linux/arch/arm64/include/asm/efi.h

#ifndef _ASM_EFI_H
#define _ASM_EFI_H

#include <asm/boot.h>
#include <asm/cpufeature.h>
#include <asm/fpsimd.h>
#include <asm/io.h>
#include <asm/memory.h>
#include <asm/mmu_context.h>
#include <asm/neon.h>
#include <asm/ptrace.h>
#include <asm/tlbflush.h>

#ifdef CONFIG_EFI
extern void efi_init(void);
#else
#define efi_init()
#endif

int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);

#define arch_efi_call_virt_setup()					\
({									\
	efi_virtmap_load();						\
	__efi_fpsimd_begin();						\
})

#define arch_efi_call_virt(p, f, args...)				\
({									\
	efi_##f##_t *__f;						\
	__f = p->f;							\
	__f(args);							\
})

#define arch_efi_call_virt_teardown()					\
({									\
	__efi_fpsimd_end();						\
	efi_virtmap_unload();						\
})

#define ARCH_EFI_IRQ_FLAGS_MASK (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)

/* arch specific definitions used by the stub code */

/*
 * AArch64 requires the DTB to be 8-byte aligned in the first 512MiB from
 * start of kernel and may not cross a 2MiB boundary. We set alignment to
 * 2MiB so we know it won't cross a 2MiB boundary.
 */
#define EFI_FDT_ALIGN	SZ_2M   /* used by allocate_new_fdt_and_exit_boot() */

/*
 * In some configurations (e.g. VMAP_STACK && 64K pages), stacks built into the
 * kernel need greater alignment than we require the segments to be padded to.
 */
#define EFI_KIMG_ALIGN	\
	(SEGMENT_ALIGN > THREAD_ALIGN ? SEGMENT_ALIGN : THREAD_ALIGN)

/* on arm64, the FDT may be located anywhere in system RAM */
static inline unsigned long efi_get_max_fdt_addr(unsigned long dram_base)
{
	return ULONG_MAX;
}

/*
 * On arm64, we have to ensure that the initrd ends up in the linear region,
 * which is a 1 GB aligned region of size '1UL << (VA_BITS - 1)' that is
 * guaranteed to cover the kernel Image.
 *
 * Since the EFI stub is part of the kernel Image, we can relax the
 * usual requirements in Documentation/arm64/booting.txt, which still
 * apply to other bootloaders, and are required for some kernel
 * configurations.
 */
static inline unsigned long efi_get_max_initrd_addr(unsigned long dram_base,
						    unsigned long image_addr)
{
	return (image_addr & ~(SZ_1G - 1UL)) + (1UL << (VA_BITS - 1));
}

#define efi_call_early(f, ...)		sys_table_arg->boottime->f(__VA_ARGS__)
#define __efi_call_early(f, ...)	f(__VA_ARGS__)
#define efi_call_runtime(f, ...)	sys_table_arg->runtime->f(__VA_ARGS__)
#define efi_is_64bit()			(true)

#define efi_call_proto(protocol, f, instance, ...)			\
	((protocol##_t *)instance)->f(instance, ##__VA_ARGS__)

#define alloc_screen_info(x...)		&screen_info
#define free_screen_info(x...)

/* redeclare as 'hidden' so the compiler will generate relative references */
extern struct screen_info screen_info __attribute__((__visibility__("hidden")));

static inline void efifb_setup_from_dmi(struct screen_info *si, const char *opt)
{
}

#define EFI_ALLOC_ALIGN		SZ_64K

/*
 * On ARM systems, virtually remapped UEFI runtime services are set up in two
 * distinct stages:
 * - The stub retrieves the final version of the memory map from UEFI, populates
 *   the virt_addr fields and calls the SetVirtualAddressMap() [SVAM] runtime
 *   service to communicate the new mapping to the firmware (Note that the new
 *   mapping is not live at this time)
 * - During an early initcall(), the EFI system table is permanently remapped
 *   and the virtual remapping of the UEFI Runtime Services regions is loaded
 *   into a private set of page tables. If this all succeeds, the Runtime
 *   Services are enabled and the EFI_RUNTIME_SERVICES bit set.
 */

static inline void efi_set_pgd(struct mm_struct *mm)
{
	__switch_mm(mm);

	if (system_uses_ttbr0_pan()) {
		if (mm != current->active_mm) {
			/*
			 * Update the current thread's saved ttbr0 since it is
			 * restored as part of a return from exception. Set
			 * the hardware TTBR0_EL1 using cpu_switch_mm()
			 * directly to enable potential errata workarounds.
			 */
			update_saved_ttbr0(current, mm);
			cpu_switch_mm(mm->pgd, mm);
		} else {
			/*
			 * Defer the switch to the current thread's TTBR0_EL1
			 * until uaccess_enable(). Restore the current
			 * thread's saved ttbr0 corresponding to its active_mm
			 * (if different from init_mm).
			 */
			cpu_set_reserved_ttbr0();
			if (current->active_mm != &init_mm)
				update_saved_ttbr0(current, current->active_mm);
		}
	}
}

void efi_virtmap_load(void);
void efi_virtmap_unload(void);

#endif /* _ASM_EFI_H */