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>

diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
index 508cfa6828c5d88cd8f616e28df686ec625dd5f5..0dc5c2b9614b8b763fbc90b36d433e95d3726af0 100644 (file)
--- a/arch/x86/boot/compressed/vmlinux.lds.S
+++ b/arch/x86/boot/compressed/vmlinux.lds.S
@@ -52,6 +52,7 @@ SECTIONS
                _data = . ;
                *(.data)
                *(.data.*)
+               *(.bss.efistub)
                _edata = . ;
        }
        . = ALIGN(L1_CACHE_BYTES);

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index aa3ab9a4105ece957fd86e13f3ae20a59dcf9d2b..8d246b51bd49a86b171878b8de77416a7ed24a93 100644 (file)
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -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

diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 96e25b17c88e324193b3378a0cad9ae9433b6ca0..5244eacc5d4ba57fc0880f0b10da2714f35555d2 100644 (file)
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -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);