linux/include/asm-x86/uaccess_32.h

#ifndef __i386_UACCESS_H
#define __i386_UACCESS_H

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

#define VERIFY_READ 0
#define VERIFY_WRITE 1

/*
 * The fs value determines whether argument validity checking should be
 * performed or not.  If get_fs() == USER_DS, checking is performed, with
 * get_fs() == KERNEL_DS, checking is bypassed.
 *
 * For historical reasons, these macros are grossly misnamed.
 */

#define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })


#define KERNEL_DS	MAKE_MM_SEG(0xFFFFFFFFUL)
#define USER_DS		MAKE_MM_SEG(PAGE_OFFSET)

#define get_ds()	(KERNEL_DS)
#define get_fs()	(current_thread_info()->addr_limit)
#define set_fs(x)	(current_thread_info()->addr_limit = (x))

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

/*
 * movsl can be slow when source and dest are not both 8-byte aligned
 */
#ifdef CONFIG_X86_INTEL_USERCOPY
extern struct movsl_mask {
	int mask;
} ____cacheline_aligned_in_smp movsl_mask;
#endif

#define __addr_ok(addr)					\
	((unsigned long __force)(addr) <		\
	 (current_thread_info()->addr_limit.seg))

/*
 * Test whether a block of memory is a valid user space address.
 * Returns 0 if the range is valid, nonzero otherwise.
 *
 * This is equivalent to the following test:
 * (u33)addr + (u33)size >= (u33)current->addr_limit.seg
 *
 * This needs 33-bit arithmetic. We have a carry...
 */
#define __range_ok(addr, size)						\
({									\
	unsigned long flag, roksum;					\
	__chk_user_ptr(addr);						\
	asm("addl %3,%1 ; sbbl %0,%0; cmpl %1,%4; sbbl $0,%0"		\
	    :"=&r" (flag), "=r" (roksum)				\
	    :"1" (addr), "g" ((int)(size)),				\
	    "rm" (current_thread_info()->addr_limit.seg));		\
	flag;								\
})

/**
 * access_ok: - Checks if a user space pointer is valid
 * @type: Type of access: %VERIFY_READ or %VERIFY_WRITE.  Note that
 *        %VERIFY_WRITE is a superset of %VERIFY_READ - if it is safe
 *        to write to a block, it is always safe to read from it.
 * @addr: User space pointer to start of block to check
 * @size: Size of block to check
 *
 * Context: User context only.  This function may sleep.
 *
 * Checks if a pointer to a block of memory in user space is valid.
 *
 * Returns true (nonzero) if the memory block may be valid, false (zero)
 * if it is definitely invalid.
 *
 * Note that, depending on architecture, this function probably just
 * checks that the pointer is in the user space range - after calling
 * this function, memory access functions may still return -EFAULT.
 */
#define access_ok(type, addr, size) (likely(__range_ok(addr, size) == 0))

/*
 * 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);

/*
 * These are the main single-value transfer routines.  They automatically
 * use the right size if we just have the right pointer type.
 *
 * This gets kind of ugly. We want to return _two_ values in "get_user()"
 * and yet we don't want to do any pointers, because that is too much
 * of a performance impact. Thus we have a few rather ugly macros here,
 * and hide all the ugliness from the user.
 *
 * The "__xxx" versions of the user access functions are versions that
 * do not verify the address space, that must have been done previously
 * with a separate "access_ok()" call (this is used when we do multiple
 * accesses to the same area of user memory).
 */

extern void __get_user_1(void);
extern void __get_user_2(void);
extern void __get_user_4(void);

#define __get_user_x(size, ret, x, ptr)	      \
	asm volatile("call __get_user_" #size \
		     :"=a" (ret),"=d" (x)     \
		     :"0" (ptr))


/* Careful: we have to cast the result to the type of the pointer
 * for sign reasons */

