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Message-ID: <25c298fe1e999f5e766dfa612f9223ea@ispras.ru>
Date: Thu, 09 Mar 2023 20:10:03 +0300
From: Evgeniy Baskov <baskov@...ras.ru>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Alexey Khoroshilov <khoroshilov@...ras.ru>,
Peter Jones <pjones@...hat.com>,
"Limonciello, Mario" <mario.limonciello@....com>,
joeyli <jlee@...e.com>, lvc-project@...uxtesting.org,
x86@...nel.org, linux-efi@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v4 15/26] efi/x86: Support extracting kernel from libstub
On 2023-03-09 19:49, Ard Biesheuvel wrote:
> On Thu, 15 Dec 2022 at 13:40, Evgeniy Baskov <baskov@...ras.ru> wrote:
>>
>> Doing it that way allows setting up stricter memory attributes,
>> simplifies boot code path and removes potential relocation
>> of kernel image.
>>
>> Wire up required interfaces and minimally initialize zero page
>> fields needed for it to function correctly.
>>
>> Tested-by: Peter Jones <pjones@...hat.com>
>> Signed-off-by: Evgeniy Baskov <baskov@...ras.ru>
>
> OK I just realized that there is a problem with this approach: since
> we now decompress the image while running in the EFI stub (i.e.,
> before ExitBootServices()), we cannot just randomly pick a
> EFI_CONVENTIONAL_MEMORY region to place the kernel, we need to
> allocate the pages using the boot services. Otherwise, subsequent
> allocations (or concurrent ones occurring in the firmware in event
> handlers etc) may land right in the middle, which is unlikely to be
> what we want.
It does allocate pages for the kernel.
I've marked the place below.
>
>
>> ---
>> arch/x86/boot/compressed/head_32.S | 50 ++++-
>> arch/x86/boot/compressed/head_64.S | 58 ++++-
>> drivers/firmware/efi/Kconfig | 2 +
>> drivers/firmware/efi/libstub/Makefile | 2 +-
>> .../firmware/efi/libstub/x86-extract-direct.c | 208
>> ++++++++++++++++++
>> drivers/firmware/efi/libstub/x86-stub.c | 119 +---------
>> drivers/firmware/efi/libstub/x86-stub.h | 14 ++
>> 7 files changed, 338 insertions(+), 115 deletions(-)
>> create mode 100644 drivers/firmware/efi/libstub/x86-extract-direct.c
>> create mode 100644 drivers/firmware/efi/libstub/x86-stub.h
>>
>> diff --git a/arch/x86/boot/compressed/head_32.S
>> b/arch/x86/boot/compressed/head_32.S
>> index ead6007df1e5..0be75e5072ae 100644
>> --- a/arch/x86/boot/compressed/head_32.S
>> +++ b/arch/x86/boot/compressed/head_32.S
>> @@ -152,11 +152,57 @@ SYM_FUNC_END(startup_32)
>>
>> #ifdef CONFIG_EFI_STUB
>> SYM_FUNC_START(efi32_stub_entry)
>> +/*
>> + * Calculate the delta between where we were compiled to run
>> + * at and where we were actually loaded at. This can only be done
>> + * with a short local call on x86. Nothing else will tell us what
>> + * address we are running at. The reserved chunk of the real-mode
>> + * data at 0x1e4 (defined as a scratch field) are used as the stack
>> + * for this calculation. Only 4 bytes are needed.
>> + */
>> + call 1f
>> +1: popl %ebx
>> + addl $_GLOBAL_OFFSET_TABLE_+(.-1b), %ebx
>> +
>> + /* Clear BSS */
>> + xorl %eax, %eax
>> + leal _bss@...OFF(%ebx), %edi
>> + leal _ebss@...OFF(%ebx), %ecx
>> + subl %edi, %ecx
>> + shrl $2, %ecx
>> + rep stosl
>> +
>> add $0x4, %esp
>> movl 8(%esp), %esi /* save boot_params pointer */
>> + movl %edx, %edi /* save GOT address */
>> call efi_main
>> - /* efi_main returns the possibly relocated address of
>> startup_32 */
>> - jmp *%eax
>> + movl %eax, %ecx
>> +
>> + /*
>> + * efi_main returns the possibly
>> + * relocated address of extracted kernel entry point.
