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> --- 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 + $(call if_changed,objcopy) + obj-$(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 a2f0cb3ca0a6..f5583473f41c 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 -- 2.24.0
