efi: stub: support running U-Boot as an EFI payload on ARM64

Implement support for launching U-Boot via an EFI stub app on ARM64.

This is more or less a straight port of the x86 implementation, but due
to the highly x86/qemu specific nature of that implementation I decided
to just split it out to its own file.

Unlike the x86 implementation, there is no debug UART here since ARM
platforms don't have a standard UART interface. However it is usually
possible to port over the debug uart implementation for you platform for
bringup purposes.

Currently this implementation doesn't provide a DTB to U-Boot and
expects U-Boot to use a built-in one, however this ought to be a fairly
trivial addition in the future.

The other significant difference to the x86 version is that rather than
copying U-Boot to CONFIG_TEXT_OFFSET, we require that U-Boot is built
position independent and copy it to EFI allocated memory.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>

Makefile

@@ -1687,19 +1687,30 @@ u-boot.bin.o: u-boot.bin FORCE
 u-boot-payload.lds: $(LDSCRIPT_EFI) FORCE
 	$(call if_changed_dep,cpp_lds)
 
+# Determine the file suffix for the efi stub implementation
+EFI_STUB_ARCH := $(if $(CONFIG_ARM64),arm64,$(if $(CONFIG_X86_64),x86,$(ARCH)))
+
 # Rule to link the EFI payload which contains a stub and a U-Boot binary
 quiet_cmd_u-boot_payload ?= LD      $@
       cmd_u-boot_payload ?= $(LD) $(LDFLAGS_EFI_PAYLOAD) -o $@ \
-      -T u-boot-payload.lds arch/x86/cpu/call32.o \
-      lib/efi/efi.o lib/efi/efi_stub.o u-boot.bin.o \
+      -T u-boot-payload.lds $(if $(CONFIG_X86),arch/x86/cpu/call32.o,) \
+      lib/efi/efi.o lib/efi/efi_stub_$(EFI_STUB_ARCH).o u-boot.bin.o \
       $(addprefix arch/$(ARCH)/lib/,$(EFISTUB))
 
+quiet_cmd_u-boot_payload_arm64.efi ?= OBJCOPY $@
+      cmd_u-boot_payload_arm64.efi ?= $(OBJCOPY) -O binary u-boot-payload $@
+
 u-boot-payload: u-boot.bin.o u-boot-payload.lds FORCE
 	$(call if_changed,u-boot_payload)
 
 OBJCOPYFLAGS_u-boot-payload.efi := $(OBJCOPYFLAGS_EFI)
+ifeq ($(CONFIG_X86),y)
 u-boot-payload.efi: u-boot-payload FORCE
 	$(call if_changed,zobjcopy)
+else
+u-boot-payload.efi: u-boot-payload FORCE
+	$(call if_changed,u-boot_payload_$(EFI_STUB_ARCH).efi)
+endif
 
 u-boot-img.bin: spl/u-boot-spl.bin u-boot.img FORCE
 	$(call if_changed,cat)

arch/arm/cpu/armv8/config.mk

@@ -10,3 +10,14 @@ PLATFORM_CPPFLAGS += $(PF_NO_UNALIGNED)
 EFI_LDS := elf_aarch64_efi.lds
 EFI_CRT0 := crt0_aarch64_efi.o
 EFI_RELOC := reloc_aarch64_efi.o
+
+LDSCRIPT_EFI := $(srctree)/arch/arm/lib/elf_aarch64_efi.lds
+EFISTUB := crt0_aarch64_efi.o reloc_aarch64_efi.o
+OBJCOPYFLAGS_EFI += --target=pei-aarch64-little
+EFIPAYLOAD_BFDTARGET := pei-aarch64-little
+EFIPAYLOAD_BFDARCH := aarch64
+LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared --no-undefined \
+		       -s -zexecstack
+
+CPPFLAGS_REMOVE_crt0-efi-aarch64.o += $(CFLAGS_NON_EFI)
+CPPFLAGS_crt0-efi-aarch64.o += $(CFLAGS_EFI)

arch/arm/include/asm/global_data.h

@@ -108,6 +108,9 @@ struct arch_global_data {
 #ifdef CONFIG_SMBIOS
 	ulong smbios_start;		/* Start address of SMBIOS table */
 #endif
+#ifdef CONFIG_EFI_STUB
+	ulong table;
+#endif
 };
 