>> + */
>> +
>> + cli
>> +
>> + /* Load new GDT */
>> + leal gdt@...OFF(%ebx), %eax
>> + movl %eax, 2(%eax)
>> + lgdt (%eax)
>> +
>> + /* Load segment registers with our descriptors */
>> + movl $__BOOT_DS, %eax
>> + movl %eax, %ds
>> + movl %eax, %es
>> + movl %eax, %fs
>> + movl %eax, %gs
>> + movl %eax, %ss
>> +
>> + /* Zero EFLAGS */
>> + pushl $0
>> + popfl
>> +
>> + jmp *%ecx
>> SYM_FUNC_END(efi32_stub_entry)
>> SYM_FUNC_ALIAS(efi_stub_entry, efi32_stub_entry)
>> #endif
>> diff --git a/arch/x86/boot/compressed/head_64.S
>> b/arch/x86/boot/compressed/head_64.S
>> index 2dd8be0583d2..7cfef7bd0424 100644
>> --- a/arch/x86/boot/compressed/head_64.S
>> +++ b/arch/x86/boot/compressed/head_64.S
>> @@ -529,12 +529,64 @@ SYM_CODE_END(startup_64)
>> .org 0x390
>> #endif
>> SYM_FUNC_START(efi64_stub_entry)
>> + /* Preserve first parameter */
>> + movq %rdi, %r10
>> +
>> + /* Clear BSS */
>> + xorl %eax, %eax
>> + leaq _bss(%rip), %rdi
>> + leaq _ebss(%rip), %rcx
>> + subq %rdi, %rcx
>> + shrq $3, %rcx
>> + rep stosq
>> +
>> and $~0xf, %rsp /* realign the stack
>> */
>> movq %rdx, %rbx /* save boot_params
>> pointer */
>> + movq %r10, %rdi
>> call efi_main
>> - movq %rbx,%rsi
>> - leaq rva(startup_64)(%rax), %rax
>> - jmp *%rax
>> +
>> + cld
>> + cli
>> +
>> + movq %rbx, %rdi /* boot_params */
>> + movq %rax, %rsi /* decompressed kernel address */
>> +
>> + /* Make sure we have GDT with 32-bit code segment */
>> + leaq gdt64(%rip), %rax
>> + addq %rax, 2(%rax)
>> + lgdt (%rax)
>> +
>> + /* Setup data segments. */
>> + xorl %eax, %eax
>> + movl %eax, %ds
>> + movl %eax, %es
>> + movl %eax, %ss
>> + movl %eax, %fs
>> + movl %eax, %gs
>> +
>> + pushq %rsi
>> + pushq %rdi
>> +
>> + call load_stage1_idt
>> + call enable_nx_if_supported
>> +
>> + call trampoline_pgtable_init
>> + movq %rax, %rdx
>> +
>> +
>> + /* Swap %rsi and %rsi */
>> + popq %rsi
>> + popq %rdi
>> +
>> + /* Save the trampoline address in RCX */
>> + movq trampoline_32bit(%rip), %rcx
>> +
>> + /* Switch to compatibility mode (CS.L = 0 CS.D = 1) via far
>> return */
>> + pushq $__KERNEL32_CS
>> + leaq TRAMPOLINE_32BIT_CODE_OFFSET(%rcx), %rax
>> + pushq %rax
>> + lretq
>> +
>> SYM_FUNC_END(efi64_stub_entry)
>> SYM_FUNC_ALIAS(efi_stub_entry, efi64_stub_entry)
>> #endif
>> diff --git a/drivers/firmware/efi/Kconfig
>> b/drivers/firmware/efi/Kconfig
>> index 043ca31c114e..f50c2a84a754 100644
>> --- a/drivers/firmware/efi/Kconfig
>> +++ b/drivers/firmware/efi/Kconfig
>> @@ -58,6 +58,8 @@ config EFI_DXE_MEM_ATTRIBUTES
>> Use DXE services to check and alter memory protection
>> attributes during boot via EFISTUB to ensure that memory
>> ranges used by the kernel are writable and executable.
