[PATCH v6 0/5] riscv: Introduce KASLR

[PATCH v6 0/5] riscv: Introduce KASLR

[Alexandre Ghiti]

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.

base-commit-tag: v6.5-rc1

Changes in v6:
  * Fix reintroduced build failures by compiling kaslr.c only for arm64
    and riscv, as suggested by Ard

Changes in v5:
  * Renamed efi-stub-kaslr.c into kaslr.c and fix commit log of patch 3,
    as suggested by Ard
  * Removed stubs since the kaslr functions were moved to their own file
    (and then does not trigger any build failure for architectures that do
    not call those functions since they are in their own compilation unit)

Changes in v4:
  * Fix efi_get_kimg macro that returned nothing
  * Moved new kaslr functions into their own files to avoid zboot link
    failures, as suggested by Ard

Changes in v3:
  * Rebase on top of 6.4-rc2
  * Make RANDOMIZE_BASE depend on 64bit
  * Fix efi_icache_sync and efi_get_kimg_min_align which were undefined
    in x86 (and certainly other archs)
  * Add patch 4 to fix warning on rv32

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 (5):
  riscv: Introduce virtual kernel mapping KASLR
  riscv: Dump out kernel offset information on panic
  arm64: libstub: Move KASLR handling functions to kaslr.c
  libstub: Fix compilation warning for rv32
  riscv: libstub: Implement KASLR by using generic functions

 arch/arm64/include/asm/efi.h              |   2 +
 arch/riscv/Kconfig                        |  19 +++
 arch/riscv/include/asm/efi.h              |   2 +
 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/Makefile     |   4 +-
 drivers/firmware/efi/libstub/arm64-stub.c | 117 ++--------------
 drivers/firmware/efi/libstub/efistub.h    |   8 ++
 drivers/firmware/efi/libstub/kaslr.c      | 159 ++++++++++++++++++++++
 drivers/firmware/efi/libstub/riscv-stub.c |  33 ++---
 15 files changed, 328 insertions(+), 126 deletions(-)
 create mode 100644 arch/riscv/kernel/pi/fdt_early.c
 create mode 100644 drivers/firmware/efi/libstub/kaslr.c

-- 
2.39.2

[PATCH v6 1/5] riscv: Introduce virtual kernel mapping KASLR

[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                   | 19 +++++++++++++++
 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, 101 insertions(+), 2 deletions(-)
 create mode 100644 arch/riscv/kernel/pi/fdt_early.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 4c07b9189c86..6a606d5b74c6 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -719,6 +719,25 @@ config RELOCATABLE
 
           If unsure, say N.
 
+config RANDOMIZE_BASE
+        bool "Randomize the address of the kernel image"
+        select RELOCATABLE
+        depends on MMU && 64BIT && !XIP_KERNEL
+        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 b55ba20903ec..5488ecc337b6 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -106,6 +106,7 @@ 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 */
@@ -185,6 +186,8 @@ 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 7b593d44c712..07915dc9279e 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 70fb31960b63..ff926531236e 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1012,11 +1012,45 @@ 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
-- 
2.39.2

[PATCH v6 2/5] riscv: Dump out kernel offset information on panic

[Alexandre Ghiti]

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 971fe776e2f8..0fb5a26ca4cc 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -21,6 +21,7 @@
 #include <linux/smp.h>
 #include <linux/efi.h>
 #include <linux/crash_dump.h>
+#include <linux/panic_notifier.h>
 
 #include <asm/acpi.h>
 #include <asm/alternative.h>
@@ -341,3 +342,27 @@ 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);
-- 
2.39.2

