#include <linux/string.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/kmsan-checks.h>

#define movs(type,to,from) \
        asm volatile("movs" type:"=&D" (to), "=&S" (from):"0" (to), "1" (from):"memory")

/* Originally from i386/string.h */
static __always_inline void rep_movs(void *to, const void *from, size_t n)
{
        unsigned long d0, d1, d2;
        asm volatile("rep movsl\n\t"
                     "testb $2,%b4\n\t"
                     "je 1f\n\t"
                     "movsw\n"
                     "1:\ttestb $1,%b4\n\t"
                     "je 2f\n\t"
                     "movsb\n"
                     "2:"
                     : "=&c" (d0), "=&D" (d1), "=&S" (d2)
                     : "0" (n / 4), "q" (n), "1" ((long)to), "2" ((long)from)
                     : "memory");
}

static void string_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
{
        const void *orig_to = to;
        const size_t orig_n = n;

        if (unlikely(!n))
                return;

        /* Align any unaligned source IO */
        if (unlikely(1 & (unsigned long)from)) {
                movs("b", to, from);
                n--;
        }
        if (n > 1 && unlikely(2 & (unsigned long)from)) {
                movs("w", to, from);
                n-=2;
        }
        rep_movs(to, (const void *)from, n);
        /* KMSAN must treat values read from devices as initialized. */
        kmsan_unpoison_memory(orig_to, orig_n);
}

static void string_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
{
        if (unlikely(!n))
                return;

        /* Make sure uninitialized memory isn't copied to devices. */
        kmsan_check_memory(from, n);
        /* Align any unaligned destination IO */
        if (unlikely(1 & (unsigned long)to)) {
                movs("b", to, from);
                n--;
        }
        if (n > 1 && unlikely(2 & (unsigned long)to)) {
                movs("w", to, from);
                n-=2;
        }
        rep_movs((void *)to, (const void *) from, n);
}

static void unrolled_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
{
        const volatile char __iomem *in = from;
        char *out = to;
        int i;

        for (i = 0; i < n; ++i)
                out[i] = readb(&in[i]);
}

static void unrolled_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
{
        volatile char __iomem *out = to;
        const char *in = from;
        int i;

        for (i = 0; i < n; ++i)
                writeb(in[i], &out[i]);
}

static void unrolled_memset_io(volatile void __iomem *a, int b, size_t c)
{
        volatile char __iomem *mem = a;
        int i;

        for (i = 0; i < c; ++i)
                writeb(b, &mem[i]);
}

void memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
{
        if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO))
                unrolled_memcpy_fromio(to, from, n);
        else
                string_memcpy_fromio(to, from, n);
}
EXPORT_SYMBOL(memcpy_fromio);

void memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
{
        if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO))
                unrolled_memcpy_toio(to, from, n);
        else
                string_memcpy_toio(to, from, n);
}
EXPORT_SYMBOL(memcpy_toio);

void memset_io(volatile void __iomem *a, int b, size_t c)
{
        if (cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) {
                unrolled_memset_io(a, b, c);
        } else {
                /*
                 * TODO: memset can mangle the IO patterns quite a bit.
                 * perhaps it would be better to use a dumb one:
                 */
                memset((void *)a, b, c);
        }
}
EXPORT_SYMBOL(memset_io);