>> + This option also enables stricter memory attributes
>> + on compressed kernel PE image.
>>
>> config EFI_PARAMS_FROM_FDT
>> bool
>> diff --git a/drivers/firmware/efi/libstub/Makefile
>> b/drivers/firmware/efi/libstub/Makefile
>> index be8b8c6e8b40..99b81c95344c 100644
>> --- a/drivers/firmware/efi/libstub/Makefile
>> +++ b/drivers/firmware/efi/libstub/Makefile
>> @@ -88,7 +88,7 @@ lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o
>> string.o intrinsics.o systable.o \
>>
>> lib-$(CONFIG_ARM) += arm32-stub.o
>> lib-$(CONFIG_ARM64) += arm64.o arm64-stub.o arm64-entry.o
>> smbios.o
>> -lib-$(CONFIG_X86) += x86-stub.o
>> +lib-$(CONFIG_X86) += x86-stub.o x86-extract-direct.o
>> lib-$(CONFIG_RISCV) += riscv.o riscv-stub.o
>> lib-$(CONFIG_LOONGARCH) += loongarch.o
>> loongarch-stub.o
>>
>> diff --git a/drivers/firmware/efi/libstub/x86-extract-direct.c
>> b/drivers/firmware/efi/libstub/x86-extract-direct.c
>> new file mode 100644
>> index 000000000000..4ecbc4a9b3ed
>> --- /dev/null
>> +++ b/drivers/firmware/efi/libstub/x86-extract-direct.c
>> @@ -0,0 +1,208 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/efi.h>
>> +#include <linux/elf.h>
>> +#include <linux/stddef.h>
>> +
>> +#include <asm/efi.h>
>> +#include <asm/e820/types.h>
>> +#include <asm/desc.h>
>> +#include <asm/boot.h>
>> +#include <asm/bootparam_utils.h>
>> +#include <asm/shared/extract.h>
>> +#include <asm/shared/pgtable.h>
>> +
>> +#include "efistub.h"
>> +#include "x86-stub.h"
>> +
>> +static efi_handle_t image_handle;
>> +
>> +static void do_puthex(unsigned long value)
>> +{
>> + efi_printk("%08lx", value);
>> +}
>> +
>> +static void do_putstr(const char *msg)
>> +{
>> + efi_printk("%s", msg);
>> +}
>> +
>> +static unsigned long do_map_range(unsigned long start,
>> + unsigned long end,
>> + unsigned int flags)
>> +{
>> + efi_status_t status;
>> +
>> + unsigned long size = end - start;
>> +
>> + if (flags & MAP_ALLOC) {
>> + unsigned long addr;
>> +
>> + status = efi_low_alloc_above(size,
>> CONFIG_PHYSICAL_ALIGN,
>> + &addr, start);
Memory for the kernel image is allocated here.
This function is getting called from the boot/compressed/misc.c with
MAP_ALLOC flag
when the address for the kernel is picked.