/**
 * get_user: - Get a simple variable from user space.
 * @x:   Variable to store result.
 * @ptr: Source address, in user space.
 *
 * Context: User context only.  This function may sleep.
 *
 * This macro copies a single simple variable from user space to kernel
 * space.  It supports simple types like char and int, but not larger
 * data types like structures or arrays.
 *
 * @ptr must have pointer-to-simple-variable type, and the result of
 * dereferencing @ptr must be assignable to @x without a cast.
 *
 * Returns zero on success, or -EFAULT on error.
 * On error, the variable @x is set to zero.
 */
#define get_user(x, ptr)						\
({									\
	int __ret_gu;							\
	unsigned long __val_gu;						\
	__chk_user_ptr(ptr);						\
	switch (sizeof(*(ptr))) {					\
	case 1:								\
		__get_user_x(1, __ret_gu, __val_gu, ptr);		\
		break;							\
	case 2:								\
		__get_user_x(2, __ret_gu, __val_gu, ptr);		\
		break;							\
	case 4:								\
		__get_user_x(4, __ret_gu, __val_gu, ptr);		\
		break;							\
	default:							\
		__get_user_x(X, __ret_gu, __val_gu, ptr);		\
		break;							\
	}								\
	(x) = (__typeof__(*(ptr)))__val_gu;				\
	__ret_gu;							\
})

extern void __put_user_bad(void);

/*
 * Strange magic calling convention: pointer in %ecx,
 * value in %eax(:%edx), return value in %eax, no clobbers.
 */
extern void __put_user_1(void);
extern void __put_user_2(void);
extern void __put_user_4(void);
extern void __put_user_8(void);

#define __put_user_x(size, x, ptr)				\
	asm volatile("call __put_user_" #size : "=a" (__ret_pu)	\
		     :"0" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")

#define __put_user_8(x, ptr)					\
	asm volatile("call __put_user_8" : "=a" (__ret_pu)	\
		     : "A" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")


/**
 * put_user: - Write a simple value into user space.
 * @x:   Value to copy to user space.
 * @ptr: Destination address, in user space.
 *
 * Context: User context only.  This function may sleep.
 *
 * This macro copies a single simple value from kernel space to user
 * space.  It supports simple types like char and int, but not larger
 * data types like structures or arrays.
 *
 * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 * to the result of dereferencing @ptr.
 *
 * Returns zero on success, or -EFAULT on error.
 */
#ifdef CONFIG_X86_WP_WORKS_OK

#define put_user(x, ptr)					\
({								\
	int __ret_pu;						\
	__typeof__(*(ptr)) __pu_val;				\
	__chk_user_ptr(ptr);					\
	__pu_val = x;						\
	switch (sizeof(*(ptr))) {				\
	case 1:							\
		__put_user_x(1, __pu_val, ptr);			\
		break;						\
	case 2:							\
		__put_user_x(2, __pu_val, ptr);			\
		break;						\
	case 4:							\
		__put_user_x(4, __pu_val, ptr);			\
		break;						\
	case 8:							\
		__put_user_8(__pu_val, ptr);			\
		break;						\
	default:						\
		__put_user_x(X, __pu_val, ptr);			\
		break;						\
	}							\
	__ret_pu;						\
})

#else
#define put_user(x, ptr)					\
({								\
	int __ret_pu;						\
	__typeof__(*(ptr))__pus_tmp = x;			\
	__ret_pu = 0;						\
	if (unlikely(__copy_to_user_ll(ptr, &__pus_tmp,		\
				       sizeof(*(ptr))) != 0))	\
		__ret_pu = -EFAULT;				\
	__ret_pu;						\
})


#endif

/**
 * __get_user: - Get a simple variable from user space, with less checking.
 * @x:   Variable to store result.
 * @ptr: Source address, in user space.
 *
 * Context: User context only.  This function may sleep.
 *
 * This macro copies a single simple variable from user space to kernel
 * space.  It supports simple types like char and int, but not larger
 * data types like structures or arrays.
 *
 * @ptr must have pointer-to-simple-variable type, and the result of
 * dereferencing @ptr must be assignable to @x without a cast.
 *
 * Caller must check the pointer with access_ok() before calling this
 * function.
 *
 * Returns zero on success, or -EFAULT on error.
 * On error, the variable @x is set to zero.
 */
#define __get_user(x, ptr)				\
	__get_user_nocheck((x), (ptr), sizeof(*(ptr)))


