efi/loongarch: Add efistub booting support

This patch adds efistub booting support, which is the standard UEFI boot
protocol for LoongArch to use.

We use generic efistub, which means we can pass boot information (i.e.,
system table, memory map, kernel command line, initrd) via a light FDT
and drop a lot of non-standard code.

We use a flat mapping to map the efi runtime in the kernel's address
space. In efi, VA = PA; in kernel, VA = PA + PAGE_OFFSET. As a result,
flat mapping is not identity mapping, SetVirtualAddressMap() is still
needed for the efi runtime.

Tested-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
[ardb: change fpic to fpie as suggested by Xi Ruoyao]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

6 files changed, 154 insertions, 10 deletions

diff --git a/arch/loongarch/kernel/efi-header.S b/arch/loongarch/kernel/efi-header.S
new file mode 100644
index 000000000000..8c1d229a2afa
--- /dev/null
+++ b/arch/loongarch/kernel/efi-header.S
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/pe.h>
+#include <linux/sizes.h>
+
+	.macro	__EFI_PE_HEADER
+	.long	PE_MAGIC
+.Lcoff_header:
+	.short	IMAGE_FILE_MACHINE_LOONGARCH64		/* Machine */
+	.short	.Lsection_count				/* NumberOfSections */
+	.long	0 					/* TimeDateStamp */
+	.long	0					/* PointerToSymbolTable */
+	.long	0					/* NumberOfSymbols */
+	.short	.Lsection_table - .Loptional_header	/* SizeOfOptionalHeader */
+	.short	IMAGE_FILE_DEBUG_STRIPPED | \
+		IMAGE_FILE_EXECUTABLE_IMAGE | \
+		IMAGE_FILE_LINE_NUMS_STRIPPED		/* Characteristics */
+
+.Loptional_header:
+	.short	PE_OPT_MAGIC_PE32PLUS			/* PE32+ format */
+	.byte	0x02					/* MajorLinkerVersion */
+	.byte	0x14					/* MinorLinkerVersion */
+	.long	__inittext_end - .Lefi_header_end	/* SizeOfCode */
+	.long	_end - __initdata_begin			/* SizeOfInitializedData */
+	.long	0					/* SizeOfUninitializedData */
+	.long	__efistub_efi_pe_entry - _head		/* AddressOfEntryPoint */
+	.long	.Lefi_header_end - _head		/* BaseOfCode */
+
+.Lextra_header_fields:
+	.quad	0					/* ImageBase */
+	.long	PECOFF_SEGMENT_ALIGN			/* SectionAlignment */
+	.long	PECOFF_FILE_ALIGN			/* 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 - _head				/* SizeOfImage */
+
+	/* Everything before the kernel image is considered part of the header */
+	.long	.Lefi_header_end - _head		/* 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	(.Lsection_table - .) / 8		/* NumberOfRvaAndSizes */
+
+	.quad	0					/* ExportTable */
+	.quad	0					/* ImportTable */
+	.quad	0					/* ResourceTable */
+	.quad	0					/* ExceptionTable */
+	.quad	0					/* CertificationTable */
+	.quad	0					/* BaseRelocationTable */
+
+	/* Section table */
+.Lsection_table:
+	.ascii	".text\0\0\0"
+	.long	__inittext_end - .Lefi_header_end	/* VirtualSize */
+	.long	.Lefi_header_end - _head		/* VirtualAddress */
+	.long	__inittext_end - .Lefi_header_end	/* SizeOfRawData */
+	.long	.Lefi_header_end - _head		/* 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	_end - __initdata_begin			/* VirtualSize */
+	.long	__initdata_begin - _head		/* VirtualAddress */
+	.long	_edata - __initdata_begin		/* SizeOfRawData */
+	.long	__initdata_begin - _head		/* 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	.Lsection_count, (. - .Lsection_table) / 40
+
+	.balign	0x10000					/* PECOFF_SEGMENT_ALIGN */
+.Lefi_header_end:
+	.endm
diff --git a/arch/loongarch/kernel/efi.c b/arch/loongarch/kernel/efi.c
index a50b60c587fa..1f1f755fb425 100644
--- a/arch/loongarch/kernel/efi.c
+++ b/arch/loongarch/kernel/efi.c
@@ -69,4 +69,7 @@ void __init efi_init(void)
 	config_tables = early_memremap(efi_config_table, efi_nr_tables * size);
 	efi_config_parse_tables(config_tables, efi_systab->nr_tables, arch_tables);
 	early_memunmap(config_tables, efi_nr_tables * size);
+
+	if (screen_info.orig_video_isVGA == VIDEO_TYPE_EFI)
+		memblock_reserve(screen_info.lfb_base, screen_info.lfb_size);
 }
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index c60eb66793e3..01bac62a6442 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -12,6 +12,26 @@
 #include <asm/loongarch.h>
 #include <asm/stackframe.h>
 