>> + if (status != EFI_SUCCESS) {
>> + efi_err("Unable to allocate memory for
>> uncompressed kernel");
>> + efi_exit(image_handle, EFI_OUT_OF_RESOURCES);
>> + }
>> +
>> + if (start != addr) {
>> + efi_debug("Unable to allocate at given
>> address"
>> + " (desired=0x%lx, actual=0x%lx)",
>> + (unsigned long)start, addr);
>> + start = addr;
>> + }
>> + }
>> +
>> + if ((flags & (MAP_PROTECT | MAP_ALLOC)) &&
>> + IS_ENABLED(CONFIG_EFI_DXE_MEM_ATTRIBUTES)) {
>> + unsigned long attr = 0;
>> +
>> + if (!(flags & MAP_EXEC))
>> + attr |= EFI_MEMORY_XP;
>> +
>> + if (!(flags & MAP_WRITE))
>> + attr |= EFI_MEMORY_RO;
>> +
>> + status = efi_adjust_memory_range_protection(start,
>> size, attr);
>> + if (status != EFI_SUCCESS)
>> + efi_err("Unable to protect memory range");
>> + }
>> +
>> + return start;
>> +}
>> +
>> +/*
>> + * Trampoline takes 3 pages and can be loaded in first megabyte of
>> memory
>> + * with its end placed between 0 and 640k where BIOS might start.
>> + * (see arch/x86/boot/compressed/pgtable_64.c)
>> + */
>> +
>> +#ifdef CONFIG_64BIT
>> +static efi_status_t prepare_trampoline(void)
>> +{
>> + efi_status_t status;
>> +
>> + status = efi_allocate_pages(TRAMPOLINE_32BIT_SIZE,
>> + (unsigned long
>> *)&trampoline_32bit,
>> + TRAMPOLINE_32BIT_PLACEMENT_MAX);
>> +
>> + if (status != EFI_SUCCESS)
>> + return status;
>> +
>> + unsigned long trampoline_start = (unsigned
>> long)trampoline_32bit;
>> +
>> + memset(trampoline_32bit, 0, TRAMPOLINE_32BIT_SIZE);
>> +
>> + if (IS_ENABLED(CONFIG_EFI_DXE_MEM_ATTRIBUTES)) {
>> + /* First page of trampoline is a top level page table
>> */
>> + efi_adjust_memory_range_protection(trampoline_start,
>> + PAGE_SIZE,
>> + EFI_MEMORY_XP);
>> + }
>> +
>> + /* Second page of trampoline is the code (with a padding) */
>> +
>> + void *caddr = (void *)trampoline_32bit +
>> TRAMPOLINE_32BIT_CODE_OFFSET;
>> +
>> + memcpy(caddr, trampoline_32bit_src,
>> TRAMPOLINE_32BIT_CODE_SIZE);
>> +
>> + if (IS_ENABLED(CONFIG_EFI_DXE_MEM_ATTRIBUTES)) {
>> + efi_adjust_memory_range_protection((unsigned
>> long)caddr,
>> + PAGE_SIZE,
>> + EFI_MEMORY_RO);
>> +
>> + /* And the last page of trampoline is the stack */
>> +
>> + efi_adjust_memory_range_protection(trampoline_start +
>> 2 * PAGE_SIZE,
>> + PAGE_SIZE,
>> + EFI_MEMORY_XP);
>> + }
>> +
>> + return EFI_SUCCESS;
>> +}
>> +#else
>> +static inline efi_status_t prepare_trampoline(void)
>> +{
>> + return EFI_SUCCESS;
>> +}
>> +#endif
>> +
>> +static efi_status_t init_loader_data(efi_handle_t handle,
>> + struct boot_params *params,
>> + struct efi_boot_memmap **map)
>> +{
>> + struct efi_info *efi = (void *)¶ms->efi_info;
>> + efi_status_t status;
>> +
>> + status = efi_get_memory_map(map, false);
>> +
>> + if (status != EFI_SUCCESS) {
>> + efi_err("Unable to get EFI memory map...\n");
>> + return status;
>> + }
>> +
>> + const char *signature = efi_is_64bit() ?
