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Message-ID: <b64914ba-6ff4-fc28-873d-8691f5293e91@ghiti.fr>
Date: Mon, 1 May 2023 10:11:39 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Palmer Dabbelt <palmer@...belt.com>, alexghiti@...osinc.com
Cc: Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
Ard Biesheuvel <ardb@...nel.org>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-efi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 3/4] arm64: libstub: Move KASLR handling functions to
efi-stub-helper.c
On 4/29/23 21:50, Palmer Dabbelt wrote:
> On Tue, 28 Mar 2023 22:29:25 PDT (-0700), alexghiti@...osinc.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@...osinc.com>
>> ---
>> drivers/firmware/efi/libstub/arm64-stub.c | 111 +------------
>
> This LGTM, but I'd prefer at least an Ack from either the Arm or EFI
> folks. I think that makes it too late for this merge window.
Note that I have a minor fix (RANDOMIZE_BASE should depend on 64BIT) and
kernel test robot reported a few warnings and errors:
ld: efi-stub-helper.c:undefined reference to `efi_icache_sync'
efi-stub-helper.c:undefined reference to `efi_get_kimg_min_align'
drivers/firmware/efi/libstub/efi-stub-helper.c:825:23: warning: implicit
declaration of function 'efi_get_kimg_min_align' is invalid in C99
I'll wait for feedbacks and send a v3.
Thanks,
Alex
>
>> .../firmware/efi/libstub/efi-stub-helper.c | 151 ++++++++++++++++++
>> drivers/firmware/efi/libstub/efistub.h | 8 +
>> 3 files changed, 167 insertions(+), 103 deletions(-)
>>
>> diff --git a/drivers/firmware/efi/libstub/arm64-stub.c
>> b/drivers/firmware/efi/libstub/arm64-stub.c
>> index d4a6b12a8741..b9e0d2cf09aa 100644
>> --- a/drivers/firmware/efi/libstub/arm64-stub.c
>> +++ b/drivers/firmware/efi/libstub/arm64-stub.c
>> @@ -14,42 +14,6 @@
>>
>> #include "efistub.h"
>>
>> -/*
>> - * Distro versions of GRUB may ignore the BSS allocation entirely
>> (i.e., fail
>> - * to provide space, and fail to zero it). Check for this condition
>> by double
>> - * checking that the first and the last byte of the image are
>> covered by the
>> - * same EFI memory map entry.
>> - */
>> -static bool check_image_region(u64 base, u64 size)
>> -{
>> - struct efi_boot_memmap *map;
>> - efi_status_t status;
>> - bool ret = false;
>> - int map_offset;
>> -
>> - status = efi_get_memory_map(&map, false);
>> - if (status != EFI_SUCCESS)
>> - return false;
>> -
>> - for (map_offset = 0; map_offset < map->map_size; map_offset +=
>> map->desc_size) {
>> - efi_memory_desc_t *md = (void *)map->map + map_offset;
>> - u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE;
>> -
>> - /*
>> - * Find the region that covers base, and return whether
>> - * it covers base+size bytes.
>> - */
>> - if (base >= md->phys_addr && base < end) {
>> - ret = (base + size) <= end;
>> - break;
>> - }
>> - }
>> -
>> - efi_bs_call(free_pool, map);
>> -
>> - return ret;
>> -}
>> -
>> efi_status_t handle_kernel_image(unsigned long *image_addr,
>> unsigned long *image_size,
>> unsigned long *reserve_addr,
>> @@ -59,31 +23,6 @@ efi_status_t handle_kernel_image(unsigned long
>> *image_addr,
>> {
>> efi_status_t status;
>> unsigned long kernel_size, kernel_codesize, kernel_memsize;
>> - u32 phys_seed = 0;
>> - u64 min_kimg_align = efi_get_kimg_min_align();
>> -
>> - if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
>> - efi_guid_t li_fixed_proto = LINUX_EFI_LOADED_IMAGE_FIXED_GUID;
>> - void *p;
>> -
>> - if (efi_nokaslr) {
>> - efi_info("KASLR disabled on kernel command line\n");
>> - } else if (efi_bs_call(handle_protocol, image_handle,
>> - &li_fixed_proto, &p) == EFI_SUCCESS) {
>> - efi_info("Image placement fixed by loader\n");
>> - } else {
>> - status = efi_get_random_bytes(sizeof(phys_seed),
>> - (u8 *)&phys_seed);
>> - if (status == EFI_NOT_FOUND) {
>> - efi_info("EFI_RNG_PROTOCOL unavailable\n");
>> - efi_nokaslr = true;
>> - } else if (status != EFI_SUCCESS) {
>> - efi_err("efi_get_random_bytes() failed (0x%lx)\n",
>> - status);
>> - efi_nokaslr = true;
>> - }
>> - }
>> - }
>>
>> if (image->image_base != _text)
>> efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has
>> bogus value\n");
>> @@ -96,49 +35,15 @@ efi_status_t handle_kernel_image(unsigned long
>> *image_addr,
>> kernel_codesize = __inittext_end - _text;
>> kernel_memsize = kernel_size + (_end - _edata);
>> *reserve_size = kernel_memsize;
>> + *image_addr = (unsigned long)_text;
>>
>> - if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
>> - /*
>> - * If KASLR is enabled, and we have some randomness available,
>> - * locate the kernel at a randomized offset in physical memory.
