/*
 * Based on arch/arm/include/asm/uaccess.h
 *
 * Copyright (C) 2012 ARM Ltd.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef __ASM_UACCESS_H
#define __ASM_UACCESS_H

/*
 * User space memory access functions
 */
#include <linux/string.h>
#include <linux/thread_info.h>

#include <asm/ptrace.h>
#include <asm/errno.h>
#include <asm/memory.h>
#include <asm/compiler.h>

#define VERIFY_READ 0
#define VERIFY_WRITE 1

/*
 * The exception table consists of pairs of addresses: the first is the
 * address of an instruction that is allowed to fault, and the second is
 * the address at which the program should continue.  No registers are
 * modified, so it is entirely up to the continuation code to figure out
 * what to do.
 *
 * All the routines below use bits of fixup code that are out of line
 * with the main instruction path.  This means when everything is well,
 * we don't even have to jump over them.  Further, they do not intrude
 * on our cache or tlb entries.
 */

struct exception_table_entry
{
        unsigned long insn, fixup;
};

extern int fixup_exception(struct pt_regs *regs);

#define KERNEL_DS       (-1UL)
#define get_ds()        (KERNEL_DS)

#define USER_DS         TASK_SIZE_64
#define get_fs()        (current_thread_info()->addr_limit)

static inline void set_fs(mm_segment_t fs)
{
        current_thread_info()->addr_limit = fs;
}

#define segment_eq(a,b) ((a) == (b))

/*
 * Return 1 if addr < current->addr_limit, 0 otherwise.
 */
#define __addr_ok(addr)                                                 \
({                                                                      \
        unsigned long flag;                                             \
        asm("cmp %1, %0; cset %0, lo"                                   \
                : "=&r" (flag)                                          \
                : "r" (addr), "0" (current_thread_info()->addr_limit)   \
                : "cc");                                                \
        flag;                                                           \
})

/*
 * Test whether a block of memory is a valid user space address.
 * Returns 1 if the range is valid, 0 otherwise.
 *
 * This is equivalent to the following test:
 * (u65)addr + (u65)size < (u65)current->addr_limit
 *
 * This needs 65-bit arithmetic.
 */
#define __range_ok(addr, size)                                          \
({                                                                      \
        unsigned long flag, roksum;                                     \
        __chk_user_ptr(addr);                                           \
        asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, cc"         \
                : "=&r" (flag), "=&r" (roksum)                          \
                : "1" (addr), "Ir" (size),                              \
                  "r" (current_thread_info()->addr_limit)               \
                : "cc");                                                \
        flag;                                                           \
})

#define access_ok(type, addr, size)     __range_ok(addr, size)

/*
 * The "__xxx" versions of the user access functions do not verify the address
 * space - it must have been done previously with a separate "access_ok()"
 * call.
 *
 * The "__xxx_error" versions set the third argument to -EFAULT if an error
 * occurs, and leave it unchanged on success.
 */
#define __get_user_asm(instr, reg, x, addr, err)                        \
        asm volatile(                                                   \
        "1:     " instr "       " reg "1, [%2]\n"                       \
        "2:\n"                                                          \
        "       .section .fixup, \"ax\"\n"                              \
        "       .align  2\n"                                            \
        "3:     mov     %w0, %3\n"                                      \
        "       mov     %1, #0\n"                                       \
        "       b       2b\n"                                           \
        "       .previous\n"                                            \
        "       .section __ex_table,\"a\"\n"                            \
        "       .align  3\n"                                            \
        "       .quad   1b, 3b\n"                                       \
        "       .previous"                                              \
        : "+r" (err), "=&r" (x)                                         \
        : "r" (addr), "i" (-EFAULT))

#define __get_user_err(x, ptr, err)                                     \
do {                                                                    \
        unsigned long __gu_val;                                         \
        __chk_user_ptr(ptr);                                            \
        switch (sizeof(*(ptr))) {                                       \
        case 1:                                                         \
                __get_user_asm("ldrb", "%w", __gu_val, (ptr), (err));   \
                break;                                                  \
        case 2:                                                         \
                __get_user_asm("ldrh", "%w", __gu_val, (ptr), (err));   \
                break;                                                  \
        case 4:                                                         \
                __get_user_asm("ldr", "%w", __gu_val, (ptr), (err));    \
                break;                                                  \
        case 8:                                                         \
                __get_user_asm("ldr", "%",  __gu_val, (ptr), (err));    \
                break;                                                  \
        default:                                                        \
                BUILD_BUG();                                            \
        }                                                               \
        (x) = (__typeof__(*(ptr)))__gu_val;                             \
} while (0)