[PATCH v6 3/5] arm64: libstub: Move KASLR handling functions to kaslr.c

[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>
---
 arch/arm64/include/asm/efi.h              |   2 +
 drivers/firmware/efi/libstub/Makefile     |   2 +-
 drivers/firmware/efi/libstub/arm64-stub.c | 117 ++--------------
 drivers/firmware/efi/libstub/efistub.h    |   8 ++
 drivers/firmware/efi/libstub/kaslr.c      | 159 ++++++++++++++++++++++
 5 files changed, 183 insertions(+), 105 deletions(-)
 create mode 100644 drivers/firmware/efi/libstub/kaslr.c

diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index 4cf2cb053bc8..46273ee89445 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/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 */
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 16d64a34d1e1..11aba8a041ec 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/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
diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
index 770b8ecb7398..452b7ccd330e 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");
@@ -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);
-		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);
+	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;
 }
@@ -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);
+}
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 6aa38a1bf126..b1a1037567ba 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/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);
diff --git a/drivers/firmware/efi/libstub/kaslr.c b/drivers/firmware/efi/libstub/kaslr.c
new file mode 100644
index 000000000000..be0c8ab0982a
--- /dev/null
+++ b/drivers/firmware/efi/libstub/kaslr.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helper functions used by the EFI stub on multiple
+ * architectures to deal with physical address space randomization.
+ */
+#include <linux/efi.h>
+
+#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;
+}
-- 
2.39.2

[PATCH v6 4/5] libstub: Fix compilation warning for rv32

[Alexandre Ghiti]

Fix the following warning which appears when compiled for rv32 by using
unsigned long type instead of u64.

../drivers/firmware/efi/libstub/efi-stub-helper.c: In function 'efi_kaslr_relocate_kernel':
../drivers/firmware/efi/libstub/efi-stub-helper.c:846:28: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
  846 |                            (u64)_end < EFI_ALLOC_LIMIT) {

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
---
 drivers/firmware/efi/libstub/kaslr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/kaslr.c b/drivers/firmware/efi/libstub/kaslr.c
index be0c8ab0982a..afb857329799 100644
--- a/drivers/firmware/efi/libstub/kaslr.c
+++ b/drivers/firmware/efi/libstub/kaslr.c
@@ -130,7 +130,7 @@ efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
 		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) {
+			   (unsigned long)_end < EFI_ALLOC_LIMIT) {
 			/*
 			 * Just execute from wherever we were loaded by the
 			 * UEFI PE/COFF loader if the placement is suitable.
-- 
2.39.2

[PATCH v6 5/5] riscv: libstub: Implement KASLR by using generic functions

[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>
---
 arch/riscv/include/asm/efi.h              |  2 ++
 arch/riscv/kernel/image-vars.h            |  1 +
 drivers/firmware/efi/libstub/Makefile     |  2 +-
 drivers/firmware/efi/libstub/riscv-stub.c | 33 +++++++++++------------
 4 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/arch/riscv/include/asm/efi.h b/arch/riscv/include/asm/efi.h
index 29e9a0d84b16..00b24ba55035 100644
--- a/arch/riscv/include/asm/efi.h
+++ b/arch/riscv/include/asm/efi.h
@@ -51,4 +51,6 @@ void efi_virtmap_unload(void);
 
 unsigned long stext_offset(void);
 
+void efi_icache_sync(unsigned long start, unsigned long end);
+
 #endif /* _ASM_EFI_H */
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/Makefile b/drivers/firmware/efi/libstub/Makefile
index 11aba8a041ec..dc90a31b189f 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -88,7 +88,7 @@ lib-$(CONFIG_EFI_GENERIC_STUB)	+= efi-stub.o string.o intrinsics.o systable.o \
 lib-$(CONFIG_ARM)		+= arm32-stub.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_RISCV)		+= kaslr.o riscv.o riscv-stub.o
 lib-$(CONFIG_LOONGARCH)		+= loongarch.o loongarch-stub.o
 
 CFLAGS_arm32-stub.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
diff --git a/drivers/firmware/efi/libstub/riscv-stub.c b/drivers/firmware/efi/libstub/riscv-stub.c
index 145c9f0ba217..c96d6dcee86c 100644
--- a/drivers/firmware/efi/libstub/riscv-stub.c
+++ b/drivers/firmware/efi/libstub/riscv-stub.c
@@ -30,32 +30,29 @@ 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;
 }
+
+void efi_icache_sync(unsigned long start, unsigned long end)
+{
+	asm volatile ("fence.i" ::: "memory");
+}
-- 
2.39.2

Re: [PATCH v6 3/5] arm64: libstub: Move KASLR handling functions to kaslr.c

[Ard Biesheuvel]

On Sat, 22 Jul 2023 at 14:42, Alexandre Ghiti <alexghiti@rivosinc.com> 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 <alexghiti@rivosinc.com>

This looks fine to me.

