Improve syscalls and user heap allocator

2 files changed, 42 insertions, 44 deletions

diff --git a/arch/x86_64/src/context_switching/syscall/syscall_handler.cpp b/arch/x86_64/src/context_switching/syscall/syscall_handler.cpp
index cd1c8a2..af6d911 100644
--- a/arch/x86_64/src/context_switching/syscall/syscall_handler.cpp
+++ b/arch/x86_64/src/context_switching/syscall/syscall_handler.cpp
@@ -1,6 +1,7 @@
 #include "arch/context_switching/syscall/syscall_handler.hpp"
 
 #include "arch/context_switching/syscall/main.hpp"
+#include "arch/exception_handling/assert.hpp"
 #include "arch/exception_handling/panic.hpp"
 #include "arch/memory/heap/global_heap_allocator.hpp"
 #include "arch/memory/main.hpp"
@@ -61,10 +62,7 @@ namespace teachos::arch::context_switching::syscall
         result = expand_user_heap();
         break;
       case type::ASSERT:
-        if (!arg_0)
-        {
-          teachos::arch::exception_handling::panic(reinterpret_cast<const char *>(arg_1));
-        }
+        teachos::arch::exception_handling::assert(arg_0, reinterpret_cast<const char *>(arg_1));
         break;
       default:
         teachos::arch::exception_handling::panic("[Syscall Handler] Invalid syscall number");
diff --git a/arch/x86_64/src/memory/heap/user_heap_allocator.cpp b/arch/x86_64/src/memory/heap/user_heap_allocator.cpp
index f3fe1c2..427a68a 100644
--- a/arch/x86_64/src/memory/heap/user_heap_allocator.cpp
+++ b/arch/x86_64/src/memory/heap/user_heap_allocator.cpp
@@ -1,8 +1,6 @@
 #include "arch/memory/heap/user_heap_allocator.hpp"
 
 #include "arch/context_switching/syscall/main.hpp"
-#include "arch/exception_handling/assert.hpp"
-#include "arch/exception_handling/panic.hpp"
 
 #include <algorithm>
 
@@ -20,24 +18,10 @@ namespace teachos::arch::memory::heap
 
     while (current != nullptr)
     {
-      // TODO: Can not access current pointer. Results in a General Protection Fault?
-      if (current->size == total_size)
+      auto memory = allocate_into_memory_block_if_big_enough(current, previous, total_size);
+      if (memory.has_value())
       {
-        auto const memory_address = remove_free_memory_block(previous, current);
-        new (memory_address) std::size_t(total_size);
-        mutex.unlock();
-        return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t));
-      }
-      else if (current->size >= total_size + min_allocatable_size())
-      {
-        // Ensure that the allocated size block is atleast 16 bytes (required because if we free the hole afterwards
-        // there needs to be enough space for a memory block). Therefore we allocate more than is actually required if
-        // the total size was less and simply deallocate it as well
-        auto const max_size = std::max(total_size, min_allocatable_size());
-        auto const memory_address = split_free_memory_block(previous, current, max_size);
-        new (memory_address) std::size_t(max_size);
-        mutex.unlock();
-        return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t));
+        return memory.value();
       }
 
       previous = current;
@@ -48,27 +32,17 @@ namespace teachos::arch::memory::heap
 
     if (current != nullptr)
     {
-      if (current->size == total_size)
-      {
-        auto const memory_address = remove_free_memory_block(previous, current);
-        new (memory_address) std::size_t(total_size);
-        mutex.unlock();
-        return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t));
-      }
-      else if (current->size >= total_size + min_allocatable_size())
+      auto memory = allocate_into_memory_block_if_big_enough(current, previous, total_size);
+      if (memory.has_value())
       {
-        // Ensure that the allocated size block is atleast 16 bytes (required because if we free the hole afterwards
-        // there needs to be enough space for a memory block). Therefore we allocate more than is actually required if
-        // the total size was less and simply deallocate it as well
-        auto const max_size = std::max(total_size, min_allocatable_size());
-        auto const memory_address = split_free_memory_block(previous, current, max_size);
-        new (memory_address) std::size_t(max_size);
-        mutex.unlock();
-        return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t));
+        return memory.value();
       }
     }
 
-    exception_handling::panic("[Linked List Allocator] Out of memory");
+    char constexpr OUT_OF_MEMORY_ERROR_MESSAGE[] = "[Linked List Allocator] Out of memory";
+    context_switching::syscall::syscall(context_switching::syscall::type::ASSERT,
+                                        {false, reinterpret_cast<uint64_t>(&OUT_OF_MEMORY_ERROR_MESSAGE)});
+    return nullptr;
   }
 
   auto user_heap_allocator::deallocate(void * pointer) noexcept -> void
@@ -102,6 +76,30 @@ namespace teachos::arch::memory::heap
     mutex.unlock();
   }
 
+  auto user_heap_allocator::allocate_into_memory_block_if_big_enough(memory_block * current, memory_block * previous,
+                                                                     std::size_t total_size) -> std::optional<void *>
+  {
+    if (current->size == total_size)
+    {
+      auto const memory_address = remove_free_memory_block(previous, current);
+      new (memory_address) std::size_t(total_size);
+      mutex.unlock();
+      return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t));
+    }
+    else if (current->size >= total_size + min_allocatable_size())
+    {
+      // Ensure that the allocated size block is atleast 16 bytes (required because if we free the hole afterwards
+      // there needs to be enough space for a memory block). Therefore we allocate more than is actually required if
+      // the total size was less and simply deallocate it as well
+      auto const max_size = std::max(total_size, min_allocatable_size());
+      auto const memory_address = split_free_memory_block(previous, current, max_size);
+      new (memory_address) std::size_t(max_size);
+      mutex.unlock();
+      return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t));
+    }
+    return std::nullopt;
+  }
+
   auto user_heap_allocator::expand_heap_if_full() -> memory_block *
   {
     auto const result = context_switching::syscall::syscall(context_switching::syscall::type::EXPAND_HEAP);
@@ -180,10 +178,12 @@ namespace teachos::arch::memory::heap
 
     // Check if the block we want to deallocate is contained in the previous block, because if it is it can only mean
     // that the block has already been deallocated and we therefore attempted a double free.
-    exception_handling::assert(previous_block == nullptr ||
-                                   start_address >=
-                                       (reinterpret_cast<std::size_t>(previous_block) + previous_block->size),
-                               "[Linked List Allocator] Attempted double free detected");
+    char constexpr DOUBLE_FREE_ERROR_MESSAGE[] = "[Linked List Allocator] Attempted double free detected";
+    context_switching::syscall::syscall(
+        context_switching::syscall::type::ASSERT,
+        {previous_block == nullptr ||
+             start_address >= (reinterpret_cast<std::size_t>(previous_block) + previous_block->size),
+         reinterpret_cast<uint64_t>(&DOUBLE_FREE_ERROR_MESSAGE)});
 
     auto const new_block = new (pointer) memory_block(block_size, next_block);
     // If we want to deallocate the first block that is before any other free block, then there exists no previous free