kernel/drivers/firmware/efi/libstub/arm32-stub.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2013 Linaro Ltd;  <roy.franz@linaro.org>
 */
#include <linux/efi.h>
#include <asm/efi.h>

#include "efistub.h"

static efi_guid_t cpu_state_guid = LINUX_EFI_ARM_CPU_STATE_TABLE_GUID;

struct efi_arm_entry_state *efi_entry_state;

static void get_cpu_state(u32 *cpsr, u32 *sctlr)
{
	asm("mrs %0, cpsr" : "=r"(*cpsr));
	if ((*cpsr & MODE_MASK) == HYP_MODE)
		asm("mrc p15, 4, %0, c1, c0, 0" : "=r"(*sctlr));
	else
		asm("mrc p15, 0, %0, c1, c0, 0" : "=r"(*sctlr));
}

efi_status_t check_platform_features(void)
{
	efi_status_t status;
	u32 cpsr, sctlr;
	int block;

	get_cpu_state(&cpsr, &sctlr);

	efi_info("Entering in %s mode with MMU %sabled\n",
		 ((cpsr & MODE_MASK) == HYP_MODE) ? "HYP" : "SVC",
		 (sctlr & 1) ? "en" : "dis");

	status = efi_bs_call(allocate_pool, EFI_LOADER_DATA,
			     sizeof(*efi_entry_state),
			     (void **)&efi_entry_state);
	if (status != EFI_SUCCESS) {
		efi_err("allocate_pool() failed\n");
		return status;
	}

	efi_entry_state->cpsr_before_ebs = cpsr;
	efi_entry_state->sctlr_before_ebs = sctlr;

	status = efi_bs_call(install_configuration_table, &cpu_state_guid,
			     efi_entry_state);
	if (status != EFI_SUCCESS) {
		efi_err("install_configuration_table() failed\n");
		goto free_state;
	}

	/* non-LPAE kernels can run anywhere */
	if (!IS_ENABLED(CONFIG_ARM_LPAE))
		return EFI_SUCCESS;

	/* LPAE kernels need compatible hardware */
	block = cpuid_feature_extract(CPUID_EXT_MMFR0, 0);
	if (block < 5) {
		efi_err("This LPAE kernel is not supported by your CPU\n");
		status = EFI_UNSUPPORTED;
		goto drop_table;
	}
	return EFI_SUCCESS;

drop_table:
	efi_bs_call(install_configuration_table, &cpu_state_guid, NULL);
free_state:
	efi_bs_call(free_pool, efi_entry_state);
	return status;
}

void efi_handle_post_ebs_state(void)
{
	get_cpu_state(&efi_entry_state->cpsr_after_ebs,
		      &efi_entry_state->sctlr_after_ebs);
}

static efi_guid_t screen_info_guid = LINUX_EFI_ARM_SCREEN_INFO_TABLE_GUID;

struct screen_info *alloc_screen_info(void)
{
	struct screen_info *si;
	efi_status_t status;

	/*
	 * Unlike on arm64, where we can directly fill out the screen_info
	 * structure from the stub, we need to allocate a buffer to hold
	 * its contents while we hand over to the kernel proper from the
	 * decompressor.
	 */
	status = efi_bs_call(allocate_pool, EFI_RUNTIME_SERVICES_DATA,
			     sizeof(*si), (void **)&si);

	if (status != EFI_SUCCESS)
		return NULL;

	status = efi_bs_call(install_configuration_table,
			     &screen_info_guid, si);
	if (status == EFI_SUCCESS)
		return si;

	efi_bs_call(free_pool, si);
	return NULL;
}

void free_screen_info(struct screen_info *si)
{
	if (!si)
		return;

	efi_bs_call(install_configuration_table, &screen_info_guid, NULL);
	efi_bs_call(free_pool, si);
}

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)
{
	const int slack = TEXT_OFFSET - 5 * PAGE_SIZE;
	int alloc_size = MAX_UNCOMP_KERNEL_SIZE + EFI_PHYS_ALIGN;
	unsigned long alloc_base, kernel_base;
	efi_status_t status;

	/*
	 * Allocate space for the decompressed kernel as low as possible.
	 * The region should be 16 MiB aligned, but the first 'slack' bytes
	 * are not used by Linux, so we allow those to be occupied by the
	 * firmware.
	 */
	status = efi_low_alloc_above(alloc_size, EFI_PAGE_SIZE, &alloc_base, 0x0);
	if (status != EFI_SUCCESS) {
		efi_err("Unable to allocate memory for uncompressed kernel.\n");
		return status;
	}

	if ((alloc_base % EFI_PHYS_ALIGN) > slack) {
		/*
		 * More than 'slack' bytes are already occupied at the base of
		 * the allocation, so we need to advance to the next 16 MiB block.
		 */
		kernel_base = round_up(alloc_base, EFI_PHYS_ALIGN);
		efi_info("Free memory starts at 0x%lx, setting kernel_base to 0x%lx\n",
			 alloc_base, kernel_base);
	} else {
		kernel_base = round_down(alloc_base, EFI_PHYS_ALIGN);
	}

	*reserve_addr = kernel_base + slack;
	*reserve_size = MAX_UNCOMP_KERNEL_SIZE;

	/* now free the parts that we will not use */
	if (*reserve_addr > alloc_base) {
		efi_bs_call(free_pages, alloc_base,
			    (*reserve_addr - alloc_base) / EFI_PAGE_SIZE);
		alloc_size -= *reserve_addr - alloc_base;
	}
	efi_bs_call(free_pages, *reserve_addr + MAX_UNCOMP_KERNEL_SIZE,
		    (alloc_size - MAX_UNCOMP_KERNEL_SIZE) / EFI_PAGE_SIZE);

	*image_addr = kernel_base + TEXT_OFFSET;
	*image_size = 0;

	efi_debug("image addr == 0x%lx, reserve_addr == 0x%lx\n",
		  *image_addr, *reserve_addr);

	return EFI_SUCCESS;
}