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OpenCloudOS-Kernel
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efi/x86: Remove __efistub_global and add relocation check 

Instead of using __efistub_global to force variables into the .data
section, leave them in the .bss but pull the EFI stub's .bss section
into .data in the linker script for the compressed kernel.

Add relocation checking for x86 as well to catch non-PC-relative
relocations that require runtime processing, since the EFI stub does not
do any runtime relocation processing.

This will catch, for example, data relocations created by static
initializers of pointers.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200416151227.3360778-3-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Arvind Sankar 2020-04-16 11:12:26 -04:00 committed by Ard Biesheuvel
parent 420b6d00ca
commit 26a92425f9
3 changed files with 22 additions and 15 deletions
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1
arch/x86/boot/compressed/vmlinux.lds.S
View File

@ -52,6 +52,7 @@ SECTIONS
_data = . ;
*(.data)
*(.data.*)
*(.bss.efistub)
_edata = . ;
}
. = ALIGN(L1_CACHE_BYTES);

32
drivers/firmware/efi/libstub/Makefile
View File

@ -60,6 +60,25 @@ lib-$(CONFIG_X86) += x86-stub.o
CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
#
# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the
# .bss section, so the .bss section of the EFI stub needs to be included in the
# .data section of the compressed kernel to ensure initialization. Rename the
# .bss section here so it's easy to pick out in the linker script.
#
STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc
STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
#
# ARM discards the .data section because it disallows r/w data in the
# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,
# which are preserved explicitly by the decompressor linker script.
#
STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
--rename-section .bss=.bss.efistub,load,alloc
STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
#
# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
@ -74,8 +93,8 @@ CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
# a verification pass to see if any absolute relocations exist in any of the
# object files.
#
extra-$(CONFIG_EFI_GENERIC_STUB) := $(lib-y)
lib-$(CONFIG_EFI_GENERIC_STUB) := $(patsubst %.o,%.stub.o,$(lib-y))
extra-y := $(lib-y)
lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
--prefix-symbols=__efistub_
@ -98,12 +117,3 @@ quiet_cmd_stubcopy = STUBCPY $@
/bin/false; \
fi; \
$(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@
#
# ARM discards the .data section because it disallows r/w data in the
# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,
# which are preserved explicitly by the decompressor linker script.
#
STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
--rename-section .bss=.bss.efistub,load,alloc
STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS

4
drivers/firmware/efi/libstub/efistub.h
View File

@ -25,11 +25,7 @@
#define EFI_ALLOC_ALIGN EFI_PAGE_SIZE
#endif
#if defined(CONFIG_X86)
#define __efistub_global __section(.data)
#else
#define __efistub_global
#endif
extern bool __pure nochunk(void);
extern bool __pure nokaslr(void);