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efi/loongarch: Randomize kernel preferred address for KASLR

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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: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
WANG Rui 2026-05-21 20:58:36 +08:00 committed by Huacai Chen
parent 5200f5f493
commit 03d8273542
3 changed files with 23 additions and 1 deletions
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4
arch/loongarch/include/asm/efi.h
View File

@ -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 */

4
drivers/firmware/efi/libstub/efi-stub-helper.c
View File

@ -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"))

16
drivers/firmware/efi/libstub/loongarch.c
View File

@ -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;