+#ifdef CONFIG_EFI_STUB
+
+#include "efi-header.S"
+
+	__HEAD
+
+_head:
+	.word	MZ_MAGIC		/* "MZ", MS-DOS header */
+	.org	0x3c			/* 0x04 ~ 0x3b reserved */
+	.long	pe_header - _head	/* Offset to the PE header */
+
+pe_header:
+	__EFI_PE_HEADER
+
+SYM_DATA(kernel_asize, .long _end - _text);
+SYM_DATA(kernel_fsize, .long _edata - _text);
+SYM_DATA(kernel_offset, .long kernel_offset - _text);
+
+#endif
+
 	__REF
 
 SYM_CODE_START(kernel_entry)			# kernel entry point
diff --git a/arch/loongarch/kernel/image-vars.h b/arch/loongarch/kernel/image-vars.h
new file mode 100644
index 000000000000..c901ebb903f2
--- /dev/null
+++ b/arch/loongarch/kernel/image-vars.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#ifndef __LOONGARCH_KERNEL_IMAGE_VARS_H
+#define __LOONGARCH_KERNEL_IMAGE_VARS_H
+
+#ifdef CONFIG_EFI_STUB
+
+__efistub_memcmp		= memcmp;
+__efistub_memchr		= memchr;
+__efistub_memcpy		= memcpy;
+__efistub_memmove		= memmove;
+__efistub_memset		= memset;
+__efistub_strcat		= strcat;
+__efistub_strcmp		= strcmp;
+__efistub_strlen		= strlen;
+__efistub_strncat		= strncat;
+__efistub_strnstr		= strnstr;
+__efistub_strnlen		= strnlen;
+__efistub_strrchr		= strrchr;
+__efistub_kernel_entry		= kernel_entry;
+__efistub_kernel_asize		= kernel_asize;
+__efistub_kernel_fsize		= kernel_fsize;
+__efistub_kernel_offset		= kernel_offset;
+__efistub_screen_info		= screen_info;
+
+#endif
+
+#endif /* __LOONGARCH_KERNEL_IMAGE_VARS_H */
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 8f5c2f9a1a83..e8714b1d94c8 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -49,9 +49,7 @@
 #define SMBIOS_CORE_PACKAGE_OFFSET	0x23
 #define LOONGSON_EFI_ENABLE		(1 << 3)
 
-#ifdef CONFIG_VT
-struct screen_info screen_info;
-#endif
+struct screen_info screen_info __section(".data");
 
 unsigned long fw_arg0, fw_arg1;
 DEFINE_PER_CPU(unsigned long, kernelsp);
@@ -122,16 +120,9 @@ static void __init parse_cpu_table(const struct dmi_header *dm)
 
 static void __init parse_bios_table(const struct dmi_header *dm)
 {
-	int bios_extern;
 	char *dmi_data = (char *)dm;
 
-	bios_extern = *(dmi_data + SMBIOS_BIOSEXTERN_OFFSET);
 	b_info.bios_size = (*(dmi_data + SMBIOS_BIOSSIZE_OFFSET) + 1) << 6;
-
-	if (bios_extern & LOONGSON_EFI_ENABLE)
-		set_bit(EFI_BOOT, &efi.flags);
-	else
-		clear_bit(EFI_BOOT, &efi.flags);
 }
 
 static void __init find_tokens(const struct dmi_header *dm, void *dummy)
diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
index 69c76f26c1c5..36d042739f3c 100644
--- a/arch/loongarch/kernel/vmlinux.lds.S
+++ b/arch/loongarch/kernel/vmlinux.lds.S
@@ -12,6 +12,7 @@
 #define BSS_FIRST_SECTIONS *(.bss..swapper_pg_dir)
 
 #include <asm-generic/vmlinux.lds.h>
+#include "image-vars.h"
 
 /*
  * Max avaliable Page Size is 64K, so we set SectionAlignment