The following KASLR implementation allows to randomize the kernel mapping:
- virtually: we expect the bootloader to provide a seed in the device-tree
- physically: only implemented in the EFI stub, it relies on the firmware to
provide a seed using EFI_RNG_PROTOCOL. arm64 has a similar implementation
hence the patch 3 factorizes KASLR related functions for riscv to take
advantage.
The new virtual kernel location is limited by the early page table that only
has one PUD and with the PMD alignment constraint, the kernel can only take
< 512 positions.
Note that the patch "riscv: Use PUD/P4D/PGD pages for the linear
mapping" is necessary to retrieve the memory below the physical kernel
address, so that the EFI stub does not have to try to relocate the kernel
as close as possible to the start of dram.
This patchset is rebased on top of:
riscv: Allow to downgrade paging mode from the command line
(https://patchwork.kernel.org/project/linux-riscv/list/?series=734849)
base-commit-tag: v6.3-rc1
Changes in v2:
* Rebase on top of 6.3-rc1
* Add a riscv cache sync after memcpying the kernel
* Add kaslr_offset implementation for KCOV
* Add forward declaration to quiet LLVM
Alexandre Ghiti (4):
riscv: Introduce virtual kernel mapping KASLR
riscv: Dump out kernel offset information on panic
arm64: libstub: Move KASLR handling functions to efi-stub-helper.c
riscv: libstub: Implement KASLR by using generic functions
arch/riscv/Kconfig | 18 +++
arch/riscv/include/asm/page.h | 3 +
arch/riscv/kernel/image-vars.h | 1 +
arch/riscv/kernel/pi/Makefile | 2 +-
arch/riscv/kernel/pi/cmdline_early.c | 13 ++
arch/riscv/kernel/pi/fdt_early.c | 30 ++++
arch/riscv/kernel/setup.c | 25 +++
arch/riscv/mm/init.c | 36 ++++-
drivers/firmware/efi/libstub/arm64-stub.c | 111 +------------
drivers/firmware/efi/libstub/arm64.c | 5 +
.../firmware/efi/libstub/efi-stub-helper.c | 151 ++++++++++++++++++
drivers/firmware/efi/libstub/efistub.h | 10 ++
drivers/firmware/efi/libstub/riscv-stub.c | 28 ++--
drivers/firmware/efi/libstub/riscv.c | 5 +
14 files changed, 315 insertions(+), 123 deletions(-)
create mode 100644 arch/riscv/kernel/pi/fdt_early.c
--
2.37.2
KASLR implementation relies on a relocatable kernel so that we can move
the kernel mapping.
The seed needed to virtually move the kernel is taken from the device tree,
so we rely on the bootloader to provide a correct seed. Zkr could be used
unconditionnally instead if implemented, but that's for another patch.
Signed-off-by: Alexandre Ghiti <[email protected]>
---
arch/riscv/Kconfig | 18 ++++++++++++++
arch/riscv/include/asm/page.h | 3 +++
arch/riscv/kernel/pi/Makefile | 2 +-
arch/riscv/kernel/pi/cmdline_early.c | 13 ++++++++++
arch/riscv/kernel/pi/fdt_early.c | 30 +++++++++++++++++++++++
arch/riscv/mm/init.c | 36 +++++++++++++++++++++++++++-
6 files changed, 100 insertions(+), 2 deletions(-)
create mode 100644 arch/riscv/kernel/pi/fdt_early.c
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 6ff9f574195d..af23750543c7 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -576,6 +576,24 @@ config RELOCATABLE
If unsure, say N.
+config RANDOMIZE_BASE
+ bool "Randomize the address of the kernel image"
+ select RELOCATABLE
+ help
+ Randomizes the virtual address at which the kernel image is
+ loaded, as a security feature that deters exploit attempts
+ relying on knowledge of the location of kernel internals.
+
+ It is the bootloader's job to provide entropy, by passing a
+ random u64 value in /chosen/kaslr-seed at kernel entry.
+
+ When booting via the UEFI stub, it will invoke the firmware's
+ EFI_RNG_PROTOCOL implementation (if available) to supply entropy
+ to the kernel proper. In addition, it will randomise the physical
+ location of the kernel Image as well.
+
+ If unsure, say N.