I can stick this on a stable branch in the EFI tree, but I don't have
anything queued up for the next window anyway, so you might as well
just take it directly.

Acked-by: Ard Biesheuvel <ardb@kernel.org>

> ---
>  arch/arm64/include/asm/efi.h              |   2 +
>  drivers/firmware/efi/libstub/Makefile     |   2 +-
>  drivers/firmware/efi/libstub/arm64-stub.c | 117 ++--------------
>  drivers/firmware/efi/libstub/efistub.h    |   8 ++
>  drivers/firmware/efi/libstub/kaslr.c      | 159 ++++++++++++++++++++++
>  5 files changed, 183 insertions(+), 105 deletions(-)
>  create mode 100644 drivers/firmware/efi/libstub/kaslr.c
>
> diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
> index 4cf2cb053bc8..46273ee89445 100644
> --- a/arch/arm64/include/asm/efi.h
> +++ b/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 */
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 16d64a34d1e1..11aba8a041ec 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/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
> diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
> index 770b8ecb7398..452b7ccd330e 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");
> @@ -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);
> -               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);
> +       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;
>  }
> @@ -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);
> +}
> diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
> index 6aa38a1bf126..b1a1037567ba 100644
> --- a/drivers/firmware/efi/libstub/efistub.h
> +++ b/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);
> diff --git a/drivers/firmware/efi/libstub/kaslr.c b/drivers/firmware/efi/libstub/kaslr.c
> new file mode 100644
> index 000000000000..be0c8ab0982a
> --- /dev/null
> +++ b/drivers/firmware/efi/libstub/kaslr.c
> @@ -0,0 +1,159 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Helper functions used by the EFI stub on multiple
> + * architectures to deal with physical address space randomization.
> + */
> +#include <linux/efi.h>
> +
> +#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;
> +}
> --
> 2.39.2
>

Re: [PATCH v6 2/5] riscv: Dump out kernel offset information on panic

[Conor Dooley]

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Hey Alex,

On Sat, Jul 22, 2023 at 02:38:47PM +0200, Alexandre Ghiti wrote:
> Dump out the KASLR virtual kernel offset when panic to help debug kernel.
> 
> Signed-off-by: Zong Li <zong.li@sifive.com>

Either you're missing a Co-developed-by: or the author of this patch is
incorrect.

> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>

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Re: [PATCH v6 0/5] riscv: Introduce KASLR

[Conor Dooley]

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Hey Alex,

On Sat, Jul 22, 2023 at 02:38:45PM +0200, Alexandre Ghiti wrote:
> 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.

I gave this all a go today, it seems to do what it it says on the tin,
and crashing my kernel does dump out an offset etc.

Tested-by: Conor Dooley <conor.dooley@microchip.com>

I'll hopefully get some time later in the week to go through the code.

Cheers,
Conor.


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Re: [PATCH v6 2/5] riscv: Dump out kernel offset information on panic

[Alexandre Ghiti]

Hi Conor,

On Mon, Jul 24, 2023 at 4:20 PM Conor Dooley <conor.dooley@microchip.com> wrote:
>
> Hey Alex,
>
> On Sat, Jul 22, 2023 at 02:38:47PM +0200, Alexandre Ghiti wrote:
> > Dump out the KASLR virtual kernel offset when panic to help debug kernel.
> >
> > Signed-off-by: Zong Li <zong.li@sifive.com>
>
> Either you're missing a Co-developed-by: or the author of this patch is
> incorrect.

Ok, I thought it would work this way, Zong first did something similar
a few years ago, so we need his name here. @Palmer Dabbelt if no other
changes are needed, do you mind replacing the SoB with a
Co-developed-by?

