initial implementation of klibc

fix linker error about ctx_switch

klibc/src/string.c

@@ -0,0 +1,107 @@
+#include <string.h>
+
+int memcmp(const void* s1, const void* s2, size_t n) {
+    const unsigned char* c1 = s1;
+    const unsigned char* c2 = s2;
+    int d = 0;
+
+    while (n--) {
+        d = (int)*c1++ - (int)*c2++;
+        if (d) break;
+    }
+
+    return d;
+}
+
+void* memmove(void* dst, const void* src, size_t n) {
+    const char* p = src;
+    char* q = dst;
+#if defined(__i386__) || defined(__x86_64__)
+    if (q < p) {
+        __asm__ volatile("cld; rep; movsb" : "+c"(n), "+S"(p), "+D"(q));
+    } else {
+        p += (n - 1);
+        q += (n - 1);
+        __asm__ volatile("std; rep; movsb; cld" : "+c"(n), "+S"(p), "+D"(q));
+    }
+#else
+    if (q < p) {
+        while (n--) {
+            *q++ = *p++;
+        }
+    } else {
+        p += n;
+        q += n;
+        while (n--) {
+            *--q = *--p;
+        }
+    }
+#endif
+
+    return dst;
+}
+
+void* memcpy(void* dst, const void* src, size_t n) {
+    const char* p = src;
+    char* q = dst;
+#if defined(__i386__)
+    size_t nl = n >> 2;
+    __asm__ volatile("cld ; rep ; movsl ; movl %3,%0 ; rep ; movsb"
+                    : "+c"(nl), "+S"(p), "+D"(q)
+                    : "r"(n & 3));
+#elif defined(__x86_64__)
+    size_t nq = n >> 3;
+    __asm__ volatile("cld ; rep ; movsq ; movl %3,%%ecx ; rep ; movsb"
+                    : "+c"(nq), "+S"(p), "+D"(q)
+                    : "r"((uint32_t)(n & 7)));
+#else
+    while (n--) {
+        *q++ = *p++;
+    }
+#endif
+
+    return dst;
+}
+
+void* memset(void* dst, int c, size_t n) {
+    char* q = dst;
+
+#if defined(__i386__)
+    size_t nl = n >> 2;
+    __asm__ volatile("cld ; rep ; stosl ; movl %3,%0 ; rep ; stosb"
+                    : "+c"(nl), "+D"(q)
+                    : "a"((unsigned char)c * 0x01010101U), "r"(n & 3));
+#elif defined(__x86_64__)
+    size_t nq = n >> 3;
+    __asm__ volatile("cld ; rep ; stosq ; movl %3,%%ecx ; rep ; stosb"
+                    : "+c"(nq), "+D"(q)
+                    : "a"((unsigned char)c * 0x0101010101010101U),
+                      "r"((uint32_t)n & 7));
+#else
+    while (n--) {
+        *q++ = c;
+    }
+#endif
+
+    return dst;
+}
+
+size_t strlen(const char* s) {
+    const char* ss = s;
+    while (*ss) ss++;
+    return ss - s;
+}
+
+int strcmp(const char* s1, const char* s2) {
+    const unsigned char* c1 = (const unsigned char*)s1;
+    const unsigned char* c2 = (const unsigned char*)s2;
+    unsigned char ch;
+    int d = 0;
+
+    while (1) {
+        d = (int)(ch = *c1++) - (int)*c2++;
+        if (d || !ch) break;
+    }
+
+    return d;
+}