/**
 * __put_user: - Write a simple value into user space, with less checking.
 * @x:   Value to copy to user space.
 * @ptr: Destination address, in user space.
 *
 * Context: User context only.  This function may sleep.
 *
 * This macro copies a single simple value from kernel space to user
 * space.  It supports simple types like char and int, but not larger
 * data types like structures or arrays.
 *
 * @ptr must have pointer-to-simple-variable type, and @x must be assignable
 * to the result of dereferencing @ptr.
 *
 * Caller must check the pointer with access_ok() before calling this
 * function.
 *
 * Returns zero on success, or -EFAULT on error.
 */
#define __put_user(x, ptr)						\
	__put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))

#define __put_user_nocheck(x, ptr, size)			\
({								\
	long __pu_err;						\
	__put_user_size((x), (ptr), (size), __pu_err, -EFAULT);	\
	__pu_err;						\
})


#define __put_user_u64(x, addr, err)					\
	asm volatile("1:	movl %%eax,0(%2)\n"			\
		     "2:	movl %%edx,4(%2)\n"			\
		     "3:\n"						\
		     ".section .fixup,\"ax\"\n"				\
		     "4:	movl %3,%0\n"				\
		     "	jmp 3b\n"					\
		     ".previous\n"					\
		     _ASM_EXTABLE(1b, 4b)				\
		     _ASM_EXTABLE(2b, 4b)				\
		     : "=r" (err)					\
		     : "A" (x), "r" (addr), "i" (-EFAULT), "0" (err))

#ifdef CONFIG_X86_WP_WORKS_OK

#define __put_user_size(x, ptr, size, retval, errret)			\
do {									\
	retval = 0;							\
	__chk_user_ptr(ptr);						\
	switch (size) {							\
	case 1:								\
		__put_user_asm(x, ptr, retval, "b", "b", "iq", errret);	\
		break;							\
	case 2:								\
		__put_user_asm(x, ptr, retval, "w", "w", "ir", errret);	\
		break;							\
	case 4:								\
		__put_user_asm(x, ptr, retval, "l", "",  "ir", errret);	\
		break;							\
	case 8:								\
		__put_user_u64((__typeof__(*ptr))(x), ptr, retval);	\
		break;							\
	default:							\
		__put_user_bad();					\
	}								\
} while (0)

#else

#define __put_user_size(x, ptr, size, retval, errret)			\
do {									\
	__typeof__(*(ptr))__pus_tmp = x;				\
	retval = 0;							\
									\
	if (unlikely(__copy_to_user_ll(ptr, &__pus_tmp, size) != 0))	\
		retval = errret;					\
} while (0)

#endif
struct __large_struct { unsigned long buf[100]; };
#define __m(x) (*(struct __large_struct __user *)(x))

/*
 * Tell gcc we read from memory instead of writing: this is because
 * we do not write to any memory gcc knows about, so there are no
 * aliasing issues.
 */
#define __put_user_asm(x, addr, err, itype, rtype, ltype, errret)	\
	asm volatile("1:	mov"itype" %"rtype"1,%2\n"		\
		     "2:\n"						\
		     ".section .fixup,\"ax\"\n"				\
		     "3:	movl %3,%0\n"				\
		     "	jmp 2b\n"					\
		     ".previous\n"					\
		     _ASM_EXTABLE(1b, 3b)				\
		     : "=r"(err)					\
		     : ltype (x), "m" (__m(addr)), "i" (errret), "0" (err))


#define __get_user_nocheck(x, ptr, size)				\
({									\
	long __gu_err;							\
	unsigned long __gu_val;						\
	__get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT);	\
	(x) = (__typeof__(*(ptr)))__gu_val;				\
	__gu_err;							\
})

extern long __get_user_bad(void);

