// 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
#ifndef __NO_FORTIFY
# define __NO_FORTIFY
#endif

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

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

        asm volatile(
                "       lghi    0,0\n"
                "0:     srst    %[e],%[s]\n"
                "       jo      0b"
                : [e] "+&a" (e), [s] "+&a" (s)
                :
                : "cc", "memory", "0");
        return (char *)e;
}

static inline char *__strnend(const char *s, size_t n)
{
        const char *p = s + n;

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

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

/**
 * 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
 */
#ifdef __HAVE_ARCH_STRNLEN
size_t strnlen(const char *s, size_t n)
{
        return __strnend(s, n) - s;
}
EXPORT_SYMBOL(strnlen);
#endif

/**
 * 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
 */
#ifdef __HAVE_ARCH_STRCAT
char *strcat(char *dest, const char *src)
{
        unsigned long dummy = 0;
        char *ret = dest;

        asm volatile(
                "       lghi    0,0\n"
                "0:     srst    %[dummy],%[dest]\n"
                "       jo      0b\n"
                "1:     mvst    %[dummy],%[src]\n"
                "       jo      1b"
                : [dummy] "+&a" (dummy), [dest] "+&a" (dest), [src] "+&a" (src)
                :
                : "cc", "memory", "0");
        return ret;
}
EXPORT_SYMBOL(strcat);
#endif

/**
 * 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.
 */
#ifdef __HAVE_ARCH_STRLCAT
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);
#endif

/**
 * 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
 */
#ifdef __HAVE_ARCH_STRNCAT
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);
#endif

/**
 * strcmp - Compare two strings
 * @s1: One string
 * @s2: Another string
 *
 * returns   0 if @s1 and @s2 are equal,
 *         < 0 if @s1 is less than @s2
 *         > 0 if @s1 is greater than @s2
 */
#ifdef __HAVE_ARCH_STRCMP
int strcmp(const char *s1, const char *s2)
{
        int ret = 0;

        asm volatile(
                "       lghi    0,0\n"
                "0:     clst    %[s1],%[s2]\n"
                "       jo      0b\n"
                "       je      1f\n"
                "       ic      %[ret],0(%[s1])\n"
                "       ic      0,0(%[s2])\n"
                "       sr      %[ret],0\n"
                "1:"
                : [ret] "+&d" (ret), [s1] "+&a" (s1), [s2] "+&a" (s2)
                :
                : "cc", "memory", "0");
        return ret;
}
EXPORT_SYMBOL(strcmp);
#endif

static inline int clcle(const char *s1, unsigned long l1,
                        const char *s2, unsigned long l2)
{
        union register_pair r1 = { .even = (unsigned long)s1, .odd = l1, };
        union register_pair r3 = { .even = (unsigned long)s2, .odd = l2, };
        int cc;

        asm volatile(
                "0:     clcle   %[r1],%[r3],0\n"
                "       jo      0b\n"
                CC_IPM(cc)
                : CC_OUT(cc, cc), [r1] "+d" (r1.pair), [r3] "+d" (r3.pair)
                :
                : CC_CLOBBER_LIST("memory"));
        return CC_TRANSFORM(cc);
}

/**
 * strstr - Find the first substring in a %NUL terminated string
 * @s1: The string to be searched
 * @s2: The string to search for
 */
#ifdef __HAVE_ARCH_STRSTR
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);
#endif

/**
 * 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
 */
#ifdef __HAVE_ARCH_MEMCHR
void *memchr(const void *s, int c, size_t n)
{
        const void *ret = s + n;

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

/**
 * memcmp - Compare two areas of memory
 * @s1: One area of memory
 * @s2: Another area of memory
 * @n: The size of the area.
 */
#ifdef __HAVE_ARCH_MEMCMP
int memcmp(const void *s1, const void *s2, size_t n)
{
        int ret;

        ret = clcle(s1, n, s2, n);
        if (ret)
                ret = ret == 1 ? -1 : 1;
        return ret;
}
EXPORT_SYMBOL(memcmp);
#endif

/**
 * 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
 */
#ifdef __HAVE_ARCH_MEMSCAN
void *memscan(void *s, int c, size_t n)
{
        const void *ret = s + n;

        asm volatile(
                "       lgr     0,%[c]\n"
                "0:     srst    %[ret],%[s]\n"
                "       jo      0b"
                : [ret] "+&a" (ret), [s] "+&a" (s)
                : [c] "d" (c)
                : "cc", "memory", "0");
        return (void *)ret;
}
EXPORT_SYMBOL(memscan);
#endif