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Date: Tue, 21 Apr 2020 13:02:02 -0700 (PDT)
From: Palmer Dabbelt <palmer@...belt.com>
To: Atish Patra <Atish.Patra@....com>
CC: linux-kernel@...r.kernel.org, Atish Patra <Atish.Patra@....com>,
ardb@...nel.org, linux-efi@...r.kernel.org,
linux-riscv@...ts.infradead.org, masahiroy@...nel.org,
xypron.glpk@....de
Subject: Re: [v4 PATCH 2/3] RISC-V: Add PE/COFF header for EFI stub
[I just saw there's a v4, so I'm moving over here]
On Mon, 20 Apr 2020 20:33:35 PDT (-0700), Atish Patra wrote:
> 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 <atish.patra@....com>
> ---
> arch/riscv/include/asm/sections.h | 13 ++++
> arch/riscv/kernel/Makefile | 4 ++
> arch/riscv/kernel/efi-header.S | 99 +++++++++++++++++++++++++++++++
> arch/riscv/kernel/head.S | 16 +++++
> arch/riscv/kernel/image-vars.h | 53 +++++++++++++++++
> arch/riscv/kernel/vmlinux.lds.S | 20 ++++++-
> 6 files changed, 203 insertions(+), 2 deletions(-)
> create mode 100644 arch/riscv/include/asm/sections.h
> create mode 100644 arch/riscv/kernel/efi-header.S
> create mode 100644 arch/riscv/kernel/image-vars.h
>
> diff --git a/arch/riscv/include/asm/sections.h b/arch/riscv/include/asm/sections.h
> new file mode 100644
> index 000000000000..3a9971b1210f
> --- /dev/null
> +++ b/arch/riscv/include/asm/sections.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> + */
> +#ifndef __ASM_SECTIONS_H
> +#define __ASM_SECTIONS_H
> +
> +#include <asm-generic/sections.h>
> +
> +extern char _start[];
> +extern char _start_kernel[];
> +
> +#endif /* __ASM_SECTIONS_H */
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index 86c83081044f..86ca755f8a9f 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -32,6 +32,10 @@ obj-y += patch.o
> obj-$(CONFIG_MMU) += vdso.o vdso/
>
> obj-$(CONFIG_RISCV_M_MODE) += clint.o traps_misaligned.o
> +OBJCOPYFLAGS := --prefix-symbols=__efistub_
> +$(obj)/%.stub.o: $(obj)/%.o FORCE
> + $(call if_changed,objcopy)
> +
> obj-$(CONFIG_FPU) += fpu.o
> obj-$(CONFIG_SMP) += smpboot.o
> obj-$(CONFIG_SMP) += smp.o
> diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi-header.S
> new file mode 100644
> index 000000000000..69dde8268527
> --- /dev/null
> +++ b/arch/riscv/kernel/efi-header.S
> @@ -0,0 +1,99 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> + * Adapted from arch/arm64/kernel/efi-header.S
> + */
> +
> +#include <linux/pe.h>
> +#include <linux/sizes.h>
> +
> + .macro __EFI_PE_HEADER
> + .long PE_MAGIC
> +coff_header:
> + .short IMAGE_FILE_MACHINE_RISCV64 // Machine
> + .short section_count // NumberOfSections
> + .long 0 // TimeDateStamp
> + .long 0 // PointerToSymbolTable
> + .long 0 // NumberOfSymbols
> + .short section_table - optional_header // SizeOfOptionalHeader
> + .short IMAGE_FILE_DEBUG_STRIPPED | \
> + IMAGE_FILE_EXECUTABLE_IMAGE | \
> + IMAGE_FILE_LINE_NUMS_STRIPPED // Characteristics
> +
> +optional_header:
> + .short PE_OPT_MAGIC_PE32PLUS // PE32+ format
> + .byte 0x02 // MajorLinkerVersion
> + .byte 0x14 // MinorLinkerVersion
> + .long __text_end - efi_header_end // SizeOfCode
> + .long _end - __text_end // SizeOfInitializedData
> + .long 0 // SizeOfUninitializedData
> + .long __efistub_efi_entry - _start // AddressOfEntryPoint
> + .long efi_header_end - _start // BaseOfCode
> +
> +extra_header_fields:
> + .quad 0 // ImageBase
> + .long SZ_4K // SectionAlignment
> + .long PECOFF_FILE_ALIGNMENT // FileAlignment
> + .short 0 // MajorOperatingSystemVersion
> + .short 0 // MinorOperatingSystemVersion
> + .short LINUX_EFISTUB_MAJOR_VERSION // MajorImageVersion