#define __get_user(x, ptr)                                              \
({                                                                      \
        int __gu_err = 0;                                               \
        __get_user_err((x), (ptr), __gu_err);                           \
        __gu_err;                                                       \
})

#define __get_user_error(x, ptr, err)                                   \
({                                                                      \
        __get_user_err((x), (ptr), (err));                              \
        (void)0;                                                        \
})

#define __get_user_unaligned __get_user

#define get_user(x, ptr)                                                \
({                                                                      \
        might_fault();                                                  \
        access_ok(VERIFY_READ, (ptr), sizeof(*(ptr))) ?                 \
                __get_user((x), (ptr)) :                                \
                ((x) = 0, -EFAULT);                                     \
})

#define __put_user_asm(instr, reg, x, addr, err)                        \
        asm volatile(                                                   \
        "1:     " instr "       " reg "1, [%2]\n"                       \
        "2:\n"                                                          \
        "       .section .fixup,\"ax\"\n"                               \
        "       .align  2\n"                                            \
        "3:     mov     %w0, %3\n"                                      \
        "       b       2b\n"                                           \
        "       .previous\n"                                            \
        "       .section __ex_table,\"a\"\n"                            \
        "       .align  3\n"                                            \
        "       .quad   1b, 3b\n"                                       \
        "       .previous"                                              \
        : "+r" (err)                                                    \
        : "r" (x), "r" (addr), "i" (-EFAULT))

#define __put_user_err(x, ptr, err)                                     \
do {                                                                    \
        __typeof__(*(ptr)) __pu_val = (x);                              \
        __chk_user_ptr(ptr);                                            \
        switch (sizeof(*(ptr))) {                                       \
        case 1:                                                         \
                __put_user_asm("strb", "%w", __pu_val, (ptr), (err));   \
                break;                                                  \
        case 2:                                                         \
                __put_user_asm("strh", "%w", __pu_val, (ptr), (err));   \
                break;                                                  \
        case 4:                                                         \
                __put_user_asm("str",  "%w", __pu_val, (ptr), (err));   \
                break;                                                  \
        case 8:                                                         \
                __put_user_asm("str",  "%", __pu_val, (ptr), (err));    \
                break;                                                  \
        default:                                                        \
                BUILD_BUG();                                            \
        }                                                               \
} while (0)

#define __put_user(x, ptr)                                              \
({                                                                      \
        int __pu_err = 0;                                               \
        __put_user_err((x), (ptr), __pu_err);                           \
        __pu_err;                                                       \
})

#define __put_user_error(x, ptr, err)                                   \
({                                                                      \
        __put_user_err((x), (ptr), (err));                              \
        (void)0;                                                        \
})

#define __put_user_unaligned __put_user

#define put_user(x, ptr)                                                \
({                                                                      \
        might_fault();                                                  \
        access_ok(VERIFY_WRITE, (ptr), sizeof(*(ptr))) ?                \
                __put_user((x), (ptr)) :                                \
                -EFAULT;                                                \
})

extern unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n);
extern unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n);
extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);

extern unsigned long __must_check __strncpy_from_user(char *to, const char __user *from, unsigned long count);
extern unsigned long __must_check __strnlen_user(const char __user *s, long n);

static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
{
        if (access_ok(VERIFY_READ, from, n))
                n = __copy_from_user(to, from, n);
        else /* security hole - plug it */
                memset(to, 0, n);
        return n;
}

static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
{
        if (access_ok(VERIFY_WRITE, to, n))
                n = __copy_to_user(to, from, n);
        return n;
}

static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)
{
        if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
                n = __copy_in_user(to, from, n);
        return n;
}

#define __copy_to_user_inatomic __copy_to_user
#define __copy_from_user_inatomic __copy_from_user

static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
{
        if (access_ok(VERIFY_WRITE, to, n))
                n = __clear_user(to, n);
        return n;
}

static inline long __must_check strncpy_from_user(char *dst, const char __user *src, long count)
{
        long res = -EFAULT;
        if (access_ok(VERIFY_READ, src, 1))
                res = __strncpy_from_user(dst, src, count);
        return res;
}

#define strlen_user(s)  strnlen_user(s, ~0UL >> 1)

static inline long __must_check strnlen_user(const char __user *s, long n)
{
        unsigned long res = 0;

        if (__addr_ok(s))
                res = __strnlen_user(s, n);

        return res;
}

#endif /* __ASM_UACCESS_H */