>> EFI64_LOADER_SIGNATURE
>> + :
>> EFI32_LOADER_SIGNATURE;
>> +
>> + memcpy(&efi->efi_loader_signature, signature, sizeof(__u32));
>> +
>> + efi->efi_memdesc_size = (*map)->desc_size;
>> + efi->efi_memdesc_version = (*map)->desc_ver;
>> + efi->efi_memmap_size = (*map)->map_size;
>> +
>> + efi_set_u64_split((unsigned long)(*map)->map,
>> + &efi->efi_memmap, &efi->efi_memmap_hi);
>> +
>> + efi_set_u64_split((unsigned long)efi_system_table,
>> + &efi->efi_systab, &efi->efi_systab_hi);
>> +
>> + image_handle = handle;
>> +
>> + return EFI_SUCCESS;
>> +}
>> +
>> +static void free_loader_data(struct boot_params *params, struct
>> efi_boot_memmap *map)
>> +{
>> + struct efi_info *efi = (void *)¶ms->efi_info;
>> +
>> + efi_bs_call(free_pool, map);
>> +
>> + efi->efi_memdesc_size = 0;
>> + efi->efi_memdesc_version = 0;
>> + efi->efi_memmap_size = 0;
>> + efi_set_u64_split(0, &efi->efi_memmap, &efi->efi_memmap_hi);
>> +}
>> +
>> +extern unsigned char input_data[];
>> +extern unsigned int input_len, output_len;
>> +
>> +unsigned long extract_kernel_direct(efi_handle_t handle, struct
>> boot_params *params)
>> +{
>> +
>> + void *res;
>> + efi_status_t status;
>> + struct efi_extract_callbacks cb = { 0 };
>> +
>> + status = prepare_trampoline();
>> +
>> + if (status != EFI_SUCCESS)
>> + return 0;
>> +
>> + /* Prepare environment for do_extract_kernel() call */
>> + struct efi_boot_memmap *map = NULL;
>> + status = init_loader_data(handle, params, &map);
>> +
>> + if (status != EFI_SUCCESS)
>> + return 0;
>> +
>> + cb.puthex = do_puthex;
>> + cb.putstr = do_putstr;
>> + cb.map_range = do_map_range;
>> +
>> + res = efi_extract_kernel(params, &cb, input_data, input_len,
>> output_len);
>> +
>> + free_loader_data(params, map);
>> +
>> + return (unsigned long)res;
>> +}
>> diff --git a/drivers/firmware/efi/libstub/x86-stub.c
>> b/drivers/firmware/efi/libstub/x86-stub.c
>> index 7fb1eff88a18..1d1ab1911fd3 100644
>> --- a/drivers/firmware/efi/libstub/x86-stub.c
>> +++ b/drivers/firmware/efi/libstub/x86-stub.c
>> @@ -17,6 +17,7 @@
>> #include <asm/boot.h>
>>
>> #include "efistub.h"
>> +#include "x86-stub.h"
>>
>> /* Maximum physical address for 64-bit kernel with 4-level paging */
>> #define MAXMEM_X86_64_4LEVEL (1ull << 46)
>> @@ -24,7 +25,7 @@
>> const efi_system_table_t *efi_system_table;
>> const efi_dxe_services_table_t *efi_dxe_table;
>> u32 image_offset __section(".data");
>> -static efi_loaded_image_t *image = NULL;
>> +static efi_loaded_image_t *image __section(".data");
>>
>> static efi_status_t
>> preserve_pci_rom_image(efi_pci_io_protocol_t *pci, struct
>> pci_setup_rom **__rom)
>> @@ -212,55 +213,9 @@ static void
>> retrieve_apple_device_properties(struct boot_params *boot_params)
>> }
>> }
>>
>> -/*
>> - * Trampoline takes 2 pages and can be loaded in first megabyte of
>> memory
>> - * with its end placed between 128k and 640k where BIOS might start.
>> - * (see arch/x86/boot/compressed/pgtable_64.c)
>> - *
>> - * We cannot find exact trampoline placement since memory map
>> - * can be modified by UEFI, and it can alter the computed address.
