memory_maps: abort in ia2_thread_metadata_get_for_current_thread on error instead of returning NULL

Author: kkysen

runtime/libia2/ia2.c

@@ -334,9 +334,7 @@ int protect_tls_pages(struct dl_phdr_info *info, size_t size, void *data) {
           exit(-1);
         }
 #if IA2_DEBUG_MEMORY
-        if (thread_metadata) {
-          thread_metadata->tls_addr_compartment1_first = (uintptr_t)start_round_down;
-        }
+        thread_metadata->tls_addr_compartment1_first = (uintptr_t)start_round_down;
 #endif
       }
       uint64_t after_untrusted_region_start = untrusted_stackptr_addr + 0x1000;
@@ -350,9 +348,7 @@ int protect_tls_pages(struct dl_phdr_info *info, size_t size, void *data) {
           exit(-1);
         }
 #if IA2_DEBUG_MEMORY
-        if (thread_metadata) {
-          thread_metadata->tls_addr_compartment1_second = (uintptr_t)after_untrusted_region_start;
-        }
+        thread_metadata->tls_addr_compartment1_second = (uintptr_t)after_untrusted_region_start;
 #endif
       }
     } else {
@@ -364,9 +360,7 @@ int protect_tls_pages(struct dl_phdr_info *info, size_t size, void *data) {
         exit(-1);
       }
 #if IA2_DEBUG_MEMORY
-      if (thread_metadata) {
-        thread_metadata->tls_addrs[pkey] = (uintptr_t)start_round_down;
-      }
+      thread_metadata->tls_addrs[pkey] = (uintptr_t)start_round_down;
 #endif
     }
   }

runtime/libia2/init.c

@@ -79,9 +79,7 @@ char *allocate_stack(int i) {
   ia2_log("allocating stack for compartment %d on thread %ld: %p..%p\n", i, (long)gettid(), stack, stack + STACK_SIZE);
 #if IA2_DEBUG_MEMORY
   struct ia2_thread_metadata *const thread_metadata = ia2_thread_metadata_get_for_current_thread();
-  if (thread_metadata) {
-    thread_metadata->stack_addrs[i] = (uintptr_t)stack;
-  }
+  thread_metadata->stack_addrs[i] = (uintptr_t)stack;
 #endif
   assert(stacks[i] == NULL); // We should only be setting this once per thread compartment right after thread creation.
   stacks[i] = stack;

runtime/libia2/memory_maps.c

@@ -15,21 +15,23 @@
 struct ia2_thread_metadata *ia2_all_threads_metadata_get_for_current_thread(struct ia2_all_threads_metadata *const this) {
   const pid_t tid = gettid();
 
-  struct ia2_thread_metadata *metadata = NULL;
   if (pthread_mutex_lock(&this->lock) != 0) {
     perror("pthread_mutex_lock in ia2_all_threads_data_lookup failed");
-    goto ret;
+    abort();
+  }
+
+  if (this->num_threads >= array_len(this->thread_metadata)) {
+    fprintf(stderr, "created %zu threads, but can't store them all (max is IA2_MAX_THREADS)\n", this->num_threads);
+    abort();
   }
+
+  struct ia2_thread_metadata *metadata = NULL;
   for (size_t i = 0; i < this->num_threads; i++) {
     if (this->tids[i] == tid) {
       metadata = &this->thread_metadata[i];
       goto unlock;
     }
   }
-  if (this->num_threads >= array_len(this->thread_metadata)) {
-    fprintf(stderr, "created %zu threads, but can't store them all (max is IA2_MAX_THREADS)\n", this->num_threads);
-    goto unlock;
-  }
 
   metadata = &this->thread_metadata[this->num_threads];
   this->tids[this->num_threads] = tid;
@@ -38,13 +40,12 @@ struct ia2_thread_metadata *ia2_all_threads_metadata_get_for_current_thread(stru
   metadata->tid = tid;
   metadata->thread = pthread_self();
 
-  goto unlock;
-
 unlock:
   if (pthread_mutex_unlock(&this->lock) != 0) {
     perror("pthread_mutex_unlock in ia2_all_threads_data_lookup failed");
+    abort();
   }
-ret:
+
   return metadata;
 }
 
@@ -112,6 +113,7 @@ static void label_memory_map(FILE *log, uintptr_t start_addr) {
   const struct ia2_addr_location location = ia2_addr_location_find(start_addr);
   const struct ia2_thread_metadata *metadata = location.thread_metadata;
 
+  // If `location.name` is non-`NULL`, then `location` was found.
   if (location.name) {
     Dl_info dl_info = {0};
     const bool has_dl_info = dladdr((void *)metadata->start_fn, &dl_info);

runtime/libia2/memory_maps.h

@@ -15,7 +15,8 @@
 
 /// Find the `struct ia2_thread_metadata*` for the current thread,
 /// adding (but not allocating) one if there isn't one yet.
-/// If there is no memory for more or an error, `NULL` is returned.
+/// If there is no memory for more or some unexpected error,
+/// it `abort`s.  `NULL` is never returned.
 /// This is a purely lookup and/or additive operation,
 /// so the lifetime of the returned `struct ia2_thread_metadata*` is infinite,
 /// and since it's thread-specific,

runtime/libia2/threads.c

@@ -32,9 +32,7 @@ void *ia2_thread_begin(void *arg) {
 
 #if IA2_DEBUG_MEMORY
   struct ia2_thread_metadata *const thread_metadata = ia2_thread_metadata_get_for_current_thread();
-  if (thread_metadata) {
-    thread_metadata->start_fn = fn;
-  }
+  thread_metadata->start_fn = fn;
 #endif
 
   init_stacks_and_setup_tls();