// SPDX-License-Identifier: GPL-2.0
/*
 * arch/arm/boot/compressed/string.c
 *
 * Small subset of simple string routines
 */

#define __NO_FORTIFY
#include <linux/string.h>

/*
 * The decompressor is built without KASan but uses the same redirects as the
 * rest of the kernel when CONFIG_KASAN is enabled, defining e.g. memcpy()
 * to __memcpy() but since we are not linking with the main kernel string
 * library in the decompressor, that will lead to link failures.
 *
 * Undefine KASan's versions, define the wrapped functions and alias them to
 * the right names so that when e.g. __memcpy() appear in the code, it will
 * still be linked to this local version of memcpy().
 */
#ifdef CONFIG_KASAN
#undef memcpy
#undef memmove
#undef memset
void *__memcpy(void *__dest, __const void *__src, size_t __n) __alias(memcpy);
void *__memmove(void *__dest, __const void *__src, size_t count) __alias(memmove);
void *__memset(void *s, int c, size_t count) __alias(memset);
#endif

void *memcpy(void *__dest, __const void *__src, size_t __n)
{
        int i = 0;
        unsigned char *d = (unsigned char *)__dest, *s = (unsigned char *)__src;

        for (i = __n >> 3; i > 0; i--) {
                *d++ = *s++;
                *d++ = *s++;
                *d++ = *s++;
                *d++ = *s++;
                *d++ = *s++;
                *d++ = *s++;
                *d++ = *s++;
                *d++ = *s++;
        }

        if (__n & 1 << 2) {
                *d++ = *s++;
                *d++ = *s++;
                *d++ = *s++;
                *d++ = *s++;
        }

        if (__n & 1 << 1) {
                *d++ = *s++;
                *d++ = *s++;
        }

        if (__n & 1)
                *d++ = *s++;

        return __dest;
}

void *memmove(void *__dest, __const void *__src, size_t count)
{
        unsigned char *d = __dest;
        const unsigned char *s = __src;

        if (__dest == __src)
                return __dest;

        if (__dest < __src)
                return memcpy(__dest, __src, count);

        while (count--)
                d[count] = s[count];
        return __dest;
}

size_t strlen(const char *s)
{
        const char *sc = s;

        while (*sc != '\0')
                sc++;
        return sc - s;
}

size_t strnlen(const char *s, size_t count)
{
        const char *sc;

        for (sc = s; count-- && *sc != '\0'; ++sc)
                /* nothing */;
        return sc - s;
}

int memcmp(const void *cs, const void *ct, size_t count)
{
        const unsigned char *su1 = cs, *su2 = ct, *end = su1 + count;
        int res = 0;

        while (su1 < end) {
                res = *su1++ - *su2++;
                if (res)
                        break;
        }
        return res;
}

int strcmp(const char *cs, const char *ct)
{
        unsigned char c1, c2;
        int res = 0;

        do {
                c1 = *cs++;
                c2 = *ct++;
                res = c1 - c2;
                if (res)
                        break;
        } while (c1);
        return res;
}

void *memchr(const void *s, int c, size_t count)
{
        const unsigned char *p = s;

        while (count--)
                if ((unsigned char)c == *p++)
                        return (void *)(p - 1);
        return NULL;
}

char *strchr(const char *s, int c)
{
        while (*s != (char)c)
                if (*s++ == '\0')
                        return NULL;
        return (char *)s;
}

char *strrchr(const char *s, int c)
{
        const char *last = NULL;
        do {
                if (*s == (char)c)
                        last = s;
        } while (*s++);
        return (char *)last;
}

#undef memset

void *memset(void *s, int c, size_t count)
{
        char *xs = s;
        while (count--)
                *xs++ = c;
        return s;
}