>> - */
>> -
>> -#define TRAMPOLINE_PLACEMENT_BASE ((128 - 8)*1024)
>> -#define TRAMPOLINE_PLACEMENT_SIZE (640*1024 - (128 - 8)*1024)
>> -
>> -void startup_32(struct boot_params *boot_params);
>> -
>> -static void
>> -setup_memory_protection(unsigned long image_base, unsigned long
>> image_size)
>> -{
>> - /*
>> - * Allow execution of possible trampoline used
>> - * for switching between 4- and 5-level page tables
>> - * and relocated kernel image.
>> - */
>> -
>> - efi_adjust_memory_range_protection(TRAMPOLINE_PLACEMENT_BASE,
>> - TRAMPOLINE_PLACEMENT_SIZE,
>> 0);
>> -
>> -#ifdef CONFIG_64BIT
>> - if (image_base != (unsigned long)startup_32)
>> - efi_adjust_memory_range_protection(image_base,
>> image_size, 0);
>> -#else
>> - /*
>> - * Clear protection flags on a whole range of possible
>> - * addresses used for KASLR. We don't need to do that
>> - * on x86_64, since KASLR/extraction is performed after
>> - * dedicated identity page tables are built and we only
>> - * need to remove possible protection on relocated image
>> - * itself disregarding further relocations.
>> - */
>> - efi_adjust_memory_range_protection(LOAD_PHYSICAL_ADDR,
>> - KERNEL_IMAGE_SIZE -
>> LOAD_PHYSICAL_ADDR,
>> - 0);
>> -#endif
>> -}
>> -
>> static const efi_char16_t apple[] = L"Apple";
>>
>> -static void setup_quirks(struct boot_params *boot_params,
>> - unsigned long image_base,
>> - unsigned long image_size)
>> +static void setup_quirks(struct boot_params *boot_params)
>> {
>> efi_char16_t *fw_vendor = (efi_char16_t *)(unsigned long)
>> efi_table_attr(efi_system_table, fw_vendor);
>> @@ -269,9 +224,6 @@ static void setup_quirks(struct boot_params
>> *boot_params,
>> if (IS_ENABLED(CONFIG_APPLE_PROPERTIES))
>> retrieve_apple_device_properties(boot_params);
>> }
>> -
>> - if (IS_ENABLED(CONFIG_EFI_DXE_MEM_ATTRIBUTES))
>> - setup_memory_protection(image_base, image_size);
>> }
>>
>> /*
>> @@ -384,7 +336,7 @@ static void setup_graphics(struct boot_params
>> *boot_params)
>> }
>>
>>
>> -static void __noreturn efi_exit(efi_handle_t handle, efi_status_t
>> status)
>> +void __noreturn efi_exit(efi_handle_t handle, efi_status_t status)
>> {
>> efi_bs_call(exit, handle, status, 0, NULL);
>> for(;;)
>> @@ -707,8 +659,7 @@ static efi_status_t exit_boot(struct boot_params
>> *boot_params, void *handle)
>> }
>>
>> /*
>> - * On success, we return the address of startup_32, which has
>> potentially been
>> - * relocated by efi_relocate_kernel.
>> + * On success, we return extracted kernel entry point.
>> * On failure, we exit to the firmware via efi_exit instead of
>> returning.
>> */
>> asmlinkage unsigned long efi_main(efi_handle_t handle,
>> @@ -733,60 +684,6 @@ asmlinkage unsigned long efi_main(efi_handle_t
>> handle,
>> efi_dxe_table = NULL;
>> }
>>
>> - /*
>> - * If the kernel isn't already loaded at a suitable address,
>> - * relocate it.
>> - *
>> - * It must be loaded above LOAD_PHYSICAL_ADDR.
>> - *
>> - * The maximum address for 64-bit is 1 << 46 for 4-level
>> paging. This
>> - * is defined as the macro MAXMEM, but unfortunately that is
>> not a
>> - * compile-time constant if 5-level paging is configured, so
>> we instead
>> - * define our own macro for use here.
