wip: only center guard on fault in it

rust/ares/Cargo.toml

@@ -44,12 +44,10 @@ name = "ares"
 path = "src/main.rs"
 
 [profile.dev]
-opt-level = 0
+opt-level = 3
-debug = true
 
 [profile.dev.package."*"]
-opt-level = 0
+opt-level = 3
-debug = true
 
 # run with e.g. 'cargo build --features check_forwarding,check_acyclic'
 [features]

rust/ares/src/serf.rs

@@ -143,7 +143,7 @@ impl Context {
         snapshot: Option<Snapshot>,
         constant_hot_state: &[HotEntry],
     ) -> Self {
-        let mut stack = NockStack::new(1024 << 10 << 10, 0);
+        let mut stack = NockStack::new(256 << 10 << 10, 0);
         let newt = Newt::new();
         let cache = Hamt::<Noun>::new(&mut stack);
 

rust/ares_guard/c-src/guard.c

@@ -1,6 +1,8 @@
 #include <setjmp.h>
 #include <signal.h>
+#include <stdbool.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/mman.h>
 #include <unistd.h>
 
@@ -38,12 +40,15 @@ _focus_guard()
     return guard_weird;
   }
 
-  // Unmark the old guard page.
+  // Unmark the old guard page if one exists.
   void *old_guard_p = guard_p;
+  if (old_guard_p != NULL) {
+    fprintf(stderr, "guard: retiring old guard page\r\n");
     if (old_guard_p != 0
         && mprotect(old_guard_p, GD_PAGESIZE, PROT_READ | PROT_WRITE) == -1) {
       return guard_armor;
     }
+  }
 
   // Place the new guard page in the low-aligned center.
   guard_p = (uint64_t *)low_p + ((high_p - low_p) / 2);
@@ -51,10 +56,13 @@ _focus_guard()
 
   // Mark the new guard page.
   if (guard_p != old_guard_p) {
+    fprintf(stderr, "guard: focused guard page\r\n");
     if (mprotect(guard_p, GD_PAGESIZE, PROT_NONE) == -1) {
       return guard_armor;
     }
   } else {
+    fprintf(stderr, "guard: spent; exiting\r\n");
+    exit(1);
     return guard_spent;
   }
 
@@ -81,12 +89,12 @@ _signal_handler(int sig, siginfo_t *si, void *unused)
       if (si->si_addr >= (void *)guard_p && 
           si->si_addr < (void *)guard_p + GD_PAGESIZE)
       {
-        fprintf(stderr, "guard: fault in guard: %p\r\n", si->si_addr);
+        fprintf(stderr, "guard: hit: %p\r\n", si->si_addr);
         err = _focus_guard();
         break;
       }
       else {
-        fprintf(stderr, "guard: fault outside guard %p\r\n", si->si_addr);
+        fprintf(stderr, "guard: weird hit: %p\r\n", si->si_addr);
         if (NULL != prev_sigsegv_handler) {
           prev_sigsegv_handler(sig, si, unused);
           break;
@@ -126,7 +134,6 @@ _register_handler()
   }
   prev_sigsegv_handler = prev_sa.sa_sigaction;
 
-  // fprintf(stderr, "guard: registered handler\r\n");
   return guard_sound;
 }
 
@@ -150,17 +157,14 @@ guard(
   const uint64_t *low_p = low_f(bounds_data, context_p);
   const uint64_t *high_p = high_f(bounds_data, context_p);
 
-  // fprintf(stderr, "guard: low: %p high: %p\r\n", (void *)low_p, (void *)high_p);
+  if (guard_p == NULL) {
-
-  // const unsigned long free_mb = (unsigned long)(high_p - low_p) / 1024 / 1024;
-  // fprintf(stderr, "guard: free space: %lu MB\r\n", free_mb);
-
     guard_err focus_err = _focus_guard();
     if (focus_err != guard_sound && focus_err != guard_spent) {
       fprintf(stderr, "guard: failed to install guard page\r\n");
       err = focus_err;
       goto fail;
     }
+  }
 
   if (_register_handler() != guard_sound) {
     err = guard_weird;
@@ -179,11 +183,6 @@ guard(
 
   *(void **)ret = result;
 
-  if (mprotect(guard_p, GD_PAGESIZE, PROT_READ | PROT_WRITE) == -1) {
-    err = guard_armor;
-    goto fail;
-  }
-
   return guard_sound;
 
 fail: