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[2.7.42.160]) by smtp.gmail.com with ESMTPSA id e12-20020a05600c218c00b003de8a1b06c0sm2386842wme.7.2023.02.15.06.52.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Feb 2023 06:52:16 -0800 (PST) From: Alexandre Ghiti To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Ard Biesheuvel , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org Cc: Alexandre Ghiti Subject: [PATCH 1/4] riscv: Introduce virtual kernel mapping KASLR Date: Wed, 15 Feb 2023 15:51:10 +0100 Message-Id: <20230215145113.465558-2-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20230215145113.465558-1-alexghiti@rivosinc.com> References: <20230215145113.465558-1-alexghiti@rivosinc.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Bj=C3=B6rn T=C3=B6pel Tested-by: Bj=C3=B6rn T=C3=B6pel --- 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 =20 If unsure, say N. =20 +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" =20 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) =20 -obj-y :=3D cmdline_early.pi.o string.pi.o ctype.pi.o lib-fdt.pi.o lib-fdt= _ro.pi.o +obj-y :=3D cmdline_early.pi.o fdt_early.pi.o string.pi.o ctype.pi.o lib-f= dt.pi.o lib-fdt_ro.pi.o extra-y :=3D $(patsubst %.pi.o,%.o,$(obj-y)) diff --git a/arch/riscv/kernel/pi/cmdline_early.c b/arch/riscv/kernel/pi/cm= dline_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) =20 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 =3D 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_ea= rly.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 +#include +#include + +u64 __init get_kaslr_seed(uintptr_t dtb_pa) +{ + int node, len; + fdt64_t *prop; + u64 ret; + + node =3D fdt_path_offset((void *)dtb_pa, "/chosen"); + if (node < 0) + return 0; + + prop =3D fdt_getprop_w((void *)dtb_pa, node, "kaslr-seed", &len); + if (!prop || len !=3D sizeof(u64)) + return 0; + + ret =3D fdt64_to_cpu(*prop); + *prop =3D 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 } =20 +#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; =20 - kernel_map.virt_addr =3D KERNEL_LINK_ADDR; +#ifdef CONFIG_RANDOMIZE_BASE + if (!__pi_set_nokaslr_from_cmdline(dtb_pa)) { + u64 kaslr_seed =3D __pi_get_kaslr_seed(dtb_pa); + u32 kernel_size =3D (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 =3D (PUD_SIZE - kernel_size) / PMD_SIZE; + + kernel_map.virt_offset =3D (kaslr_seed % nr_pos) * PMD_SIZE; + } +#endif + + kernel_map.virt_addr =3D KERNEL_LINK_ADDR + kernel_map.virt_offset; kernel_map.page_offset =3D _AC(CONFIG_PAGE_OFFSET, UL); =20 #ifdef CONFIG_XIP_KERNEL --=20 2.37.2 From nobody Thu Sep 11 22:33:09 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F823C636D4 for ; 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[2.7.42.160]) by smtp.gmail.com with ESMTPSA id u13-20020a5d514d000000b002c3f50228afsm15411785wrt.3.2023.02.15.06.53.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Feb 2023 06:53:17 -0800 (PST) From: Alexandre Ghiti To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Ard Biesheuvel , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org Cc: Alexandre Ghiti , Zong Li Subject: [PATCH 2/4] riscv: Dump out kernel offset information on panic Date: Wed, 15 Feb 2023 15:51:11 +0100 Message-Id: <20230215145113.465558-3-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20230215145113.465558-1-alexghiti@rivosinc.com> References: <20230215145113.465558-1-alexghiti@rivosinc.