Commit 03d82735 authored by WANG Rui's avatar WANG Rui Committed by Huacai Chen
Browse files

efi/loongarch: Randomize kernel preferred address for KASLR 



Introduce efi_get_kimg_kaslr_address() helper to compute the preferred
kernel image load address dynamically when CONFIG_RANDOMIZE_BASE is
enabled. The function derives a random offset by using the EFI-provided
randomness combined with the timer tick value, and constrains it within
CONFIG_RANDOMIZE_BASE_MAX_OFFSET.

Update EFI_KIMG_PREFERRED_ADDRESS to call this helper so that the EFI
stub can select a randomized load address when KASLR is active, while
preserving the original base address behavior when KASLR is disabled or
"nokaslr" is specified.

Note: LoongArch can't KASLR for hibernation, so set efi_nokaslr to true
if "resume=<devname>" is explicitly specified in cmdline.

Acked-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarWANG Rui <wangrui@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 5200f5f4

arch/loongarch/include/asm/efi.h

+3 −1
Original line number Diff line number Diff line
@@ -30,6 +30,8 @@ static inline unsigned long efi_get_kimg_min_align(void) 
	return SZ_2M;

}



#define EFI_KIMG_PREFERRED_ADDRESS	PHYSADDR(VMLINUX_LOAD_ADDRESS)

unsigned long efi_get_kimg_kaslr_address(void);



#define EFI_KIMG_PREFERRED_ADDRESS efi_get_kimg_kaslr_address()



#endif /* _ASM_LOONGARCH_EFI_H */

drivers/firmware/efi/libstub/efi-stub-helper.c

+4 −0
Original line number Diff line number Diff line
@@ -79,6 +79,10 @@ efi_status_t efi_parse_options(char const *cmdline) 
			efi_noinitrd = true;

		} else if (IS_ENABLED(CONFIG_X86_64) && !strcmp(param, "no5lvl")) {

			efi_no5lvl = true;

		} else if (IS_ENABLED(CONFIG_LOONGARCH) &&

			   IS_ENABLED(CONFIG_HIBERNATION) &&

			   !strcmp(param, "resume") && val) {

			efi_nokaslr = true; /* LoongArch can't KASLR for hibernation */

		} else if (IS_ENABLED(CONFIG_ARCH_HAS_MEM_ENCRYPT) &&

			   !strcmp(param, "mem_encrypt") && val) {

			if (parse_option_str(val, "on"))

drivers/firmware/efi/libstub/loongarch.c

+16 −0
Original line number Diff line number Diff line
@@ -23,6 +23,22 @@ void efi_cache_sync_image(unsigned long image_base, unsigned long alloc_size) 
	asm volatile ("ibar 0" ::: "memory");

}



unsigned long efi_get_kimg_kaslr_address(void)

{

	unsigned int random_offset = 0;



#ifdef CONFIG_RANDOMIZE_BASE

	if (!efi_nokaslr) {

		efi_get_random_bytes(sizeof(random_offset), (u8 *)&random_offset);

		random_offset ^= (random_get_entropy() << 16);

		random_offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);

		random_offset = ALIGN(random_offset + SZ_64K, SZ_64K);

	}

#endif



	return PHYSADDR(VMLINUX_LOAD_ADDRESS) + random_offset;

}



struct exit_boot_struct {

	efi_memory_desc_t	*runtime_map;

	int			runtime_entry_count;