Thanks,

Alex

>
> > Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Re: [PATCH v6 0/5] riscv: Introduce KASLR

[Alexandre Ghiti]

On Mon, Jul 24, 2023 at 4:32 PM Conor Dooley <conor.dooley@microchip.com> wrote:
>
> Hey Alex,
>
> On Sat, Jul 22, 2023 at 02:38:45PM +0200, Alexandre Ghiti wrote:
> > 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.
>
> I gave this all a go today, it seems to do what it it says on the tin,
> and crashing my kernel does dump out an offset etc.
>
> Tested-by: Conor Dooley <conor.dooley@microchip.com>

Great, thanks for testing!

>
> I'll hopefully get some time later in the week to go through the code.

I will be on holiday in 3 weeks, you have some time, no worries :)

Thanks again,

Alex

>
> Cheers,
> Conor.
>

Re: [PATCH v6 2/5] riscv: Dump out kernel offset information on panic

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 806 bytes --]

On Tue, Jul 25, 2023 at 09:05:37AM +0200, Alexandre Ghiti wrote:
> Hi Conor,
> 
> On Mon, Jul 24, 2023 at 4:20 PM Conor Dooley <conor.dooley@microchip.com> wrote:
> >
> > Hey Alex,
> >
> > On Sat, Jul 22, 2023 at 02:38:47PM +0200, Alexandre Ghiti wrote:
> > > Dump out the KASLR virtual kernel offset when panic to help debug kernel.
> > >
> > > Signed-off-by: Zong Li <zong.li@sifive.com>
> >
> > Either you're missing a Co-developed-by: or the author of this patch is
> > incorrect.
> 
> Ok, I thought it would work this way, Zong first did something similar
> a few years ago, so we need his name here. @Palmer Dabbelt if no other
> changes are needed, do you mind replacing the SoB with a
> Co-developed-by?

You can't have a Co-developed-by without a SoB, so both are needed :)

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Re: [PATCH v6 0/5] riscv: Introduce KASLR

[Song Shuai]

Hi, Alex:

在 2023/7/22 20:38, Alexandre Ghiti 写道:
> 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.
> 

I have gone through the code and tested this series with RiscVVirt edk2.
All seems good to me, you can add :

Tested-by: Song Shuai <songshuaishuai@tinylab.org>

And a few questions about patch 2 ("riscv: Dump out kernel offset 
information on panic"):

1. The dump_kernel_offset() function would output "Kernel Offset: 0x0 
from 0xffffffff80000000" when booting with "nokaslr" option.

How about disabling the registration of "kernel_offset_notifier" with 
"nokaslr" option?

2. Inspired by patch 2, I added the Crash KASLR support based on this 
series [1].
So is it necessary to keep this patch if we have Crash KASLR support?


[1]: 
https://lore.kernel.org/linux-riscv/20230815104800.705753-1-songshuaishuai@tinylab.org/T/#u

> base-commit-tag: v6.5-rc1
> 
> Changes in v6:
>    * Fix reintroduced build failures by compiling kaslr.c only for arm64
>      and riscv, as suggested by Ard
> 
> Changes in v5:
>    * Renamed efi-stub-kaslr.c into kaslr.c and fix commit log of patch 3,
>      as suggested by Ard
>    * Removed stubs since the kaslr functions were moved to their own file
>      (and then does not trigger any build failure for architectures that do
>      not call those functions since they are in their own compilation unit)
> 
> Changes in v4:
>    * Fix efi_get_kimg macro that returned nothing
>    * Moved new kaslr functions into their own files to avoid zboot link
>      failures, as suggested by Ard
> 
> Changes in v3:
>    * Rebase on top of 6.4-rc2
>    * Make RANDOMIZE_BASE depend on 64bit
>    * Fix efi_icache_sync and efi_get_kimg_min_align which were undefined
>      in x86 (and certainly other archs)
>    * Add patch 4 to fix warning on rv32
> 
> 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 (5):
>    riscv: Introduce virtual kernel mapping KASLR
>    riscv: Dump out kernel offset information on panic
>    arm64: libstub: Move KASLR handling functions to kaslr.c
>    libstub: Fix compilation warning for rv32
>    riscv: libstub: Implement KASLR by using generic functions
> 
>   arch/arm64/include/asm/efi.h              |   2 +
>   arch/riscv/Kconfig                        |  19 +++
>   arch/riscv/include/asm/efi.h              |   2 +
>   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/Makefile     |   4 +-
>   drivers/firmware/efi/libstub/arm64-stub.c | 117 ++--------------
>   drivers/firmware/efi/libstub/efistub.h    |   8 ++
>   drivers/firmware/efi/libstub/kaslr.c      | 159 ++++++++++++++++++++++
>   drivers/firmware/efi/libstub/riscv-stub.c |  33 ++---
>   15 files changed, 328 insertions(+), 126 deletions(-)
>   create mode 100644 arch/riscv/kernel/pi/fdt_early.c
>   create mode 100644 drivers/firmware/efi/libstub/kaslr.c
> 

