// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 */

#include <linux/err.h>
#include <linux/highmem.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <asm/current.h>
#include <asm/page.h>
#include <kern_util.h>
#include <asm/futex.h>
#include <os.h>

pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
{
        pgd_t *pgd;
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;

        if (mm == NULL)
                return NULL;

        pgd = pgd_offset(mm, addr);
        if (!pgd_present(*pgd))
                return NULL;

        p4d = p4d_offset(pgd, addr);
        if (!p4d_present(*p4d))
                return NULL;

        pud = pud_offset(p4d, addr);
        if (!pud_present(*pud))
                return NULL;

        pmd = pmd_offset(pud, addr);
        if (!pmd_present(*pmd))
                return NULL;

        return pte_offset_kernel(pmd, addr);
}

static pte_t *maybe_map(unsigned long virt, int is_write)
{
        pte_t *pte = virt_to_pte(current->mm, virt);
        int err, dummy_code;

        if ((pte == NULL) || !pte_present(*pte) ||
            (is_write && !pte_write(*pte))) {
                err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
                if (err)
                        return NULL;
                pte = virt_to_pte(current->mm, virt);
        }
        if (!pte_present(*pte))
                pte = NULL;

        return pte;
}

static int do_op_one_page(unsigned long addr, int len, int is_write,
                 int (*op)(unsigned long addr, int len, void *arg), void *arg)
{
        struct page *page;
        pte_t *pte;
        int n;

        pte = maybe_map(addr, is_write);
        if (pte == NULL)
                return -1;

        page = pte_page(*pte);
#ifdef CONFIG_64BIT
        pagefault_disable();
        addr = (unsigned long) page_address(page) +
                (addr & ~PAGE_MASK);
#else
        addr = (unsigned long) kmap_atomic(page) +
                (addr & ~PAGE_MASK);
#endif
        n = (*op)(addr, len, arg);

#ifdef CONFIG_64BIT
        pagefault_enable();
#else
        kunmap_atomic((void *)addr);
#endif

        return n;
}

static long buffer_op(unsigned long addr, int len, int is_write,
                      int (*op)(unsigned long, int, void *), void *arg)
{
        long size, remain, n;

        size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
        remain = len;

        n = do_op_one_page(addr, size, is_write, op, arg);
        if (n != 0) {
                remain = (n < 0 ? remain : 0);
                goto out;
        }

        addr += size;
        remain -= size;
        if (remain == 0)
                goto out;

        while (addr < ((addr + remain) & PAGE_MASK)) {
                n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
                if (n != 0) {
                        remain = (n < 0 ? remain : 0);
                        goto out;
                }

                addr += PAGE_SIZE;
                remain -= PAGE_SIZE;
        }
        if (remain == 0)
                goto out;

        n = do_op_one_page(addr, remain, is_write, op, arg);
        if (n != 0) {
                remain = (n < 0 ? remain : 0);
                goto out;
        }

        return 0;
 out:
        return remain;
}

static int copy_chunk_from_user(unsigned long from, int len, void *arg)
{
        unsigned long *to_ptr = arg, to = *to_ptr;

        memcpy((void *) to, (void *) from, len);
        *to_ptr += len;
        return 0;
}

unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n)
{
        return buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to);
}
EXPORT_SYMBOL(raw_copy_from_user);

static int copy_chunk_to_user(unsigned long to, int len, void *arg)
{
        unsigned long *from_ptr = arg, from = *from_ptr;

        memcpy((void *) to, (void *) from, len);
        *from_ptr += len;
        return 0;
}

unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
{
        return buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from);
}
EXPORT_SYMBOL(raw_copy_to_user);

static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
{
        char **to_ptr = arg, *to = *to_ptr;
        int n;

        strncpy(to, (void *) from, len);
        n = strnlen(to, len);
        *to_ptr += n;

        if (n < len)
                return 1;
        return 0;
}

long strncpy_from_user(char *dst, const char __user *src, long count)
{
        long n;
        char *ptr = dst;

        if (!access_ok(src, 1))
                return -EFAULT;
        n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
                      &ptr);
        if (n != 0)
                return -EFAULT;
        return strnlen(dst, count);
}
EXPORT_SYMBOL(strncpy_from_user);

