Use the new batched user accesses in generic user string handling

This converts the generic user string functions to use the batched user
access functions.

It makes a big difference on Skylake, which is the first x86
microarchitecture to implement SMAP.  The STAC/CLAC instructions are not
very fast, and doing them for each access inside the loop that copies
strings from user space (which is what the pathname handling does for
every pathname the kernel uses, for example) is very inefficient.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index e0af6ff73d146cfa3356080ebcb1bbea36cd1f96..33840324138c21fc427c5c8dcbda66cb64ab3636 100644 (file)
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -39,7 +39,7 @@ static inline long do_strncpy_from_user(char *dst, const char __user *src, long
                unsigned long c, data;
 
                /* Fall back to byte-at-a-time if we get a page fault */
-               if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
+               if (unlikely(unsafe_get_user(c,(unsigned long __user *)(src+res))))
                        break;
                *(unsigned long *)(dst+res) = c;
                if (has_zero(c, &data, &constants)) {
@@ -55,7 +55,7 @@ byte_at_a_time:
        while (max) {
                char c;
 
-               if (unlikely(__get_user(c,src+res)))
+               if (unlikely(unsafe_get_user(c,src+res)))
                        return -EFAULT;
                dst[res] = c;
                if (!c)
@@ -107,7 +107,12 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
        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);
+               long retval;
+
+               user_access_begin();
+               retval = do_strncpy_from_user(dst, src, count, max);
+               user_access_end();
+               return retval;
        }
        return -EFAULT;
 }

diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
index 3a5f2b366d84ed209a012cf62491ca30f6a8bca8..2625943625d7fb229e6e2cf104e5d84c95246ffa 100644 (file)
--- a/lib/strnlen_user.c
+++ b/lib/strnlen_user.c
@@ -45,7 +45,7 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count,
        src -= align;
        max += align;
 
-       if (unlikely(__get_user(c,(unsigned long __user *)src)))
+       if (unlikely(unsafe_get_user(c,(unsigned long __user *)src)))
                return 0;
        c |= aligned_byte_mask(align);
 
@@ -61,7 +61,7 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count,
                if (unlikely(max <= sizeof(unsigned long)))
                        break;
                max -= sizeof(unsigned long);
-               if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
+               if (unlikely(unsafe_get_user(c,(unsigned long __user *)(src+res))))
                        return 0;
        }
        res -= align;
@@ -112,7 +112,12 @@ long strnlen_user(const char __user *str, long count)
        src_addr = (unsigned long)str;
        if (likely(src_addr < max_addr)) {
                unsigned long max = max_addr - src_addr;
-               return do_strnlen_user(str, count, max);
+               long retval;
+
+               user_access_begin();
+               retval = do_strnlen_user(str, count, max);
+               user_access_end();
+               return retval;
        }
        return 0;
 }
@@ -141,7 +146,12 @@ long strlen_user(const char __user *str)
        src_addr = (unsigned long)str;
        if (likely(src_addr < max_addr)) {
                unsigned long max = max_addr - src_addr;
-               return do_strnlen_user(str, ~0ul, max);
+               long retval;
+
+               user_access_begin();
+               retval = do_strnlen_user(str, ~0ul, max);
+               user_access_end();
+               return retval;
        }
        return 0;
 }