-- 
Thanks
Song Shuai

Re: [PATCH v6 0/5] riscv: Introduce KASLR

[Alexandre Ghiti]

Hi Song,

On Tue, Aug 15, 2023 at 1:24 PM Song Shuai <songshuaishuai@tinylab.org> wrote:
>
>
> Hi, Alex:
>
> 在 2023/7/22 20:38, Alexandre Ghiti 写道:
> > 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.
> >
>
> I have gone through the code and tested this series with RiscVVirt edk2.
> All seems good to me, you can add :
>
> Tested-by: Song Shuai <songshuaishuai@tinylab.org>
>
> And a few questions about patch 2 ("riscv: Dump out kernel offset
> information on panic"):
>
> 1. The dump_kernel_offset() function would output "Kernel Offset: 0x0
> from 0xffffffff80000000" when booting with "nokaslr" option.
>
> How about disabling the registration of "kernel_offset_notifier" with
> "nokaslr" option?

I'd rather keep it as it shows the "nokaslr" flag was taken into account.

>
> 2. Inspired by patch 2, I added the Crash KASLR support based on this
> series [1].
> So is it necessary to keep this patch if we have Crash KASLR support?

I don't understand your question here

>
>
> [1]:
> https://lore.kernel.org/linux-riscv/20230815104800.705753-1-songshuaishuai@tinylab.org/T/#u
>
> > base-commit-tag: v6.5-rc1
> >
> > Changes in v6:
> >    * Fix reintroduced build failures by compiling kaslr.c only for arm64
> >      and riscv, as suggested by Ard
> >
> > Changes in v5:
> >    * Renamed efi-stub-kaslr.c into kaslr.c and fix commit log of patch 3,
> >      as suggested by Ard
> >    * Removed stubs since the kaslr functions were moved to their own file
> >      (and then does not trigger any build failure for architectures that do
> >      not call those functions since they are in their own compilation unit)
> >
> > Changes in v4:
> >    * Fix efi_get_kimg macro that returned nothing
> >    * Moved new kaslr functions into their own files to avoid zboot link
> >      failures, as suggested by Ard
> >
> > Changes in v3:
> >    * Rebase on top of 6.4-rc2
> >    * Make RANDOMIZE_BASE depend on 64bit
> >    * Fix efi_icache_sync and efi_get_kimg_min_align which were undefined
> >      in x86 (and certainly other archs)
> >    * Add patch 4 to fix warning on rv32
> >
> > 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 (5):
> >    riscv: Introduce virtual kernel mapping KASLR
> >    riscv: Dump out kernel offset information on panic
> >    arm64: libstub: Move KASLR handling functions to kaslr.c
> >    libstub: Fix compilation warning for rv32
> >    riscv: libstub: Implement KASLR by using generic functions
> >
> >   arch/arm64/include/asm/efi.h              |   2 +
> >   arch/riscv/Kconfig                        |  19 +++
> >   arch/riscv/include/asm/efi.h              |   2 +
> >   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/Makefile     |   4 +-
> >   drivers/firmware/efi/libstub/arm64-stub.c | 117 ++--------------
> >   drivers/firmware/efi/libstub/efistub.h    |   8 ++
> >   drivers/firmware/efi/libstub/kaslr.c      | 159 ++++++++++++++++++++++
> >   drivers/firmware/efi/libstub/riscv-stub.c |  33 ++---
> >   15 files changed, 328 insertions(+), 126 deletions(-)
> >   create mode 100644 arch/riscv/kernel/pi/fdt_early.c
> >   create mode 100644 drivers/firmware/efi/libstub/kaslr.c
> >
>
> --
> Thanks
> Song Shuai