>> - */
>> - status = efi_random_alloc(*reserve_size, min_kimg_align,
>> - reserve_addr, phys_seed,
>> - EFI_LOADER_CODE);
>> - if (status != EFI_SUCCESS)
>> - efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
>> - } else {
>> - status = EFI_OUT_OF_RESOURCES;
>> - }
>> -
>> - if (status != EFI_SUCCESS) {
>> - if (!check_image_region((u64)_text, kernel_memsize)) {
>> - efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI
>> memory region\n");
>> - } else if (IS_ALIGNED((u64)_text, min_kimg_align) &&
>> - (u64)_end < EFI_ALLOC_LIMIT) {
>> - /*
>> - * Just execute from wherever we were loaded by the
>> - * UEFI PE/COFF loader if the placement is suitable.
>> - */
>> - *image_addr = (u64)_text;
>> - *reserve_size = 0;
>> - return EFI_SUCCESS;
>> - }
>> -
>> - status = efi_allocate_pages_aligned(*reserve_size,
>> reserve_addr,
>> - ULONG_MAX, min_kimg_align,
>> - EFI_LOADER_CODE);
>> -
>> - if (status != EFI_SUCCESS) {
>> - efi_err("Failed to relocate kernel\n");
>> - *reserve_size = 0;
>> - return status;
>> - }
>> - }
>> -
>> - *image_addr = *reserve_addr;
>> - memcpy((void *)*image_addr, _text, kernel_size);
>> - caches_clean_inval_pou(*image_addr, *image_addr + kernel_codesize);
>> + status = efi_kaslr_relocate_kernel(image_addr,
>> + reserve_addr, reserve_size,
>> + kernel_size, kernel_codesize,
>> + kernel_memsize,
>> + efi_kaslr_get_phys_seed(image_handle));
>> + if (status != EFI_SUCCESS)
>> + return status;
>>
>> return EFI_SUCCESS;
>> }
>> diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c
>> b/drivers/firmware/efi/libstub/efi-stub-helper.c
>> index 1e0203d74691..40ac2625949c 100644
>> --- a/drivers/firmware/efi/libstub/efi-stub-helper.c
>> +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
>> @@ -718,3 +718,154 @@ void efi_remap_image(unsigned long image_base,
>> unsigned alloc_size,
>> efi_warn("Failed to remap data region non-executable\n");
>> }
>> }
>> +
>> +/**
>> + * efi_kaslr_get_phys_seed() - Get random seed for physical kernel
>> KASLR
>> + * @image_handle: Handle to the image
>> + *
>> + * If KASLR is not disabled, obtain a random seed using
>> EFI_RNG_PROTOCOL
>> + * that will be used to move the kernel physical mapping.
>> + *
>> + * Return: the random seed
>> + */
>> +u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle)
>> +{
>> + efi_status_t status;
>> + u32 phys_seed;
>> + efi_guid_t li_fixed_proto = LINUX_EFI_LOADED_IMAGE_FIXED_GUID;
>> + void *p;
>> +
>> + if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
>> + return 0;
>> +
>> + if (efi_nokaslr) {
>> + efi_info("KASLR disabled on kernel command line\n");
>> + } else if (efi_bs_call(handle_protocol, image_handle,
>> + &li_fixed_proto, &p) == EFI_SUCCESS) {
>> + efi_info("Image placement fixed by loader\n");
>> + } else {
>> + status = efi_get_random_bytes(sizeof(phys_seed),
>> + (u8 *)&phys_seed);
>> + if (status == EFI_SUCCESS) {
>> + return phys_seed;
>> + } else if (status == EFI_NOT_FOUND) {
>> + efi_info("EFI_RNG_PROTOCOL unavailable\n");
>> + efi_nokaslr = true;
>> + } else if (status != EFI_SUCCESS) {
>> + efi_err("efi_get_random_bytes() failed (0x%lx)\n",
>> + status);
>> + efi_nokaslr = true;
>> + }
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +/*
>> + * Distro versions of GRUB may ignore the BSS allocation entirely
>> (i.e., fail
>> + * to provide space, and fail to zero it). Check for this condition
>> by double
>> + * checking that the first and the last byte of the image are
>> covered by the
>> + * same EFI memory map entry.
