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 <[email protected]>
---
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
+ .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 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
+ * 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
+#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
On Wed, 26 Feb 2020 at 02:10, Atish Patra <[email protected]> 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 <[email protected]>
> ---
> 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
>
On Wed, 2020-02-26 at 08:14 +0100, Ard Biesheuvel wrote:
> On Wed, 26 Feb 2020 at 02:10, Atish Patra <[email protected]>
> 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 <[email protected]>
> > ---
> > 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
>
Sure.
> > + .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.
>
Ahh I see. I was not sure how to use the debug feature :). Can we do
the same in U-boot ?
How about adding it back later once I can verify it with EDK2 ?
> > + /*
> > + * 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?
Sorry. I should have removed the comment. We keep the the _start and
.head.text section aligned to a PAGE_SIZE anyways using the linker
script.
>
> > + * 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.
>
There should have been a "j _start_kernel" after the "MZ" ascii. I just
tested EFI kernel can now boot as a normal kernel as well with that
change. Thanks for pointing that out.
> > +#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
> >
--
Regards,
Atish
On Thu, 27 Feb 2020 at 02:29, Atish Patra <[email protected]> wrote:
>
> On Wed, 2020-02-26 at 08:14 +0100, Ard Biesheuvel wrote:
> > On Wed, 26 Feb 2020 at 02:10, Atish Patra <[email protected]>
> > 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 <[email protected]>
> > > ---
> > > 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
> >
>
> Sure.
>
> > > + .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.
> >
>
> Ahh I see. I was not sure how to use the debug feature :). Can we do
> the same in U-boot ?
>
You could, but I doubt it has been implemented yet.
Adding the debug header will cause the firmware to record the image
path and its load address in a special debug table, which the firmware
can use to expose the load address and path of the image as it is
loaded (i.e. before moving itself into place)
When I run this under a DEBUG build of EDK2, it prints a line like
add-symbol-file /home/ardbie01/linux-build-arm64/vmlinux 0x74E0B000
which I can paste into the GDB command window, set a breakpoint on
efi_entry(), and single step through the stub.
> How about adding it back later once I can verify it with EDK2 ?
>
Sure, that is fine
> > > + /*
> > > + * 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?
>
> Sorry. I should have removed the comment. We keep the the _start and
> .head.text section aligned to a PAGE_SIZE anyways using the linker
> script.
ok
> >
> > > + * 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.
> >
>
> There should have been a "j _start_kernel" after the "MZ" ascii. I just
> tested EFI kernel can now boot as a normal kernel as well with that
> change. Thanks for pointing that out.
>
Sure
> > > +#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
> > >
>
> --
> Regards,
> Atish