Thanks for testing this and your suggestions!

Alex

Re: [PATCH v6 0/5] riscv: Introduce KASLR

[Song Shuai]

在 2023/8/17 21:10, Alexandre Ghiti 写道:
> Hi Song,
> 
> On Tue, Aug 15, 2023 at 1:24 PM Song Shuai <songshuaishuai@tinylab.org> wrote:
>>
>>
>> Hi, Alex:
>>
>> 在 2023/7/22 20:38, Alexandre Ghiti 写道:
>>> 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.
>>>
>>
>> I have gone through the code and tested this series with RiscVVirt edk2.
>> All seems good to me, you can add :
>>
>> Tested-by: Song Shuai <songshuaishuai@tinylab.org>
>>
>> And a few questions about patch 2 ("riscv: Dump out kernel offset
>> information on panic"):
>>
>> 1. The dump_kernel_offset() function would output "Kernel Offset: 0x0
>> from 0xffffffff80000000" when booting with "nokaslr" option.
>>
>> How about disabling the registration of "kernel_offset_notifier" with
>> "nokaslr" option?
> 
> I'd rather keep it as it shows the "nokaslr" flag was taken into account.
> 
>>
>> 2. Inspired by patch 2, I added the Crash KASLR support based on this
>> series [1].
>> So is it necessary to keep this patch if we have Crash KASLR support?
> 
> I don't understand your question here

Crash can automatically calculate virt_offset by comparing the vmlinux 
and vmcore. If this patch is just intended to assist Crash in setting 
the "--kaslr offset," it might be deleted; if not just keep it. 	

> 
>>
>>
>> [1]:
>> https://lore.kernel.org/linux-riscv/20230815104800.705753-1-songshuaishuai@tinylab.org/T/#u
>>
>>> base-commit-tag: v6.5-rc1
>>>
>>> Changes in v6:
>>>     * Fix reintroduced build failures by compiling kaslr.c only for arm64
>>>       and riscv, as suggested by Ard
>>>
>>> Changes in v5:
>>>     * Renamed efi-stub-kaslr.c into kaslr.c and fix commit log of patch 3,
>>>       as suggested by Ard
>>>     * Removed stubs since the kaslr functions were moved to their own file
>>>       (and then does not trigger any build failure for architectures that do
>>>       not call those functions since they are in their own compilation unit)
>>>
>>> Changes in v4:
>>>     * Fix efi_get_kimg macro that returned nothing
>>>     * Moved new kaslr functions into their own files to avoid zboot link
>>>       failures, as suggested by Ard
>>>
>>> Changes in v3:
>>>     * Rebase on top of 6.4-rc2
>>>     * Make RANDOMIZE_BASE depend on 64bit
>>>     * Fix efi_icache_sync and efi_get_kimg_min_align which were undefined
>>>       in x86 (and certainly other archs)
>>>     * Add patch 4 to fix warning on rv32
>>>
>>> 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 (5):
>>>     riscv: Introduce virtual kernel mapping KASLR
>>>     riscv: Dump out kernel offset information on panic
>>>     arm64: libstub: Move KASLR handling functions to kaslr.c
>>>     libstub: Fix compilation warning for rv32
>>>     riscv: libstub: Implement KASLR by using generic functions
>>>
>>>    arch/arm64/include/asm/efi.h              |   2 +
>>>    arch/riscv/Kconfig                        |  19 +++
>>>    arch/riscv/include/asm/efi.h              |   2 +
>>>    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/Makefile     |   4 +-
>>>    drivers/firmware/efi/libstub/arm64-stub.c | 117 ++--------------
>>>    drivers/firmware/efi/libstub/efistub.h    |   8 ++
>>>    drivers/firmware/efi/libstub/kaslr.c      | 159 ++++++++++++++++++++++
>>>    drivers/firmware/efi/libstub/riscv-stub.c |  33 ++---
>>>    15 files changed, 328 insertions(+), 126 deletions(-)
>>>    create mode 100644 arch/riscv/kernel/pi/fdt_early.c
>>>    create mode 100644 drivers/firmware/efi/libstub/kaslr.c
>>>
>>
>> --
>> Thanks
>> Song Shuai
> 
> Thanks for testing this and your suggestions!
> 
> Alex
> 

