// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains KASAN shadow initialization code.
 *
 * Copyright (c) 2015 Samsung Electronics Co., Ltd.
 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
 */

#include <linux/memblock.h>
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/pfn.h>
#include <linux/slab.h>
#include <linux/pgalloc.h>

#include <asm/page.h>

#include "kasan.h"

/*
 * This page serves two purposes:
 *   - It used as early shadow memory. The entire shadow region populated
 *     with this page, before we will be able to setup normal shadow memory.
 *   - Latter it reused it as zero shadow to cover large ranges of memory
 *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
 */
unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;

#if CONFIG_PGTABLE_LEVELS > 4
p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
static inline bool kasan_p4d_table(pgd_t pgd)
{
        return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
}
#else
static inline bool kasan_p4d_table(pgd_t pgd)
{
        return false;
}
#endif
#if CONFIG_PGTABLE_LEVELS > 3
pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
static inline bool kasan_pud_table(p4d_t p4d)
{
        return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
}
#else
static inline bool kasan_pud_table(p4d_t p4d)
{
        return false;
}
#endif
#if CONFIG_PGTABLE_LEVELS > 2
pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
static inline bool kasan_pmd_table(pud_t pud)
{
        return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
}
#else
static inline bool kasan_pmd_table(pud_t pud)
{
        return false;
}
#endif
pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
        __page_aligned_bss;

static inline bool kasan_pte_table(pmd_t pmd)
{
        return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
}

static inline bool kasan_early_shadow_page_entry(pte_t pte)
{
        return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
}

static __init void *early_alloc(size_t size, int node)
{
        void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
                                           MEMBLOCK_ALLOC_ACCESSIBLE, node);

        if (!ptr)
                panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
                      __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));

        return ptr;
}

static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
                                unsigned long end)
{
        pte_t *pte = pte_offset_kernel(pmd, addr);
        pte_t zero_pte;

        zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
                                PAGE_KERNEL);
        zero_pte = pte_wrprotect(zero_pte);

        while (addr + PAGE_SIZE <= end) {
                set_pte_at(&init_mm, addr, pte, zero_pte);
                addr += PAGE_SIZE;
                pte = pte_offset_kernel(pmd, addr);
        }
}

static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
                                unsigned long end)
{
        pmd_t *pmd = pmd_offset(pud, addr);
        unsigned long next;

        do {
                next = pmd_addr_end(addr, end);

                if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
                        pmd_populate_kernel(&init_mm, pmd,
                                        lm_alias(kasan_early_shadow_pte));
                        continue;
                }

                if (pmd_none(*pmd)) {
                        pte_t *p;

                        if (slab_is_available())
                                p = pte_alloc_one_kernel(&init_mm);
                        else {
                                p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
                                kernel_pte_init(p);
                        }
                        if (!p)
                                return -ENOMEM;

                        pmd_populate_kernel(&init_mm, pmd, p);
                }
                zero_pte_populate(pmd, addr, next);
        } while (pmd++, addr = next, addr != end);

        return 0;
}

static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
                                unsigned long end)
{
        pud_t *pud = pud_offset(p4d, addr);
        unsigned long next;

        do {
                next = pud_addr_end(addr, end);
                if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
                        pmd_t *pmd;

                        pud_populate(&init_mm, pud,
                                        lm_alias(kasan_early_shadow_pmd));
                        pmd = pmd_offset(pud, addr);
                        pmd_populate_kernel(&init_mm, pmd,
                                        lm_alias(kasan_early_shadow_pte));
                        continue;
                }

                if (pud_none(*pud)) {
                        pmd_t *p;

                        if (slab_is_available()) {
                                p = pmd_alloc(&init_mm, pud, addr);
                                if (!p)
                                        return -ENOMEM;
                        } else {
                                p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
                                pmd_init(p);
                                pud_populate(&init_mm, pud, p);
                        }
                }
                zero_pmd_populate(pud, addr, next);
        } while (pud++, addr = next, addr != end);

        return 0;
}

static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
                                unsigned long end)
{
        p4d_t *p4d = p4d_offset(pgd, addr);
        unsigned long next;

        do {
                next = p4d_addr_end(addr, end);
                if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
                        pud_t *pud;
                        pmd_t *pmd;

