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RISC-V: Add PE/COFF header for EFI stub
Linux kernel Image can appear as an EFI application With appropriate PE/COFF header fields in the beginning of the Image header. An EFI application loader can directly load a Linux kernel Image and an EFI stub residing in kernel can boot Linux kernel directly. Add the necessary PE/COFF header. Signed-off-by: Atish Patra <[email protected]> Link: https://lore.kernel.org/r/[email protected] [ardb: - use C prefix for c.li to ensure the expected opcode is emitted - align all image sections according to PE/COFF section alignment ] Signed-off-by: Ard Biesheuvel <[email protected]> Reviewed-by: Anup Patel <[email protected]> Signed-off-by: Palmer Dabbelt <[email protected]>
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‎arch/riscv/include/asm/sections.h

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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2020 Western Digital Corporation or its affiliates.
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*/
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#ifndef __ASM_SECTIONS_H
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#define __ASM_SECTIONS_H
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#include <asm-generic/sections.h>
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extern char _start[];
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extern char _start_kernel[];
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#endif /* __ASM_SECTIONS_H */

‎arch/riscv/kernel/efi-header.S

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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2020 Western Digital Corporation or its affiliates.
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* Adapted from arch/arm64/kernel/efi-header.S
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*/
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#include <linux/pe.h>
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#include <linux/sizes.h>
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.macro __EFI_PE_HEADER
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.long PE_MAGIC
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coff_header:
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#ifdef CONFIG_64BIT
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.short IMAGE_FILE_MACHINE_RISCV64 // Machine
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#else
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.short IMAGE_FILE_MACHINE_RISCV32 // Machine
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#endif
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.short section_count // NumberOfSections
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.long 0 // TimeDateStamp
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.long 0 // PointerToSymbolTable
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.long 0 // NumberOfSymbols
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.short section_table - optional_header // SizeOfOptionalHeader
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.short IMAGE_FILE_DEBUG_STRIPPED | \
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IMAGE_FILE_EXECUTABLE_IMAGE | \
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IMAGE_FILE_LINE_NUMS_STRIPPED // Characteristics
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optional_header:
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#ifdef CONFIG_64BIT
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.short PE_OPT_MAGIC_PE32PLUS // PE32+ format
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#else
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.short PE_OPT_MAGIC_PE32 // PE32 format
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#endif
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.byte 0x02 // MajorLinkerVersion
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.byte 0x14 // MinorLinkerVersion
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.long __pecoff_text_end - efi_header_end // SizeOfCode
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.long __pecoff_data_virt_size // SizeOfInitializedData
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.long 0 // SizeOfUninitializedData
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.long __efistub_efi_pe_entry - _start // AddressOfEntryPoint
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.long efi_header_end - _start // BaseOfCode
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#ifdef CONFIG_32BIT
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.long __pecoff_text_end - _start // BaseOfData
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#endif
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extra_header_fields:
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.quad 0 // ImageBase
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.long PECOFF_SECTION_ALIGNMENT // SectionAlignment
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.long PECOFF_FILE_ALIGNMENT // FileAlignment
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.short 0 // MajorOperatingSystemVersion
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.short 0 // MinorOperatingSystemVersion
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.short LINUX_EFISTUB_MAJOR_VERSION // MajorImageVersion
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.short LINUX_EFISTUB_MINOR_VERSION // MinorImageVersion
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.short 0 // MajorSubsystemVersion
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.short 0 // MinorSubsystemVersion
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.long 0 // Win32VersionValue
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.long _end - _start // SizeOfImage
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// Everything before the kernel image is considered part of the header
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.long efi_header_end - _start // SizeOfHeaders
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.long 0 // CheckSum
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.short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem
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.short 0 // DllCharacteristics
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.quad 0 // SizeOfStackReserve
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.quad 0 // SizeOfStackCommit
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.quad 0 // SizeOfHeapReserve
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.quad 0 // SizeOfHeapCommit
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.long 0 // LoaderFlags
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.long (section_table - .) / 8 // NumberOfRvaAndSizes
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.quad 0 // ExportTable
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.quad 0 // ImportTable
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.quad 0 // ResourceTable
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.quad 0 // ExceptionTable
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.quad 0 // CertificationTable
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.quad 0 // BaseRelocationTable
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// Section table
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section_table:
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.ascii ".text\0\0\0"
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.long __pecoff_text_end - efi_header_end // VirtualSize
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.long efi_header_end - _start // VirtualAddress
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.long __pecoff_text_end - efi_header_end // SizeOfRawData
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.long efi_header_end - _start // PointerToRawData
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.long 0 // PointerToRelocations
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.long 0 // PointerToLineNumbers
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.short 0 // NumberOfRelocations
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.short 0 // NumberOfLineNumbers
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.long IMAGE_SCN_CNT_CODE | \
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IMAGE_SCN_MEM_READ | \
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IMAGE_SCN_MEM_EXECUTE // Characteristics
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.ascii ".data\0\0\0"
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.long __pecoff_data_virt_size // VirtualSize
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.long __pecoff_text_end - _start // VirtualAddress
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.long __pecoff_data_raw_size // SizeOfRawData
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.long __pecoff_text_end - _start // PointerToRawData
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.long 0 // PointerToRelocations
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.long 0 // PointerToLineNumbers
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.short 0 // NumberOfRelocations
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.short 0 // NumberOfLineNumbers
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.long IMAGE_SCN_CNT_INITIALIZED_DATA | \
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IMAGE_SCN_MEM_READ | \
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IMAGE_SCN_MEM_WRITE // Characteristics
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.set section_count, (. - section_table) / 40
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.balign 0x1000
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efi_header_end:
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.endm

‎arch/riscv/kernel/head.S

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@@ -12,6 +12,7 @@
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#include <asm/csr.h>
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#include <asm/hwcap.h>
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#include <asm/image.h>
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#include "efi-header.S"
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__HEAD
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ENTRY(_start)
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* Do not modify it without modifying the structure and all bootloaders
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* that expects this header format!!
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*/
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#ifdef CONFIG_EFI
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/*
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* This instruction decodes to "MZ" ASCII required by UEFI.
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*/
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c.li s4,-13
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j _start_kernel
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#else
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/* jump to start kernel */
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j _start_kernel
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/* reserved */
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.word 0
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#endif
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.balign 8
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#if __riscv_xlen == 64
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/* Image load offset(2MB) from start of RAM */
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.ascii RISCV_IMAGE_MAGIC
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.balign 4
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.ascii RISCV_IMAGE_MAGIC2
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#ifdef CONFIG_EFI
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.word pe_head_start - _start
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pe_head_start:
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__EFI_PE_HEADER
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#else
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.word 0
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#endif
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.align 2
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#ifdef CONFIG_MMU

‎arch/riscv/kernel/image-vars.h

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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2020 Western Digital Corporation or its affiliates.
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* Linker script variables to be set after section resolution, as
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* ld.lld does not like variables assigned before SECTIONS is processed.
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* Based on arch/arm64/kerne/image-vars.h
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*/
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#ifndef __RISCV_KERNEL_IMAGE_VARS_H
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#define __RISCV_KERNEL_IMAGE_VARS_H
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#ifndef LINKER_SCRIPT
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#error This file should only be included in vmlinux.lds.S
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#endif
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#ifdef CONFIG_EFI
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/*
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* The EFI stub has its own symbol namespace prefixed by __efistub_, to
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* isolate it from the kernel proper. The following symbols are legally
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* accessed by the stub, so provide some aliases to make them accessible.
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* Only include data symbols here, or text symbols of functions that are
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* guaranteed to be safe when executed at another offset than they were
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* linked at. The routines below are all implemented in assembler in a
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* position independent manner
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*/
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__efistub_memcmp = memcmp;
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__efistub_memchr = memchr;
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__efistub_memcpy = memcpy;
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__efistub_memmove = memmove;
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__efistub_memset = memset;
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__efistub_strlen = strlen;
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__efistub_strnlen = strnlen;
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__efistub_strcmp = strcmp;
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__efistub_strncmp = strncmp;
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__efistub_strrchr = strrchr;
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#ifdef CONFIG_KASAN
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__efistub___memcpy = memcpy;
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__efistub___memmove = memmove;
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__efistub___memset = memset;
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#endif
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__efistub__start = _start;
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__efistub__start_kernel = _start_kernel;
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__efistub__end = _end;
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__efistub__edata = _edata;
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__efistub_screen_info = screen_info;
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#endif
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#endif /* __RISCV_KERNEL_IMAGE_VARS_H */

‎arch/riscv/kernel/vmlinux.lds.S

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@@ -10,13 +10,17 @@
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#include <asm/cache.h>
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#include <asm/thread_info.h>
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#include <asm/set_memory.h>
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#include "image-vars.h"
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#include <linux/sizes.h>
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OUTPUT_ARCH(riscv)
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ENTRY(_start)
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jiffies = jiffies_64;
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PECOFF_SECTION_ALIGNMENT = 0x1000;
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PECOFF_FILE_ALIGNMENT = 0x200;
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SECTIONS
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{
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/* Beginning of code and text segment */
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_etext = .;
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}
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#ifdef CONFIG_EFI
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. = ALIGN(PECOFF_SECTION_ALIGNMENT);
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__pecoff_text_end = .;
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#endif
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/* Start of data section */
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_sdata = .;
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RO_DATA(SECTION_ALIGN)
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.sdata : {
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__global_pointer$ = . + 0x800;
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*(.sdata*)
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/* End of data section */
87-
_edata = .;
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}
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#ifdef CONFIG_EFI
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.pecoff_edata_padding : { BYTE(0); . = ALIGN(PECOFF_FILE_ALIGNMENT); }
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__pecoff_data_raw_size = ABSOLUTE(. - __pecoff_text_end);
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#endif
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/* End of data section */
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_edata = .;
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BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
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.rel.dyn : {
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*(.rel.dyn*)
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}
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#ifdef CONFIG_EFI
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. = ALIGN(PECOFF_SECTION_ALIGNMENT);
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__pecoff_data_virt_size = ABSOLUTE(. - __pecoff_text_end);
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#endif
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_end = .;
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STABS_DEBUG

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