// SPDX-License-Identifier: GPL-2.0
/*
 *    Optimized string functions
 *
 *  S390 version
 *    Copyright IBM Corp. 2004
 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
 */

#define IN_ARCH_STRING_C 1

#include <linux/types.h>
#include <linux/string.h>
#include <linux/export.h>

/*
 * Helper functions to find the end of a string
 */
static inline char *__strend(const char *s)
{
        register unsigned long r0 asm("0") = 0;

        asm volatile ("0: srst  %0,%1\n"
                      "   jo    0b"
                      : "+d" (r0), "+a" (s) :  : "cc", "memory");
        return (char *) r0;
}

static inline char *__strnend(const char *s, size_t n)
{
        register unsigned long r0 asm("0") = 0;
        const char *p = s + n;

        asm volatile ("0: srst  %0,%1\n"
                      "   jo    0b"
                      : "+d" (p), "+a" (s) : "d" (r0) : "cc", "memory");
        return (char *) p;
}

/**
 * strlen - Find the length of a string
 * @s: The string to be sized
 *
 * returns the length of @s
 */
size_t strlen(const char *s)
{
        return __strend(s) - s;
}
EXPORT_SYMBOL(strlen);

/**
 * strnlen - Find the length of a length-limited string
 * @s: The string to be sized
 * @n: The maximum number of bytes to search
 *
 * returns the minimum of the length of @s and @n
 */
size_t strnlen(const char * s, size_t n)
{
        return __strnend(s, n) - s;
}
EXPORT_SYMBOL(strnlen);

/**
 * strcpy - Copy a %NUL terminated string
 * @dest: Where to copy the string to
 * @src: Where to copy the string from
 *
 * returns a pointer to @dest
 */
char *strcpy(char *dest, const char *src)
{
        register int r0 asm("0") = 0;
        char *ret = dest;

        asm volatile ("0: mvst  %0,%1\n"
                      "   jo    0b"
                      : "+&a" (dest), "+&a" (src) : "d" (r0)
                      : "cc", "memory" );
        return ret;
}
EXPORT_SYMBOL(strcpy);

/**
 * strlcpy - Copy a %NUL terminated string into a sized buffer
 * @dest: Where to copy the string to
 * @src: Where to copy the string from
 * @size: size of destination buffer
 *
 * Compatible with *BSD: the result is always a valid
 * NUL-terminated string that fits in the buffer (unless,
 * of course, the buffer size is zero). It does not pad
 * out the result like strncpy() does.
 */
size_t strlcpy(char *dest, const char *src, size_t size)
{
        size_t ret = __strend(src) - src;

        if (size) {
                size_t len = (ret >= size) ? size-1 : ret;
                dest[len] = '\0';
                memcpy(dest, src, len);
        }
        return ret;
}
EXPORT_SYMBOL(strlcpy);

/**
 * strncpy - Copy a length-limited, %NUL-terminated string
 * @dest: Where to copy the string to
 * @src: Where to copy the string from
 * @n: The maximum number of bytes to copy
 *
 * The result is not %NUL-terminated if the source exceeds
 * @n bytes.
 */
char *strncpy(char *dest, const char *src, size_t n)
{
        size_t len = __strnend(src, n) - src;
        memset(dest + len, 0, n - len);
        memcpy(dest, src, len);
        return dest;
}
EXPORT_SYMBOL(strncpy);

/**
 * strcat - Append one %NUL-terminated string to another
 * @dest: The string to be appended to
 * @src: The string to append to it
 *
 * returns a pointer to @dest
 */
char *strcat(char *dest, const char *src)
{
        register int r0 asm("0") = 0;
        unsigned long dummy;
        char *ret = dest;

        asm volatile ("0: srst  %0,%1\n"
                      "   jo    0b\n"
                      "1: mvst  %0,%2\n"
                      "   jo    1b"
                      : "=&a" (dummy), "+a" (dest), "+a" (src)
                      : "d" (r0), "0" (0UL) : "cc", "memory" );
        return ret;
}
EXPORT_SYMBOL(strcat);

/**
 * strlcat - Append a length-limited, %NUL-terminated string to another
 * @dest: The string to be appended to
 * @src: The string to append to it
 * @n: The size of the destination buffer.
 */
size_t strlcat(char *dest, const char *src, size_t n)
{
        size_t dsize = __strend(dest) - dest;
        size_t len = __strend(src) - src;
        size_t res = dsize + len;

        if (dsize < n) {
                dest += dsize;
                n -= dsize;
                if (len >= n)
                        len = n - 1;
                dest[len] = '\0';
                memcpy(dest, src, len);
        }
        return res;
}
EXPORT_SYMBOL(strlcat);

