[PATCH V3] asm-generic: add a generic uaccess.h

[Arnd Bergmann <arnd@arndb.de>]

This adds a new asm-generic/uaccess.h file that should be usable
by both all NOMMU architectures out of the box. Architectures with
an MMU should override the __access_ok(), __copy_from_user() and
__copy_to_user definitions with their own functions to provide
correct exception handling.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
new file mode 100644
index 0000000..deb1722
--- /dev/null
+++ b/include/asm-generic/uaccess.h
@@ -0,0 +1,319 @@
+#ifndef __ASM_GENERIC_UACCESS_H
+#define __ASM_GENERIC_UACCESS_H
+
+/*
+ * User space memory access functions, these should work
+ * on a ny machine that has kernel and user data in the same
+ * address space, e.g. all NOMMU machines.
+ */
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+
+#include <asm/segment.h>
+
+#ifndef get_fs
+#define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
+#define KERNEL_DS	MAKE_MM_SEG(~0UL)
+#define USER_DS		MAKE_MM_SEG(TASK_SIZE - 1)
+
+#define get_ds() (KERNEL_DS)
+#define get_fs() (current_thread_info()->addr_limit)
+
+static inline void set_fs(mm_segment_t fs)
+{
+	current_thread_info()->addr_limit = fs;
+}
+#endif
+
+#define segment_eq(a, b) ((a).seg == (b).seg)
+
+#define VERIFY_READ	0
+#define VERIFY_WRITE	1
+
+#define access_ok(type, addr, size) __access_ok((unsigned long)(addr),(size))
+
+/*
+ * The architecture should really override this if possible, at least
+ * doing a check on the get_fs()
+ */
+#ifndef __access_ok
+static inline int __access_ok(unsigned long addr, unsigned long size)
+{
+	return 1;
+}
+#endif
+
+/*
+ * 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;
+};
+
+/* Returns 0 if exception not found and fixup otherwise.  */
+extern unsigned long search_exception_table(unsigned long);
+
+/*
+ * architectures with an MMU should override these two
+ */
+#ifndef __copy_from_user
+static inline __must_check long __copy_from_user(void *to,
+		const void __user * from, unsigned long n)
+{
+	if (__builtin_constant_p(n)) {
+		switch(n) {
+		case 1:
+			*(u8 *)to = *(u8 __force *)from;
+			return 0;
+		case 2:
+			*(u16 *)to = *(u16 __force *)from;
+			return 0;
+		case 4:
+			*(u32 *)to = *(u32 __force *)from;
+			return 0;
+#ifdef CONFIG_64BIT
+		case 8:
+			*(u64 *)to = *(u64 __force *)from;
+			return 0;
+#endif
+		default:
+			break;
+		}
+	}
+
+	memcpy(to, (const void __force *)from, n);
+	return 0;
+}
+#endif
+
+#ifndef __copy_to_user
+static inline __must_check long __copy_to_user(void __user *to,
+		const void *from, unsigned long n)
+{
+	if (__builtin_constant_p(n)) {
+		switch(n) {
+		case 1:
+			*(u8 __force *)to = *(u8 *)from;
+			return 0;
+		case 2:
+			*(u16 __force *)to = *(u16 *)from;
+			return 0;
+		case 4:
+			*(u32 __force *)to = *(u32 *)from;
+			return 0;
+#ifdef CONFIG_64BIT
+		case 8:
+			*(u64 __force *)to = *(u64 *)from;
+			return 0;
+#endif
+		default:
+			break;
+		}
+	}
+
+	memcpy((void __force *)to, from, n);
+	return 0;
+}
+#endif
+
+/*
+ * These are the main single-value transfer routines.  They automatically
+ * use the right size if we just have the right pointer type.
+ * This version just falls back to copy_{from,to}_user, which should
+ * provide a fast-path for small values. 
