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.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/arm64/include/asm/efi.h

@@ -168,4 +168,6 @@ static inline void efi_capsule_flush_cache_range(void *addr, int size)
 
 efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f);
 
+void efi_icache_sync(unsigned long start, unsigned long end);
+
 #endif /* _ASM_EFI_H */

drivers/firmware/efi/libstub/Makefile

@@ -86,7 +86,7 @@ lib-$(CONFIG_EFI_GENERIC_STUB)	+= efi-stub.o string.o intrinsics.o systable.o \
 				   screen_info.o efi-stub-entry.o
 
 lib-$(CONFIG_ARM)		+= arm32-stub.o
-lib-$(CONFIG_ARM64)		+= arm64.o arm64-stub.o smbios.o
+lib-$(CONFIG_ARM64)		+= kaslr.o arm64.o arm64-stub.o smbios.o
 lib-$(CONFIG_X86)		+= x86-stub.o
 lib-$(CONFIG_RISCV)		+= riscv.o riscv-stub.o
 lib-$(CONFIG_LOONGARCH)		+= loongarch.o loongarch-stub.o

drivers/firmware/efi/libstub/arm64-stub.c

@@ -14,42 +14,6 @@
 
 #include "efistub.h"
 
-/*
- * 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;
-
-	status = efi_get_memory_map(&map, false);
-	if (status != EFI_SUCCESS)
-		return false;
-
-	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;
-		}
-	}
-
-	efi_bs_call(free_pool, map);
-
-	return ret;
-}
-
 efi_status_t handle_kernel_image(unsigned long *image_addr,
 				 unsigned long *image_size,
 				 unsigned long *reserve_addr,
@@ -59,31 +23,6 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 {
 	efi_status_t status;
 	unsigned long kernel_size, kernel_codesize, kernel_memsize;
-	u32 phys_seed = 0;
-	u64 min_kimg_align = efi_get_kimg_min_align();
-
-	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
-		efi_guid_t li_fixed_proto = LINUX_EFI_LOADED_IMAGE_FIXED_GUID;
-		void *p;
-
-		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_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;
-			}
-		}
-	}
 
 	if (image->image_base != _text) {
 		efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");
@@ -98,50 +37,15 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 	kernel_codesize = __inittext_end - _text;
 	kernel_memsize = kernel_size + (_end - _edata);
 	*reserve_size = kernel_memsize;
+	*image_addr = (unsigned long)_text;
 
-	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);
+	status = efi_kaslr_relocate_kernel(image_addr,
+					   reserve_addr, reserve_size,
+					   kernel_size, kernel_codesize,
+					   kernel_memsize,
+					   efi_kaslr_get_phys_seed(image_handle));
 	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((u64)_text, kernel_memsize)) {
-			efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
-		} else if (IS_ALIGNED((u64)_text, 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.
-			 */
-			*image_addr = (u64)_text;
-			*reserve_size = 0;
-			return EFI_SUCCESS;
-		}
-
-		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
-						    ULONG_MAX, min_kimg_align,
-						    EFI_LOADER_CODE);
-
-		if (status != EFI_SUCCESS) {
-			efi_err("Failed to relocate kernel\n");
-			*reserve_size = 0;
 		return status;
-		}
-	}
-
-	*image_addr = *reserve_addr;
-	memcpy((void *)*image_addr, _text, kernel_size);
-	caches_clean_inval_pou(*image_addr, *image_addr + kernel_codesize);
-	efi_remap_image(*image_addr, *reserve_size, kernel_codesize);
 
 	return EFI_SUCCESS;
 }
@@ -159,3 +63,8 @@ unsigned long primary_entry_offset(void)
 	 */
 	return (char *)primary_entry - _text;
 }
+
+void efi_icache_sync(unsigned long start, unsigned long end)
+{
+	caches_clean_inval_pou(start, end);
+}

drivers/firmware/efi/libstub/efistub.h

@@ -1132,6 +1132,14 @@ const u8 *__efi_get_smbios_string(const struct efi_smbios_record *record,
 
 void efi_remap_image(unsigned long image_base, unsigned alloc_size,
 		     unsigned long code_size);
+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);
+u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle);
 
 asmlinkage efi_status_t __efiapi
 efi_zboot_entry(efi_handle_t handle, efi_system_table_t *systab);

drivers/firmware/efi/libstub/kaslr.c

+// 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>
+
+#include "efistub.h"
+
+/**
+ * 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;
+
+	if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
+		return 0;
+
+	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;
+
+	status = efi_get_memory_map(&map, false);
+	if (status != EFI_SUCCESS)
+		return false;
+
+	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;
+		}
+	}
+
+	efi_bs_call(free_pool, map);
+
+	return ret;
+}
+
+/**
+ * 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();
+
+	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;
+		}
+
+		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
+						    ULONG_MAX, min_kimg_align,
+						    EFI_LOADER_CODE);
+
+		if (status != EFI_SUCCESS) {
+			efi_err("Failed to relocate kernel\n");
+			*reserve_size = 0;
+			return status;
+		}
+	}
+
+	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);
+
+	return status;
+}