> + .short LINUX_EFISTUB_MINOR_VERSION // MinorImageVersion
> + .short 0 // MajorSubsystemVersion
> + .short 0 // MinorSubsystemVersion
> + .long 0 // Win32VersionValue
> +
> + .long _end - _start // SizeOfImage
> +
> + // Everything before the kernel image is considered part of the header
> + .long efi_header_end - _start // SizeOfHeaders
> + .long 0 // CheckSum
> + .short IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem
> + .short 0 // DllCharacteristics
> + .quad 0 // SizeOfStackReserve
> + .quad 0 // SizeOfStackCommit
> + .quad 0 // SizeOfHeapReserve
> + .quad 0 // SizeOfHeapCommit
> + .long 0 // LoaderFlags
> + .long (section_table - .) / 8 // NumberOfRvaAndSizes
> +
> + .quad 0 // ExportTable
> + .quad 0 // ImportTable
> + .quad 0 // ResourceTable
> + .quad 0 // ExceptionTable
> + .quad 0 // CertificationTable
> + .quad 0 // BaseRelocationTable
> +
> + // Section table
> +section_table:
> + .ascii ".text\0\0\0"
> + .long __text_end - efi_header_end // VirtualSize
> + .long efi_header_end - _start // VirtualAddress
> + .long __text_end - efi_header_end // SizeOfRawData
> + .long efi_header_end - _start // PointerToRawData
> +
> + .long 0 // PointerToRelocations
> + .long 0 // PointerToLineNumbers
> + .short 0 // NumberOfRelocations
> + .short 0 // NumberOfLineNumbers
> + .long IMAGE_SCN_CNT_CODE | \
> + IMAGE_SCN_MEM_READ | \
> + IMAGE_SCN_MEM_EXECUTE // Characteristics
> +
> + .ascii ".data\0\0\0"
> + .long __data_virt_size // VirtualSize
> + .long __text_end - _start // VirtualAddress
> + .long __data_raw_size // SizeOfRawData
> + .long __text_end - _start // PointerToRawData
> +
> + .long 0 // PointerToRelocations
> + .long 0 // PointerToLineNumbers
> + .short 0 // NumberOfRelocations
> + .short 0 // NumberOfLineNumbers
> + .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
> + IMAGE_SCN_MEM_READ | \
> + IMAGE_SCN_MEM_WRITE // Characteristics
> +
> + .set section_count, (. - section_table) / 40
> +
> +efi_header_end:
> + .endm
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 98a406474e7d..ddd613dac9d6 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -13,6 +13,7 @@
> #include <asm/csr.h>
> #include <asm/hwcap.h>
> #include <asm/image.h>
> +#include "efi-header.S"
>
> __HEAD
> ENTRY(_start)
> @@ -22,10 +23,18 @@ ENTRY(_start)
> * Do not modify it without modifying the structure and all bootloaders
> * that expects this header format!!
> */
> +#ifdef CONFIG_EFI
> + /*
> + * This instruction decodes to "MZ" ASCII required by UEFI.
> + */
> + li s4,-13
This needs to be a c.li in order to encode as "MZ". It'd be cleaner to
explicitly write it that way rather that having the assembler transparently
compress it, but we definately need to have Kconfig make EFI select ISA_C.
> + j _start_kernel
> +#else
> /* jump to start kernel */
> j _start_kernel
> /* reserved */
> .word 0
> +#endif
> .balign 8
> #if __riscv_xlen == 64
> /* Image load offset(2MB) from start of RAM */
> @@ -43,7 +52,14 @@ ENTRY(_start)
> .ascii RISCV_IMAGE_MAGIC
> .balign 4
> .ascii RISCV_IMAGE_MAGIC2
> +#ifdef CONFIG_EFI
> + .word pe_head_start - _start
> +pe_head_start:
> +
> + __EFI_PE_HEADER
> +#else
> .word 0
> +#endif
>
> .align 2
> #ifdef CONFIG_MMU
> diff --git a/arch/riscv/kernel/image-vars.h b/arch/riscv/kernel/image-vars.h
> new file mode 100644
> index 000000000000..bd8b764f0ad9
> --- /dev/null
> +++ b/arch/riscv/kernel/image-vars.h
> @@ -0,0 +1,53 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> + * Linker script variables to be set after section resolution, as
> + * ld.lld does not like variables assigned before SECTIONS is processed.
