/*
 * This file contains kasan initialization code for ARM64.
 *
 * Copyright (c) 2015 Samsung Electronics Co., Ltd.
 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#define pr_fmt(fmt) "kasan: " fmt
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/memblock.h>
#include <linux/start_kernel.h>

#include <asm/mmu_context.h>
#include <asm/kernel-pgtable.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>

static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);

static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr,
                                        unsigned long end)
{
        pte_t *pte;
        unsigned long next;

        if (pmd_none(*pmd))
                pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);

        pte = pte_offset_kimg(pmd, addr);
        do {
                next = addr + PAGE_SIZE;
                set_pte(pte, pfn_pte(virt_to_pfn(kasan_zero_page),
                                        PAGE_KERNEL));
        } while (pte++, addr = next, addr != end && pte_none(*pte));
}

static void __init kasan_early_pmd_populate(pud_t *pud,
                                        unsigned long addr,
                                        unsigned long end)
{
        pmd_t *pmd;
        unsigned long next;

        if (pud_none(*pud))
                pud_populate(&init_mm, pud, kasan_zero_pmd);

        pmd = pmd_offset_kimg(pud, addr);
        do {
                next = pmd_addr_end(addr, end);
                kasan_early_pte_populate(pmd, addr, next);
        } while (pmd++, addr = next, addr != end && pmd_none(*pmd));
}

static void __init kasan_early_pud_populate(pgd_t *pgd,
                                        unsigned long addr,
                                        unsigned long end)
{
        pud_t *pud;
        unsigned long next;

        if (pgd_none(*pgd))
                pgd_populate(&init_mm, pgd, kasan_zero_pud);

        pud = pud_offset_kimg(pgd, addr);
        do {
                next = pud_addr_end(addr, end);
                kasan_early_pmd_populate(pud, addr, next);
        } while (pud++, addr = next, addr != end && pud_none(*pud));
}

static void __init kasan_map_early_shadow(void)
{
        unsigned long addr = KASAN_SHADOW_START;
        unsigned long end = KASAN_SHADOW_END;
        unsigned long next;
        pgd_t *pgd;

        pgd = pgd_offset_k(addr);
        do {
                next = pgd_addr_end(addr, end);
                kasan_early_pud_populate(pgd, addr, next);
        } while (pgd++, addr = next, addr != end);
}

asmlinkage void __init kasan_early_init(void)
{
        BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_END - (1UL << 61));
        BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
        BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
        kasan_map_early_shadow();
}

/*
 * Copy the current shadow region into a new pgdir.
 */
void __init kasan_copy_shadow(pgd_t *pgdir)
{
        pgd_t *pgd, *pgd_new, *pgd_end;

        pgd = pgd_offset_k(KASAN_SHADOW_START);
        pgd_end = pgd_offset_k(KASAN_SHADOW_END);
        pgd_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START);
        do {
                set_pgd(pgd_new, *pgd);
        } while (pgd++, pgd_new++, pgd != pgd_end);
}

static void __init clear_pgds(unsigned long start,
                        unsigned long end)
{
        /*
         * Remove references to kasan page tables from
         * swapper_pg_dir. pgd_clear() can't be used
         * here because it's nop on 2,3-level pagetable setups
         */
        for (; start < end; start += PGDIR_SIZE)
                set_pgd(pgd_offset_k(start), __pgd(0));
}

void __init kasan_init(void)
{
        u64 kimg_shadow_start, kimg_shadow_end;
        u64 mod_shadow_start, mod_shadow_end;
        struct memblock_region *reg;
        int i;

        kimg_shadow_start = (u64)kasan_mem_to_shadow(_text);
        kimg_shadow_end = (u64)kasan_mem_to_shadow(_end);

        mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
        mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);

        /*
         * We are going to perform proper setup of shadow memory.
         * At first we should unmap early shadow (clear_pgds() call bellow).
         * However, instrumented code couldn't execute without shadow memory.
         * tmp_pg_dir used to keep early shadow mapped until full shadow
         * setup will be finished.
         */
        memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
        dsb(ishst);
        cpu_replace_ttbr1(tmp_pg_dir);

        clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);

        vmemmap_populate(kimg_shadow_start, kimg_shadow_end,
                         pfn_to_nid(virt_to_pfn(_text)));

        /*
         * vmemmap_populate() has populated the shadow region that covers the
         * kernel image with SWAPPER_BLOCK_SIZE mappings, so we have to round
         * the start and end addresses to SWAPPER_BLOCK_SIZE as well, to prevent
         * kasan_populate_zero_shadow() from replacing the page table entries
         * (PMD or PTE) at the edges of the shadow region for the kernel
         * image.
         */
        kimg_shadow_start = round_down(kimg_shadow_start, SWAPPER_BLOCK_SIZE);
        kimg_shadow_end = round_up(kimg_shadow_end, SWAPPER_BLOCK_SIZE);

        kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
                                   (void *)mod_shadow_start);
        kasan_populate_zero_shadow((void *)kimg_shadow_end,
                                   kasan_mem_to_shadow((void *)PAGE_OFFSET));

        if (kimg_shadow_start > mod_shadow_end)
                kasan_populate_zero_shadow((void *)mod_shadow_end,
                                           (void *)kimg_shadow_start);

        for_each_memblock(memory, reg) {
                void *start = (void *)__phys_to_virt(reg->base);
                void *end = (void *)__phys_to_virt(reg->base + reg->size);

                if (start >= end)
                        break;

                /*
                 * end + 1 here is intentional. We check several shadow bytes in
                 * advance to slightly speed up fastpath. In some rare cases
                 * we could cross boundary of mapped shadow, so we just map
                 * some more here.
                 */
                vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
                                (unsigned long)kasan_mem_to_shadow(end) + 1,
                                pfn_to_nid(virt_to_pfn(start)));
        }

        /*
         * KAsan may reuse the contents of kasan_zero_pte directly, so we
         * should make sure that it maps the zero page read-only.
         */
        for (i = 0; i < PTRS_PER_PTE; i++)
                set_pte(&kasan_zero_pte[i],
                        pfn_pte(virt_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));

        memset(kasan_zero_page, 0, PAGE_SIZE);
        cpu_replace_ttbr1(swapper_pg_dir);

        /* At this point kasan is fully initialized. Enable error messages */
        init_task.kasan_depth = 0;
        pr_info("KernelAddressSanitizer initialized\n");
}