Commit 8a6e40e1 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Catalin Marinas
Browse files

arm64: head: move dynamic shadow call stack patching into early C runtime 



Once we update the early kernel mapping code to only map the kernel once
with the right permissions, we can no longer perform code patching via
this mapping.

So move this code to an earlier stage of the boot, right after applying
the relocations.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20240214122845.2033971-54-ardb+git@google.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent dcfe969a

arch/arm64/include/asm/scs.h

+2 −2
Original line number Diff line number Diff line
@@ -72,8 +72,8 @@ static inline void dynamic_scs_init(void) 
static inline void dynamic_scs_init(void) {}

#endif



int scs_patch(const u8 eh_frame[], int size);

asmlinkage void scs_patch_vmlinux(void);

int __pi_scs_patch(const u8 eh_frame[], int size);

asmlinkage void __pi_scs_patch_vmlinux(void);



#endif /* __ASSEMBLY __ */

arch/arm64/kernel/Makefile

+0 −8
Original line number Diff line number Diff line
@@ -71,14 +71,6 @@ obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o 
obj-$(CONFIG_ARM64_MTE)			+= mte.o

obj-y					+= vdso-wrap.o

obj-$(CONFIG_COMPAT_VDSO)		+= vdso32-wrap.o

obj-$(CONFIG_UNWIND_PATCH_PAC_INTO_SCS)	+= patch-scs.o



# We need to prevent the SCS patching code from patching itself. Using

# -mbranch-protection=none here to avoid the patchable PAC opcodes from being

# generated triggers an issue with full LTO on Clang, which stops emitting PAC

# instructions altogether. So disable LTO as well for the compilation unit.

CFLAGS_patch-scs.o			+= -mbranch-protection=none

CFLAGS_REMOVE_patch-scs.o		+= $(CC_FLAGS_LTO)



# Force dependency (vdso*-wrap.S includes vdso.so through incbin)

$(obj)/vdso-wrap.o: $(obj)/vdso/vdso.so

arch/arm64/kernel/head.S

+5 −3
Original line number Diff line number Diff line
@@ -490,9 +490,6 @@ SYM_FUNC_START_LOCAL(__primary_switched) 
#endif

#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)

	bl	kasan_early_init

#endif

#ifdef CONFIG_UNWIND_PATCH_PAC_INTO_SCS

	bl	scs_patch_vmlinux

#endif

	mov	x0, x20

	bl	finalise_el2			// Prefer VHE if possible
@@ -794,6 +791,11 @@ SYM_FUNC_START_LOCAL(__primary_switch) 
#ifdef CONFIG_RELOCATABLE

	mov	x0, x23

	bl	__pi_relocate_kernel

#endif

#ifdef CONFIG_UNWIND_PATCH_PAC_INTO_SCS

	ldr	x0, =__eh_frame_start

	ldr	x1, =__eh_frame_end

	bl	__pi_scs_patch_vmlinux

#endif

	ldr	x8, =__primary_switched

	adrp	x0, KERNEL_START		// __pa(KERNEL_START)

arch/arm64/kernel/module.c

+1 −1
Original line number Diff line number Diff line
@@ -595,7 +595,7 @@ int module_finalize(const Elf_Ehdr *hdr, 
	if (scs_is_dynamic()) {

		s = find_section(hdr, sechdrs, ".init.eh_frame");

		if (s)

			scs_patch((void *)s->sh_addr, s->sh_size);

			__pi_scs_patch((void *)s->sh_addr, s->sh_size);

	}



	return module_init_ftrace_plt(hdr, sechdrs, me);

arch/arm64/kernel/pi/Makefile

+6 −4
Original line number Diff line number Diff line
@@ -38,7 +38,9 @@ $(obj)/lib-%.pi.o: OBJCOPYFLAGS += --prefix-alloc-sections=.init 
$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE

	$(call if_changed_rule,cc_o_c)



obj-y				:= idreg-override.pi.o lib-fdt.pi.o lib-fdt_ro.pi.o

obj-y					:= idreg-override.pi.o \

					   lib-fdt.pi.o lib-fdt_ro.pi.o

obj-$(CONFIG_RELOCATABLE)		+= relocate.pi.o

obj-$(CONFIG_RANDOMIZE_BASE)		+= kaslr_early.pi.o

obj-$(CONFIG_UNWIND_PATCH_PAC_INTO_SCS)	+= patch-scs.pi.o

extra-y					:= $(patsubst %.pi.o,%.o,$(obj-y))