+ */
+#define __put_user(x, ptr) \
+({								\
+	__typeof__(*(ptr)) __x = (x);				\
+	int __pu_err = -EFAULT;					\
+        __chk_user_ptr(ptr);					\
+	switch (sizeof (*(ptr))) {				\
+	case 1:							\
+	case 2:							\
+	case 4:							\
+	case 8:							\
+		__pu_err = __put_user_fn(sizeof (*(ptr)),	\
+					 ptr, &__x);		\
+		break;						\
+	default:						\
+		__put_user_bad();				\
+		break;						\
+	 }							\
+	__pu_err;						\
+})
+
+#define put_user(x, ptr)					\
+({								\
+	might_sleep();						\
+	__access_ok(ptr, sizeof (*ptr)) ?			\
+		__put_user(x, ptr) :				\
+		-EFAULT;					\
+})
+
+static inline int __put_user_fn(size_t size, void __user *ptr, void *x)
+{
+	size = __copy_to_user(ptr, x, size);
+	return size ? -EFAULT : size;
+}
+
+extern int __put_user_bad(void) __attribute__((noreturn));
+
+#define __get_user(x, ptr)					\
+({								\
+	int __gu_err = -EFAULT;					\
+	__chk_user_ptr(ptr);					\
+	switch (sizeof(*(ptr))) {				\
+	case 1: {						\
+		unsigned char __x;				\
+		__gu_err = __get_user_fn(sizeof (*(ptr)),	\
+					 ptr, &__x);		\
+		(x) = *(__force __typeof__(*(ptr)) *) &__x;	\
+		break;						\
+	};							\
+	case 2: {						\
+		unsigned short __x;				\
+		__gu_err = __get_user_fn(sizeof (*(ptr)),	\
+					 ptr, &__x);		\
+		(x) = *(__force __typeof__(*(ptr)) *) &__x;	\
+		break;						\
+	};							\
+	case 4: {						\
+		unsigned int __x;				\
+		__gu_err = __get_user_fn(sizeof (*(ptr)),	\
+					 ptr, &__x);		\
+		(x) = *(__force __typeof__(*(ptr)) *) &__x;	\
+		break;						\
+	};							\
+	case 8: {						\
+		unsigned long long __x;				\
+		__gu_err = __get_user_fn(sizeof (*(ptr)),	\
+					 ptr, &__x);		\
+		(x) = *(__force __typeof__(*(ptr)) *) &__x;	\
+		break;						\
+	};							\
+	default:						\
+		__get_user_bad();				\
+		break;						\
+	}							\
+	__gu_err;						\
+})
+
+#define get_user(x, ptr)					\
+({								\
+	might_sleep();						\
+	__access_ok(ptr, sizeof (*ptr)) ?			\
+		__get_user(x, ptr) :				\
+		-EFAULT;					\
+})
+
+static inline int __get_user_fn(size_t size, const void __user *ptr, void *x)
+{
+	size = __copy_from_user(x, ptr, size);
+	return size ? -EFAULT : size;
+}
+
+extern int __get_user_bad(void) __attribute__((noreturn));
+
+#ifndef __copy_from_user_inatomic
+#define __copy_from_user_inatomic __copy_from_user
+#endif
+
+#ifndef __copy_to_user_inatomic
+#define __copy_to_user_inatomic __copy_to_user
+#endif
+
+static inline long copy_from_user(void *to,
+		const void __user * from, unsigned long n)
+{
+	might_sleep();
+	if (__access_ok(from, n))
+		return __copy_from_user(to, from, n);
+	else
+		return n;
+}
+
+static inline long copy_to_user(void __user *to,
+		const void *from, unsigned long n)
+{
+	might_sleep();
+	if (__access_ok(to, n))
+		return __copy_to_user(to, from, n);
+	else
+		return n;
+}
+
+/*
+ * Copy a null terminated string from userspace.
+ */
+#ifndef __strncpy_from_user
+static inline long
+__strncpy_from_user(char *dst, const char __user *src, long count)
+{
+	char *tmp;
+	strncpy(dst, (const char __force *)src, count);
+	for (tmp = dst; *tmp && count > 0; tmp++, count--)
+		;
+	return (tmp - dst);
+}
+#endif
+
+static inline long
+strncpy_from_user(char *dst, const char __user *src, long count)
+{
+	if (!__access_ok(src, 1))
+		return -EFAULT;
+	return __strncpy_from_user(dst, src, count);
+}
+
+/*
+ * Return the size of a string (including the ending 0)
+ *
+ * Return 0 on exception, a value greater than N if too long
+ */
+#ifndef strnlen_user
+static inline long strnlen_user(const char __user *src, long n)
+{
+	return strlen((void * __force)src) + 1;
+}
+#endif
+
+static inline long strlen_user(const char __user *src)
+{
+	return strnlen_user(src, 32767);
+}
+
+/*
+ * Zero Userspace
+ */
+#ifndef __clear_user
+static inline __must_check unsigned long
+__clear_user(void __user *to, unsigned long n)
+{
+	memset((void __force *)to, 0, n);
+	return 0;
+}
+#endif
+
+static inline __must_check unsigned long
+clear_user(void __user *to, unsigned long n)
+{
+	might_sleep();
+	if (!__access_ok(to, n))
+		return n;
+
+	return __clear_user(to, n);
+}
+
+#endif /* __ASM_GENERIC_UACCESS_H */