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>

arch/loongarch/Kconfig

@@ -317,6 +317,15 @@ config EFI
 	  This enables the kernel to use EFI runtime services that are
 	  available (such as the EFI variable services).
 
+config EFI_STUB
+	bool "EFI boot stub support"
+	default y
+	depends on EFI
+	select EFI_GENERIC_STUB
+	help
+	  This kernel feature allows the kernel to be loaded directly by
+	  EFI firmware without the use of a bootloader.
+
 config SMP
 	bool "Multi-Processing support"
 	help

arch/loongarch/Makefile

@@ -7,7 +7,11 @@ boot	:= arch/loongarch/boot
 
 KBUILD_DEFCONFIG := loongson3_defconfig
 
-KBUILD_IMAGE	= $(boot)/vmlinux
+ifndef CONFIG_EFI_STUB
+KBUILD_IMAGE	:= $(boot)/vmlinux.elf
+else
+KBUILD_IMAGE	:= $(boot)/vmlinux.efi
+endif
 
 #
 # Select the object file format to substitute into the linker script.
@@ -75,6 +79,7 @@ endif
 head-y := arch/loongarch/kernel/head.o
 
 libs-y += arch/loongarch/lib/
+libs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
 
 ifeq ($(KBUILD_EXTMOD),)
 prepare: vdso_prepare
@@ -86,10 +91,10 @@ PHONY += vdso_install
 vdso_install:
 	$(Q)$(MAKE) $(build)=arch/loongarch/vdso $@
 
-all:	$(KBUILD_IMAGE)
+all:	$(notdir $(KBUILD_IMAGE))
 
-$(KBUILD_IMAGE): vmlinux
-	$(Q)$(MAKE) $(build)=$(boot) $(bootvars-y) $@
+vmlinux.elf vmlinux.efi: vmlinux
+	$(Q)$(MAKE) $(build)=$(boot) $(bootvars-y) $(boot)/$@
 
 install:
 	$(Q)install -D -m 755 $(KBUILD_IMAGE) $(INSTALL_PATH)/vmlinux-$(KERNELRELEASE)

arch/loongarch/boot/Makefile

@@ -8,9 +8,13 @@ drop-sections := .comment .note .options .note.gnu.build-id
 strip-flags   := $(addprefix --remove-section=,$(drop-sections)) -S
 OBJCOPYFLAGS_vmlinux.efi := -O binary $(strip-flags)
 
-targets := vmlinux
 quiet_cmd_strip = STRIP	  $@
       cmd_strip = $(STRIP) -s -o $@ $<
 
-$(obj)/vmlinux: vmlinux FORCE
+targets := vmlinux.elf
+$(obj)/vmlinux.elf: vmlinux FORCE
 	$(call if_changed,strip)
+
+targets += vmlinux.efi
+$(obj)/vmlinux.efi: vmlinux FORCE
+	$(call if_changed,objcopy)

arch/loongarch/include/asm/efi.h

@@ -17,9 +17,16 @@ void efifb_setup_from_dmi(struct screen_info *si, const char *opt);
 #define arch_efi_call_virt_teardown()
 
 #define EFI_ALLOC_ALIGN		SZ_64K
+#define EFI_RT_VIRTUAL_OFFSET	CSR_DMW0_BASE
 
-struct screen_info *alloc_screen_info(void);
-void free_screen_info(struct screen_info *si);
+static inline struct screen_info *alloc_screen_info(void)
+{
+	return &screen_info;
+}
+
+static inline void free_screen_info(struct screen_info *si)
+{
+}
 
 static inline unsigned long efi_get_max_initrd_addr(unsigned long image_addr)
 {

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

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);
 }

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

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 */

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)

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

drivers/firmware/efi/Kconfig

@@ -107,7 +107,7 @@ config EFI_GENERIC_STUB
 
 config EFI_ARMSTUB_DTB_LOADER
 	bool "Enable the DTB loader"
-	depends on EFI_GENERIC_STUB && !RISCV
+	depends on EFI_GENERIC_STUB && !RISCV && !LOONGARCH
 	default y
 	help
 	  Select this config option to add support for the dtb= command
@@ -124,7 +124,7 @@ config EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER
 	bool "Enable the command line initrd loader" if !X86
 	depends on EFI_STUB && (EFI_GENERIC_STUB || X86)
 	default y if X86
-	depends on !RISCV
+	depends on !RISCV && !LOONGARCH
 	help
 	  Select this config option to add support for the initrd= command
 	  line parameter, allowing an initrd that resides on the same volume

drivers/firmware/efi/libstub/Makefile

@@ -26,6 +26,8 @@ cflags-$(CONFIG_ARM)		:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
 				   $(call cc-option,-mno-single-pic-base)
 cflags-$(CONFIG_RISCV)		:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
 				   -fpic
+cflags-$(CONFIG_LOONGARCH)	:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
+				   -fpie
 
 cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt
 
@@ -70,6 +72,8 @@ lib-$(CONFIG_ARM)		+= arm32-stub.o
 lib-$(CONFIG_ARM64)		+= arm64-stub.o
 lib-$(CONFIG_X86)		+= x86-stub.o
 lib-$(CONFIG_RISCV)		+= riscv-stub.o
+lib-$(CONFIG_LOONGARCH)		+= loongarch-stub.o
+
 CFLAGS_arm32-stub.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
 
 # Even when -mbranch-protection=none is set, Clang will generate a
@@ -125,6 +129,12 @@ STUBCOPY_FLAGS-$(CONFIG_RISCV)	+= --prefix-alloc-sections=.init \
 				   --prefix-symbols=__efistub_
 STUBCOPY_RELOC-$(CONFIG_RISCV)	:= R_RISCV_HI20
 