static int clear_chunk(unsigned long addr, int len, void *unused)
{
        memset((void *) addr, 0, len);
        return 0;
}

unsigned long __clear_user(void __user *mem, unsigned long len)
{
        return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
}
EXPORT_SYMBOL(__clear_user);

static int strnlen_chunk(unsigned long str, int len, void *arg)
{
        int *len_ptr = arg, n;

        n = strnlen((void *) str, len);
        *len_ptr += n;

        if (n < len)
                return 1;
        return 0;
}

long strnlen_user(const char __user *str, long len)
{
        int count = 0, n;

        if (!access_ok(str, 1))
                return -EFAULT;
        n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
        if (n == 0)
                return count + 1;
        return 0;
}
EXPORT_SYMBOL(strnlen_user);

/**
 * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant
 *                        argument and comparison of the previous
 *                        futex value with another constant.
 *
 * @op:         operation to execute
 * @oparg:      argument to operation
 * @oval:       old value at uaddr
 * @uaddr:      pointer to user space address
 *
 * Return:
 * 0 - On success
 * -EFAULT - User access resulted in a page fault
 * -EAGAIN - Atomic operation was unable to complete due to contention
 * -ENOSYS - Operation not supported
 */

int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
{
        int oldval, ret;
        struct page *page;
        unsigned long addr = (unsigned long) uaddr;
        pte_t *pte;

        ret = -EFAULT;
        if (!access_ok(uaddr, sizeof(*uaddr)))
                return -EFAULT;
        preempt_disable();
        pte = maybe_map(addr, 1);
        if (pte == NULL)
                goto out_inuser;

        page = pte_page(*pte);
#ifdef CONFIG_64BIT
        pagefault_disable();
        addr = (unsigned long) page_address(page) +
                        (((unsigned long) addr) & ~PAGE_MASK);
#else
        addr = (unsigned long) kmap_atomic(page) +
                ((unsigned long) addr & ~PAGE_MASK);
#endif
        uaddr = (u32 *) addr;
        oldval = *uaddr;

        ret = 0;

        switch (op) {
        case FUTEX_OP_SET:
                *uaddr = oparg;
                break;
        case FUTEX_OP_ADD:
                *uaddr += oparg;
                break;
        case FUTEX_OP_OR:
                *uaddr |= oparg;
                break;
        case FUTEX_OP_ANDN:
                *uaddr &= ~oparg;
                break;
        case FUTEX_OP_XOR:
                *uaddr ^= oparg;
                break;
        default:
                ret = -ENOSYS;
        }
#ifdef CONFIG_64BIT
        pagefault_enable();
#else
        kunmap_atomic((void *)addr);
#endif

out_inuser:
        preempt_enable();

        if (ret == 0)
                *oval = oldval;

        return ret;
}
EXPORT_SYMBOL(arch_futex_atomic_op_inuser);

/**
 * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
 *                              uaddr with newval if the current value is
 *                              oldval.
 * @uval:       pointer to store content of @uaddr
 * @uaddr:      pointer to user space address
 * @oldval:     old value
 * @newval:     new value to store to @uaddr
 *
 * Return:
 * 0 - On success
 * -EFAULT - User access resulted in a page fault
 * -EAGAIN - Atomic operation was unable to complete due to contention
 */

int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
                              u32 oldval, u32 newval)
{
        struct page *page;
        pte_t *pte;
        int ret = -EFAULT;

        if (!access_ok(uaddr, sizeof(*uaddr)))
                return -EFAULT;

        preempt_disable();
        pte = maybe_map((unsigned long) uaddr, 1);
        if (pte == NULL)
                goto out_inatomic;

        page = pte_page(*pte);
#ifdef CONFIG_64BIT
        pagefault_disable();
        uaddr = page_address(page) + (((unsigned long) uaddr) & ~PAGE_MASK);
#else
        uaddr = kmap_atomic(page) + ((unsigned long) uaddr & ~PAGE_MASK);
#endif

        *uval = *uaddr;

        ret = cmpxchg(uaddr, oldval, newval);

#ifdef CONFIG_64BIT
        pagefault_enable();
#else
        kunmap_atomic(uaddr);
#endif
        ret = 0;

out_inatomic:
        preempt_enable();
        return ret;
}
EXPORT_SYMBOL(futex_atomic_cmpxchg_inatomic);