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Dump out the KASLR virtual kernel offset when panic to help debug kernel. Signed-off-by: Zong Li Signed-off-by: Alexandre Ghiti Reviewed-by: Bj=C3=B6rn T=C3=B6pel Tested-by: Bj=C3=B6rn T=C3=B6pel --- 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 #include #include +#include =20 #include #include @@ -330,3 +331,27 @@ void free_initmem(void) =20 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 =3D { + .notifier_call =3D 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); --=20 2.37.2 From nobody Thu Sep 11 22:33:09 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE616C636CC for ; Wed, 15 Feb 2023 14:54:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229926AbjBOOyX (ORCPT ); Wed, 15 Feb 2023 09:54:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50324 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229608AbjBOOyV (ORCPT ); Wed, 15 Feb 2023 09:54:21 -0500 Received: from mail-wm1-x32b.google.com (mail-wm1-x32b.google.com [IPv6:2a00:1450:4864:20::32b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0D51725E1D for ; Wed, 15 Feb 2023 06:54:20 -0800 (PST) Received: by mail-wm1-x32b.google.com with SMTP id f47-20020a05600c492f00b003dc584a7b7eso1769555wmp.3 for ; Wed, 15 Feb 2023 06:54:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=o4BvO75ZXrS10LcJgsz5zZo07cuKH8B95qcklsNq3N4=; b=eJwhJ0KloQW4mUrbp/N3CD+WQpxcec1WXR77m6jHwd2ZBGUgvgl59M61JDT9YepATU GcEXqyFBrXjKS40imQJoOKr008H1gWwgRIDNGNNLxMJr6Be/ZBn8lMJjqGXSL5vBz1oc 4UxXpwDr5Aw3SHaLbU2+tEqHHkpSpIXrlyccNsgfJZj6JTRIgFX+oUH73RUl8pk754gt HUIm85UIWorCz5T435tLoiMQWdCWQJSK0vJtREOnuBnhF7B6plkQT56+vEtDlDoBWZaw zszx7g1tyrR10lOVOMhlWI8NNdUcTzF54Si7ByUYk+Ff+n5JtKXZ+nQ4q0DouiKsN1dB ju2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=o4BvO75ZXrS10LcJgsz5zZo07cuKH8B95qcklsNq3N4=; b=ZwxT7twXUsqjw/bu6kk8pPLtR6SCwSvryV7HPDTbr1SbghtZda+YfJ5hx3Dn/RyJIo CxujXSq/57VxZRHFd1gulRlVRY1sYdXmV5eN6rBNQVjfZ6zgTGyv/iewXRePW7Vn6PAI tuTRy9K1VIgZjUdcFrEfCxjWRGM7gvzPIcItB/K8e0rnVUtfemWm4nkRGHKydFmc9BAk dTs0eASr9ffXhz9b0LZ0Sg2qDvGYSvgfXJ1CJiDQi8WK8lHUoMF8CW9R9WHhCu4999+R 8Y//AszDuxOzTXoRgqO5xTz0Hr7VHIalmERlZXeQFYC8+PkTPPfFH9U+cX5QbMQdHLk6 QOXw== X-Gm-Message-State: AO0yUKW4l322LF0p+ZTXrASuVEj7qFElAA51hSHhEYziEtVaX4Q66NM7 B4Oze2+/fXdMYuEPjThj1XVrVw== X-Google-Smtp-Source: AK7set+z1EuF/qTEsW13BueUE8joVeOlGJPKhW0X4Yacc2kbVno1G0GuXcjMOyleMwbiyg2+WUkCcg== X-Received: by 2002:a05:600c:5128:b0:3de:e8c5:d833 with SMTP id o40-20020a05600c512800b003dee8c5d833mr2690072wms.22.1676472858522; Wed, 15 Feb 2023 06:54:18 -0800 (PST) Received: from alex-rivos.home (lfbn-lyo-1-450-160.w2-7.abo.wanadoo.fr. [2.7.42.160]) by smtp.gmail.com with ESMTPSA id i29-20020a1c541d000000b003dc4fd6e624sm2358568wmb.19.2023.02.15.06.54.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Feb 2023 06:54:18 -0800 (PST) From: Alexandre Ghiti To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Ard Biesheuvel , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org Cc: Alexandre Ghiti Subject: [PATCH 3/4] arm64: libstub: Move KASLR handling functions to efi-stub-helper.c Date: Wed, 15 Feb 2023 15:51:12 +0100 Message-Id: <20230215145113.465558-4-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20230215145113.465558-1-alexghiti@rivosinc.com> References: <20230215145113.465558-1-alexghiti@rivosinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This prepares for riscv to use the same functions to handle the p=C4=A5ysic= al kernel move when KASLR is enabled. Signed-off-by: Alexandre Ghiti Reviewed-by: Bj=C3=B6rn T=C3=B6pel Tested-by: Bj=C3=B6rn T=C3=B6pel --- 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/e= fi/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 @@ =20 #include "efistub.h" =20 -/* - * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., f= ail - * to provide space, and fail to zero it). Check for this condition by dou= ble - * checking that the first and the last byte of the image are covered by t= he - * 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 =3D false; - int map_offset; - - status =3D efi_get_memory_map(&map, false); - if (status !