 #include <asm-generic/global_data.h>

arch/arm/lib/Makefile

@@ -131,3 +131,5 @@ CFLAGS_REMOVE_$(EFI_CRT0) := $(CFLAGS_NON_EFI)
 
 CFLAGS_$(EFI_RELOC) := $(CFLAGS_EFI)
 CFLAGS_REMOVE_$(EFI_RELOC) := $(CFLAGS_NON_EFI)
+
+extra-$(CONFIG_EFI_STUB) += $(EFI_CRT0) $(EFI_RELOC)

include/efi.h

@@ -547,7 +547,7 @@ struct efi_tpm_plat {
 extern char image_base[];
 
 /* Start and end of U-Boot image (for payload) */
-extern char _binary_u_boot_bin_start[], _binary_u_boot_bin_end[];
+extern char _binary_u_boot_bin_start[], _binary_u_boot_bin_end[], _binary_u_boot_bin_size[];
 
 /*
  * Variable Attributes

lib/efi/Kconfig

@@ -1,9 +1,9 @@
 menu "U-Boot as UEFI application"
-	depends on X86
+	depends on X86 || ARM
 
 config EFI
 	bool "Support running U-Boot from EFI"
-	depends on X86
+	depends on X86 || ARM
 	imply X86_TSC_READ_BASE
 	help
 	  U-Boot can be started from EFI on certain platforms. This allows
@@ -13,10 +13,11 @@ config EFI
 
 choice
 	prompt "Select EFI mode to use"
-	depends on X86 && EFI
+	depends on EFI
 
 config EFI_APP
 	bool "Support running as an EFI application"
+	depends on !ARM
 	select CHARSET
 	help
 	  Build U-Boot as an application which can be started from EFI. This
@@ -26,6 +27,7 @@ config EFI_APP
 	  to EFI.
 
 config EFI_STUB
+	select POSITION_INDEPENDENT if ARM
 	bool "Support running as an EFI payload"
 
 endchoice
@@ -59,6 +61,7 @@ choice
 	  this may produce no error message - it just won't start!
 
 config EFI_STUB_32BIT
+	depends on !ARM
 	bool "Produce a stub for running with 32-bit EFI"
 
 config EFI_STUB_64BIT

lib/efi/Makefile

@@ -5,13 +5,23 @@
 obj-$(CONFIG_EFI_APP) += efi_app.o efi.o efi_app_init.o efi_vars.o efi_dtb.o
 obj-$(CONFIG_EFI_STUB) += efi_info.o
 
-CFLAGS_REMOVE_efi_stub.o := -mregparm=3 \
-	$(if $(CONFIG_EFI_STUB_64BIT),-march=i386 -m32)
-CFLAGS_efi_stub.o := -fpic -fshort-wchar \
-	$(if $(CONFIG_EFI_STUB_64BIT),-m64)
-CFLAGS_REMOVE_efi.o := -mregparm=3 \
-	$(if $(CONFIG_EFI_STUB_64BIT),-march=i386 -m32)
-CFLAGS_efi.o := -fpic -fshort-wchar \
-	$(if $(CONFIG_EFI_STUB_64BIT),-m64)
+ifeq ($(CONFIG_ARM64),y)
+efi_stub.o := efi_stub_arm64.o
+else
+efi_stub.o := efi_stub_x86.o
 
-extra-$(CONFIG_EFI_STUB) += efi_stub.o efi.o
+ifeq ($(CONFIG_EFI_STUB_64BIT),y) # && !CONFIG_ARM64
+CFLAGS_REMOVE_$(efi_stub.o) := -march=i386 -m32
+CFLAGS_$(efi_stub.o) := -m64
+CFLAGS_REMOVE_efi.o := -march=i386 -m32
+CFLAGS_efi.o := -fpic -m64
+endif
+endif
+
+CFLAGS_REMOVE_$(efi_stub.o) += -mregparm=3
+CFLAGS_$(efi_stub.o) += -fpic -fshort-wchar
+CFLAGS_REMOVE_efi.o += -mregparm=3
+CFLAGS_efi.o += -fpic -fshort-wchar
+
+$(info removing flags $(CFLAGS_REMOVE_$(efi_stub.o)))
+extra-$(CONFIG_EFI_STUB) += $(efi_stub.o) efi.o

lib/efi/efi_info.c

@@ -10,6 +10,8 @@
 #include <mapmem.h>
 #include <asm/global_data.h>
 
+DECLARE_GLOBAL_DATA_PTR;
+
 int efi_info_get(enum efi_entry_t type, void **datap, int *sizep)
 {
 	struct efi_entry_hdr *entry;
@@ -42,5 +44,5 @@ int efi_info_get(enum efi_entry_t type, void **datap, int *sizep)
 err:
 	unmap_sysmem(info);
 
