gcc hacks: busy_loop and prevent_reorder

userland/gcc/busy_loop.c

@@ -0,0 +1,29 @@
+/* https://cirosantilli.com/linux-kernel-module-cheat#compilers */
+
+#include <stdlib.h>
+
+void __attribute__ ((noinline)) busy_loop(
+    unsigned long long max,
+    unsigned long long max2
+) {
+    for (unsigned i = 0; i < max; i++) {
+        for (unsigned j = 0; j < max2; j++) {
+            __asm__ __volatile__ ("" : "+g" (j), "+g" (j) : :);
+        }
+    }
+}
+
+int main(int argc, char **argv) {
+    unsigned long long max, max2;
+    if (argc > 1) {
+        max = strtoll(argv[1], NULL, 0);
+    } else {
+        max = 1;
+    }
+    if (argc > 2) {
+        max2 = strtoll(argv[2], NULL, 0);
+    } else {
+        max2 = 1;
+    }
+    busy_loop(max, max2);
+}