Re: [PATCH v6 5/9] RISC-V: Add PE/COFF header for EFI stub

From: Atish Patra
Date: Tue Aug 25 2020 - 15:10:41 EST

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In reply to: Palmer Dabbelt: "Re: [PATCH v6 5/9] RISC-V: Add PE/COFF header for EFI stub"
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On Tue, Aug 25, 2020 at 11:04 AM Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:
>
> On Wed, 19 Aug 2020 15:24:21 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@xxxxxxx>
> > Link: https://lore.kernel.org/r/20200421033336.9663-3-atish.patra@xxxxxxx
> > [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 <ardb@xxxxxxxxxx>
> > Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>
> > ---
> > arch/riscv/include/asm/sections.h | 13 ++++
> > arch/riscv/kernel/Makefile | 4 ++
> > arch/riscv/kernel/efi-header.S | 104 ++++++++++++++++++++++++++++++
> > arch/riscv/kernel/head.S | 16 +++++
> > arch/riscv/kernel/image-vars.h | 51 +++++++++++++++
> > arch/riscv/kernel/vmlinux.lds.S | 22 ++++++-
> > 6 files changed, 208 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 a5287ab9f7f2..eabec4dce50b 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)
> > +
>
> Is there a reason this is below those objects?
Nope.

I don't really care, but it
> triggered a merge conflict and it seems cleaner above so I put it up there.
>

Sure. Thanks.

> > 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..822b4c9ff2bb
> > --- /dev/null
> > +++ b/arch/riscv/kernel/efi-header.S
> > @@ -0,0 +1,104 @@
> > +/* 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:
> > +#ifdef CONFIG_64BIT
> > + .short IMAGE_FILE_MACHINE_RISCV64 // Machine
> > +#else
> > + .short IMAGE_FILE_MACHINE_RISCV32 // Machine
> > +#endif
> > + .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 __pecoff_text_end - efi_header_end // SizeOfCode
> > + .long __pecoff_data_virt_size // SizeOfInitializedData
> > + .long 0 // SizeOfUninitializedData
> > + .long __efistub_efi_pe_entry - _start // AddressOfEntryPoint
> > + .long efi_header_end - _start // BaseOfCode
> > +
> > +extra_header_fields:
> > + .quad 0 // ImageBase
> > + .long PECOFF_SECTION_ALIGNMENT // 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 __pecoff_text_end - efi_header_end // VirtualSize
> > + .long efi_header_end - _start // VirtualAddress
> > + .long __pecoff_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 __pecoff_data_virt_size // VirtualSize
> > + .long __pecoff_text_end - _start // VirtualAddress
> > + .long __pecoff_data_raw_size // SizeOfRawData
> > + .long __pecoff_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
> > +
> > + .balign 0x1000
> > +efi_header_end:
> > + .endm
> > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> > index c6a37e8231a8..3631147732ee 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.
> > + */
> > + c.li s4,-13
> > + 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..8c212efb37a6
> > --- /dev/null
> > +++ b/arch/riscv/kernel/image-vars.h
> > @@ -0,0 +1,51 @@
> > +/* 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
> > +
> > +/*
> > + * 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 f3586e31ed1e..6dcf790282dd 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 +18,9 @@ ENTRY(_start)
> >
> > jiffies = jiffies_64;
> >
> > +PECOFF_SECTION_ALIGNMENT = 0x1000;
> > +PECOFF_FILE_ALIGNMENT = 0x200;
> > +
> > SECTIONS
> > {
> > /* Beginning of code and text segment */
> > @@ -76,6 +80,10 @@ SECTIONS
> >
> > EXCEPTION_TABLE(0x10)
> >
> > +#ifdef CONFIG_EFI
> > + . = ALIGN(PECOFF_SECTION_ALIGNMENT);
> > + __pecoff_text_end = .;
> > +#endif
> > . = ALIGN(SECTION_ALIGN);
> > _data = .;
> >
> > @@ -83,16 +91,26 @@ SECTIONS
> > .sdata : {
> > __global_pointer$ = . + 0x800;
> > *(.sdata*)
> > - /* End of data section */
> > - _edata = .;
> > }
> >
> > +#ifdef CONFIG_EFI
> > + .pecoff_edata_padding : { BYTE(0); . = ALIGN(PECOFF_FILE_ALIGNMENT); }
> > + __pecoff_data_raw_size = ABSOLUTE(. - __pecoff_text_end);
> > +#endif
> > +
> > + /* End of data section */
> > + _edata = .;
> > +
> > BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
> >
> > .rel.dyn : {
> > *(.rel.dyn*)
> > }
> >
> > +#ifdef CONFIG_EFI
> > + . = ALIGN(PECOFF_SECTION_ALIGNMENT);
> > + __pecoff_data_virt_size = ABSOLUTE(. - __pecoff_text_end);
> > +#endif
> > _end = .;
> >
> > STABS_DEBUG

--
Regards,
Atish

Next message: Pekka Enberg: "[RFC PATCH] x86/mm/fault: Inline page fault paths to reduce kernel text size"
Previous message: Rob Herring: "Re: [PATCH v5 1/5] dt-bindings: irqchip: Add PRU-ICSS interrupt controller bindings"
In reply to: Palmer Dabbelt: "Re: [PATCH v6 5/9] RISC-V: Add PE/COFF header for EFI stub"
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