-	return ret;
+	return -ENOSYS;
 }

lib/efi/efi_stub_arm64.c

@@ -0,0 +1,236 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2015 Google, Inc
+ * Copyright (c) 2024 Linaro, Ltd.
+ *
+ * EFI information obtained here:
+ * http://wiki.phoenix.com/wiki/index.php/EFI_BOOT_SERVICES
+ *
+ * Call ExitBootServices() and launch U-Boot from an EFI environment.
+ */
+
+#include <debug_uart.h>
+#include <efi.h>
+#include <efi_api.h>
+#include <malloc.h>
+#include <asm/io.h>
+#include <linux/err.h>
+#include <linux/types.h>
+
+static bool ebs_called;
+
+void _debug_uart_putc(int ch)
+{
+	struct efi_priv *priv = efi_get_priv();
+
+	if (ch == '\n')
+		_debug_uart_putc('\r');
+	/*
+	 * After calling EBS we can't log anywhere.
+	 * NOTE: for development it is possible to re-implement
+	 * your boards debug uart here like in efi_stub.c for x86.
+	 */
+	if (!ebs_called)
+		efi_putc(priv, ch);
+}
+
+void _debug_uart_init(void) {}
+
+DEBUG_UART_FUNCS;
+
+void putc(const char ch)
+{
+	_debug_uart_putc(ch);
+}
+
+void puts(const char *str)
+{
+	while (*str)
+		putc(*str++);
+}
+
+
+void *memcpy(void *dest, const void *src, size_t size)
+{
+	unsigned char *dptr = dest;
+	const unsigned char *ptr = src;
+	const unsigned char *end = src + size;
+
+	while (ptr < end)
+		*dptr++ = *ptr++;
+
+	return dest;
+}
+
+void *memset(void *inptr, int ch, size_t size)
+{
+	char *ptr = inptr;
+	char *end = ptr + size;
+
+	while (ptr < end)
+		*ptr++ = ch;
+
+	return ptr;
+}
+
+/**
+ * setup_info_table() - sets up a table containing information from EFI
+ *
+ * We must call exit_boot_services() before jumping out of the stub into U-Boot
+ * proper, so that U-Boot has full control of peripherals, memory, etc.
+ *
+ * Once we do this, we cannot call any boot-services functions so we must find
+ * out everything we need to before doing that.
+ *
+ * Set up a struct efi_info_hdr table which can hold various records (e.g.
+ * struct efi_entry_memmap) with information obtained from EFI.
+ *
+ * @priv: Pointer to our private information which contains the list
+ * @size: Size of the table to allocate
+ * Return: 0 if OK, non-zero on error
+ */
+static int setup_info_table(struct efi_priv *priv, int size)
+{
+	struct efi_info_hdr *info;
+	efi_status_t ret;
+
+	/* Get some memory for our info table */
+	priv->info_size = size;
+	info = efi_malloc(priv, priv->info_size, &ret);
+	if (ret) {
+		printhex2(ret);
+		puts(" No memory for info table: ");
+		return ret;
+	}
+
+	memset(info, '\0', sizeof(*info));
+	info->version = EFI_TABLE_VERSION;
+	info->hdr_size = sizeof(*info);
+	priv->info = info;
+	priv->next_hdr = (char *)info + info->hdr_size;
+
+	return 0;
+}
+
+/**
+ * add_entry_addr() - Add a new entry to the efi_info list
+ *
+ * This adds an entry, consisting of a tag and two lots of data. This avoids the
+ * caller having to coalesce the data first
+ *
+ * @priv: Pointer to our private information which contains the list
+ * @type: Type of the entry to add
+ * @ptr1: Pointer to first data block to add
+ * @size1: Size of first data block in bytes (can be 0)
+ * @ptr2: Pointer to second data block to add
+ * @size2: Size of second data block in bytes (can be 0)
