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 --- init/Kconfig | 3 +++ 1 file changed, 3 insertions(+) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index bd7d650d4a99..d96127ebc44e 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -30,6 +30,9 @@ config CC_CAN_LINK config CC_HAS_ASM_GOTO def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) +config TOOLS_SUPPORT_RELR + def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh) + config CC_HAS_WARN_MAYBE_UNINITIALIZED def_bool $(cc-option,-Wmaybe-uninitialized) help -- cgit