Linux Kernel  3.7.1
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
memcpy_user_64.c
Go to the documentation of this file.
1 /*
2  * Copyright 2011 Tilera Corporation. All Rights Reserved.
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License
6  * as published by the Free Software Foundation, version 2.
7  *
8  * This program is distributed in the hope that it will be useful, but
9  * WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11  * NON INFRINGEMENT. See the GNU General Public License for
12  * more details.
13  *
14  * Do memcpy(), but trap and return "n" when a load or store faults.
15  *
16  * Note: this idiom only works when memcpy() compiles to a leaf function.
17  * Here leaf function not only means it does not have calls, but also
18  * requires no stack operations (sp, stack frame pointer) and no
19  * use of callee-saved registers, else "jrp lr" will be incorrect since
20  * unwinding stack frame is bypassed. Since memcpy() is not complex so
21  * these conditions are satisfied here, but we need to be careful when
22  * modifying this file. This is not a clean solution but is the best
23  * one so far.
24  *
25  * Also note that we are capturing "n" from the containing scope here.
26  */
27 
28 #define _ST(p, inst, v) \
29  ({ \
30  asm("1: " #inst " %0, %1;" \
31  ".pushsection .coldtext.memcpy,\"ax\";" \
32  "2: { move r0, %2; jrp lr };" \
33  ".section __ex_table,\"a\";" \
34  ".quad 1b, 2b;" \
35  ".popsection" \
36  : "=m" (*(p)) : "r" (v), "r" (n)); \
37  })
38 
39 #define _LD(p, inst) \
40  ({ \
41  unsigned long __v; \
42  asm("1: " #inst " %0, %1;" \
43  ".pushsection .coldtext.memcpy,\"ax\";" \
44  "2: { move r0, %2; jrp lr };" \
45  ".section __ex_table,\"a\";" \
46  ".quad 1b, 2b;" \
47  ".popsection" \
48  : "=r" (__v) : "m" (*(p)), "r" (n)); \
49  __v; \
50  })
51 
52 #define USERCOPY_FUNC __copy_to_user_inatomic
53 #define ST1(p, v) _ST((p), st1, (v))
54 #define ST2(p, v) _ST((p), st2, (v))
55 #define ST4(p, v) _ST((p), st4, (v))
56 #define ST8(p, v) _ST((p), st, (v))
57 #define LD1 LD
58 #define LD2 LD
59 #define LD4 LD
60 #define LD8 LD
61 #include "memcpy_64.c"
62 
63 #define USERCOPY_FUNC __copy_from_user_inatomic
64 #define ST1 ST
65 #define ST2 ST
66 #define ST4 ST
67 #define ST8 ST
68 #define LD1(p) _LD((p), ld1u)
69 #define LD2(p) _LD((p), ld2u)
70 #define LD4(p) _LD((p), ld4u)
71 #define LD8(p) _LD((p), ld)
72 #include "memcpy_64.c"
73 
74 #define USERCOPY_FUNC __copy_in_user_inatomic
75 #define ST1(p, v) _ST((p), st1, (v))
76 #define ST2(p, v) _ST((p), st2, (v))
77 #define ST4(p, v) _ST((p), st4, (v))
78 #define ST8(p, v) _ST((p), st, (v))
79 #define LD1(p) _LD((p), ld1u)
80 #define LD2(p) _LD((p), ld2u)
81 #define LD4(p) _LD((p), ld4u)
82 #define LD8(p) _LD((p), ld)
83 #include "memcpy_64.c"
84 
85 unsigned long __copy_from_user_zeroing(void *to, const void __user *from,
86  unsigned long n)
87 {
88  unsigned long rc = __copy_from_user_inatomic(to, from, n);
89  if (unlikely(rc))
90  memset(to + n - rc, 0, rc);
91  return rc;
92 }