>> - *
>> - * For 32-bit, the maximum address is complicated to figure
>> out, for
>> - * now use KERNEL_IMAGE_SIZE, which will be 512MiB, the same
>> as what
>> - * KASLR uses.
>> - *
>> - * Also relocate it if image_offset is zero, i.e. the kernel
>> wasn't
>> - * loaded by LoadImage, but rather by a bootloader that called
>> the
>> - * handover entry. The reason we must always relocate in this
>> case is
>> - * to handle the case of systemd-boot booting a unified kernel
>> image,
>> - * which is a PE executable that contains the bzImage and an
>> initrd as
>> - * COFF sections. The initrd section is placed after the
>> bzImage
>> - * without ensuring that there are at least init_size bytes
>> available
>> - * for the bzImage, and thus the compressed kernel's startup
>> code may
>> - * overwrite the initrd unless it is moved out of the way.
>> - */
>> -
>> - buffer_start = ALIGN(bzimage_addr - image_offset,
>> - hdr->kernel_alignment);
>> - buffer_end = buffer_start + hdr->init_size;
>> -
>> - if ((buffer_start < LOAD_PHYSICAL_ADDR)
>> ||
>> - (IS_ENABLED(CONFIG_X86_32) && buffer_end >
>> KERNEL_IMAGE_SIZE) ||
>> - (IS_ENABLED(CONFIG_X86_64) && buffer_end >
>> MAXMEM_X86_64_4LEVEL) ||
>> - (image_offset == 0)) {
>> - extern char _bss[];
>> -
>> - status = efi_relocate_kernel(&bzimage_addr,
>> - (unsigned long)_bss -
>> bzimage_addr,
>> - hdr->init_size,
>> - hdr->pref_address,
>> - hdr->kernel_alignment,
>> - LOAD_PHYSICAL_ADDR);
>> - if (status != EFI_SUCCESS) {
>> - efi_err("efi_relocate_kernel() failed!\n");
>> - goto fail;
>> - }
>> - /*
>> - * Now that we've copied the kernel elsewhere, we no
>> longer
>> - * have a set up block before startup_32(), so reset
>> image_offset
>> - * to zero in case it was set earlier.
>> - */
>> - image_offset = 0;
>> - }
>> -
>> #ifdef CONFIG_CMDLINE_BOOL
>> status = efi_parse_options(CONFIG_CMDLINE);
>> if (status != EFI_SUCCESS) {
>> @@ -843,7 +740,11 @@ asmlinkage unsigned long efi_main(efi_handle_t
>> handle,
>>
>> setup_efi_pci(boot_params);
>>
>> - setup_quirks(boot_params, bzimage_addr, buffer_end -
>> buffer_start);
>> + setup_quirks(boot_params);
>> +
>> + bzimage_addr = extract_kernel_direct(handle, boot_params);
>> + if (!bzimage_addr)
>> + goto fail;
>>
>> status = exit_boot(boot_params, handle);
>> if (status != EFI_SUCCESS) {
>> diff --git a/drivers/firmware/efi/libstub/x86-stub.h
>> b/drivers/firmware/efi/libstub/x86-stub.h
>> new file mode 100644
>> index 000000000000..baecc7c6e602
>> --- /dev/null
>> +++ b/drivers/firmware/efi/libstub/x86-stub.h
>> @@ -0,0 +1,14 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +
>> +#ifndef _DRIVERS_FIRMWARE_EFI_X86STUB_H
>> +#define _DRIVERS_FIRMWARE_EFI_X86STUB_H
>> +
>> +#include <linux/efi.h>
>> +
>> +#include <asm/bootparam.h>
>> +
>> +void __noreturn efi_exit(efi_handle_t handle, efi_status_t status);
>> +unsigned long extract_kernel_direct(efi_handle_t handle, struct
>> boot_params *boot_params);
>> +void startup_32(struct boot_params *boot_params);
>> +
>> +#endif
>> --
>> 2.37.4
>>
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