Kernel: Allow preventing kmalloc and kfree

For "destructive" disallowance of allocations throughout the system,
Thread gains a member that controls whether allocations are currently
allowed or not. kmalloc checks this member on both allocations and
deallocations (with the exception of early boot) and panics the kernel
if allocations are disabled. This will allow for critical sections that
can't be allowed to allocate to fail-fast, making for easier debugging.

PS: My first proper Kernel commit :^)

1 files changed, 8 insertions, 2 deletions

diff --git a/Kernel/Heap/kmalloc.cpp b/Kernel/Heap/kmalloc.cpp
index 6a3c21211f..5f8800acdb 100644
--- a/Kernel/Heap/kmalloc.cpp
+++ b/Kernel/Heap/kmalloc.cpp
@@ -362,8 +362,12 @@ void* kmalloc(size_t size)
     Thread* current_thread = Thread::current();
     if (!current_thread)
         current_thread = Processor::idle_thread();
-    if (current_thread)
+    if (current_thread) {
+        // FIXME: By the time we check this, we have already allocated above.
+        //        This means that in the case of an infinite recursion, we can't catch it this way.
+        VERIFY(current_thread->is_allocation_enabled());
         PerformanceManager::add_kmalloc_perf_event(*current_thread, size, (FlatPtr)ptr);
+    }
 
     return ptr;
 }
@@ -384,8 +388,10 @@ void kfree_sized(void* ptr, size_t size)
         Thread* current_thread = Thread::current();
         if (!current_thread)
             current_thread = Processor::idle_thread();
-        if (current_thread)
+        if (current_thread) {
+            VERIFY(current_thread->is_allocation_enabled());
             PerformanceManager::add_kfree_perf_event(*current_thread, 0, (FlatPtr)ptr);
+        }
     }
 
     g_kmalloc_global->deallocate(ptr, size);