#define __get_user_size(x, ptr, size, retval, errret)			\
do {									\
	retval = 0;							\
	__chk_user_ptr(ptr);						\
	switch (size) {							\
	case 1:								\
		__get_user_asm(x, ptr, retval, "b", "b", "=q", errret);	\
		break;							\
	case 2:								\
		__get_user_asm(x, ptr, retval, "w", "w", "=r", errret);	\
		break;							\
	case 4:								\
		__get_user_asm(x, ptr, retval, "l", "", "=r", errret);	\
		break;							\
	default:							\
		(x) = __get_user_bad();					\
	}								\
} while (0)

#define __get_user_asm(x, addr, err, itype, rtype, ltype, errret)	\
	asm volatile("1:	mov"itype" %2,%"rtype"1\n"		\
		     "2:\n"						\
		     ".section .fixup,\"ax\"\n"				\
		     "3:	movl %3,%0\n"				\
		     "	xor"itype" %"rtype"1,%"rtype"1\n"		\
		     "	jmp 2b\n"					\
		     ".previous\n"					\
		     _ASM_EXTABLE(1b, 3b)				\
		     : "=r" (err), ltype (x)				\
		     : "m" (__m(addr)), "i" (errret), "0" (err))


unsigned long __must_check __copy_to_user_ll
		(void __user *to, const void *from, unsigned long n);
unsigned long __must_check __copy_from_user_ll
		(void *to, const void __user *from, unsigned long n);
unsigned long __must_check __copy_from_user_ll_nozero
		(void *to, const void __user *from, unsigned long n);
unsigned long __must_check __copy_from_user_ll_nocache
		(void *to, const void __user *from, unsigned long n);
unsigned long __must_check __copy_from_user_ll_nocache_nozero
		(void *to, const void __user *from, unsigned long n);

/**
 * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
 * @to:   Destination address, in user space.
 * @from: Source address, in kernel space.
 * @n:    Number of bytes to copy.
 *
 * Context: User context only.
 *
 * Copy data from kernel space to user space.  Caller must check
 * the specified block with access_ok() before calling this function.
 * The caller should also make sure he pins the user space address
 * so that the we don't result in page fault and sleep.
 *
 * Here we special-case 1, 2 and 4-byte copy_*_user invocations.  On a fault
 * we return the initial request size (1, 2 or 4), as copy_*_user should do.
 * If a store crosses a page boundary and gets a fault, the x86 will not write
 * anything, so this is accurate.
 */

static __always_inline unsigned long __must_check
__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
{
	if (__builtin_constant_p(n)) {
		unsigned long ret;

		switch (n) {
		case 1:
			__put_user_size(*(u8 *)from, (u8 __user *)to,
					1, ret, 1);
			return ret;
		case 2:
			__put_user_size(*(u16 *)from, (u16 __user *)to,
					2, ret, 2);
			return ret;
		case 4:
			__put_user_size(*(u32 *)from, (u32 __user *)to,
					4, ret, 4);
			return ret;
		}
	}
	return __copy_to_user_ll(to, from, n);
}

/**
 * __copy_to_user: - Copy a block of data into user space, with less checking.
 * @to:   Destination address, in user space.
 * @from: Source address, in kernel space.
 * @n:    Number of bytes to copy.
 *
 * Context: User context only.  This function may sleep.
 *
 * Copy data from kernel space to user space.  Caller must check
 * the specified block with access_ok() before calling this function.
 *
 * Returns number of bytes that could not be copied.
 * On success, this will be zero.
 */
static __always_inline unsigned long __must_check
__copy_to_user(void __user *to, const void *from, unsigned long n)
{
       might_sleep();
       return __copy_to_user_inatomic(to, from, n);
}

static __always_inline unsigned long
__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
{
	/* Avoid zeroing the tail if the copy fails..
	 * If 'n' is constant and 1, 2, or 4, we do still zero on a failure,
	 * but as the zeroing behaviour is only significant when n is not
	 * constant, that shouldn't be a problem.
	 */
	if (__builtin_constant_p(n)) {
		unsigned long ret;

		switch (n) {
		case 1:
			__get_user_size(*(u8 *)to, from, 1, ret, 1);
			return ret;
		case 2:
			__get_user_size(*(u16 *)to, from, 2, ret, 2);
			return ret;
		case 4:
			__get_user_size(*(u32 *)to, from, 4, ret, 4);
			return ret;
		}
	}
	return __copy_from_user_ll_nozero(to, from, n);
}