=3D EFI_SUCCESS) - return false; - - for (map_offset =3D 0; map_offset < map->map_size; map_offset +=3D map->d= esc_size) { - efi_memory_desc_t *md =3D (void *)map->map + map_offset; - u64 end =3D 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 >=3D md->phys_addr && base < end) { - ret =3D (base + size) <=3D 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_ad= dr, { efi_status_t status; unsigned long kernel_size, kernel_memsize =3D 0; - u32 phys_seed =3D 0; - u64 min_kimg_align =3D efi_get_kimg_min_align(); - - if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { - efi_guid_t li_fixed_proto =3D 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) =3D=3D EFI_SUCCESS) { - efi_info("Image placement fixed by loader\n"); - } else { - status =3D efi_get_random_bytes(sizeof(phys_seed), - (u8 *)&phys_seed); - if (status =3D=3D EFI_NOT_FOUND) { - efi_info("EFI_RNG_PROTOCOL unavailable\n"); - efi_nokaslr =3D true; - } else if (status !=3D EFI_SUCCESS) { - efi_err("efi_get_random_bytes() failed (0x%lx)\n", - status); - efi_nokaslr =3D true; - } - } - } =20 if (image->image_base !=3D _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_a= ddr, kernel_size =3D _edata - _text; kernel_memsize =3D kernel_size + (_end - _edata); *reserve_size =3D kernel_memsize; + *image_addr =3D (unsigned long)_text; =20 - if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed !=3D 0) { - /* - * If KASLR is enabled, and we have some randomness available, - * locate the kernel at a randomized offset in physical memory. - */ - status =3D efi_random_alloc(*reserve_size, min_kimg_align, - reserve_addr, phys_seed, - EFI_LOADER_CODE); - if (status !=3D EFI_SUCCESS) - efi_warn("efi_random_alloc() failed: 0x%lx\n", status); - } else { - status =3D EFI_OUT_OF_RESOURCES; - } - - if (status !=3D 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 =3D (u64)_text; - *reserve_size =3D 0; - goto clean_image_to_poc; - } - - status =3D efi_allocate_pages_aligned(*reserve_size, reserve_addr, - ULONG_MAX, min_kimg_align, - EFI_LOADER_CODE); - - if (status !=3D EFI_SUCCESS) { - efi_err("Failed to relocate kernel\n"); - *reserve_size =3D 0; - return status; - } - } - - *image_addr =3D *reserve_addr; - memcpy((void *)*image_addr, _text, kernel_size); + status =3D efi_kaslr_relocate_kernel(image_addr, + reserve_addr, reserve_size, + kernel_size, kernel_memsize, + efi_kaslr_get_phys_seed(image_handle)); + if (status !=3D EFI_SUCCESS) + return status; =20 -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/firmw= are/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) =20 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 =3D 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) =3D=3D EFI_SUCCESS) { + efi_info("Image placement fixed by loader\n"); + } else { + status =3D efi_get_random_bytes(sizeof(phys_seed), + (u8 *)&phys_seed); + if (status =3D=3D EFI_SUCCESS) + return phys_seed; + else if (status =3D=3D EFI_NOT_FOUND) { + efi_info("EFI_RNG_PROTOCOL unavailable\n"); + efi_nokaslr =3D true; + } else if (status !=3D EFI_SUCCESS) { + efi_err("efi_get_random_bytes() failed (0x%lx)\n", + status); + efi_nokaslr =3D true; + } + } + + return 0; +} + +/* + * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., f= ail + * to provide space, and fail to zero it). Check for this condition by dou= ble + * checking that the first and the last byte of the image are covered by t= he + * 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 =3D false; + int map_offset; + + status =3D efi_get_memory_map(&map, false); + if (status !=3D EFI_SUCCESS) + return false; + + for (map_offset =3D 0; map_offset < map->map_size; map_offset +=3D map->d= esc_size) { + efi_memory_desc_t *md =3D (void *)map->map + map_offset; + u64 end =3D 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 >=3D md->phys_addr && base < end) { + ret =3D (base + size) <=3D end; + break; + } + } + + efi_bs_call(free_pool, map); + + return ret; +} + +/** + * efi_kaslr_relocate_kernel() - Relocate the kernel (random if KASLR enab= led) + * @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 =3D efi_get_kimg_min_align(); + + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed !