tile: add <asm/word-at-a-time.h> and enable support functions

This change enables the generic strncpy_from_user() and strnlen_user()
using word-at-a-time.h.  The tile implementation is trivial since
both tilepro and tilegx have SIMD operations that do byte-wise
comparisons against immediate zero for each byte, and return an
0x01 byte in each position where there is a 0x00 byte.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>

2 files changed, 46 insertions, 56 deletions

diff --git a/arch/tile/include/asm/uaccess.h b/arch/tile/include/asm/uaccess.h
index f41cb53cf645..d598c11a82d9 100644
--- a/arch/tile/include/asm/uaccess.h
+++ b/arch/tile/include/asm/uaccess.h
@@ -65,6 +65,13 @@ static inline int is_arch_mappable_range(unsigned long addr,
 #endif
 
 /*
+ * Note that using this definition ignores is_arch_mappable_range(),
+ * so on tilepro code that uses user_addr_max() is constrained not
+ * to reference the tilepro user-interrupt region.
+ */
+#define user_addr_max() (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.
  */
@@ -465,62 +472,9 @@ copy_in_user(void __user *to, const void __user *from, unsigned long n)
 #endif
 
 
-/**
- * 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.
- */
-extern long strnlen_user_asm(const char __user *str, long n);
-static inline long __must_check strnlen_user(const char __user *str, long n)
-{
-	might_fault();
-	return strnlen_user_asm(str, n);
-}
-#define strlen_user(str) strnlen_user(str, LONG_MAX)
-
-/**
- * strncpy_from_user: - Copy a NUL terminated string from userspace, with less checking.
- * @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.
- * Caller must check the specified block with access_ok() before calling
- * this function.
- *
- * 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.
- */
-extern long strncpy_from_user_asm(char *dst, const char __user *src, long);
-static inline long __must_check __strncpy_from_user(
-	char *dst, const char __user *src, long count)
-{
-	might_fault();
-	return strncpy_from_user_asm(dst, src, count);
-}
-static inline long __must_check strncpy_from_user(
-	char *dst, const char __user *src, long count)
-{
-	if (access_ok(VERIFY_READ, src, 1))
-		return __strncpy_from_user(dst, src, count);
-	return -EFAULT;
-}
+extern long strnlen_user(const char __user *str, long n);
+extern long strlen_user(const char __user *str);
+extern long strncpy_from_user(char *dst, const char __user *src, long);
 
 /**
  * clear_user: - Zero a block of memory in user space.
diff --git a/arch/tile/include/asm/word-at-a-time.h b/arch/tile/include/asm/word-at-a-time.h
new file mode 100644
index 000000000000..9e5ce0d7b292
--- /dev/null
+++ b/arch/tile/include/asm/word-at-a-time.h
@@ -0,0 +1,36 @@
+#ifndef _ASM_WORD_AT_A_TIME_H
+#define _ASM_WORD_AT_A_TIME_H
+
+#include <asm/byteorder.h>
+
+struct word_at_a_time { /* unused */ };
+#define WORD_AT_A_TIME_CONSTANTS {}
+
+/* Generate 0x01 byte values for non-zero bytes using a SIMD instruction. */
+static inline unsigned long has_zero(unsigned long val, unsigned long *data,
+				     const struct word_at_a_time *c)
+{
+#ifdef __tilegx__
+	unsigned long mask = __insn_v1cmpeqi(val, 0);
+#else /* tilepro */
+	unsigned long mask = __insn_seqib(val, 0);
+#endif
+	*data = mask;
+	return mask;
+}
+
+/* These operations are both nops. */
+#define prep_zero_mask(val, data, c) (data)
+#define create_zero_mask(data) (data)
+
+/* And this operation just depends on endianness. */
+static inline long find_zero(unsigned long mask)
+{
+#ifdef __BIG_ENDIAN
+	return __builtin_clzl(mask) >> 3;
+#else
+	return __builtin_ctzl(mask) >> 3;
+#endif
+}
+
+#endif /* _ASM_WORD_AT_A_TIME_H */