+
endmenu # "Kernel features"
menu "Boot options"
diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index ea1a0e237211..e0c8a1c8b22a 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -107,6 +107,7 @@ typedef struct page *pgtable_t;
struct kernel_mapping {
unsigned long page_offset;
unsigned long virt_addr;
+ unsigned long virt_offset;
uintptr_t phys_addr;
uintptr_t size;
/* Offset between linear mapping virtual address and kernel load address */
@@ -186,6 +187,8 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x);
#define sym_to_pfn(x) __phys_to_pfn(__pa_symbol(x))
+unsigned long kaslr_offset(void);
+
#endif /* __ASSEMBLY__ */
#define virt_addr_valid(vaddr) ({ \
diff --git a/arch/riscv/kernel/pi/Makefile b/arch/riscv/kernel/pi/Makefile
index 42c58f4ab53b..edb3218bfb36 100644
--- a/arch/riscv/kernel/pi/Makefile
+++ b/arch/riscv/kernel/pi/Makefile
@@ -35,5 +35,5 @@ $(obj)/string.o: $(srctree)/lib/string.c FORCE
$(obj)/ctype.o: $(srctree)/lib/ctype.c FORCE
$(call if_changed_rule,cc_o_c)
-obj-y := cmdline_early.pi.o string.pi.o ctype.pi.o lib-fdt.pi.o lib-fdt_ro.pi.o
+obj-y := cmdline_early.pi.o fdt_early.pi.o string.pi.o ctype.pi.o lib-fdt.pi.o lib-fdt_ro.pi.o
extra-y := $(patsubst %.pi.o,%.o,$(obj-y))
diff --git a/arch/riscv/kernel/pi/cmdline_early.c b/arch/riscv/kernel/pi/cmdline_early.c
index 05652d13c746..68e786c84c94 100644
--- a/arch/riscv/kernel/pi/cmdline_early.c
+++ b/arch/riscv/kernel/pi/cmdline_early.c
@@ -14,6 +14,7 @@ static char early_cmdline[COMMAND_LINE_SIZE];
* LLVM complain because the function is actually unused in this file).
*/
u64 set_satp_mode_from_cmdline(uintptr_t dtb_pa);
+bool set_nokaslr_from_cmdline(uintptr_t dtb_pa);
static char *get_early_cmdline(uintptr_t dtb_pa)
{
@@ -60,3 +61,15 @@ u64 set_satp_mode_from_cmdline(uintptr_t dtb_pa)
return match_noXlvl(cmdline);
}
+
+static bool match_nokaslr(char *cmdline)
+{
+ return strstr(cmdline, "nokaslr");
+}
+
+bool set_nokaslr_from_cmdline(uintptr_t dtb_pa)
+{
+ char *cmdline = get_early_cmdline(dtb_pa);
+
+ return match_nokaslr(cmdline);
+}
diff --git a/arch/riscv/kernel/pi/fdt_early.c b/arch/riscv/kernel/pi/fdt_early.c
new file mode 100644
index 000000000000..899610e042ab
--- /dev/null
+++ b/arch/riscv/kernel/pi/fdt_early.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/libfdt.h>
+
+/*
+ * Declare the functions that are exported (but prefixed) here so that LLVM
+ * does not complain it lacks the 'static' keyword (which, if added, makes
+ * LLVM complain because the function is actually unused in this file).
+ */
+u64 get_kaslr_seed(uintptr_t dtb_pa);
+
+u64 get_kaslr_seed(uintptr_t dtb_pa)
+{
+ int node, len;
+ fdt64_t *prop;
+ u64 ret;
+
+ node = fdt_path_offset((void *)dtb_pa, "/chosen");
+ if (node < 0)
+ return 0;
+
+ prop = fdt_getprop_w((void *)dtb_pa, node, "kaslr-seed", &len);
+ if (!prop || len != sizeof(u64))
+ return 0;
+
+ ret = fdt64_to_cpu(*prop);
+ *prop = 0;
+ return ret;
+}
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 3ad771571c2d..3e535a88a065 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1033,11 +1033,45 @@ static void __init pt_ops_set_late(void)
#endif
}
+#ifdef CONFIG_RANDOMIZE_BASE
+extern bool __init __pi_set_nokaslr_from_cmdline(uintptr_t dtb_pa);
+extern u64 __init __pi_get_kaslr_seed(uintptr_t dtb_pa);
+
+static int __init print_nokaslr(char *p)
+{
+ pr_info("Disabled KASLR");
+ return 0;
+}
+early_param("nokaslr", print_nokaslr);
+
+unsigned long kaslr_offset(void)
+{
+ return kernel_map.virt_offset;
+}
+#endif
+
asmlinkage void __init setup_vm(uintptr_t dtb_pa)
{
pmd_t __maybe_unused fix_bmap_spmd, fix_bmap_epmd;
- kernel_map.virt_addr = KERNEL_LINK_ADDR;
+#ifdef CONFIG_RANDOMIZE_BASE
+ if (!__pi_set_nokaslr_from_cmdline(dtb_pa)) {
+ u64 kaslr_seed = __pi_get_kaslr_seed(dtb_pa);
+ u32 kernel_size = (uintptr_t)(&_end) - (uintptr_t)(&_start);
+ u32 nr_pos;
+
+ /*
+ * Compute the number of positions available: we are limited
+ * by the early page table that only has one PUD and we must
+ * be aligned on PMD_SIZE.