/**
 * strncat - Append a length-limited, %NUL-terminated string to another
 * @dest: The string to be appended to
 * @src: The string to append to it
 * @n: The maximum numbers of bytes to copy
 *
 * returns a pointer to @dest
 *
 * Note that in contrast to strncpy, strncat ensures the result is
 * terminated.
 */
char *strncat(char *dest, const char *src, size_t n)
{
        size_t len = __strnend(src, n) - src;
        char *p = __strend(dest);

        p[len] = '\0';
        memcpy(p, src, len);
        return dest;
}
EXPORT_SYMBOL(strncat);

/**
 * strcmp - Compare two strings
 * @cs: One string
 * @ct: Another string
 *
 * returns   0 if @cs and @ct are equal,
 *         < 0 if @cs is less than @ct
 *         > 0 if @cs is greater than @ct
 */
int strcmp(const char *cs, const char *ct)
{
        register int r0 asm("0") = 0;
        int ret = 0;

        asm volatile ("0: clst %2,%3\n"
                      "   jo   0b\n"
                      "   je   1f\n"
                      "   ic   %0,0(%2)\n"
                      "   ic   %1,0(%3)\n"
                      "   sr   %0,%1\n"
                      "1:"
                      : "+d" (ret), "+d" (r0), "+a" (cs), "+a" (ct)
                      : : "cc", "memory");
        return ret;
}
EXPORT_SYMBOL(strcmp);

/**
 * strrchr - Find the last occurrence of a character in a string
 * @s: The string to be searched
 * @c: The character to search for
 */
char * strrchr(const char * s, int c)
{
       size_t len = __strend(s) - s;

       if (len)
               do {
                       if (s[len] == (char) c)
                               return (char *) s + len;
               } while (--len > 0);
       return NULL;
}
EXPORT_SYMBOL(strrchr);

static inline int clcle(const char *s1, unsigned long l1,
                        const char *s2, unsigned long l2)
{
        register unsigned long r2 asm("2") = (unsigned long) s1;
        register unsigned long r3 asm("3") = (unsigned long) l1;
        register unsigned long r4 asm("4") = (unsigned long) s2;
        register unsigned long r5 asm("5") = (unsigned long) l2;
        int cc;

        asm volatile ("0: clcle %1,%3,0\n"
                      "   jo    0b\n"
                      "   ipm   %0\n"
                      "   srl   %0,28"
                      : "=&d" (cc), "+a" (r2), "+a" (r3),
                        "+a" (r4), "+a" (r5) : : "cc", "memory");
        return cc;
}

/**
 * strstr - Find the first substring in a %NUL terminated string
 * @s1: The string to be searched
 * @s2: The string to search for
 */
char * strstr(const char * s1,const char * s2)
{
        int l1, l2;

        l2 = __strend(s2) - s2;
        if (!l2)
                return (char *) s1;
        l1 = __strend(s1) - s1;
        while (l1-- >= l2) {
                int cc;

                cc = clcle(s1, l2, s2, l2);
                if (!cc)
                        return (char *) s1;
                s1++;
        }
        return NULL;
}
EXPORT_SYMBOL(strstr);

/**
 * memchr - Find a character in an area of memory.
 * @s: The memory area
 * @c: The byte to search for
 * @n: The size of the area.
 *
 * returns the address of the first occurrence of @c, or %NULL
 * if @c is not found
 */
void *memchr(const void *s, int c, size_t n)
{
        register int r0 asm("0") = (char) c;
        const void *ret = s + n;

        asm volatile ("0: srst  %0,%1\n"
                      "   jo    0b\n"
                      "   jl    1f\n"
                      "   la    %0,0\n"
                      "1:"
                      : "+a" (ret), "+&a" (s) : "d" (r0) : "cc", "memory");
        return (void *) ret;
}
EXPORT_SYMBOL(memchr);

/**
 * memcmp - Compare two areas of memory
 * @cs: One area of memory
 * @ct: Another area of memory
 * @count: The size of the area.
 */
int memcmp(const void *cs, const void *ct, size_t n)
{
        int ret;

        ret = clcle(cs, n, ct, n);
        if (ret)
                ret = ret == 1 ? -1 : 1;
        return ret;
}
EXPORT_SYMBOL(memcmp);

/**
 * memscan - Find a character in an area of memory.
 * @s: The memory area
 * @c: The byte to search for
 * @n: The size of the area.
 *
 * returns the address of the first occurrence of @c, or 1 byte past
 * the area if @c is not found
 */
void *memscan(void *s, int c, size_t n)
{
        register int r0 asm("0") = (char) c;
        const void *ret = s + n;

        asm volatile ("0: srst  %0,%1\n"
                      "   jo    0b\n"
                      : "+a" (ret), "+&a" (s) : "d" (r0) : "cc", "memory");
        return (void *) ret;
}
EXPORT_SYMBOL(memscan);