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

Arnd Bergmann
2009-05-01T13:13:56Z

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 */