-- 
Thanks
Song Shuai

Re: [PATCH v6 0/5] riscv: Introduce KASLR

[Sami Tolvanen]

Hi Alexandre,

On Sat, Jul 22, 2023 at 5:39 AM Alexandre Ghiti <alexghiti@rivosinc.com> wrote:
>
> 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.
>
> base-commit-tag: v6.5-rc1

Thanks for continuing to work on this!

I reviewed the patches and the code looks correct to me. I also
applied the series on top of v6.5 and after patching qemu to provide a
kaslr-seed, I confirmed that the virtual offset appears to be random
and is printed out when I panic the machine:

# echo PANIC > /sys/kernel/debug/provoke-crash/DIRECT
[   17.510012] lkdtm: Performing direct entry PANIC
[   17.510411] Kernel panic - not syncing: dumptest
[...]
[   17.518693] Kernel Offset: 0x32c00000 from 0xffffffff80000000

For the series:
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>

I didn't test the EFI bits, but the rest of the series:
Tested-by: Sami Tolvanen <samitolvanen@google.com>

Conor, in another reply you mentioned you're planning on reviewing the
patches as well. Did you have any feedback or concerns?

Sami

Re: [PATCH v6 0/5] riscv: Introduce KASLR

[Conor Dooley]

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On Wed, Aug 30, 2023 at 02:30:31PM -0700, Sami Tolvanen wrote:

> Conor, in another reply you mentioned you're planning on reviewing the
> patches as well. Did you have any feedback or concerns?

I didn't even look at it again. Been really short on time & I guess just
deleted it from my queue when I noticed I'd tested it before.

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Re: [PATCH v6 0/5] riscv: Introduce KASLR

[Charlie Jenkins]

On Wed, Aug 30, 2023 at 02:30:31PM -0700, Sami Tolvanen wrote:
> Hi Alexandre,
> 
> On Sat, Jul 22, 2023 at 5:39 AM Alexandre Ghiti <alexghiti@rivosinc.com> wrote:
> >
> > 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.
> >
> > base-commit-tag: v6.5-rc1
> 
> Thanks for continuing to work on this!
> 
> I reviewed the patches and the code looks correct to me. I also
> applied the series on top of v6.5 and after patching qemu to provide a
> kaslr-seed, I confirmed that the virtual offset appears to be random
> and is printed out when I panic the machine:
> 
> # echo PANIC > /sys/kernel/debug/provoke-crash/DIRECT
> [   17.510012] lkdtm: Performing direct entry PANIC
> [   17.510411] Kernel panic - not syncing: dumptest
> [...]
> [   17.518693] Kernel Offset: 0x32c00000 from 0xffffffff80000000
> 
> For the series:
> Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
> 
> I didn't test the EFI bits, but the rest of the series:
> Tested-by: Sami Tolvanen <samitolvanen@google.com>
> 
> Conor, in another reply you mentioned you're planning on reviewing the
> patches as well. Did you have any feedback or concerns?
> 
> Sami
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

In addition to testing this patch in QEMU by patching like Sami did, I
also booted this with a Debian kernel and tested it with EFI. I was able
to use lkdtm as Sami did to force a panic and see the kernel offset
changing in both scenarios.

Tested-by: Charlie Jenkins <charlie@rivosinc.com>

- Charlie