feat: add streq

user/mmapexecvictim.c

@@ -0,0 +1,40 @@
+#include "ulib.h"
+
+/*
+ * Spawned by mmaptest.c to prove that a real jump into a mapping that never
+ * asked for mmapProtExec turns into a genuine SIGSEGV (isr.c's tryResolve-
+ * UserPageFault I/D-bit short-circuit, not an infinite fault loop and not
+ * a kernel-wide panic) rather than silently letting the CPU execute
+ * whatever bytes happen to sit there -- the exact NX enforcement gap
+ * fs.h's own mmapProtExec doc comment used to name as unimplemented. This
+ * process is expected to die, not return 0; its own final "FAIL" print/
+ * return only runs if that protection was somehow NOT enforced.
+ */
+
+typedef void (*victimFn)(void);
+
+int main(void)
+{
+    print("mmapexecvictim: start\n");
+
+    void* addr = userMmap(0, 4096, mmapProtRead | mmapProtWrite, mmapAnonymous, -1, 0);
+    if (addr == userMmapFailed) {
+        print("mmapexecvictim: FAIL mmap\n");
+        return 1;
+    }
+
+    /* A real `ret` instruction (0xC3) -- harmless if it ever actually runs,
+       since the point is that it must never get the chance to. */
+    volatile unsigned char* code = (volatile unsigned char*)addr;
+    code[0] = 0xC3;
+    print("mmapexecvictim: write-ok\n");
+
+    /* PROT_READ|PROT_WRITE only -- no PROT_EXEC -- so this call's own
+       instruction fetch must be refused by the CPU's own NX bit and turn
+       into a real SIGSEGV delivered against THIS process alone. */
+    victimFn fn = (victimFn)addr;
+    fn();
+
+    print("mmapexecvictim: FAIL exec should have segfaulted\n");
+    return 1;
+}