                        p4d_populate_kernel(addr, p4d,
                                        lm_alias(kasan_early_shadow_pud));
                        pud = pud_offset(p4d, addr);
                        pud_populate(&init_mm, pud,
                                        lm_alias(kasan_early_shadow_pmd));
                        pmd = pmd_offset(pud, addr);
                        pmd_populate_kernel(&init_mm, pmd,
                                        lm_alias(kasan_early_shadow_pte));
                        continue;
                }

                if (p4d_none(*p4d)) {
                        pud_t *p;

                        if (slab_is_available()) {
                                p = pud_alloc(&init_mm, p4d, addr);
                                if (!p)
                                        return -ENOMEM;
                        } else {
                                p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
                                pud_init(p);
                                p4d_populate_kernel(addr, p4d, p);
                        }
                }
                zero_pud_populate(p4d, addr, next);
        } while (p4d++, addr = next, addr != end);

        return 0;
}

/**
 * kasan_populate_early_shadow - populate shadow memory region with
 *                               kasan_early_shadow_page
 * @shadow_start: start of the memory range to populate
 * @shadow_end: end of the memory range to populate
 */
int __ref kasan_populate_early_shadow(const void *shadow_start,
                                        const void *shadow_end)
{
        unsigned long addr = (unsigned long)shadow_start;
        unsigned long end = (unsigned long)shadow_end;
        pgd_t *pgd = pgd_offset_k(addr);
        unsigned long next;

        do {
                next = pgd_addr_end(addr, end);

                if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
                        p4d_t *p4d;
                        pud_t *pud;
                        pmd_t *pmd;

                        /*
                         * kasan_early_shadow_pud should be populated with pmds
                         * at this moment.
                         * [pud,pmd]_populate*() below needed only for
                         * 3,2 - level page tables where we don't have
                         * puds,pmds, so pgd_populate(), pud_populate()
                         * is noops.
                         */
                        pgd_populate_kernel(addr, pgd,
                                        lm_alias(kasan_early_shadow_p4d));
                        p4d = p4d_offset(pgd, addr);
                        p4d_populate_kernel(addr, p4d,
                                        lm_alias(kasan_early_shadow_pud));
                        pud = pud_offset(p4d, addr);
                        pud_populate(&init_mm, pud,
                                        lm_alias(kasan_early_shadow_pmd));
                        pmd = pmd_offset(pud, addr);
                        pmd_populate_kernel(&init_mm, pmd,
                                        lm_alias(kasan_early_shadow_pte));
                        continue;
                }

                if (pgd_none(*pgd)) {

                        if (slab_is_available()) {
                                if (!p4d_alloc(&init_mm, pgd, addr))
                                        return -ENOMEM;
                        } else {
                                pgd_populate_kernel(addr, pgd,
                                        early_alloc(PAGE_SIZE, NUMA_NO_NODE));
                        }
                }
                zero_p4d_populate(pgd, addr, next);
        } while (pgd++, addr = next, addr != end);

        return 0;
}

static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
{
        pte_t *pte;
        int i;

        for (i = 0; i < PTRS_PER_PTE; i++) {
                pte = pte_start + i;
                if (!pte_none(ptep_get(pte)))
                        return;
        }

        pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
        pmd_clear(pmd);
}

static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
{
        pmd_t *pmd;
        int i;

        for (i = 0; i < PTRS_PER_PMD; i++) {
                pmd = pmd_start + i;
                if (!pmd_none(*pmd))
                        return;
        }

        pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
        pud_clear(pud);
}

static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
{
        pud_t *pud;
        int i;

        for (i = 0; i < PTRS_PER_PUD; i++) {
                pud = pud_start + i;
                if (!pud_none(*pud))
                        return;
        }

        pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
        p4d_clear(p4d);
}

static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
{
        p4d_t *p4d;
        int i;