+ */
+ nr_pos = (PUD_SIZE - kernel_size) / PMD_SIZE;
+
+ kernel_map.virt_offset = (kaslr_seed % nr_pos) * PMD_SIZE;
+ }
+#endif
+
+ kernel_map.virt_addr = KERNEL_LINK_ADDR + kernel_map.virt_offset;
kernel_map.page_offset = _AC(CONFIG_PAGE_OFFSET, UL);
#ifdef CONFIG_XIP_KERNEL
--
2.37.2
Dump out the KASLR virtual kernel offset when panic to help debug kernel.
Signed-off-by: Zong Li <[email protected]>
Signed-off-by: Alexandre Ghiti <[email protected]>
---
arch/riscv/kernel/setup.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 376d2827e736..c6937839bbd8 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -20,6 +20,7 @@
#include <linux/smp.h>
#include <linux/efi.h>
#include <linux/crash_dump.h>
+#include <linux/panic_notifier.h>
#include <asm/alternative.h>
#include <asm/cacheflush.h>
@@ -333,3 +334,27 @@ void free_initmem(void)
free_initmem_default(POISON_FREE_INITMEM);
}
+
+static int dump_kernel_offset(struct notifier_block *self,
+ unsigned long v, void *p)
+{
+ pr_emerg("Kernel Offset: 0x%lx from 0x%lx\n",
+ kernel_map.virt_offset,
+ KERNEL_LINK_ADDR);
+
+ return 0;
+}
+
+static struct notifier_block kernel_offset_notifier = {
+ .notifier_call = dump_kernel_offset
+};
+
+static int __init register_kernel_offset_dumper(void)
+{
+ if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
+ atomic_notifier_chain_register(&panic_notifier_list,
+ &kernel_offset_notifier);
+
+ return 0;
+}
+device_initcall(register_kernel_offset_dumper);
--
2.37.2
This prepares for riscv to use the same functions to handle the pĥysical
kernel move when KASLR is enabled.
Signed-off-by: Alexandre Ghiti <[email protected]>
---
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
We can now use arm64 functions to handle the move of the kernel physical
mapping: if KASLR is enabled, we will try to get a random seed from the
firmware, if not possible, the kernel will be moved to a location that
suits its alignment constraints.
Signed-off-by: Alexandre Ghiti <[email protected]>
---
arch/riscv/kernel/image-vars.h | 1 +
drivers/firmware/efi/libstub/arm64.c | 5 ++++
.../firmware/efi/libstub/efi-stub-helper.c | 2 +-
drivers/firmware/efi/libstub/efistub.h | 2 ++
drivers/firmware/efi/libstub/riscv-stub.c | 28 +++++++------------
drivers/firmware/efi/libstub/riscv.c | 5 ++++
6 files changed, 24 insertions(+), 19 deletions(-)
diff --git a/arch/riscv/kernel/image-vars.h b/arch/riscv/kernel/image-vars.h
index 15616155008c..ea1a10355ce9 100644
--- a/arch/riscv/kernel/image-vars.h
+++ b/arch/riscv/kernel/image-vars.h
@@ -27,6 +27,7 @@ __efistub__start = _start;
__efistub__start_kernel = _start_kernel;
__efistub__end = _end;
__efistub__edata = _edata;
+__efistub___init_text_end = __init_text_end;
__efistub_screen_info = screen_info;
#endif
diff --git a/drivers/firmware/efi/libstub/arm64.c b/drivers/firmware/efi/libstub/arm64.c
index 399770266372..48bc7428d6df 100644
--- a/drivers/firmware/efi/libstub/arm64.c
+++ b/drivers/firmware/efi/libstub/arm64.c
@@ -108,3 +108,8 @@ void __noreturn efi_enter_kernel(unsigned long entrypoint,
enter_kernel = (void *)entrypoint + primary_entry_offset();
enter_kernel(fdt_addr, 0, 0, 0);
}
+
+void efi_icache_sync(unsigned long start, unsigned long end)
+{
+ caches_clean_inval_pou(start, end);
+}
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 40ac2625949c..63c7275d42e7 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -865,7 +865,7 @@ efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
memcpy((void *)*reserve_addr, (void *)*image_addr, kernel_size);
*image_addr = *reserve_addr;
- caches_clean_inval_pou(*image_addr, *image_addr + kernel_codesize);
+ efi_icache_sync(*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 64273371ce96..9ce114e04b23 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -1107,4 +1107,6 @@ efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
