* [PATCH 1/4] riscv: Introduce virtual kernel mapping KASLR
2023-02-15 14:51 [PATCH 0/4] riscv: Introduce KASLR Alexandre Ghiti
@ 2023-02-15 14:51 ` Alexandre Ghiti
2023-02-15 14:51 ` [PATCH 2/4] riscv: Dump out kernel offset information on panic Alexandre Ghiti
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Alexandre Ghiti @ 2023-02-15 14:51 UTC (permalink / raw)
To: Paul Walmsley, Palmer Dabbelt, Albert Ou, Ard Biesheuvel,
linux-riscv, linux-kernel, linux-efi
Cc: Alexandre Ghiti
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 <alexghiti@rivosinc.com>
---
arch/riscv/Kconfig | 18 ++++++++++++++++
arch/riscv/include/asm/page.h | 1 +
arch/riscv/kernel/pi/Makefile | 2 +-
arch/riscv/kernel/pi/cmdline_early.c | 12 +++++++++++
arch/riscv/kernel/pi/fdt_early.c | 23 +++++++++++++++++++++
arch/riscv/mm/init.c | 31 +++++++++++++++++++++++++++-
6 files changed, 85 insertions(+), 2 deletions(-)
create mode 100644 arch/riscv/kernel/pi/fdt_early.c
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index e3b7608d23ae..70082bd978cf 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -559,6 +559,24 @@ 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 bd7b9dda1e4f..11c9aa4931c7 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 */
diff --git a/arch/riscv/kernel/pi/Makefile b/arch/riscv/kernel/pi/Makefile
index 554e936ef0b6..d997d08ae593 100644
--- a/arch/riscv/kernel/pi/Makefile
+++ b/arch/riscv/kernel/pi/Makefile
@@ -30,5 +30,5 @@ $(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 5ae7b853fa66..8d898cc6e7ff 100644
--- a/arch/riscv/kernel/pi/cmdline_early.c
+++ b/arch/riscv/kernel/pi/cmdline_early.c
@@ -50,3 +50,15 @@ u64 __init set_satp_mode_from_cmdline(uintptr_t dtb_pa)
return match_noXlvl(cmdline);
}
+
+static bool __init match_nokaslr(char *cmdline)
+{
+ return strstr(cmdline, "nokaslr");
+}
+
+bool __init 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..a51f00021886
--- /dev/null
+++ b/arch/riscv/kernel/pi/fdt_early.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/libfdt.h>
+
+u64 __init 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 aa4f1dc6df58..e6a7e6f5c75d 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1032,11 +1032,40 @@ 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);
+#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
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH 2/4] riscv: Dump out kernel offset information on panic
2023-02-15 14:51 [PATCH 0/4] riscv: Introduce KASLR Alexandre Ghiti
2023-02-15 14:51 ` [PATCH 1/4] riscv: Introduce virtual kernel mapping KASLR Alexandre Ghiti
@ 2023-02-15 14:51 ` Alexandre Ghiti
2023-02-15 14:51 ` [PATCH 3/4] arm64: libstub: Move KASLR handling functions to efi-stub-helper.c Alexandre Ghiti
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Alexandre Ghiti @ 2023-02-15 14:51 UTC (permalink / raw)
To: Paul Walmsley, Palmer Dabbelt, Albert Ou, Ard Biesheuvel,
linux-riscv, linux-kernel, linux-efi
Cc: Alexandre Ghiti, Zong Li
Dump out the KASLR virtual kernel offset when panic to help debug kernel.
Signed-off-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
---
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 86acd690d529..d33065f4c084 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>
@@ -330,3 +331,27 @@ 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
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH 3/4] arm64: libstub: Move KASLR handling functions to efi-stub-helper.c
2023-02-15 14:51 [PATCH 0/4] riscv: Introduce KASLR Alexandre Ghiti
2023-02-15 14:51 ` [PATCH 1/4] riscv: Introduce virtual kernel mapping KASLR Alexandre Ghiti
2023-02-15 14:51 ` [PATCH 2/4] riscv: Dump out kernel offset information on panic Alexandre Ghiti
@ 2023-02-15 14:51 ` Alexandre Ghiti
2023-02-15 14:51 ` [PATCH 4/4] riscv: libstub: Implement KASLR by using generic functions Alexandre Ghiti
2023-02-21 15:50 ` [PATCH 0/4] riscv: Introduce KASLR Björn Töpel
4 siblings, 0 replies; 6+ messages in thread
From: Alexandre Ghiti @ 2023-02-15 14:51 UTC (permalink / raw)
To: Paul Walmsley, Palmer Dabbelt, Albert Ou, Ard Biesheuvel,
linux-riscv, linux-kernel, linux-efi
Cc: Alexandre Ghiti
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>
---
drivers/firmware/efi/libstub/arm64-stub.c | 110 +------------
.../firmware/efi/libstub/efi-stub-helper.c | 147 ++++++++++++++++++
drivers/firmware/efi/libstub/efistub.h | 8 +
3 files changed, 162 insertions(+), 103 deletions(-)
diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
index 7327b98d8e3f..86ea9bfa6513 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_memsize = 0;
- 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");
@@ -95,50 +34,15 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
kernel_size = _edata - _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;
- goto clean_image_to_poc;
- }
-
- 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);
+ status = efi_kaslr_relocate_kernel(image_addr,
+ reserve_addr, reserve_size,
+ kernel_size, kernel_memsize,
+ efi_kaslr_get_phys_seed(image_handle));
+ if (status != EFI_SUCCESS)
+ return status;
-clean_image_to_poc:
/*
* Clean the copied Image to the PoC, and ensure it is not shadowed by
* stale icache entries from before relocation.
