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Commit 4274636c authored by Sami Tolvanen's avatar Sami Tolvanen
Browse files

ANDROID: kbuild: ensure __cfi_check is correctly aligned 



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: default avatarSami Tolvanen <samitolvanen@google.com>
parent c5c2143f

Makefile

+1 −1
Original line number Diff line number Diff line
@@ -880,7 +880,7 @@ LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5 
KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG)

KBUILD_LDFLAGS_MODULE += $(LD_FLAGS_LTO_CLANG)



KBUILD_LDS_MODULE += $(srctree)/scripts/module-lto.lds

KBUILD_LDS_MODULE += scripts/module-lto.lds

endif



ifdef CONFIG_LTO

scripts/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -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



subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins

subdir-$(CONFIG_MODVERSIONS) += genksyms

subdir-$(CONFIG_SECURITY_SELINUX) += selinux

scripts/module-lto.lds→scripts/module-lto.lds.S

+13 −1
Original line number Diff line number Diff line 
/* 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*)

	}



}