>> + */
>> +static bool check_image_region(u64 base, u64 size)
>> +{
>> + struct efi_boot_memmap *map;
>> + efi_status_t status;
>> + bool ret = false;
>> + int map_offset;
>> +
>> + status = efi_get_memory_map(&map, false);
>> + if (status != EFI_SUCCESS)
>> + return false;
>> +
>> + for (map_offset = 0; map_offset < map->map_size; map_offset +=
>> map->desc_size) {
>> + efi_memory_desc_t *md = (void *)map->map + map_offset;
>> + u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE;
>> +
>> + /*
>> + * Find the region that covers base, and return whether
>> + * it covers base+size bytes.
>> + */
>> + if (base >= md->phys_addr && base < end) {
>> + ret = (base + size) <= end;
>> + break;
>> + }
>> + }
>> +
>> + efi_bs_call(free_pool, map);
>> +
>> + return ret;
>> +}
>> +
>> +/**
>> + * efi_kaslr_relocate_kernel() - Relocate the kernel (random if
>> KASLR enabled)
>> + * @image_addr: Pointer to the current kernel location
>> + * @reserve_addr: Pointer to the relocated kernel location
>> + * @reserve_size: Size of the relocated kernel
>> + * @kernel_size: Size of the text + data
>> + * @kernel_codesize: Size of the text
>> + * @kernel_memsize: Size of the text + data + bss
>> + * @phys_seed: Random seed used for the relocation
>> + *
>> + * If KASLR is not enabled, this function relocates the kernel to a
>> fixed
>> + * address (or leave it as its current location). If KASLR is
>> enabled, the
>> + * kernel physical location is randomized using the seed in parameter.
>> + *
>> + * Return: status code, EFI_SUCCESS if relocation is successful
>> + */
>> +efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
>> + unsigned long *reserve_addr,
>> + unsigned long *reserve_size,
>> + unsigned long kernel_size,
>> + unsigned long kernel_codesize,
>> + unsigned long kernel_memsize,
>> + u32 phys_seed)
>> +{
>> + efi_status_t status;
>> + u64 min_kimg_align = efi_get_kimg_min_align();
>> +
>> + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
>> + /*
>> + * If KASLR is enabled, and we have some randomness available,
>> + * locate the kernel at a randomized offset in physical memory.
>> + */
>> + status = efi_random_alloc(*reserve_size, min_kimg_align,
>> + reserve_addr, phys_seed,
>> + EFI_LOADER_CODE);
>> + if (status != EFI_SUCCESS)
>> + efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
>> + } else {
>> + status = EFI_OUT_OF_RESOURCES;
>> + }
>> +
>> + if (status != EFI_SUCCESS) {
>> + if (!check_image_region(*image_addr, kernel_memsize)) {
>> + efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI
>> memory region\n");
>> + } else if (IS_ALIGNED(*image_addr, min_kimg_align) &&
>> + (u64)_end < EFI_ALLOC_LIMIT) {
>> + /*
>> + * Just execute from wherever we were loaded by the
>> + * UEFI PE/COFF loader if the placement is suitable.
>> + */
>> + *reserve_size = 0;
>> + return EFI_SUCCESS;
>> + }
>> +
>> + status = efi_allocate_pages_aligned(*reserve_size,
>> reserve_addr,
>> + ULONG_MAX, min_kimg_align,
>> + EFI_LOADER_CODE);
>> +
>> + if (status != EFI_SUCCESS) {
>> + efi_err("Failed to relocate kernel\n");
>> + *reserve_size = 0;
>> + return status;
>> + }
>> + }
>> +
>> + memcpy((void *)*reserve_addr, (void *)*image_addr, kernel_size);
>> + *image_addr = *reserve_addr;
>> +
>> + caches_clean_inval_pou(*image_addr, *image_addr + kernel_codesize);
>> +
>> + return status;
>> +}
>> diff --git a/drivers/firmware/efi/libstub/efistub.h
>> b/drivers/firmware/efi/libstub/efistub.h
>> index 6bd3bb86d967..64273371ce96 100644
>> --- a/drivers/firmware/efi/libstub/efistub.h
>> +++ b/drivers/firmware/efi/libstub/efistub.h
>> @@ -1098,5 +1098,13 @@ const u8 *__efi_get_smbios_string(u8 type, int
>> offset, int recsize);
>>
>> void efi_remap_image(unsigned long image_base, unsigned alloc_size,
>> unsigned long code_size);
>> +efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
>> + unsigned long *reserve_addr,
>> + unsigned long *reserve_size,
>> + unsigned long kernel_size,
>> + unsigned long kernel_codesize,
>> + unsigned long kernel_memsize,
>> + u32 phys_seed);
>> +u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle);
>>
>> #endif
>
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