From 5cf896fb6be3effd9aea455b22213e27be8bdb1d Mon Sep 17 00:00:00 2001 From: Peter Collingbourne Date: Wed, 31 Jul 2019 18:18:42 -0700 Subject: 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 Tested-by: Nick Desaulniers Reviewed-by: Nick Desaulniers Signed-off-by: Will Deacon --- arch/arm64/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/arm64/Kconfig') 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 -- cgit v1.2.3