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arm64: libstub: Move KASLR handling functions to kaslr.c
This prepares for riscv to use the same functions to handle the pĥysical kernel move when KASLR is enabled. Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com> Acked-by: Ard Biesheuvel <ardb@kernel.org> Tested-by: Conor Dooley <conor.dooley@microchip.com> Tested-by: Song Shuai <songshuaishuai@tinylab.org> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Sami Tolvanen <samitolvanen@google.com> Link: https://lore.kernel.org/r/20230722123850.634544-4-alexghiti@rivosinc.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,159 @@ | ||
| // SPDX-License-Identifier: GPL-2.0 | ||
| /* | ||
| * Helper functions used by the EFI stub on multiple | ||
| * architectures to deal with physical address space randomization. | ||
| */ | ||
| #include <linux/efi.h> | ||
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| #include "efistub.h" | ||
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| /** | ||
| * efi_kaslr_get_phys_seed() - Get random seed for physical kernel KASLR | ||
| * @image_handle: Handle to the image | ||
| * | ||
| * If KASLR is not disabled, obtain a random seed using EFI_RNG_PROTOCOL | ||
| * that will be used to move the kernel physical mapping. | ||
| * | ||
| * Return: the random seed | ||
| */ | ||
| u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle) | ||
| { | ||
| efi_status_t status; | ||
| u32 phys_seed; | ||
| efi_guid_t li_fixed_proto = LINUX_EFI_LOADED_IMAGE_FIXED_GUID; | ||
| void *p; | ||
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|
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| if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE)) | ||
| return 0; | ||
|
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| if (efi_nokaslr) { | ||
| efi_info("KASLR disabled on kernel command line\n"); | ||
| } else if (efi_bs_call(handle_protocol, image_handle, | ||
| &li_fixed_proto, &p) == EFI_SUCCESS) { | ||
| efi_info("Image placement fixed by loader\n"); | ||
| } else { | ||
| status = efi_get_random_bytes(sizeof(phys_seed), | ||
| (u8 *)&phys_seed); | ||
| if (status == EFI_SUCCESS) { | ||
| return phys_seed; | ||
| } else if (status == EFI_NOT_FOUND) { | ||
| efi_info("EFI_RNG_PROTOCOL unavailable\n"); | ||
| efi_nokaslr = true; | ||
| } else if (status != EFI_SUCCESS) { | ||
| efi_err("efi_get_random_bytes() failed (0x%lx)\n", | ||
| status); | ||
| efi_nokaslr = true; | ||
| } | ||
| } | ||
|
|
||
| return 0; | ||
| } | ||
|
|
||
| /* | ||
| * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., fail | ||
| * to provide space, and fail to zero it). Check for this condition by double | ||
| * checking that the first and the last byte of the image are covered by the | ||
| * same EFI memory map entry. | ||
| */ | ||
| static bool check_image_region(u64 base, u64 size) | ||
| { | ||
| struct efi_boot_memmap *map; | ||
| efi_status_t status; | ||
| bool ret = false; | ||
| int map_offset; | ||
|
|
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| status = efi_get_memory_map(&map, false); | ||
| if (status != EFI_SUCCESS) | ||
| return false; | ||
|
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| for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) { | ||
| efi_memory_desc_t *md = (void *)map->map + map_offset; | ||
| u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE; | ||
|
|
||
| /* | ||
| * Find the region that covers base, and return whether | ||
| * it covers base+size bytes. | ||
| */ | ||
| if (base >= md->phys_addr && base < end) { | ||
| ret = (base + size) <= end; | ||
| break; | ||
| } | ||
| } | ||
|
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| efi_bs_call(free_pool, map); | ||
|
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| return ret; | ||
| } | ||
|
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| /** | ||
| * efi_kaslr_relocate_kernel() - Relocate the kernel (random if KASLR enabled) | ||
| * @image_addr: Pointer to the current kernel location | ||
| * @reserve_addr: Pointer to the relocated kernel location | ||
| * @reserve_size: Size of the relocated kernel | ||
| * @kernel_size: Size of the text + data | ||
| * @kernel_codesize: Size of the text | ||
| * @kernel_memsize: Size of the text + data + bss | ||
| * @phys_seed: Random seed used for the relocation | ||
| * | ||
| * If KASLR is not enabled, this function relocates the kernel to a fixed | ||
| * address (or leave it as its current location). If KASLR is enabled, the | ||
| * kernel physical location is randomized using the seed in parameter. | ||
| * | ||
| * Return: status code, EFI_SUCCESS if relocation is successful | ||
| */ | ||
| efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr, | ||
| unsigned long *reserve_addr, | ||
| unsigned long *reserve_size, | ||
| unsigned long kernel_size, | ||
| unsigned long kernel_codesize, | ||
| unsigned long kernel_memsize, | ||
| u32 phys_seed) | ||
| { | ||
| efi_status_t status; | ||
| u64 min_kimg_align = efi_get_kimg_min_align(); | ||
|
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| if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) { | ||
| /* | ||
| * If KASLR is enabled, and we have some randomness available, | ||
| * locate the kernel at a randomized offset in physical memory. | ||
| */ | ||
| status = efi_random_alloc(*reserve_size, min_kimg_align, | ||
| reserve_addr, phys_seed, | ||
| EFI_LOADER_CODE); | ||
| if (status != EFI_SUCCESS) | ||
| efi_warn("efi_random_alloc() failed: 0x%lx\n", status); | ||
| } else { | ||
| status = EFI_OUT_OF_RESOURCES; | ||
| } | ||
|
|
||
| if (status != EFI_SUCCESS) { | ||
| if (!check_image_region(*image_addr, kernel_memsize)) { | ||
| efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n"); | ||
| } else if (IS_ALIGNED(*image_addr, min_kimg_align) && | ||
| (u64)_end < EFI_ALLOC_LIMIT) { | ||
| /* | ||
| * Just execute from wherever we were loaded by the | ||
| * UEFI PE/COFF loader if the placement is suitable. | ||
| */ | ||
| *reserve_size = 0; | ||
| return EFI_SUCCESS; | ||
| } | ||
|
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| status = efi_allocate_pages_aligned(*reserve_size, reserve_addr, | ||
| ULONG_MAX, min_kimg_align, | ||
| EFI_LOADER_CODE); | ||
|
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| if (status != EFI_SUCCESS) { | ||
| efi_err("Failed to relocate kernel\n"); | ||
| *reserve_size = 0; | ||
| return status; | ||
| } | ||
| } | ||
|
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| memcpy((void *)*reserve_addr, (void *)*image_addr, kernel_size); | ||
| *image_addr = *reserve_addr; | ||
| efi_icache_sync(*image_addr, *image_addr + kernel_codesize); | ||
| efi_remap_image(*image_addr, *reserve_size, kernel_codesize); | ||
|
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| return status; | ||
| } |