> + * Based on arch/arm64/kerne/image-vars.h
> + */
> +#ifndef __RISCV_KERNEL_IMAGE_VARS_H
> +#define __RISCV_KERNEL_IMAGE_VARS_H
> +
> +#ifndef LINKER_SCRIPT
> +#error This file should only be included in vmlinux.lds.S
> +#endif
> +
> +#ifdef CONFIG_EFI
> +
> +__efistub_stext_offset = _start_kernel - _start;
> +
> +/*
> + * The EFI stub has its own symbol namespace prefixed by __efistub_, to
> + * isolate it from the kernel proper. The following symbols are legally
> + * accessed by the stub, so provide some aliases to make them accessible.
> + * Only include data symbols here, or text symbols of functions that are
> + * guaranteed to be safe when executed at another offset than they were
> + * linked at. The routines below are all implemented in assembler in a
> + * position independent manner
> + */
> +__efistub_memcmp = memcmp;
> +__efistub_memchr = memchr;
> +__efistub_memcpy = memcpy;
> +__efistub_memmove = memmove;
> +__efistub_memset = memset;
> +__efistub_strlen = strlen;
> +__efistub_strnlen = strnlen;
> +__efistub_strcmp = strcmp;
> +__efistub_strncmp = strncmp;
> +__efistub_strrchr = strrchr;
> +
> +#ifdef CONFIG_KASAN
> +__efistub___memcpy = memcpy;
> +__efistub___memmove = memmove;
> +__efistub___memset = memset;
> +#endif
> +
> +__efistub__start = _start;
> +__efistub__start_kernel = _start_kernel;
> +__efistub__end = _end;
> +__efistub__edata = _edata;
> +__efistub_screen_info = screen_info;
> +
> +#endif
> +
> +#endif /* __RISCV_KERNEL_IMAGE_VARS_H */
> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
> index 0339b6bbe11a..20ebf7e8c215 100644
> --- a/arch/riscv/kernel/vmlinux.lds.S
> +++ b/arch/riscv/kernel/vmlinux.lds.S
> @@ -10,6 +10,7 @@
> #include <asm/cache.h>
> #include <asm/thread_info.h>
> #include <asm/set_memory.h>
> +#include "image-vars.h"
>
> #include <linux/sizes.h>
> OUTPUT_ARCH(riscv)
> @@ -17,6 +18,14 @@ ENTRY(_start)
>
> jiffies = jiffies_64;
>
> +PECOFF_FILE_ALIGNMENT = 0x200;
> +#ifdef CONFIG_EFI
> +#define PECOFF_EDATA_PADDING \
> + .pecoff_edata_padding : { BYTE(0); . = ALIGN(PECOFF_FILE_ALIGNMENT); }
> +#else
> +#define PECOFF_EDATA_PADDING
> +#endif
> +
> SECTIONS
> {
> /* Beginning of code and text segment */
> @@ -62,6 +71,8 @@ SECTIONS
> _etext = .;
> }
>
> + __text_end = .;
> +
> /* Start of data section */
> _sdata = .;
> RO_DATA(SECTION_ALIGN)
> @@ -78,9 +89,12 @@ SECTIONS
> .sdata : {
> __global_pointer$ = . + 0x800;
> *(.sdata*)
> - /* End of data section */
> - _edata = .;
> }
> + PECOFF_EDATA_PADDING
> + __data_raw_size = ABSOLUTE(. - __text_end);
> +
> + /* End of data section */
> + _edata = .;
>
> BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
>
> @@ -88,6 +102,8 @@ SECTIONS
> *(.rel.dyn*)
> }
>
> + __data_virt_size = ABSOLUTE(. - __text_end);
> +
> _end = .;
>
> STABS_DEBUG
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