/**
 * __copy_from_user: - Copy a block of data from user space, with less checking.
 * @to:   Destination address, in kernel space.
 * @from: Source address, in user space.
 * @n:    Number of bytes to copy.
 *
 * Context: User context only.  This function may sleep.
 *
 * Copy data from user space to kernel space.  Caller must check
 * the specified block with access_ok() before calling this function.
 *
 * Returns number of bytes that could not be copied.
 * On success, this will be zero.
 *
 * If some data could not be copied, this function will pad the copied
 * data to the requested size using zero bytes.
 *
 * An alternate version - __copy_from_user_inatomic() - may be called from
 * atomic context and will fail rather than sleep.  In this case the
 * uncopied bytes will *NOT* be padded with zeros.  See fs/filemap.h
 * for explanation of why this is needed.
 */
static __always_inline unsigned long
__copy_from_user(void *to, const void __user *from, unsigned long n)
{
	might_sleep();
	if (__builtin_constant_p(n)) {
		unsigned long ret;

		switch (n) {
		case 1:
			__get_user_size(*(u8 *)to, from, 1, ret, 1);
			return ret;
		case 2:
			__get_user_size(*(u16 *)to, from, 2, ret, 2);
			return ret;
		case 4:
			__get_user_size(*(u32 *)to, from, 4, ret, 4);
			return ret;
		}
	}
	return __copy_from_user_ll(to, from, n);
}

#define ARCH_HAS_NOCACHE_UACCESS

static __always_inline unsigned long __copy_from_user_nocache(void *to,
				const void __user *from, unsigned long n)
{
	might_sleep();
	if (__builtin_constant_p(n)) {
		unsigned long ret;

		switch (n) {
		case 1:
			__get_user_size(*(u8 *)to, from, 1, ret, 1);
			return ret;
		case 2:
			__get_user_size(*(u16 *)to, from, 2, ret, 2);
			return ret;
		case 4:
			__get_user_size(*(u32 *)to, from, 4, ret, 4);
			return ret;
		}
	}
	return __copy_from_user_ll_nocache(to, from, n);
}

static __always_inline unsigned long
__copy_from_user_inatomic_nocache(void *to, const void __user *from,
				  unsigned long n)
{
       return __copy_from_user_ll_nocache_nozero(to, from, n);
}

unsigned long __must_check copy_to_user(void __user *to,
					const void *from, unsigned long n);
unsigned long __must_check copy_from_user(void *to,
					  const void __user *from,
					  unsigned long n);
long __must_check strncpy_from_user(char *dst, const char __user *src,
				    long count);
long __must_check __strncpy_from_user(char *dst,
				      const char __user *src, long count);

/**
 * strlen_user: - Get the size of a string in user space.
 * @str: The string to measure.
 *
 * Context: User context only.  This function may sleep.
 *
 * Get the size of a NUL-terminated string in user space.
 *
 * Returns the size of the string INCLUDING the terminating NUL.
 * On exception, returns 0.
 *
 * If there is a limit on the length of a valid string, you may wish to
 * consider using strnlen_user() instead.
 */
#define strlen_user(str) strnlen_user(str, LONG_MAX)

long strnlen_user(const char __user *str, long n);
unsigned long __must_check clear_user(void __user *mem, unsigned long len);
unsigned long __must_check __clear_user(void __user *mem, unsigned long len);

#endif /* __i386_UACCESS_H */