path: root/arch/arm64/Makefile
diff options
authorArd Biesheuvel <>2015-11-24 12:37:35 +0100
committerCatalin Marinas <>2016-02-24 14:57:24 +0000
commitfd045f6cd98ec4953147b318418bd45e441e52a3 (patch)
tree833eab1f579ef3f22fdf52ea3f58ffbab939eb36 /arch/arm64/Makefile
parentf98deee9a9f8c47d05a0f64d86440882dca772ff (diff)
arm64: add support for module PLTs
This adds support for emitting PLTs at module load time for relative branches that are out of range. This is a prerequisite for KASLR, which may place the kernel and the modules anywhere in the vmalloc area, making it more likely that branch target offsets exceed the maximum range of +/- 128 MB. In this version, I removed the distinction between relocations against .init executable sections and ordinary executable sections. The reason is that it is hardly worth the trouble, given that .init.text usually does not contain that many far branches, and this version now only reserves PLT entry space for jump and call relocations against undefined symbols (since symbols defined in the same module can be assumed to be within +/- 128 MB) For example, the mac80211.ko module (which is fairly sizable at ~400 KB) built with -mcmodel=large gives the following relocation counts: relocs branches unique !local .text 3925 3347 518 219 .init.text 11 8 7 1 .exit.text 4 4 4 1 .text.unlikely 81 67 36 17 ('unique' means branches to unique type/symbol/addend combos, of which !local is the subset referring to undefined symbols) IOW, we are only emitting a single PLT entry for the .init sections, and we are better off just adding it to the core PLT section instead. Signed-off-by: Ard Biesheuvel <> Signed-off-by: Catalin Marinas <>
Diffstat (limited to 'arch/arm64/Makefile')
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 307237cfe728..a6bba9623836 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -43,10 +43,14 @@ endif
CHECKFLAGS += -D__aarch64__
-ifeq ($(CONFIG_ARM64_ERRATUM_843419), y)
KBUILD_CFLAGS_MODULE += -mcmodel=large
+KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/arm64/kernel/
# Default value
head-y := arch/arm64/kernel/head.o