+ */
+static void add_entry_addr(struct efi_priv *priv, enum efi_entry_t type,
+			   void *ptr1, int size1, void *ptr2, int size2)
+{
+	struct efi_entry_hdr *hdr = priv->next_hdr;
+
+	hdr->type = type;
+	hdr->size = size1 + size2;
+	hdr->addr = 0;
+	hdr->link = ALIGN(sizeof(*hdr) + hdr->size, 16);
+	priv->next_hdr += hdr->link;
+	memcpy(hdr + 1, ptr1, size1);
+	memcpy((void *)(hdr + 1) + size1, ptr2, size2);
+	priv->info->total_size = (ulong)priv->next_hdr - (ulong)priv->info;
+}
+
+/**
+ * efi_main() - Start an EFI image
+ *
+ * This function is called by our EFI start-up code. It handles running
+ * U-Boot. If it returns, EFI will continue.
+ */
+efi_status_t EFIAPI efi_main(efi_handle_t image,
+			     struct efi_system_table *sys_table)
+{
+	struct efi_priv local_priv, *priv = &local_priv;
+	struct efi_boot_services *boot = sys_table->boottime;
+	struct efi_entry_memmap map;
+	struct efi_gop *gop;
+	struct efi_entry_gopmode mode;
+	struct efi_entry_systable table;
+	efi_guid_t efi_gop_guid = EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID;
+	efi_status_t ret;
+
+	ebs_called = false;
+
+	ret = efi_init(priv, "Payload", image, sys_table);
+	if (ret) {
+		printhex2(ret);
+		puts(" efi_init() failed\n");
+		return ret;
+	}
+	efi_set_priv(priv);
+
+	phys_addr_t reloc_addr = ULONG_MAX;
+	ret = boot->allocate_pages(EFI_ALLOCATE_MAX_ADDRESS, EFI_LOADER_CODE,
+				   (phys_addr_t)_binary_u_boot_bin_size / EFI_PAGE_SIZE,
+				   &reloc_addr);
+	if (ret != EFI_SUCCESS) {
+		puts("Failed to allocate memory for U-Boot: ");
+		printhex2(ret);
+		putc('\n');
+		return ret;
+	}
+
+	ret = efi_store_memory_map(priv);
+	if (ret)
+		return ret;
+
+	ret = setup_info_table(priv, priv->memmap_size + 128);
+	if (ret)
+		return ret;
+
+	ret = boot->locate_protocol(&efi_gop_guid, NULL, (void **)&gop);
+	if (ret) {
+		puts(" GOP unavailable\n");
+	} else {
+		mode.fb_base = gop->mode->fb_base;
+		mode.fb_size = gop->mode->fb_size;
+		mode.info_size = gop->mode->info_size;
+		add_entry_addr(priv, EFIET_GOP_MODE, &mode, sizeof(mode),
+			       gop->mode->info,
+			       sizeof(struct efi_gop_mode_info));
+	}
+
+	table.sys_table = (ulong)sys_table;
+	add_entry_addr(priv, EFIET_SYS_TABLE, &table, sizeof(table), NULL, 0);
+
+	ret = efi_call_exit_boot_services();
+	if (ret)
+		return ret;
+
+	/* The EFI console won't work now :( */
+	ebs_called = true;
+
+	map.version = priv->memmap_version;
+	map.desc_size = priv->memmap_desc_size;
+	add_entry_addr(priv, EFIET_MEMORY_MAP, &map, sizeof(map),
+		       priv->memmap_desc, priv->memmap_size);
+	add_entry_addr(priv, EFIET_END, NULL, 0, 0, 0);
+
+	memcpy((void *)reloc_addr, _binary_u_boot_bin_start,
+	       (ulong)_binary_u_boot_bin_end -
+	       (ulong)_binary_u_boot_bin_start);
+
+/* This will only work if you patched your own debug uart into this file. */
+#ifdef DEBUG
+	puts("EFI table at ");
+	printhex8((ulong)priv->info);
+	puts(" size ");
+	printhex8(priv->info->total_size);
+	putc('\n');
+#endif
+	typedef void (*func_t)(u64 x0, u64 x1, u64 x2, u64 x3);
+
+	puts("Jumping to U-Boot\n");
+	((func_t)reloc_addr)((phys_addr_t)priv->info, 0, 0, 0);
+
+	return EFI_LOAD_ERROR;
+}