[RFT PATCH v4 5/9] RISC-V: Add PE/COFF header for EFI stub

Atish Patra
2020-07-29T23:36:58Z

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@wdc.com>
Link: https://lore.kernel.org/r/20200421033336.9663-3-atish.patra@wdc.com
[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@kernel.org>
---
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 b355cf485671..6f7a3b3771fd 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 eb123eda3663..3a05a9222b82 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 e6f8016b366a..2616230da1e7 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