diff options
| -rw-r--r-- | arch/x86/boot/compressed/Makefile | 14 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/head_32.S | 28 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 8 |
3 files changed, 49 insertions, 1 deletions
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 6915ff2bd996..8774cb23064f 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -26,7 +26,7 @@ targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \ vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4 KBUILD_CFLAGS := -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2 -KBUILD_CFLAGS += -fno-strict-aliasing -fPIC +KBUILD_CFLAGS += -fno-strict-aliasing $(call cc-option, -fPIE, -fPIC) KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING cflags-$(CONFIG_X86_32) := -march=i386 cflags-$(CONFIG_X86_64) := -mcmodel=small @@ -40,6 +40,18 @@ GCOV_PROFILE := n UBSAN_SANITIZE :=n LDFLAGS := -m elf_$(UTS_MACHINE) +ifeq ($(CONFIG_RELOCATABLE),y) +# If kernel is relocatable, build compressed kernel as PIE. +ifeq ($(CONFIG_X86_32),y) +LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker) +else +# To build 64-bit compressed kernel as PIE, we disable relocation +# overflow check to avoid relocation overflow error with a new linker +# command-line option, -z noreloc-overflow. +LDFLAGS += $(shell $(LD) --help 2>&1 | grep -q "\-z noreloc-overflow" \ + && echo "-z noreloc-overflow -pie --no-dynamic-linker") +endif +endif LDFLAGS_vmlinux := -T hostprogs-y := mkpiggy diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 8ef964ddc18e..0256064da8da 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -31,6 +31,34 @@ #include <asm/asm-offsets.h> #include <asm/bootparam.h> +/* + * The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X + * relocation to get the symbol address in PIC. When the compressed x86 + * kernel isn't built as PIC, the linker optimizes R_386_GOT32X + * relocations to their fixed symbol addresses. However, when the + * compressed x86 kernel is loaded at a different address, it leads + * to the following load failure: + * + * Failed to allocate space for phdrs + * + * during the decompression stage. + * + * If the compressed x86 kernel is relocatable at run-time, it should be + * compiled with -fPIE, instead of -fPIC, if possible and should be built as + * Position Independent Executable (PIE) so that linker won't optimize + * R_386_GOT32X relocation to its fixed symbol address. Older + * linkers generate R_386_32 relocations against locally defined symbols, + * _bss, _ebss, _got and _egot, in PIE. It isn't wrong, just less + * optimal than R_386_RELATIVE. But the x86 kernel fails to properly handle + * R_386_32 relocations when relocating the kernel. To generate + * R_386_RELATIVE relocations, we mark _bss, _ebss, _got and _egot as + * hidden: + */ + .hidden _bss + .hidden _ebss + .hidden _got + .hidden _egot + __HEAD ENTRY(startup_32) #ifdef CONFIG_EFI_STUB diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index b0c0d16ef58d..86558a199139 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -33,6 +33,14 @@ #include <asm/asm-offsets.h> #include <asm/bootparam.h> +/* + * Locally defined symbols should be marked hidden: + */ + .hidden _bss + .hidden _ebss + .hidden _got + .hidden _egot + __HEAD .code32 ENTRY(startup_32) |