[PATCH v2 3/4] arm64: libstub: Move KASLR handling functions to efi-stub-helper.c
Alexandre Ghiti
alexghiti at rivosinc.com
Tue Mar 28 22:29:25 PDT 2023
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 at rivosinc.com>
---
drivers/firmware/efi/libstub/arm64-stub.c | 111 +------------
.../firmware/efi/libstub/efi-stub-helper.c | 151 ++++++++++++++++++
drivers/firmware/efi/libstub/efistub.h | 8 +
3 files changed, 167 insertions(+), 103 deletions(-)
diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
index d4a6b12a8741..b9e0d2cf09aa 100644
--- a/drivers/firmware/efi/libstub/arm64-stub.c
+++ b/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");
@@ -96,49 +35,15 @@ 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);
- 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);
+ 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)
+ return status;
return EFI_SUCCESS;
}
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 1e0203d74691..40ac2625949c 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -718,3 +718,154 @@ void efi_remap_image(unsigned long image_base, unsigned alloc_size,
efi_warn("Failed to remap data region non-executable\n");
}
}
+
+/**
+ * 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;
+
+ caches_clean_inval_pou(*image_addr, *image_addr + kernel_codesize);
+
+ return status;
+}
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 6bd3bb86d967..64273371ce96 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -1098,5 +1098,13 @@ const u8 *__efi_get_smbios_string(u8 type, int offset, int recsize);
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);
#endif
--
2.37.2
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