arch/x86/lib/iomem.c

   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 */
  10 static __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
  26 static 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, (const void *)from, n);
  44         /* KMSAN must treat values read from devices as initialized. */
  45         kmsan_unpoison_memory(orig_to, orig_n);
  46 }
  47
  48 static 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(from, 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((void *)to, (const void *) from, n);
  65 }
  66
  67 static 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(&in[i]);
  75 }
  76
  77 static 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(in[i], &out[i]);
  85 }
  86
  87 static 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(b, &mem[i]);
  94 }
  95
  96 void memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
  97 {
  98         if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO))
  99                 unrolled_memcpy_fromio(to, from, n);
 100         else
 101                 string_memcpy_fromio(to, from, n);
 102 }
 103 EXPORT_SYMBOL(memcpy_fromio);
 104
 105 void memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
 106 {
 107         if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO))
 108                 unrolled_memcpy_toio(to, from, n);
 109         else
 110                 string_memcpy_toio(to, from, n);
 111 }
 112 EXPORT_SYMBOL(memcpy_toio);
 113
 114 void memset_io(volatile void __iomem *a, int b, size_t c)
 115 {
 116         if (cc_platform_has(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 }
 126 EXPORT_SYMBOL(memset_io);