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authorPeter Collingbourne <pcc@google.com>2019-07-31 18:18:42 -0700
committerWill Deacon <will@kernel.org>2019-08-05 12:35:35 +0100
commit5cf896fb6be3effd9aea455b22213e27be8bdb1d (patch)
tree563e83ed04a2de71b65e831896bf52e0eaf31af0 /Makefile
parent66cbdf5d0c96f5fe570b548e764583ea9d793077 (diff)
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 'Makefile')
-rw-r--r--Makefile4
1 files changed, 4 insertions, 0 deletions
diff --git a/Makefile b/Makefile
index 23cdf1f41364..9e6ec0c9962c 100644
--- a/Makefile
+++ b/Makefile
@@ -912,6 +912,10 @@ ifeq ($(CONFIG_STRIP_ASM_SYMS),y)
LDFLAGS_vmlinux += $(call ld-option, -X,)
endif
+ifeq ($(CONFIG_RELR),y)
+LDFLAGS_vmlinux += --pack-dyn-relocs=relr
+endif
+
# insure the checker run with the right endianness
CHECKFLAGS += $(if $(CONFIG_CPU_BIG_ENDIAN),-mbig-endian,-mlittle-endian)

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