Add test case for mmaped stacks.

Make sure that the guard page leads to sigsegv as expected.

lib/pls/include/pls/internal/base/stack_allocator.h

@@ -18,6 +18,7 @@ class heap_stack_allocator : public stack_allocator {
 };
 
 class mmap_stack_allocator : public stack_allocator {
+ public:
   char *allocate_stack(size_t size) override;
   void free_stack(size_t, char *stack) override;
 };

test/CMakeLists.txt

@@ -2,5 +2,6 @@ add_executable(tests
         main.cpp
         data_structures_test.cpp
         base_tests.cpp
-        scheduling_tests.cpp)
+        scheduling_tests.cpp
+        test_helpers.h)
 target_link_libraries(tests catch2 pls)

test/base_tests.cpp

@@ -2,26 +2,53 @@
 
 #include "pls/internal/base/spin_lock.h"
 #include "pls/internal/base/system_details.h"
+#include "pls/internal/base/stack_allocator.h"
+
+#include "test_helpers.h"
 
-#include <vector>
 #include <mutex>
+#include <atomic>
 #include <thread>
 
 using namespace pls::internal::base;
 
-static bool base_tests_visited;
-static int base_tests_local_value_one;
-static std::vector<int> base_tests_local_value_two;
-
 int base_tests_shared_counter;
 
+TEST_CASE("mmap stack allocator", "[internal/base/stack_allocator.h") {
+  mmap_stack_allocator stack_allocator;
+
+  char *stack = stack_allocator.allocate_stack(4096);
+
+  SECTION("stack passes in valid range") {
+    stack[0] = 'a';
+    stack[4096 - 1] = 'a';
+
+    REQUIRE(true);
+  }
+
+  SECTION("guard page sigsev on overflow") {
+    REQUIRE(CHECK_ABORT([&]() { stack[-10] = 'a'; }));
+  }
+
+  stack_allocator.free_stack(4096, stack);
+
+  SECTION("stack unmaps after free") {
+    REQUIRE(CHECK_ABORT([&]() { stack[0] = 'a'; }));
+  }
+}
+
 TEST_CASE("spinlock protects concurrent counter", "[internal/data_structures/spinlock.h]") {
-  constexpr int num_iterations = 1000000;
+  constexpr int num_iterations = 10000;
   base_tests_shared_counter = 0;
+  std::atomic<int> barrier{2};
+
   spin_lock lock{};
 
   SECTION("lock can be used by itself") {
     std::thread t1{[&]() {
+      barrier--;
+      while (barrier != 0);
+
       for (int i = 0; i < num_iterations; i++) {
         lock.lock();
         base_tests_shared_counter++;
@@ -29,6 +56,9 @@ TEST_CASE("spinlock protects concurrent counter", "[internal/data_structures/spi
       }
     }};
     std::thread t2{[&]() {
+      barrier--;
+      while(barrier != 0);
+
       for (int i = 0; i < num_iterations; i++) {
         lock.lock();
         base_tests_shared_counter--;

test/test_helpers.h

+#ifndef PLS_TEST_TEST_HELPERS_H_
+#define PLS_TEST_TEST_HELPERS_H_
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <cstdlib>
+#include <csignal>
+
+// Source: https://stackoverflow.com/questions/15749071/fork-and-wait-in-c
+// Works well enough for our purpose.
+void abort_handler(int) {
+  std::exit(1);
+}
+
+template<class F>
+bool CHECK_ABORT(F &&f) {
+  //spawn a new process
+  auto child_pid = fork();
+
+  //if the fork succeed
+  if (child_pid >= 0) {
+
+    //if we are in the child process
+    if (child_pid == 0) {
+      // Re-direct the signal handlers added by catch to simply exit with an error code
+      std::signal(SIGABRT, abort_handler);
+      std::signal(SIGFPE, abort_handler);
+      std::signal(SIGSEGV, abort_handler);
+      std::signal(SIGILL, abort_handler);
+
+      //call the lambda that we expect to abort
+      f();
+
+      //if the function didn't abort, we'll exit cleanly
+      std::exit(EXIT_SUCCESS);
+    }
+  }
+
+  //determine if the child process aborted
+  int exit_status;
+  wait(&exit_status);
+
+  //we check the exit status instead of a signal interrupt, because
+  //Catch is going to catch the signal and exit with an error
+  bool aborted = exit_status != 0;
+
+  return aborted;
+}
+
+#endif //PLS_TEST_TEST_HELPERS_H_