        for (i = 0; i < PTRS_PER_P4D; i++) {
                p4d = p4d_start + i;
                if (!p4d_none(*p4d))
                        return;
        }

        p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
        pgd_clear(pgd);
}

static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
                                unsigned long end)
{
        unsigned long next;
        pte_t ptent;

        for (; addr < end; addr = next, pte++) {
                next = (addr + PAGE_SIZE) & PAGE_MASK;
                if (next > end)
                        next = end;

                ptent = ptep_get(pte);

                if (!pte_present(ptent))
                        continue;

                if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
                        continue;
                pte_clear(&init_mm, addr, pte);
        }
}

static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
                                unsigned long end)
{
        unsigned long next;

        for (; addr < end; addr = next, pmd++) {
                pte_t *pte;

                next = pmd_addr_end(addr, end);

                if (!pmd_present(*pmd))
                        continue;

                if (kasan_pte_table(*pmd)) {
                        if (IS_ALIGNED(addr, PMD_SIZE) &&
                            IS_ALIGNED(next, PMD_SIZE)) {
                                pmd_clear(pmd);
                                continue;
                        }
                }
                pte = pte_offset_kernel(pmd, addr);
                kasan_remove_pte_table(pte, addr, next);
                kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
        }
}

static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
                                unsigned long end)
{
        unsigned long next;

        for (; addr < end; addr = next, pud++) {
                pmd_t *pmd, *pmd_base;

                next = pud_addr_end(addr, end);

                if (!pud_present(*pud))
                        continue;

                if (kasan_pmd_table(*pud)) {
                        if (IS_ALIGNED(addr, PUD_SIZE) &&
                            IS_ALIGNED(next, PUD_SIZE)) {
                                pud_clear(pud);
                                continue;
                        }
                }
                pmd = pmd_offset(pud, addr);
                pmd_base = pmd_offset(pud, 0);
                kasan_remove_pmd_table(pmd, addr, next);
                kasan_free_pmd(pmd_base, pud);
        }
}

static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
                                unsigned long end)
{
        unsigned long next;

        for (; addr < end; addr = next, p4d++) {
                pud_t *pud;

                next = p4d_addr_end(addr, end);

                if (!p4d_present(*p4d))
                        continue;

                if (kasan_pud_table(*p4d)) {
                        if (IS_ALIGNED(addr, P4D_SIZE) &&
                            IS_ALIGNED(next, P4D_SIZE)) {
                                p4d_clear(p4d);
                                continue;
                        }
                }
                pud = pud_offset(p4d, addr);
                kasan_remove_pud_table(pud, addr, next);
                kasan_free_pud(pud_offset(p4d, 0), p4d);
        }
}

void kasan_remove_zero_shadow(void *start, unsigned long size)
{
        unsigned long addr, end, next;
        pgd_t *pgd;

        addr = (unsigned long)kasan_mem_to_shadow(start);
        end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);

        if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
            WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
                return;

        for (; addr < end; addr = next) {
                p4d_t *p4d;

                next = pgd_addr_end(addr, end);

                pgd = pgd_offset_k(addr);
                if (!pgd_present(*pgd))
                        continue;

                if (kasan_p4d_table(*pgd)) {
                        if (IS_ALIGNED(addr, PGDIR_SIZE) &&
                            IS_ALIGNED(next, PGDIR_SIZE)) {
                                pgd_clear(pgd);
                                continue;
                        }
                }

                p4d = p4d_offset(pgd, addr);
                kasan_remove_p4d_table(p4d, addr, next);
                kasan_free_p4d(p4d_offset(pgd, 0), pgd);
        }
}

int kasan_add_zero_shadow(void *start, unsigned long size)
{
        int ret;
        void *shadow_start, *shadow_end;

        shadow_start = kasan_mem_to_shadow(start);
        shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);

        if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
            WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
                return -EINVAL;

        ret = kasan_populate_early_shadow(shadow_start, shadow_end);
        if (ret)
                kasan_remove_zero_shadow(start, size);
        return ret;
}