add test_strlen() wrapper

Author: tiedaoxiaotubie

runtime/LibcWrappers.cpp

@@ -659,4 +659,39 @@ int SYM(strncmp)(const char *a, const char *b, size_t n) {
                               reinterpret_cast<uintptr_t>(SYM(strncmp)));
     return result;
 }
+
+uint32_t SYM(strlen)(const char *s) {
+    tryAlternative(s, _sym_get_parameter_expression(0), SYM(strlen));
+
+    // HACK! we regard strlen as a special strchr(s, '\0')
+    auto *result = strchr(s, 0);
+    _sym_set_return_expression(nullptr);
+
+    if (isConcrete(s, result != nullptr ? (result - s) : strlen(s)))
+        return (result - s);
+
+    // We force set the value of c to \x00, it should be a concrete value
+    auto *cExpr = _sym_build_integer(0, 8);
+
+    size_t length = result != nullptr ? (result - s) : strlen(s);
+    auto shadow = ReadOnlyShadow(s, length);
+    auto shadowIt = shadow.begin();
+    for (size_t i = 0; i < length; i++) {
+        _sym_push_path_constraint(
+                _sym_build_not_equal(
+                        (*shadowIt != nullptr) ? *shadowIt : _sym_build_integer(s[i], 8),
+                        cExpr),
+                /*taken*/ 1, reinterpret_cast<uintptr_t>(SYM(strchr)));
+        ++shadowIt;
+    }
+
+    // HACK! The last byte must be \x00!
+    _sym_push_path_constraint(
+            _sym_build_equal(
+                    (*shadowIt != nullptr) ? *shadowIt : _sym_build_integer(0, 8),
+                    cExpr),
+            /*taken*/ 1, reinterpret_cast<uintptr_t>(SYM(strchr)));
+
+    return (result - s);
+}
 }

runtime/test_wrappers/test_strlen.c

@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+int main(int argc, char *argv[]) {
+
+  char    buf[1024];
+  ssize_t i;
+  if ((i = read(0, buf, sizeof(buf) - 1)) < 24) return 0;
+  buf[i] = 0;
+  if (buf[0] != 'A') return 0;
+  if (buf[1] != 'B') return 0;
+  if (buf[2] != 'C') return 0;
+  if (buf[3] != 'D') return 0;
+  if (memcmp(buf + 4, "1234", 4) || memcmp(buf + 8, "EFGH", 4)) return 0;
+  if (strlen(buf + 12) == 5) {
+    printf("The string length after buf + 12 is: %lu\n", strlen(buf+12));
+    printf("HIT!\n");
+  } else {
+    printf("The string length after buf + 12 is: %lu\n", strlen(buf+12));
+    printf("strchr(buf+12) is: %s\n", strchr(buf+12, '\0'));
+    printf("NOT HIT!\n");
+  }
+
+  return 0;
+
+}