u32 phys_seed);
u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle);
+void efi_icache_sync(unsigned long start, unsigned long end);
+
#endif
diff --git a/drivers/firmware/efi/libstub/riscv-stub.c b/drivers/firmware/efi/libstub/riscv-stub.c
index 145c9f0ba217..7af07b33a993 100644
--- a/drivers/firmware/efi/libstub/riscv-stub.c
+++ b/drivers/firmware/efi/libstub/riscv-stub.c
@@ -30,32 +30,24 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
efi_loaded_image_t *image,
efi_handle_t image_handle)
{
- unsigned long kernel_size = 0;
- unsigned long preferred_addr;
+ unsigned long kernel_size, kernel_codesize, kernel_memsize;
efi_status_t status;
kernel_size = _edata - _start;
+ kernel_codesize = __init_text_end - _start;
+ kernel_memsize = kernel_size + (_end - _edata);
*image_addr = (unsigned long)_start;
- *image_size = kernel_size + (_end - _edata);
-
- /*
- * RISC-V kernel maps PAGE_OFFSET virtual address to the same physical
- * address where kernel is booted. That's why kernel should boot from
- * as low as possible to avoid wastage of memory. Currently, dram_base
- * is occupied by the firmware. So the preferred address for kernel to
- * boot is next aligned address. If preferred address is not available,
- * relocate_kernel will fall back to efi_low_alloc_above to allocate
- * lowest possible memory region as long as the address and size meets
- * the alignment constraints.
- */
- preferred_addr = EFI_KIMG_PREFERRED_ADDRESS;
- status = efi_relocate_kernel(image_addr, kernel_size, *image_size,
- preferred_addr, efi_get_kimg_min_align(),
- 0x0);
+ *image_size = kernel_memsize;
+ *reserve_size = *image_size;
+ 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_err("Failed to relocate kernel\n");
*image_size = 0;
}
+
return status;
}
diff --git a/drivers/firmware/efi/libstub/riscv.c b/drivers/firmware/efi/libstub/riscv.c
index 8022b104c3e6..365f891e598f 100644
--- a/drivers/firmware/efi/libstub/riscv.c
+++ b/drivers/firmware/efi/libstub/riscv.c
@@ -96,3 +96,8 @@ void __noreturn efi_enter_kernel(unsigned long entrypoint, unsigned long fdt,
csr_write(CSR_SATP, 0);
jump_kernel(hartid, fdt);
}
+
+void efi_icache_sync(unsigned long start, unsigned long end)
+{
+ asm volatile ("fence.i" ::: "memory");
+}
--
2.37.2
On Tue, 28 Mar 2023 22:29:25 PDT (-0700), [email protected] wrote:
> This prepares for riscv to use the same functions to handle the pĥysical
> kernel move when KASLR is enabled.
>
> Signed-off-by: Alexandre Ghiti <[email protected]>
> ---
> drivers/firmware/efi/libstub/arm64-stub.c | 111 +------------
This LGTM, but I'd prefer at least an Ack from either the Arm or EFI
folks. I think that makes it too late for this merge window.
> .../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
On 4/29/23 21:50, Palmer Dabbelt wrote:
> On Tue, 28 Mar 2023 22:29:25 PDT (-0700), [email protected] wrote:
>> This prepares for riscv to use the same functions to handle the pĥysical
>> kernel move when KASLR is enabled.
>>
>> Signed-off-by: Alexandre Ghiti <[email protected]>
>> ---
>> drivers/firmware/efi/libstub/arm64-stub.c | 111 +------------
>
> This LGTM, but I'd prefer at least an Ack from either the Arm or EFI
> folks. I think that makes it too late for this merge window.
Note that I have a minor fix (RANDOMIZE_BASE should depend on 64BIT) and
kernel test robot reported a few warnings and errors:
ld: efi-stub-helper.c:undefined reference to `efi_icache_sync'
efi-stub-helper.c:undefined reference to `efi_get_kimg_min_align'
drivers/firmware/efi/libstub/efi-stub-helper.c:825:23: warning: implicit
declaration of function 'efi_get_kimg_min_align' is invalid in C99
I'll wait for feedbacks and send a v3.
Thanks,
Alex
>
>> .../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
>
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