diff options
| author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2014-08-13 17:53:03 (GMT) |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2014-08-19 18:26:09 (GMT) |
| commit | 4190312beb2acfb7bfb1bb971e24a759aa96b0e8 (patch) | |
| tree | 8de244a8483bf476270dfea7b49585fd86494cdd | |
| parent | 503e6636b6f96056210062be703356f4253b6db9 (diff) | |
| download | linux-4190312beb2acfb7bfb1bb971e24a759aa96b0e8.tar.xz | |
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 <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
| -rw-r--r-- | arch/arm64/Makefile | 2 | ||||
| -rw-r--r-- | arch/arm64/kernel/head.S | 8 |
2 files changed, 5 insertions, 5 deletions
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 5783354..2df5e5d 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. ifeq ($(CONFIG_ARM64_RANDOMIZE_TEXT_OFFSET), y) -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())}') else TEXT_OFFSET := 0x00080000 endif diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 144f105..bed0283 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -38,11 +38,11 @@ #define KERNEL_RAM_VADDR (PAGE_OFFSET + TEXT_OFFSET) -#if (TEXT_OFFSET & 0xf) != 0 -#error TEXT_OFFSET must be at least 16B aligned -#elif (PAGE_OFFSET & 0xfffff) != 0 +#if (TEXT_OFFSET & 0xfff) != 0 +#error TEXT_OFFSET must be at least 4KB aligned +#elif (PAGE_OFFSET & 0x1fffff) != 0 #error PAGE_OFFSET must be at least 2MB aligned -#elif TEXT_OFFSET > 0xfffff +#elif TEXT_OFFSET > 0x1fffff #error TEXT_OFFSET must be less than 2MB #endif |