lib: Sparc's strncpy_from_user is generic enough, move under lib/

[linux-2.6-block.git] / lib / strncpy_from_user.c

diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
new file mode 100644 (file)
index 0000000..c4c09b0
--- /dev/null
+++ b/lib/strncpy_from_user.c
@@ -0,0 +1,146 @@
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+
+#include <asm/byteorder.h>
+
+static inline long find_zero(unsigned long mask)
+{
+       long byte = 0;
+
+#ifdef __BIG_ENDIAN
+#ifdef CONFIG_64BIT
+       if (mask >> 32)
+               mask >>= 32;
+       else
+               byte = 4;
+#endif
+       if (mask >> 16)
+               mask >>= 16;
+       else
+               byte += 2;
+       return (mask >> 8) ? byte : byte + 1;
+#else
+#ifdef CONFIG_64BIT
+       if (!((unsigned int) mask)) {
+               mask >>= 32;
+               byte = 4;
+       }
+#endif
+       if (!(mask & 0xffff)) {
+               mask >>= 16;
+               byte += 2;
+       }
+       return (mask & 0xff) ? byte : byte + 1;
+#endif
+}
+
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+#define IS_UNALIGNED(src, dst) 0
+#else
+#define IS_UNALIGNED(src, dst) \
+       (((long) dst | (long) src) & (sizeof(long) - 1))
+#endif
+
+/*
+ * Do a strncpy, return length of string without final '\0'.
+ * 'count' is the user-supplied count (return 'count' if we
+ * hit it), 'max' is the address space maximum (and we return
+ * -EFAULT if we hit it).
+ */
+static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max)
+{
+       const unsigned long high_bits = REPEAT_BYTE(0xfe) + 1;
+       const unsigned long low_bits = REPEAT_BYTE(0x7f);
+       long res = 0;
+
+       /*
+        * Truncate 'max' to the user-specified limit, so that
+        * we only have one limit we need to check in the loop
+        */
+       if (max > count)
+               max = count;
+
+       if (IS_UNALIGNED(src, dst))
+               goto byte_at_a_time;
+
+       while (max >= sizeof(unsigned long)) {
+               unsigned long c, v, rhs;
+
+               /* Fall back to byte-at-a-time if we get a page fault */
+               if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
+                       break;
+               rhs = c | low_bits;
+               v = (c + high_bits) & ~rhs;
+               *(unsigned long *)(dst+res) = c;
+               if (v) {
+                       v = (c & low_bits) + low_bits;
+                       v = ~(v | rhs);
+                       return res + find_zero(v);
+               }
+               res += sizeof(unsigned long);
+               max -= sizeof(unsigned long);
+       }
+
+byte_at_a_time:
+       while (max) {
+               char c;
+
+               if (unlikely(__get_user(c,src+res)))
+                       return -EFAULT;
+               dst[res] = c;
+               if (!c)
+                       return res;
+               res++;
+               max--;
+       }
+
+       /*
+        * Uhhuh. We hit 'max'. But was that the user-specified maximum
+        * too? If so, that's ok - we got as much as the user asked for.
+        */
+       if (res >= count)
+               return res;
+
+       /*
+        * Nope: we hit the address space limit, and we still had more
+        * characters the caller would have wanted. That's an EFAULT.
+        */
+       return -EFAULT;
+}
+
+/**
+ * strncpy_from_user: - Copy a NUL terminated string from userspace.
+ * @dst:   Destination address, in kernel space.  This buffer must be at
+ *         least @count bytes long.
+ * @src:   Source address, in user space.
+ * @count: Maximum number of bytes to copy, including the trailing NUL.
+ *
+ * Copies a NUL-terminated string from userspace to kernel space.
+ *
+ * On success, returns the length of the string (not including the trailing
+ * NUL).
+ *
+ * If access to userspace fails, returns -EFAULT (some data may have been
+ * copied).
+ *
+ * If @count is smaller than the length of the string, copies @count bytes
+ * and returns @count.
+ */
+long strncpy_from_user(char *dst, const char __user *src, long count)
+{
+       unsigned long max_addr, src_addr;
+
+       if (unlikely(count <= 0))
+               return 0;
+
+       max_addr = user_addr_max();
+       src_addr = (unsigned long)src;
+       if (likely(src_addr < max_addr)) {
+               unsigned long max = max_addr - src_addr;
+               return do_strncpy_from_user(dst, src, count, max);
+       }
+       return -EFAULT;
+}
+EXPORT_SYMBOL(strncpy_from_user);