same time, update the code so it chooses from the interval [0..2MB) as the author originally intended. Reviewed-by: Mark Rutland <> Signed-off-by: Ard Biesheuvel <> Signed-off-by: Will Deacon <>
Diffstat (limited to 'arch/arm64/Makefile')
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 57833546bf00..2df5e5daeebe 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -39,7 +39,7 @@ head-y := arch/arm64/kernel/head.o
# The byte offset of the kernel image in RAM from the start of RAM.
-TEXT_OFFSET := $(shell awk 'BEGIN {srand(); printf "0x%04x0\n", int(65535 * rand())}')
+TEXT_OFFSET := $(shell awk 'BEGIN {srand(); printf "0x%03x000\n", int(512 * rand())}')
TEXT_OFFSET := 0x00080000