// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2016 Linaro Ltd;  <ard.biesheuvel@linaro.org>
 */

#include <linux/efi.h>
#include <linux/log2.h>
#include <asm/efi.h>

#include "efistub.h"

/*
 * Return the number of slots covered by this entry, i.e., the number of
 * addresses it covers that are suitably aligned and supply enough room
 * for the allocation.
 */
static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
                                         unsigned long size,
                                         unsigned long align_shift,
                                         u64 alloc_min, u64 alloc_max)
{
        unsigned long align = 1UL << align_shift;
        u64 first_slot, last_slot, region_end;

        if (md->type != EFI_CONVENTIONAL_MEMORY)
                return 0;

        if (md->attribute & EFI_MEMORY_HOT_PLUGGABLE)
                return 0;

        if (efi_soft_reserve_enabled() &&
            (md->attribute & EFI_MEMORY_SP))
                return 0;

        region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
                         alloc_max);
        if (region_end < size)
                return 0;

        first_slot = round_up(max(md->phys_addr, alloc_min), align);
        last_slot = round_down(region_end - size + 1, align);

        if (first_slot > last_slot)
                return 0;

        return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1;
}

/*
 * The UEFI memory descriptors have a virtual address field that is only used
 * when installing the virtual mapping using SetVirtualAddressMap(). Since it
 * is unused here, we can reuse it to keep track of each descriptor's slot
 * count.
 */
#define MD_NUM_SLOTS(md)        ((md)->virt_addr)

efi_status_t efi_random_alloc(unsigned long size,
                              unsigned long align,
                              unsigned long *addr,
                              unsigned long random_seed,
                              int memory_type,
                              unsigned long alloc_min,
                              unsigned long alloc_max)
{
        struct efi_boot_memmap *map __free(efi_pool) = NULL;
        unsigned long total_slots = 0, target_slot;
        unsigned long total_mirrored_slots = 0;
        efi_status_t status;
        int map_offset;

        status = efi_get_memory_map(&map, false);
        if (status != EFI_SUCCESS)
                return status;

        if (align < EFI_ALLOC_ALIGN)
                align = EFI_ALLOC_ALIGN;

        /* Avoid address 0x0, as it can be mistaken for NULL */
        if (alloc_min == 0)
                alloc_min = align;

        size = round_up(size, EFI_ALLOC_ALIGN);

        /* count the suitable slots in each memory map entry */
        for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
                efi_memory_desc_t *md = (void *)map->map + map_offset;
                unsigned long slots;

                slots = get_entry_num_slots(md, size, ilog2(align), alloc_min,
                                            alloc_max);
                MD_NUM_SLOTS(md) = slots;
                total_slots += slots;
                if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
                        total_mirrored_slots += slots;
        }

        /* consider only mirrored slots for randomization if any exist */
        if (total_mirrored_slots > 0)
                total_slots = total_mirrored_slots;

        /* find a random number between 0 and total_slots */
        target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;

        /*
         * target_slot is now a value in the range [0, total_slots), and so
         * it corresponds with exactly one of the suitable slots we recorded
         * when iterating over the memory map the first time around.
         *
         * So iterate over the memory map again, subtracting the number of
         * slots of each entry at each iteration, until we have found the entry
         * that covers our chosen slot. Use the residual value of target_slot
         * to calculate the randomly chosen address, and allocate it directly
         * using EFI_ALLOCATE_ADDRESS.
         */
        status = EFI_OUT_OF_RESOURCES;
        for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
                efi_memory_desc_t *md = (void *)map->map + map_offset;
                efi_physical_addr_t target;
                unsigned long pages;

                if (total_mirrored_slots > 0 &&
                    !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
                        continue;

                if (target_slot >= MD_NUM_SLOTS(md)) {
                        target_slot -= MD_NUM_SLOTS(md);
                        continue;
                }

                target = round_up(max_t(u64, md->phys_addr, alloc_min), align) + target_slot * align;
                pages = size / EFI_PAGE_SIZE;

                status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
                                     memory_type, pages, &target);
                if (status == EFI_SUCCESS)
                        *addr = target;
                break;
        }

        return status;
}