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index f5a4bdacac64..ebf72beee4f5 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -651,3 +651,150 @@ efi_status_t efi_wait_for_key(unsigned long usec, efi_input_key_t *key)
return status;
}
+
+/**
+ * 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_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_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;
+
+ return status;
+}
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 5b8f2c411ed8..747f33763df0 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -1076,4 +1076,12 @@ struct efi_smbios_type1_record {
const u8 *__efi_get_smbios_string(u8 type, int offset, int recsize);
+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_memsize,
+ u32 phys_seed);
+u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle);
+
#endif
--
2.37.2
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH 4/4] riscv: libstub: Implement KASLR by using generic functions
2023-02-15 14:51 [PATCH 0/4] riscv: Introduce KASLR Alexandre Ghiti
` (2 preceding siblings ...)
2023-02-15 14:51 ` [PATCH 3/4] arm64: libstub: Move KASLR handling functions to efi-stub-helper.c Alexandre Ghiti
@ 2023-02-15 14:51 ` Alexandre Ghiti
2023-02-21 15:50 ` [PATCH 0/4] riscv: Introduce KASLR Björn Töpel
4 siblings, 0 replies; 6+ messages in thread
From: Alexandre Ghiti @ 2023-02-15 14:51 UTC (permalink / raw)
To: Paul Walmsley, Palmer Dabbelt, Albert Ou, Ard Biesheuvel,
linux-riscv, linux-kernel, linux-efi
Cc: Alexandre Ghiti
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 <alexghiti@rivosinc.com>
---
drivers/firmware/efi/libstub/riscv-stub.c | 27 ++++++++---------------
1 file changed, 9 insertions(+), 18 deletions(-)
diff --git a/drivers/firmware/efi/libstub/riscv-stub.c b/drivers/firmware/efi/libstub/riscv-stub.c
index 145c9f0ba217..0c3c4a13afa1 100644
--- a/drivers/firmware/efi/libstub/riscv-stub.c
+++ b/drivers/firmware/efi/libstub/riscv-stub.c
@@ -30,32 +30,23 @@ 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_memsize = 0;
efi_status_t status;
kernel_size = _edata - _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_memsize,
+ efi_kaslr_get_phys_seed(image_handle));
if (status != EFI_SUCCESS) {
efi_err("Failed to relocate kernel\n");
*image_size = 0;
}
+
return status;
}
--
2.37.2
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 0/4] riscv: Introduce KASLR
2023-02-15 14:51 [PATCH 0/4] riscv: Introduce KASLR Alexandre Ghiti
` (3 preceding siblings ...)
2023-02-15 14:51 ` [PATCH 4/4] riscv: libstub: Implement KASLR by using generic functions Alexandre Ghiti
@ 2023-02-21 15:50 ` Björn Töpel
4 siblings, 0 replies; 6+ messages in thread
From: Björn Töpel @ 2023-02-21 15:50 UTC (permalink / raw)
To: Alexandre Ghiti, Paul Walmsley, Palmer Dabbelt, Albert Ou,
Ard Biesheuvel, linux-riscv, linux-kernel, linux-efi
Cc: Alexandre Ghiti
Alexandre Ghiti <alexghiti@rivosinc.com> writes:
> 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:
>
> Introduce 64b relocatable kernel (https://lore.kernel.org/lkml/20230215143626.453491-1-alexghiti@rivosinc.com/)
> RISC-V kasan rework (https://lore.kernel.org/lkml/Y6TTvku%2FyuSjm42j@spud/T/)
> riscv: Use PUD/P4D/PGD pages for the linear mapping (https://lore.kernel.org/lkml/20230125114229.hrhsyw4aegrnmoau@orel/T/)
> riscv: Allow to downgrade paging mode from the command line (https://lore.kernel.org/lkml/CAHVXubjeSMvfTPnvrnYRupOGx6+vUvUGfRS3piTeo=TH2cHKNg@mail.gmail.com/)
> base-commit-tag: v6.2-rc7
>
> This patchset was tested with u-boot boottime service for the seed on:
> - ubuntu defconfig + kasan outline (sv39, sv48, sv57): OK
> - ubuntu defconfig + kasan inline (sv39, sv48, sv57): OK
> - ubuntu defconfg (sv39, sv48, sv57): OK
I've taken the series for a spin (qemu u-boot UEFI, and qemu non-UEFI),
on-top of the patches outline above, but with 6.2 proper.
For the series:
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
^ permalink raw reply [flat|nested] 6+ messages in thread