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Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Uros Bizjak , Dennis Zhou , Tejun Heo , Christoph Lameter , Mathieu Desnoyers , Paolo Bonzini , Vitaly Kuznetsov , Juergen Gross , Boris Ostrovsky , Greg Kroah-Hartman , Arnd Bergmann , Masahiro Yamada , Kees Cook , Nathan Chancellor , Keith Packard , Justin Stitt , Josh Poimboeuf , Arnaldo Carvalho de Melo , Namhyung Kim , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , linux-doc@vger.kernel.org, linux-pm@vger.kernel.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, linux-efi@vger.kernel.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-perf-users@vger.kernel.org, rust-for-linux@vger.kernel.org, llvm@lists.linux.dev From: Ard Biesheuvel As an intermediate step towards enabling PIE linking for the 64-bit x86 kernel, enable PIE codegen for all objects that are linked into the kernel proper. This substantially reduces the number of relocations that need to be processed when booting a relocatable KASLR kernel. Before (size in bytes of the reloc table): 797372 arch/x86/boot/compressed/vmlinux.relocs After: 400252 arch/x86/boot/compressed/vmlinux.relocs Signed-off-by: Ard Biesheuvel --- arch/x86/Makefile | 11 ++++++++++- arch/x86/boot/Makefile | 1 + arch/x86/boot/compressed/Makefile | 2 +- arch/x86/entry/vdso/Makefile | 1 + arch/x86/realmode/rm/Makefile | 1 + include/asm-generic/vmlinux.lds.h | 1 + 6 files changed, 15 insertions(+), 2 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index b78b7623a4a9..83d20f402535 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -193,13 +193,22 @@ else KBUILD_RUSTFLAGS += -Cno-redzone=y KBUILD_RUSTFLAGS += -Ccode-model=kernel + PIE_CFLAGS-y := -fpie -mcmodel=small \ + -include $(srctree)/include/linux/hidden.h + + PIE_CFLAGS-$(CONFIG_CC_IS_GCC) += $(call cc-option.-mdirect-extern-access) + PIE_CFLAGS-$(CONFIG_CC_IS_CLANG) += -fdirect-access-external-data + ifeq ($(CONFIG_STACKPROTECTOR),y) KBUILD_CFLAGS += -mstack-protector-guard-symbol=fixed_percpu_data + + # the 'small' C model defaults to %fs + PIE_CFLAGS-$(CONFIG_SMP) += -mstack-protector-guard-reg=gs endif # Don't emit relaxable GOTPCREL relocations KBUILD_AFLAGS_KERNEL += -Wa,-mrelax-relocations=no - KBUILD_CFLAGS_KERNEL += -Wa,-mrelax-relocations=no + KBUILD_CFLAGS_KERNEL += -Wa,-mrelax-relocations=no $(PIE_CFLAGS-y) endif # diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile index 9cc0ff6e9067..4d3ba35cb619 100644 --- a/arch/x86/boot/Makefile +++ b/arch/x86/boot/Makefile @@ -57,6 +57,7 @@ KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) KBUILD_CFLAGS += -fno-asynchronous-unwind-tables KBUILD_CFLAGS += $(CONFIG_CC_IMPLICIT_FALLTHROUGH) +KBUILD_CFLAGS_KERNEL := $(obj)/bzImage: asflags-y := $(SVGA_MODE) diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index f2051644de94..c362d36b5b69 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -73,7 +73,7 @@ LDFLAGS_vmlinux += -T hostprogs := mkpiggy HOST_EXTRACFLAGS += -I$(srctree)/tools/include -sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|__start_rodata\|__bss_start\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p' +sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABbCDdGRSTtVW] \(_text\|__start_rodata\|__bss_start\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p' quiet_cmd_voffset = VOFFSET $@ cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@ diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index c9216ac4fb1e..7af9fecf9abb 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -141,6 +141,7 @@ endif endif $(obj)/vdso32.so.dbg: KBUILD_CFLAGS = $(KBUILD_CFLAGS_32) +$(obj)/vdso32.so.dbg: KBUILD_CFLAGS_KERNEL := $(obj)/vdso32.so.dbg: $(obj)/vdso32/vdso32.lds $(vobjs32) FORCE $(call if_changed,vdso_and_check) diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile index a0fb39abc5c8..70bf0a26da91 100644 --- a/arch/x86/realmode/rm/Makefile +++ b/arch/x86/realmode/rm/Makefile @@ -67,3 +67,4 @@ KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \ -I$(srctree)/arch/x86/boot KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ KBUILD_CFLAGS += -fno-asynchronous-unwind-tables +KBUILD_CFLAGS_KERNEL := diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 2b079f73820f..3a084ac77109 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -349,6 +349,7 @@ *(DATA_MAIN) \ *(.data..decrypted) \ *(.ref.data) \ + *(.data.rel*) \ *(.data..shared_aligned) /* percpu related */ \ *(.data.unlikely) \ __start_once = .; \