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| author | Peter Collingbourne <pcc@google.com> | 2019-07-31 18:18:42 -0700 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2019-08-05 12:35:35 +0100 |
| commit | 5cf896fb6be3effd9aea455b22213e27be8bdb1d (patch) | |
| tree | 563e83ed04a2de71b65e831896bf52e0eaf31af0 /arch/arm64/Kconfig | |
| parent | 66cbdf5d0c96f5fe570b548e764583ea9d793077 (diff) | |
| download | lwn-5cf896fb6be3effd9aea455b22213e27be8bdb1d.tar.gz lwn-5cf896fb6be3effd9aea455b22213e27be8bdb1d.zip | |
arm64: Add support for relocating the kernel with RELR relocations
RELR is a relocation packing format for relative relocations.
The format is described in a generic-abi proposal:
https://groups.google.com/d/topic/generic-abi/bX460iggiKg/discussion
The LLD linker can be instructed to pack relocations in the RELR
format by passing the flag --pack-dyn-relocs=relr.
This patch adds a new config option, CONFIG_RELR. Enabling this option
instructs the linker to pack vmlinux's relative relocations in the RELR
format, and causes the kernel to apply the relocations at startup along
with the RELA relocations. RELA relocations still need to be applied
because the linker will emit RELA relative relocations if they are
unrepresentable in the RELR format (i.e. address not a multiple of 2).
Enabling CONFIG_RELR reduces the size of a defconfig kernel image
with CONFIG_RANDOMIZE_BASE by 3.5MB/16% uncompressed, or 550KB/5%
compressed (lz4).
Signed-off-by: Peter Collingbourne <pcc@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/Kconfig')
| -rw-r--r-- | arch/arm64/Kconfig | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 3adcec05b1f6..2681eb79c40b 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1467,6 +1467,7 @@ endif config RELOCATABLE bool + select ARCH_HAS_RELR help This builds the kernel as a Position Independent Executable (PIE), which retains all relocation metadata required to relocate the |