wip: debugging

rust/ares/src/interpreter.rs

@@ -375,11 +375,10 @@ extern "C" fn rust_callback(arg: *mut c_void) -> *mut c_void {
 
 pub fn call_with_guard<F: FnMut() -> Result>(
     f: F,
-    stack: *mut *mut c_void,
-    alloc: *mut *mut c_void,
+    stack: *const c_void,
+    alloc: *const c_void,
     ret: *mut *mut c_void,
 ) -> Result {
-    eprintln!("call_with_guard");
     let boxed_f = Box::new(f);
 
     unsafe {
@@ -988,8 +987,8 @@ pub fn interpret(context: &mut Context, mut subject: Noun, formula: Noun) -> Res
                     };
                 }
             },
-            stack_p as *mut *mut c_void,
-            alloc_p as *mut *mut c_void,
+            stack_p as *const c_void,
+            alloc_p as *const c_void,
             std::ptr::null_mut() as *mut *mut c_void,
             )
         })

rust/ares_guard/c-src/guard.c

@@ -21,12 +21,13 @@ volatile sig_atomic_t err = guard_sound;
 guard_err _focus_guard() {
   // Check for strange situations.
   if (stack_p == NULL || alloc_p == NULL) {
+    fprintf(stderr, "guard: stack or alloc pointer is null\r\n");
     return guard_weird;
   }
 
   // Unmark the old guard page.
   void *old_guard_p = guard_p;
-  if (mprotect(old_guard_p, GD_PAGESIZE, PROT_READ | PROT_WRITE) == -1) {
+  if (old_guard_p != NULL && mprotect(old_guard_p, GD_PAGESIZE, PROT_READ | PROT_WRITE) == -1) {
     return guard_armor;
   }
 
@@ -56,6 +57,7 @@ guard_err _focus_guard() {
 
 guard_err _slash_guard(void *si_addr) {
   if (si_addr >= guard_p && si_addr < guard_p + GD_PAGESIZE) {
+    fprintf(stderr, "guard: slash\r\n");
     return _focus_guard();
   }
 
@@ -65,11 +67,11 @@ guard_err _slash_guard(void *si_addr) {
 void _signal_handler(int sig, siginfo_t *si, void *unused) {
   switch (sig) {
     case SIGSEGV:
-      fprintf(stderr, "guard: caught sigsegv\r\n");
+      fprintf(stderr, "guard: segfault at %p\r\n", si->si_addr);
+      fprintf(stderr, "guard: guard    at %p\r\n", guard_p);
       err = _slash_guard(si->si_addr);
       break;
     case SIGINT:
-      fprintf(stderr, "guard: caught sigint\r\n");
       err = guard_erupt;
       break;
     default:
@@ -91,19 +93,25 @@ guard_err _register_handler() {
   return guard_sound;
 }
 
-void guard(void *(*f)(void *), void *arg, void *const *const stack, void *const *const alloc, void **ret) {
-  stack_p = *stack;
-  alloc_p = *alloc;
+void guard(void *(*f)(void *), void *arg, void *const stack, void *const alloc, void **ret) {
+  stack_p = stack;
+  alloc_p = alloc;
 
   if (_register_handler() != guard_sound) {
     err = guard_weird;
     goto fail;
   }
 
-  fprintf(stderr, "guard: installing guard page\r\n");
-  if (guard_p == NULL && (err = _focus_guard()) != guard_sound) {
-    goto fail;
+  if (guard_p == NULL) {
+    fprintf(stderr, "guard: installing guard page\r\n");
+    guard_err install_err = _focus_guard();
+    if (install_err != guard_sound) {
+      fprintf(stderr, "guard: failed to install guard page\r\n");
+      err = install_err;
+      goto fail;
+    }
   }
+  fprintf(stderr, "guard: guard page installed at %p\r\n", guard_p);
 
   *ret = f(arg);
 
@@ -114,6 +122,7 @@ void guard(void *(*f)(void *), void *arg, void *const *const stack, void *const
   return;
 
 fail:
+  fprintf(stderr, "guard: error %d\r\n", err);
   *ret = (void *) &err;
   return;
 }

rust/ares_guard/c-src/guard.h

@@ -30,7 +30,7 @@
  * error will be written to the `ret` pointer. The caller is then responsible
  * for handling this error and aborting with a `bail:meme`.
  */
-void guard(void *(*f)(void *), void *arg, void *const *const stack, void *const *const alloc, void **ret);
+void guard(void *(*f)(void *), void *arg, void *const stack, void *const alloc, void **ret);
 
 typedef enum {
   guard_sound = 0, // job's done

rust/ares_guard/src/lib.rs

@@ -2,4 +2,22 @@
 #![allow(non_camel_case_types)]
 #![allow(non_snake_case)]
 
-include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
+
+extern "C" {
+    #[doc = " Execute the given closure `f` within the memory arena between the\n `stack` and `alloc` pointers, with guard page protection. Write either\n `f`'s succesful result or a `guard_err` to the given `ret` pointer.\n\n Memory\n ------\n The free memory arena between the `stack` and `alloc` pointers is part of a\n NockStack frame, which may either face east or west. If the frame faces\n east, the `stack` pointer will be greater than the `alloc` pointer. If it\n faces west, the `stack` pointer will be less than the `alloc` pointer.\n\n All the pages in the memory arena are marked clean (`PROT_READ | PROT_WRITE`)\n by default, with the exception of a single guard page in the middle of the\n arena, which is marked with `PROT_NONE`.\n\n Guard\n -----\n This function protects the free memory arena between the `stack` and `alloc`\n pointers with a guard page. A guard page is simply a single page of memory\n which is marked with `PROT_NONE`. Since all other pages are marked clean by\n default, a SIGSEGV will only be raised if the `f` function attempts to write\n to the guard page. When it does, the signal handler will attempt to re-center\n the guard page in the remaining free space left in the arena. If there is no\n more free space, then memory exhaustion has occurred and the `guard_spent`\n error will be written to the `ret` pointer. The caller is then responsible\n for handling this error and aborting with a `bail:meme`."]
+    pub fn guard(
+        f: ::std::option::Option<
+            unsafe extern "C" fn(arg1: *mut ::std::os::raw::c_void) -> *mut ::std::os::raw::c_void,
+        >,
+        arg: *mut ::std::os::raw::c_void,
+        stack: *const ::std::os::raw::c_void,
+        alloc: *const ::std::os::raw::c_void,
+        ret: *mut *mut ::std::os::raw::c_void,
+    );
+}
+pub const guard_err_guard_sound: guard_err = 0;
+pub const guard_err_guard_armor: guard_err = 1;
+pub const guard_err_guard_weird: guard_err = 2;
+pub const guard_err_guard_spent: guard_err = 3;
+pub const guard_err_guard_erupt: guard_err = 4;
+pub type guard_err = ::std::os::raw::c_uint;