=3D 0) { + /* + * If KASLR is enabled, and we have some randomness available, + * locate the kernel at a randomized offset in physical memory. + */ + status =3D efi_random_alloc(*reserve_size, min_kimg_align, + reserve_addr, phys_seed, + EFI_LOADER_CODE); + if (status !=3D EFI_SUCCESS) + efi_warn("efi_random_alloc() failed: 0x%lx\n", status); + } else { + status =3D EFI_OUT_OF_RESOURCES; + } + + if (status !=3D 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 =3D 0; + return EFI_SUCCESS; + } + + status =3D efi_allocate_pages_aligned(*reserve_size, reserve_addr, + ULONG_MAX, min_kimg_align, + EFI_LOADER_CODE); + + if (status !=3D EFI_SUCCESS) { + efi_err("Failed to relocate kernel\n"); + *reserve_size =3D 0; + return status; + } + } + + memcpy((void *)*reserve_addr, (void *)*image_addr, kernel_size); + *image_addr =3D *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 { =20 const u8 *__efi_get_smbios_string(u8 type, int offset, int recsize); =20 +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 --=20 2.37.2 From nobody Thu Sep 11 22:33:09 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DA94AC636D4 for ; Wed, 15 Feb 2023 14:56:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229595AbjBOO4C (ORCPT ); Wed, 15 Feb 2023 09:56:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229920AbjBOOzx (ORCPT ); Wed, 15 Feb 2023 09:55:53 -0500 Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 075E33B0D0 for ; Wed, 15 Feb 2023 06:55:22 -0800 (PST) Received: by mail-wr1-x42b.google.com with SMTP id a2so19443096wrd.6 for ; 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Wed, 15 Feb 2023 06:55:19 -0800 (PST) Received: from alex-rivos.home (lfbn-lyo-1-450-160.w2-7.abo.wanadoo.fr. [2.7.42.160]) by smtp.gmail.com with ESMTPSA id v17-20020a05600c445100b003dc1a525f22sm2637468wmn.25.2023.02.15.06.55.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Feb 2023 06:55:19 -0800 (PST) From: Alexandre Ghiti To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Ard Biesheuvel , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org Cc: Alexandre Ghiti Subject: [PATCH 4/4] riscv: libstub: Implement KASLR by using generic functions Date: Wed, 15 Feb 2023 15:51:13 +0100 Message-Id: <20230215145113.465558-5-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20230215145113.465558-1-alexghiti@rivosinc.com> References: <20230215145113.465558-1-alexghiti@rivosinc.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Bj=C3=B6rn T=C3=B6pel Tested-by: Bj=C3=B6rn T=C3=B6pel --- 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/e= fi/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_a= ddr, efi_loaded_image_t *image, efi_handle_t image_handle) { - unsigned long kernel_size =3D 0; - unsigned long preferred_addr; + unsigned long kernel_size, kernel_memsize =3D 0; efi_status_t status; =20 kernel_size =3D _edata - _start; + kernel_memsize =3D kernel_size + (_end - _edata); *image_addr =3D (unsigned long)_start; - *image_size =3D 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 =3D EFI_KIMG_PREFERRED_ADDRESS; - status =3D efi_relocate_kernel(image_addr, kernel_size, *image_size, - preferred_addr, efi_get_kimg_min_align(), - 0x0); + *image_size =3D kernel_memsize; + *reserve_size =3D *image_size; =20 + status =3D efi_kaslr_relocate_kernel(image_addr, + reserve_addr, reserve_size, + kernel_size, kernel_memsize, + efi_kaslr_get_phys_seed(image_handle)); if (status !=3D EFI_SUCCESS) { efi_err("Failed to relocate kernel\n"); *image_size =3D 0; } + return status; } --=20 2.37.2