+# For LoongArch, keep all the symbols in .init section and make sure that no
+# absolute symbols references exist.
+STUBCOPY_FLAGS-$(CONFIG_LOONGARCH)	+= --prefix-alloc-sections=.init \
+					   --prefix-symbols=__efistub_
+STUBCOPY_RELOC-$(CONFIG_LOONGARCH)	:= R_LARCH_MARK_LA
+
 $(obj)/%.stub.o: $(obj)/%.o FORCE
 	$(call if_changed,stubcopy)
 

drivers/firmware/efi/libstub/efi-stub.c

@@ -40,14 +40,22 @@
 
 #ifdef CONFIG_ARM64
 # define EFI_RT_VIRTUAL_LIMIT	DEFAULT_MAP_WINDOW_64
-#elif defined(CONFIG_RISCV)
+#elif defined(CONFIG_RISCV) || defined(CONFIG_LOONGARCH)
 # define EFI_RT_VIRTUAL_LIMIT	TASK_SIZE_MIN
-#else
+#else /* Only if TASK_SIZE is a constant */
 # define EFI_RT_VIRTUAL_LIMIT	TASK_SIZE
 #endif
 
+/*
+ * Some architectures map the EFI regions into the kernel's linear map using a
+ * fixed offset.
+ */
+#ifndef EFI_RT_VIRTUAL_OFFSET
+#define EFI_RT_VIRTUAL_OFFSET	0
+#endif
+
 static u64 virtmap_base = EFI_RT_VIRTUAL_BASE;
-static bool flat_va_mapping;
+static bool flat_va_mapping = (EFI_RT_VIRTUAL_OFFSET != 0);
 
 const efi_system_table_t *efi_system_table;
 
@@ -254,8 +262,8 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
 	 * The easiest way to achieve that is to simply use a 1:1 mapping.
 	 */
 	prop_tbl = get_efi_config_table(EFI_PROPERTIES_TABLE_GUID);
-	flat_va_mapping = prop_tbl &&
-			  (prop_tbl->memory_protection_attribute &
+	flat_va_mapping |= prop_tbl &&
+			   (prop_tbl->memory_protection_attribute &
 			   EFI_PROPERTIES_RUNTIME_MEMORY_PROTECTION_NON_EXECUTABLE_PE_DATA);
 
 	/* force efi_novamap if SetVirtualAddressMap() is unsupported */
@@ -338,7 +346,7 @@ void efi_get_virtmap(efi_memory_desc_t *memory_map, unsigned long map_size,
 		paddr = in->phys_addr;
 		size = in->num_pages * EFI_PAGE_SIZE;
 
-		in->virt_addr = in->phys_addr;
+		in->virt_addr = in->phys_addr + EFI_RT_VIRTUAL_OFFSET;
 		if (efi_novamap) {
 			continue;
 		}

drivers/firmware/efi/libstub/loongarch-stub.c

@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Author: Yun Liu <liuyun@loongson.cn>
+ *         Huacai Chen <chenhuacai@loongson.cn>
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#include <asm/efi.h>
+#include <asm/addrspace.h>
+#include "efistub.h"
+
+typedef void __noreturn (*kernel_entry_t)(bool efi, unsigned long fdt);
+
+extern int kernel_asize;
+extern int kernel_fsize;
+extern int kernel_offset;
+extern kernel_entry_t kernel_entry;
+
+efi_status_t check_platform_features(void)
+{
+	return EFI_SUCCESS;
+}
+
+efi_status_t handle_kernel_image(unsigned long *image_addr,
+				 unsigned long *image_size,
+				 unsigned long *reserve_addr,
+				 unsigned long *reserve_size,
+				 efi_loaded_image_t *image,
+				 efi_handle_t image_handle)
+{
+	efi_status_t status;
+	unsigned long kernel_addr = 0;
+
+	kernel_addr = (unsigned long)&kernel_offset - kernel_offset;
+
+	status = efi_relocate_kernel(&kernel_addr, kernel_fsize, kernel_asize,
+				     PHYSADDR(VMLINUX_LOAD_ADDRESS), SZ_2M, 0x0);
+
+	*image_addr = kernel_addr;
+	*image_size = kernel_asize;
+
+	return status;
+}
+
+void __noreturn efi_enter_kernel(unsigned long entrypoint, unsigned long fdt, unsigned long fdt_size)
+{
+	kernel_entry_t real_kernel_entry;
+
+	/* Config Direct Mapping */
+	csr_write64(CSR_DMW0_INIT, LOONGARCH_CSR_DMWIN0);
+	csr_write64(CSR_DMW1_INIT, LOONGARCH_CSR_DMWIN1);
+
+	real_kernel_entry = (kernel_entry_t)
+		((unsigned long)&kernel_entry - entrypoint + VMLINUX_LOAD_ADDRESS);
+
+	if (!efi_novamap)
+		real_kernel_entry(true, fdt);
+	else
+		real_kernel_entry(false, fdt);
+}

include/linux/pe.h

@@ -65,6 +65,8 @@
 #define	IMAGE_FILE_MACHINE_SH5		0x01a8
 #define	IMAGE_FILE_MACHINE_THUMB	0x01c2
 #define	IMAGE_FILE_MACHINE_WCEMIPSV2	0x0169
+#define	IMAGE_FILE_MACHINE_LOONGARCH32	0x6232
+#define	IMAGE_FILE_MACHINE_LOONGARCH64	0x6264
 
 /* flags */
 #define IMAGE_FILE_RELOCS_STRIPPED           0x0001