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Tue, 28 Apr 2026 22:14:01 -0700 (PDT) From: WANG Rui To: Huacai Chen , Ard Biesheuvel Cc: WANG Xuerui , Ilias Apalodimas , Haiyong Sun , Lisa Robinson , loongarch@lists.linux.dev, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, WANG Rui Subject: [PATCH v3 1/3] efi/loongarch: Randomize kernel preferred address for KASLR Date: Wed, 29 Apr 2026 13:13:16 +0800 Message-ID: <20260429051318.1581350-2-r@hev.cc> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260429051318.1581350-1-r@hev.cc> References: <20260429051318.1581350-1-r@hev.cc> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Introduce efi_get_kimg_kaslr_address() to compute the preferred kernel image address dynamically when CONFIG_RANDOMIZE_BASE is enabled. The function derives a random offset using EFI-provided randomness combined with the timer 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. Signed-off-by: WANG Rui --- arch/loongarch/include/asm/efi.h | 4 +++- drivers/firmware/efi/libstub/loongarch.c | 16 ++++++++++++++++ 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/arch/loongarch/include/asm/efi.h b/arch/loongarch/include/asm/efi.h index eddc8e79b3fa..f831320efd41 100644 --- a/arch/loongarch/include/asm/efi.h +++ b/arch/loongarch/include/asm/efi.h @@ -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 */ diff --git a/drivers/firmware/efi/libstub/loongarch.c b/drivers/firmware/efi/libstub/loongarch.c index 9825f5218137..51997a0e83bd 100644 --- a/drivers/firmware/efi/libstub/loongarch.c +++ b/drivers/firmware/efi/libstub/loongarch.c @@ -38,6 +38,22 @@ static efi_status_t exit_boot_func(struct efi_boot_memmap *map, void *priv) return EFI_SUCCESS; } +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; +} + unsigned long __weak kernel_entry_address(unsigned long kernel_addr, efi_loaded_image_t *image) { -- 2.54.0