// SPDX-License-Identifier: GPL-2.0-only
/*
 * Fixmap manipulation code
 */

#include <linux/bug.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/libfdt.h>
#include <linux/memory.h>
#include <linux/mm.h>
#include <linux/sizes.h>

#include <asm/fixmap.h>
#include <asm/kernel-pgtable.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>

/* ensure that the fixmap region does not grow down into the PCI I/O region */
static_assert(FIXADDR_TOT_START > PCI_IO_END);

#define NR_BM_PTE_TABLES \
        SPAN_NR_ENTRIES(FIXADDR_TOT_START, FIXADDR_TOP, PMD_SHIFT)
#define NR_BM_PMD_TABLES \
        SPAN_NR_ENTRIES(FIXADDR_TOT_START, FIXADDR_TOP, PUD_SHIFT)

static_assert(NR_BM_PMD_TABLES == 1);

#define __BM_TABLE_IDX(addr, shift) \
        (((addr) >> (shift)) - (FIXADDR_TOT_START >> (shift)))

#define BM_PTE_TABLE_IDX(addr)  __BM_TABLE_IDX(addr, PMD_SHIFT)

static pte_t bm_pte[NR_BM_PTE_TABLES][PTRS_PER_PTE] __page_aligned_bss;
static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;

static inline pte_t *fixmap_pte(unsigned long addr)
{
        return &bm_pte[BM_PTE_TABLE_IDX(addr)][pte_index(addr)];
}

static void __init early_fixmap_init_pte(pmd_t *pmdp, unsigned long addr)
{
        pmd_t pmd = READ_ONCE(*pmdp);
        pte_t *ptep;

        if (pmd_none(pmd)) {
                ptep = bm_pte[BM_PTE_TABLE_IDX(addr)];
                __pmd_populate(pmdp, __pa_symbol(ptep),
                               PMD_TYPE_TABLE | PMD_TABLE_AF);
        }
}

static void __init early_fixmap_init_pmd(pud_t *pudp, unsigned long addr,
                                         unsigned long end)
{
        unsigned long next;
        pud_t pud = READ_ONCE(*pudp);
        pmd_t *pmdp;

        if (pud_none(pud))
                __pud_populate(pudp, __pa_symbol(bm_pmd),
                               PUD_TYPE_TABLE | PUD_TABLE_AF);

        pmdp = pmd_offset_kimg(pudp, addr);
        do {
                next = pmd_addr_end(addr, end);
                early_fixmap_init_pte(pmdp, addr);
        } while (pmdp++, addr = next, addr != end);
}


static void __init early_fixmap_init_pud(p4d_t *p4dp, unsigned long addr,
                                         unsigned long end)
{
        p4d_t p4d = READ_ONCE(*p4dp);
        pud_t *pudp;

        if (CONFIG_PGTABLE_LEVELS > 3 && !p4d_none(p4d) &&
            p4d_page_paddr(p4d) != __pa_symbol(bm_pud)) {
                /*
                 * We only end up here if the kernel mapping and the fixmap
                 * share the top level pgd entry, which should only happen on
                 * 16k/4 levels configurations.
                 */
                BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
        }

        if (p4d_none(p4d))
                __p4d_populate(p4dp, __pa_symbol(bm_pud),
                               P4D_TYPE_TABLE | P4D_TABLE_AF);

        pudp = pud_offset_kimg(p4dp, addr);
        early_fixmap_init_pmd(pudp, addr, end);
}

/*
 * The p*d_populate functions call virt_to_phys implicitly so they can't be used
 * directly on kernel symbols (bm_p*d). This function is called too early to use
 * lm_alias so __p*d_populate functions must be used to populate with the
 * physical address from __pa_symbol.
 */
void __init early_fixmap_init(void)
{
        unsigned long addr = FIXADDR_TOT_START;
        unsigned long end = FIXADDR_TOP;

        pgd_t *pgdp = pgd_offset_k(addr);
        p4d_t *p4dp = p4d_offset_kimg(pgdp, addr);

        early_fixmap_init_pud(p4dp, addr, end);
}

/*
 * Unusually, this is also called in IRQ context (ghes_iounmap_irq) so if we
 * ever need to use IPIs for TLB broadcasting, then we're in trouble here.
 */
void __set_fixmap(enum fixed_addresses idx,
                               phys_addr_t phys, pgprot_t flags)
{
        unsigned long addr = __fix_to_virt(idx);
        pte_t *ptep;

        BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);

        ptep = fixmap_pte(addr);

        if (pgprot_val(flags)) {
                __set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, flags));
        } else {
                __pte_clear(&init_mm, addr, ptep);
                flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
        }
}

void *__init fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
{
        const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
        phys_addr_t dt_phys_base;
        int offset;
        void *dt_virt;

        /*
         * Check whether the physical FDT address is set and meets the minimum
         * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
         * at least 8 bytes so that we can always access the magic and size
         * fields of the FDT header after mapping the first chunk, double check
         * here if that is indeed the case.
         */
        BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
        if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
                return NULL;

        dt_phys_base = round_down(dt_phys, PAGE_SIZE);
        offset = dt_phys % PAGE_SIZE;
        dt_virt = (void *)dt_virt_base + offset;

        /* map the first chunk so we can read the size from the header */
        create_mapping_noalloc(dt_phys_base, dt_virt_base, PAGE_SIZE, prot);

        if (fdt_magic(dt_virt) != FDT_MAGIC)
                return NULL;

        *size = fdt_totalsize(dt_virt);
        if (*size > MAX_FDT_SIZE)
                return NULL;

        if (offset + *size > PAGE_SIZE) {
                create_mapping_noalloc(dt_phys_base, dt_virt_base,
                                       offset + *size, prot);
        }

        return dt_virt;
}