1#include <linux/string.h>
2#include <linux/module.h>
3#include <linux/io.h>
4#include <linux/kmsan-checks.h>
5
6#define movs(type,to,from) \
7 asm volatile("movs" type:"=&D" (to), "=&S" (from):"0" (to), "1" (from):"memory")
8
9/* Originally from i386/string.h */
10static __always_inline void rep_movs(void *to, const void *from, size_t n)
11{
12 unsigned long d0, d1, d2;
13 asm volatile("rep movsl\n\t"
14 "testb $2,%b4\n\t"
15 "je 1f\n\t"
16 "movsw\n"
17 "1:\ttestb $1,%b4\n\t"
18 "je 2f\n\t"
19 "movsb\n"
20 "2:"
21 : "=&c" (d0), "=&D" (d1), "=&S" (d2)
22 : "0" (n / 4), "q" (n), "1" ((long)to), "2" ((long)from)
23 : "memory");
24}
25
26static void string_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
27{
28 const void *orig_to = to;
29 const size_t orig_n = n;
30
31 if (unlikely(!n))
32 return;
33
34 /* Align any unaligned source IO */
35 if (unlikely(1 & (unsigned long)from)) {
36 movs("b", to, from);
37 n--;
38 }
39 if (n > 1 && unlikely(2 & (unsigned long)from)) {
40 movs("w", to, from);
41 n-=2;
42 }
43 rep_movs(to, from: (const void *)from, n);
44 /* KMSAN must treat values read from devices as initialized. */
45 kmsan_unpoison_memory(address: orig_to, size: orig_n);
46}
47
48static void string_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
49{
50 if (unlikely(!n))
51 return;
52
53 /* Make sure uninitialized memory isn't copied to devices. */
54 kmsan_check_memory(address: from, size: n);
55 /* Align any unaligned destination IO */
56 if (unlikely(1 & (unsigned long)to)) {
57 movs("b", to, from);
58 n--;
59 }
60 if (n > 1 && unlikely(2 & (unsigned long)to)) {
61 movs("w", to, from);
62 n-=2;
63 }
64 rep_movs(to: (void *)to, from: (const void *) from, n);
65}
66
67static void unrolled_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
68{
69 const volatile char __iomem *in = from;
70 char *out = to;
71 int i;
72
73 for (i = 0; i < n; ++i)
74 out[i] = readb(addr: &in[i]);
75}
76
77static void unrolled_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
78{
79 volatile char __iomem *out = to;
80 const char *in = from;
81 int i;
82
83 for (i = 0; i < n; ++i)
84 writeb(val: in[i], addr: &out[i]);
85}
86
87static void unrolled_memset_io(volatile void __iomem *a, int b, size_t c)
88{
89 volatile char __iomem *mem = a;
90 int i;
91
92 for (i = 0; i < c; ++i)
93 writeb(val: b, addr: &mem[i]);
94}
95
96void memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
97{
98 if (cc_platform_has(attr: CC_ATTR_GUEST_UNROLL_STRING_IO))
99 unrolled_memcpy_fromio(to, from, n);
100 else
101 string_memcpy_fromio(to, from, n);
102}
103EXPORT_SYMBOL(memcpy_fromio);
104
105void memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
106{
107 if (cc_platform_has(attr: CC_ATTR_GUEST_UNROLL_STRING_IO))
108 unrolled_memcpy_toio(to, from, n);
109 else
110 string_memcpy_toio(to, from, n);
111}
112EXPORT_SYMBOL(memcpy_toio);
113
114void memset_io(volatile void __iomem *a, int b, size_t c)
115{
116 if (cc_platform_has(attr: CC_ATTR_GUEST_UNROLL_STRING_IO)) {
117 unrolled_memset_io(a, b, c);
118 } else {
119 /*
120 * TODO: memset can mangle the IO patterns quite a bit.
121 * perhaps it would be better to use a dumb one:
122 */
123 memset((void *)a, b, c);
124 }
125}
126EXPORT_SYMBOL(memset_io);
127

source code of linux/arch/x86/lib/iomem.c