Commit d8da19fb authored by Youling Tang's avatar Youling Tang Committed by Huacai Chen
Browse files

LoongArch: Add support for kernel relocation 



This config allows to compile kernel as PIE and to relocate it at any
virtual address at runtime: this paves the way to KASLR.

Runtime relocation is possible since relocation metadata are embedded
into the kernel.

Signed-off-by: default avatarYouling Tang <tangyouling@loongson.cn>
Signed-off-by: Xi Ruoyao <xry111@xry111.site> # Use arch_initcall
Signed-off-by: Jinyang He <hejinyang@loongson.cn> # Provide la_abs relocation code
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 396233c6

arch/loongarch/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -493,6 +493,14 @@ config PHYSICAL_START 
	  specified in the "crashkernel=YM@XM" command line boot parameter

	  passed to the panic-ed kernel).



config RELOCATABLE

	bool "Relocatable kernel"

	help

	  This builds the kernel as a Position Independent Executable (PIE),

	  which retains all relocation metadata required, so as to relocate

	  the kernel binary at runtime to a different virtual address from

	  its link address.



config SECCOMP

	bool "Enable seccomp to safely compute untrusted bytecode"

	depends on PROC_FS

arch/loongarch/Makefile

+5 −0
Original line number Diff line number Diff line
@@ -71,6 +71,11 @@ KBUILD_AFLAGS_MODULE += -Wa,-mla-global-with-abs 
KBUILD_CFLAGS_MODULE		+= -fplt -Wa,-mla-global-with-abs,-mla-local-with-abs

endif



ifeq ($(CONFIG_RELOCATABLE),y)

KBUILD_CFLAGS_KERNEL		+= -fPIE

LDFLAGS_vmlinux			+= -static -pie --no-dynamic-linker -z notext

endif



cflags-y += -ffreestanding

cflags-y += $(call cc-option, -mno-check-zero-division)

arch/loongarch/include/asm/asmmacro.h

+13 −0
Original line number Diff line number Diff line
@@ -275,7 +275,20 @@ 
.endm



.macro la_abs reg, sym

#ifndef CONFIG_RELOCATABLE

	la.abs	\reg, \sym

#else

	766:

	lu12i.w	\reg, 0

	ori	\reg, \reg, 0

	lu32i.d	\reg, 0

	lu52i.d	\reg, \reg, 0

	.pushsection ".la_abs", "aw", %progbits

	768:

	.dword	768b-766b

	.dword	\sym

	.popsection

#endif

.endm



#endif /* _ASM_ASMMACRO_H */

arch/loongarch/include/asm/setup.h

+16 −0
Original line number Diff line number Diff line
@@ -21,4 +21,20 @@ extern void per_cpu_trap_init(int cpu); 
extern void set_handler(unsigned long offset, void *addr, unsigned long len);

extern void set_merr_handler(unsigned long offset, void *addr, unsigned long len);



#ifdef CONFIG_RELOCATABLE



struct rela_la_abs {

	long offset;

	long symvalue;

};



extern long __la_abs_begin;

extern long __la_abs_end;

extern long __rela_dyn_begin;

extern long __rela_dyn_end;



extern void __init relocate_kernel(void);



#endif



#endif /* __SETUP_H */

arch/loongarch/kernel/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -41,6 +41,8 @@ obj-$(CONFIG_NUMA) += numa.o 


obj-$(CONFIG_MAGIC_SYSRQ)	+= sysrq.o



obj-$(CONFIG_RELOCATABLE)	+= relocate.o



obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o

obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o