x86: remove more uaccess_32.h complexity

I'm looking at trying to possibly merge the 32-bit and 64-bit versions
of the x86 uaccess.h implementation, but first this needs to be cleaned
up.

For example, the 32-bit version of "__copy_from_user_inatomic()" is
mostly the special cases for the constant size, and it's actually almost
never relevant.  Most users aren't actually using a constant size
anyway, and the few cases that do small constant copies are better off
just using __get_user() instead.

So get rid of the unnecessary complexity.

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

4 files changed, 3 insertions, 31 deletions

diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h
index 537cc883ea29..4b32da24faaf 100644
--- a/arch/x86/include/asm/uaccess_32.h
+++ b/arch/x86/include/asm/uaccess_32.h
@@ -65,32 +65,6 @@ __copy_to_user(void __user *to, const void *from, unsigned long n)
 static __always_inline unsigned long
 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
 {
-        /* Avoid zeroing the tail if the copy fails..
-         * If 'n' is constant and 1, 2, or 4, we do still zero on a failure,
-         * but as the zeroing behaviour is only significant when n is not
-         * constant, that shouldn't be a problem.
-         */
-        if (__builtin_constant_p(n)) {
-                unsigned long ret;
-
-                switch (n) {
-                case 1:
-                        __uaccess_begin();
-                        __get_user_size(*(u8 *)to, from, 1, ret, 1);
-                        __uaccess_end();
-                        return ret;
-                case 2:
-                        __uaccess_begin();
-                        __get_user_size(*(u16 *)to, from, 2, ret, 2);
-                        __uaccess_end();
-                        return ret;
-                case 4:
-                        __uaccess_begin();
-                        __get_user_size(*(u32 *)to, from, 4, ret, 4);
-                        __uaccess_end();
-                        return ret;
-                }
-        }
         return __copy_from_user_ll_nozero(to, from, n);
 }
 
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 7edc95edfaee..c01f733ff2e1 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1694,8 +1694,7 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
         int result;
 
         pagefault_disable();
-        result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
-                                                        sizeof(opcode));
+        result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);
         pagefault_enable();
 
         if (likely(result == 0))
diff --git a/kernel/futex.c b/kernel/futex.c
index c20f06f38ef3..ee25f5ba4aca 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -729,7 +729,7 @@ static int get_futex_value_locked(u32 *dest, u32 __user *from)
         int ret;
 
         pagefault_disable();
-        ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
+        ret = __get_user(*dest, from);
         pagefault_enable();
 
         return ret ? -EFAULT : 0;
diff --git a/mm/maccess.c b/mm/maccess.c
index d159b1c96e48..78f9274dd49d 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -96,8 +96,7 @@ long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
         pagefault_disable();
 
         do {
-                ret = __copy_from_user_inatomic(dst++,
-                                                (const void __user __force *)src++, 1);
+                ret = __get_user(*dst++, (const char __user __force *)src++);
         } while (dst[-1] && ret == 0 && src - unsafe_addr < count);
 
         dst[-1] = '\0';