thesis: Complete 2.2

thesis/listings/intercept-preload.c

@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <dlfcn.h>
+
+static void *(*__real_malloc)(size_t);
+
+static int mode = 0;
+
+static void fin(void) {
+    if (mode > 0) fprintf(stderr, "intercept: stopped\n");
+    mode = 0;
+}
+
+static void init(void) {
+    if (mode) return;
+    mode = -1;
+    if (((__real_malloc) = dlsym(RTLD_NEXT, "malloc")) == NULL) {
+        fprintf(stderr, "intercept: unable to load symbol '%s': %s",
+            "malloc", strerror(errno));
+        return;
+    }
+    atexit(fin);
+    fprintf(stderr, "intercept: intercepting function calls\n");
+    mode = 1;
+}
+
+void *malloc(size_t size) {
+    init();
+    // before call to malloc
+    void *ret = __real_malloc(size);
+    // after call to malloc
+    return ret;
+}