On Wed, 26 Feb 2020 at 02:10, Atish Patra <atish.patra@xxxxxxx> 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> > --- > arch/riscv/include/asm/Kbuild | 1 - > arch/riscv/include/asm/sections.h | 13 ++++ > arch/riscv/kernel/Makefile | 4 ++ > arch/riscv/kernel/efi-header.S | 107 ++++++++++++++++++++++++++++++ > arch/riscv/kernel/head.S | 15 +++++ > arch/riscv/kernel/image-vars.h | 52 +++++++++++++++ > arch/riscv/kernel/vmlinux.lds.S | 27 ++++++-- > 7 files changed, 212 insertions(+), 7 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/Kbuild b/arch/riscv/include/asm/Kbuild > index 517394390106..ef797fe44934 100644 > --- a/arch/riscv/include/asm/Kbuild > +++ b/arch/riscv/include/asm/Kbuild > @@ -24,7 +24,6 @@ generic-y += local64.h > generic-y += mm-arch-hooks.h > generic-y += percpu.h > generic-y += preempt.h > -generic-y += sections.h > generic-y += serial.h > generic-y += shmparam.h > generic-y += topology.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 9601ac907f70..471b1c73f77d 100644 > --- a/arch/riscv/kernel/Makefile > +++ b/arch/riscv/kernel/Makefile > @@ -29,6 +29,10 @@ obj-y += cacheinfo.o > obj-$(CONFIG_MMU) += vdso.o vdso/ > > obj-$(CONFIG_RISCV_M_MODE) += clint.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..af959e748d93 > --- /dev/null > +++ b/arch/riscv/kernel/efi-header.S > @@ -0,0 +1,107 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2019 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 0 // MajorImageVersion > + .short 0 // MinorImageVersion Put LINUX_EFISTUB_MAJOR_VERSION and LINUX_EFISTUB_MINOR_VERSION here > + .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 > + You dropped the debug header here, which is actually *very* useful if you want to single step through the stub from DEBUG edk2 firmware. > + /* > + * EFI will load .text onwards at the 4k section alignment > + * described in the PE/COFF header. To ensure that instruction > + * sequences using an adrp and a :lo12: immediate will function Surely, this is inaccurate for RISC-V? > + * correctly at this alignment, we must ensure that .text is > + * placed at a 4k boundary in the Image to begin with. > + */ > + .align 12 > +efi_header_end: > + .endm > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S > index ac5b0e0a02f6..835dc76de285 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 +23,17 @@ 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 What happens if you try to do plain boot on an EFI kernel? On ARM and x86, we took care to use a 'MZ' opcode that behaves as a pseudo-NOP, and jump to start_kernel right after, so if you boot the EFI kernel as a normal kernel, it still works. > +#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 +51,14 @@ 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..57abb85065e9 > --- /dev/null > +++ b/arch/riscv/kernel/image-vars.h > @@ -0,0 +1,52 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * 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 b32640300d07..933b9e9a4b39 100644 > --- a/arch/riscv/kernel/vmlinux.lds.S > +++ b/arch/riscv/kernel/vmlinux.lds.S > @@ -9,6 +9,7 @@ > #include <asm/page.h> > #include <asm/cache.h> > #include <asm/thread_info.h> > +#include "image-vars.h" > > #include <linux/sizes.h> > OUTPUT_ARCH(riscv) > @@ -16,6 +17,14 @@ 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 */ > @@ -26,12 +35,15 @@ SECTIONS > > __init_begin = .; > INIT_TEXT_SECTION(PAGE_SIZE) > + > + /* Start of data section */ > INIT_DATA_SECTION(16) > /* we have to discard exit text and such at runtime, not link time */ > .exit.text : > { > EXIT_TEXT > } > + > .exit.data : > { > EXIT_DATA > @@ -54,7 +66,8 @@ SECTIONS > _etext = .; > } > > - /* Start of data section */ > + __text_end = .; > + > _sdata = .; > RO_DATA(L1_CACHE_BYTES) > .srodata : { > @@ -65,19 +78,21 @@ SECTIONS > .sdata : { > __global_pointer$ = . + 0x800; > *(.sdata*) > - /* End of data section */ > - _edata = .; > *(.sbss*) > } > - > - BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0) > - > + PECOFF_EDATA_PADDING > + __data_raw_size = ABSOLUTE(. - __text_end); > + /* End of data section */ > + _edata = .; > EXCEPTION_TABLE(0x10) > > .rel.dyn : { > *(.rel.dyn*) > } > > + BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0) > + __data_virt_size = ABSOLUTE(. - __text_end); > + > _end = .; > > STABS_DEBUG > -- > 2.24.0 >