diff options
| author | Ard Biesheuvel <ardb@kernel.org> | 2024-01-21 23:57:59 +0100 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2024-01-22 09:18:07 +0100 |
| commit | 019a7844cc2a63d08a2b5f396f68e2c547224ae7 (patch) | |
| tree | be8b5c534666fb5b8c0f034d950280cc59612cea | |
| parent | 52c7992d3f3de385354688197345ec48b720ee2a (diff) | |
| download | linux-x86-pic.tar.gz | |
x86: Build the core kernel with position independent codegenx86-pic
Pass the -fpie flag to the compiler when building objects that are
intended for the core kernel. This ensures that all implicit symbol
references are emitted using RIP-relative relocations, allowing the code
to be executed correctly even if it runs from a different virtual
address than the address it was linked/loaded/relocated to run at.
This is necessary to ensure that all C code that gets pulled in by the
early startup code runs correctly without the need for disgusting hacks
in the code to force RIP-relative references.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
| -rw-r--r-- | arch/x86/Makefile | 7 | ||||
| -rw-r--r-- | arch/x86/entry/vdso/Makefile | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/Makefile | 4 | ||||
| -rw-r--r-- | arch/x86/realmode/rm/Makefile | 1 | ||||
| -rw-r--r-- | include/asm-generic/vmlinux.lds.h | 2 |
5 files changed, 9 insertions, 7 deletions
diff --git a/arch/x86/Makefile b/arch/x86/Makefile index bed0850d91b0d5..0382a953409959 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -165,11 +165,13 @@ else KBUILD_RUSTFLAGS += $(rustflags-y) KBUILD_CFLAGS += -mno-red-zone - KBUILD_CFLAGS += -mcmodel=kernel + KBUILD_CFLAGS_MODULE += -mcmodel=kernel KBUILD_RUSTFLAGS += -Cno-redzone=y - KBUILD_RUSTFLAGS += -Ccode-model=kernel + KBUILD_RUSTFLAGS_KERNEL += -Ccode-model=small + KBUILD_RUSTFLAGS_MODULE += -Ccode-model=kernel PIE_CFLAGS := -fpie -mcmodel=small \ + $(call cc-option,-Wa$(comma)-mrelax-relocations=no) \ -include $(srctree)/include/linux/hidden.h ifeq ($(CONFIG_STACKPROTECTOR),y) @@ -178,6 +180,7 @@ else endif endif + KBUILD_CFLAGS_KERNEL += $(PIE_CFLAGS) export PIE_CFLAGS endif diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index b1b8dd1608f7eb..e2c79d4c141760 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -149,7 +149,7 @@ $(obj)/vdso32.so.dbg: KBUILD_AFLAGS = $(KBUILD_AFLAGS_32) $(obj)/vdso32.so.dbg: asflags-$(CONFIG_X86_64) += -m32 KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS)) -KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32)) +KBUILD_CFLAGS_32 := $(filter-out -mcmodel=small,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out $(RANDSTRUCT_CFLAGS),$(KBUILD_CFLAGS_32)) diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 65194ca79b5c16..0000325ab98f4d 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -21,10 +21,6 @@ CFLAGS_REMOVE_sev.o = -pg CFLAGS_REMOVE_rethook.o = -pg endif -# head64.c contains C code that may execute from a different virtual address -# than it was linked at, so we always build it using PIE codegen -CFLAGS_head64.o += $(PIE_CFLAGS) - KASAN_SANITIZE_head$(BITS).o := n KASAN_SANITIZE_dumpstack.o := n KASAN_SANITIZE_dumpstack_$(BITS).o := n diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile index f614009d3e4e2e..fdb8e780f90316 100644 --- a/arch/x86/realmode/rm/Makefile +++ b/arch/x86/realmode/rm/Makefile @@ -76,5 +76,6 @@ 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 := $(filter-out $(PIE_CFLAGS),$(KBUILD_CFLAGS_KERNEL)) GCOV_PROFILE := n UBSAN_SANITIZE := n diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index ef45331fb04379..9518b87207e8e2 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -355,6 +355,7 @@ *(.data..decrypted) \ *(.ref.data) \ *(.data..shared_aligned) /* percpu related */ \ + *(.data.rel .data.rel.*) \ MEM_KEEP(init.data*) \ *(.data.unlikely) \ __start_once = .; \ @@ -477,6 +478,7 @@ .rodata : AT(ADDR(.rodata) - LOAD_OFFSET) { \ __start_rodata = .; \ *(.rodata) *(.rodata.*) \ + *(.data.rel.ro*) \ SCHED_DATA \ RO_AFTER_INIT_DATA /* Read only after init */ \ . = ALIGN(8); \ |