add _mi_os_guard_page_size

src/os.c

@@ -61,8 +61,16 @@ size_t _mi_os_large_page_size(void) {
   return (mi_os_mem_config.large_page_size != 0 ? mi_os_mem_config.large_page_size : _mi_os_page_size());
 }
 
+size_t _mi_os_guard_page_size(void) {
+  const size_t gsize = _mi_os_page_size();
+  mi_assert(gsize <= (MI_ARENA_SLICE_SIZE/8));
+  return gsize;
+}
+
 size_t _mi_os_virtual_address_bits(void) {
-  return mi_os_mem_config.virtual_address_bits;
+  const size_t vbits = mi_os_mem_config.virtual_address_bits;
+  mi_assert(vbits <= MI_MAX_VABITS);
+  return vbits;
 }
 
 bool _mi_os_use_large_page(size_t size, size_t alignment) {
@@ -99,6 +107,50 @@ void* _mi_os_get_aligned_hint(size_t try_alignment, size_t size) {
   return NULL;
 }
 
+// In secure mode, return the size of a guard page, otherwise 0
+size_t _mi_os_secure_guard_page_size(void) {
+  #if MI_SECURE > 0
+  return _mi_os_guard_page_size();
+  #else
+  return 0;
+  #endif
+}
+
+// In secure mode, try to decommit an area and output a warning if this fails. 
+bool _mi_os_secure_guard_page_set_at(void* addr, bool is_pinned) {
+  if (addr == NULL) return true;
+  #if MI_SECURE > 0
+  const bool ok = (is_pinned ? false : _mi_os_decommit(addr, _mi_os_secure_guard_page_size()));
+  if (!ok) {
+    _mi_error_message(EINVAL, "secure level %d, but failed to commit guard page (at %p of size %zu)\n", MI_SECURE, addr, _mi_os_secure_guard_page_size());
+  }
+  return ok;
+  #else
+  MI_UNUSED(is_pinned);
+  return true;
+  #endif
+}
+
+// In secure mode, try to decommit an area and output a warning if this fails. 
+bool _mi_os_secure_guard_page_set_before(void* addr, bool is_pinned) {
+  return _mi_os_secure_guard_page_set_at((uint8_t*)addr - _mi_os_secure_guard_page_size(), is_pinned);
+}
+
+// In secure mode, try to recommit an area
+bool _mi_os_secure_guard_page_reset_at(void* addr) {
+  if (addr == NULL) return true;
+  #if MI_SECURE > 0
+  return _mi_os_commit(addr, _mi_os_secure_guard_page_size(), NULL);
+  #else
+  return true;
+  #endif
+}
+
+// In secure mode, try to recommit an area
+bool _mi_os_secure_guard_page_reset_before(void* addr) {
+  return _mi_os_secure_guard_page_reset_at((uint8_t*)addr - _mi_os_secure_guard_page_size());
+}
+
 
 /* -----------------------------------------------------------
   Free memory