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ANDROID: kbuild: ensure __cfi_check is correctly aligned

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On modules with no executable code, LLVM generates a __cfi_check stub,
but won't align it to page size as expected. This change ensures the
function is at the beginning of the .text section and correctly aligned
for the CFI shadow.

Bug: 148458318
Change-Id: I85ea31fa851bc23988f649b021b3ac7e9d9dcb38
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
This commit is contained in:
Sami Tolvanen 2020-03-31 14:32:27 -07:00
parent a898a4764c
commit 166a538d15
3 changed files with 16 additions and 2 deletions
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2
Makefile
View file

@ -827,7 +827,7 @@ LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5
KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG)
KBUILD_LDFLAGS_MODULE += $(LD_FLAGS_LTO_CLANG)
KBUILD_LDFLAGS_MODULE += -T $(srctree)/scripts/module-lto.lds
KBUILD_LDFLAGS_MODULE += -T scripts/module-lto.lds
# allow disabling only clang LTO where needed
DISABLE_LTO_CLANG := -fno-lto

2
scripts/Makefile
View file

@ -31,6 +31,8 @@ always := $(hostprogs-y) $(hostprogs-m)
# The following hostprogs-y programs are only build on demand
hostprogs-y += unifdef
extra-$(CONFIG_LTO_CLANG) += module-lto.lds
# These targets are used internally to avoid "is up to date" messages
PHONY += build_unifdef
build_unifdef: $(obj)/unifdef

14
scripts/module-lto.lds → scripts/module-lto.lds.S
View file

@ -1,3 +1,6 @@
/* SPDX-License-Identifier: GPL-2.0 */
#include <asm/page.h>
/*
* With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and
* -ffunction-sections, which increases the size of the final module.
@ -18,5 +21,14 @@ SECTIONS {
.rela.rodata : { *(.rela.rodata .rela.rodata.[0-9a-zA-Z_]*) }
.rela.text : { *(.rela.text .rela.text.[0-9a-zA-Z_]*) }
.rodata : { *(.rodata .rodata.[0-9a-zA-Z_]*) }
.text : { *(.text .text.[0-9a-zA-Z_]*) }
/*
* With CFI_CLANG, ensure __cfi_check is at the beginning of the
* .text section, and that the section is aligned to page size.
*/
.text : ALIGN(PAGE_SIZE) {
*(.text.__cfi_check)
*(.text .text.[0-9a-zA-Z_]* .text..L.cfi*)
}
}