// SPDX-License-Identifier: GPL-2.0-only
/*
 * Extensible Firmware Interface
 *
 * Based on Extensible Firmware Interface Specification version 2.4
 *
 * Copyright (C) 2013, 2014 Linaro Ltd.
 */

#include <linux/efi.h>
#include <linux/init.h>
#include <linux/kmemleak.h>
#include <linux/kthread.h>
#include <linux/screen_info.h>
#include <linux/vmalloc.h>

#include <asm/efi.h>
#include <asm/stacktrace.h>
#include <asm/vmap_stack.h>

static bool region_is_misaligned(const efi_memory_desc_t *md)
{
        if (PAGE_SIZE == EFI_PAGE_SIZE)
                return false;
        return !PAGE_ALIGNED(md->phys_addr) ||
               !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT);
}

/*
 * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
 * executable, everything else can be mapped with the XN bits
 * set. Also take the new (optional) RO/XP bits into account.
 */
static __init ptdesc_t create_mapping_protection(efi_memory_desc_t *md)
{
        u64 attr = md->attribute;
        u32 type = md->type;

        if (type == EFI_MEMORY_MAPPED_IO) {
                pgprot_t prot = __pgprot(PROT_DEVICE_nGnRE);

                if (arm64_is_protected_mmio(md->phys_addr,
                                            md->num_pages << EFI_PAGE_SHIFT))
                        prot = pgprot_encrypted(prot);
                else
                        prot = pgprot_decrypted(prot);
                return pgprot_val(prot);
        }

        if (region_is_misaligned(md)) {
                static bool __initdata code_is_misaligned;

                /*
                 * Regions that are not aligned to the OS page size cannot be
                 * mapped with strict permissions, as those might interfere
                 * with the permissions that are needed by the adjacent
                 * region's mapping. However, if we haven't encountered any
                 * misaligned runtime code regions so far, we can safely use
                 * non-executable permissions for non-code regions.
                 */
                code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE);

                return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC)
                                          : pgprot_val(PAGE_KERNEL);
        }

        /* R-- */
        if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
            (EFI_MEMORY_XP | EFI_MEMORY_RO))
                return pgprot_val(PAGE_KERNEL_RO);

        /* R-X */
        if (attr & EFI_MEMORY_RO)
                return pgprot_val(PAGE_KERNEL_ROX);

        /* RW- */
        if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
             EFI_MEMORY_XP) ||
            type != EFI_RUNTIME_SERVICES_CODE)
                return pgprot_val(PAGE_KERNEL);

        /* RWX */
        return pgprot_val(PAGE_KERNEL_EXEC);
}

int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
{
        ptdesc_t prot_val = create_mapping_protection(md);
        bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
                                   md->type == EFI_RUNTIME_SERVICES_DATA);

        /*
         * If this region is not aligned to the page size used by the OS, the
         * mapping will be rounded outwards, and may end up sharing a page
         * frame with an adjacent runtime memory region. Given that the page
         * table descriptor covering the shared page will be rewritten when the
         * adjacent region gets mapped, we must avoid block mappings here so we
         * don't have to worry about splitting them when that happens.
         */
        if (region_is_misaligned(md))
                page_mappings_only = true;

        create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
                           md->num_pages << EFI_PAGE_SHIFT,
                           __pgprot(prot_val | PTE_NG), page_mappings_only);
        return 0;
}

struct set_perm_data {
        const efi_memory_desc_t *md;
        bool                    has_bti;
};

static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
{
        struct set_perm_data *spd = data;
        const efi_memory_desc_t *md = spd->md;
        pte_t pte = __ptep_get(ptep);

        if (md->attribute & EFI_MEMORY_RO)
                pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
        if (md->attribute & EFI_MEMORY_XP)
                pte = set_pte_bit(pte, __pgprot(PTE_PXN));
        else if (system_supports_bti_kernel() && spd->has_bti)
                pte = set_pte_bit(pte, __pgprot(PTE_GP));
        __set_pte(ptep, pte);
        return 0;
}

int __init efi_set_mapping_permissions(struct mm_struct *mm,
                                       efi_memory_desc_t *md,
                                       bool has_bti)
{
        struct set_perm_data data = { md, has_bti };

        BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
               md->type != EFI_RUNTIME_SERVICES_DATA);

        if (region_is_misaligned(md))
                return 0;

        /*
         * Calling apply_to_page_range() is only safe on regions that are
         * guaranteed to be mapped down to pages. Since we are only called
         * for regions that have been mapped using efi_create_mapping() above
         * (and this is checked by the generic Memory Attributes table parsing
         * routines), there is no need to check that again here.
         */
        return apply_to_page_range(mm, md->virt_addr,
                                   md->num_pages << EFI_PAGE_SHIFT,
                                   set_permissions, &data);
}

/*
 * UpdateCapsule() depends on the system being shutdown via
 * ResetSystem().
 */
bool efi_poweroff_required(void)
{
        return efi_enabled(EFI_RUNTIME_SERVICES);
}

asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
{
        pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
        return s;
}

void arch_efi_call_virt_setup(void)
{
        efi_runtime_assert_lock_held();

        if (preemptible() && (current->flags & PF_KTHREAD)) {
                /*
                 * Disable migration to ensure that a preempted EFI runtime
                 * service call will be resumed on the same CPU. This avoids
                 * potential issues with EFI runtime calls that are preempted
                 * while polling for an asynchronous completion of a secure
                 * firmware call, which may not permit the CPU to change.
                 */
                migrate_disable();
                kthread_use_mm(&efi_mm);
        } else {
                efi_virtmap_load();
        }

        /*
         * Enable access to the valid TTBR0_EL1 and invoke the errata
         * workaround directly since there is no return from exception when
         * invoking the EFI run-time services.
         */
        uaccess_ttbr0_enable();
        post_ttbr_update_workaround();

        __efi_fpsimd_begin();
}

void arch_efi_call_virt_teardown(void)
{
        __efi_fpsimd_end();

        /*
         * Defer the switch to the current thread's TTBR0_EL1 until
         * uaccess_enable(). Do so before efi_virtmap_unload() updates the
         * saved TTBR0 value, so the userland page tables are not activated
         * inadvertently over the back of an exception.
         */
        uaccess_ttbr0_disable();

        if (preemptible() && (current->flags & PF_KTHREAD)) {
                kthread_unuse_mm(&efi_mm);
                migrate_enable();
        } else {
                efi_virtmap_unload();
        }
}

asmlinkage u64 *efi_rt_stack_top __ro_after_init;

asmlinkage efi_status_t __efi_rt_asm_recover(void);

bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
{
         /* Check whether the exception occurred while running the firmware */
        if (!current_in_efi() || regs->pc >= TASK_SIZE_64)
                return false;

        pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
        add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
        clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);

        regs->regs[0]   = EFI_ABORTED;
        regs->regs[30]  = efi_rt_stack_top[-1];
        regs->pc        = (u64)__efi_rt_asm_recover;

        if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
                regs->regs[18] = efi_rt_stack_top[-2];

        return true;
}

/* EFI requires 8 KiB of stack space for runtime services */
static_assert(THREAD_SIZE >= SZ_8K);

static int __init arm64_efi_rt_init(void)
{
        void *p;

        if (!efi_enabled(EFI_RUNTIME_SERVICES))
                return 0;

        p = arch_alloc_vmap_stack(THREAD_SIZE, NUMA_NO_NODE);
        if (!p) {
                pr_warn("Failed to allocate EFI runtime stack\n");
                clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
                return -ENOMEM;
        }

        kmemleak_not_leak(p);
        efi_rt_stack_top = p + THREAD_SIZE;
        return 0;
}
core_initcall(arm64_efi_rt_init);