ports/gcc: Fix --with-build-sysroot and enable asserts

kernel/src/arch/x86_64/CPU.cpp

@@ -75,6 +75,16 @@ void decode_page_fault_error_code(u64 code)
             (code & PF_RESERVED) ? " | Reserved bits set" : "", (code & PF_NX_VIOLATION) ? " | NX violation" : "");
 }
 
+static void check_stack(Thread* current, Registers* regs)
+{
+    if (regs->rsp < current->stack.bottom() || regs->rsp >= current->stack.top())
+        kerrorln("Abnormal stack (RSP outside the normal range, %.16lx-%.16lx)", current->stack.bottom(),
+                 current->stack.top());
+
+    if (regs->rsp >= (current->stack.bottom() - ARCH_PAGE_SIZE) && regs->rsp < current->stack.bottom())
+        kerrorln("Likely stack overflow (CPU exception inside guard page)");
+}
+
 void handle_cpu_exception(int signo, const char* err, Registers* regs)
 {
     if (err) kerrorln("Caught CPU exception: %s", err);
@@ -89,8 +99,11 @@ void handle_cpu_exception(int signo, const char* err, Registers* regs)
 
     if (!is_in_kernel(regs))
     {
-        Scheduler::current()->send_signal(signo);
+        auto* current = Scheduler::current();
-        Scheduler::current()->process_pending_signals(regs);
+        check_stack(current, regs);
+
+        current->send_signal(signo);
+        current->process_pending_signals(regs);
         return;
     }
 
@@ -103,6 +116,8 @@ void handle_page_fault(Registers* regs)
     asm volatile("mov %%cr2, %0" : "=r"(cr2));
     kerrorln("Page fault while accessing %lx!", cr2);
 
+    if (cr2 <= ARCH_PAGE_SIZE) kerrorln("Looks like a null pointer dereference!");
+
     decode_page_fault_error_code(regs->error);
 
     handle_cpu_exception(SIGSEGV, nullptr, regs);

kernel/src/thread/ThreadImage.cpp

@@ -11,16 +11,17 @@ static constexpr u64 THREAD_STACK_BASE = 0x10000;
 
 static Result<void> create_user_stack(Stack& user_stack, AddressSpace* space)
 {
-    TRY(MemoryManager::alloc_at_zeroed(THREAD_STACK_BASE, DEFAULT_USER_STACK_PAGES,
-                                       MMU::ReadWrite | MMU::NoExecute | MMU::User));
-
-    auto guard = make_scope_guard([] { MemoryManager::unmap_owned(THREAD_STACK_BASE, DEFAULT_USER_STACK_PAGES); });
-
     if (!TRY(space->test_and_alloc_region(THREAD_STACK_BASE, DEFAULT_USER_STACK_PAGES, PROT_READ | PROT_WRITE,
                                           MAP_ANONYMOUS | MAP_PRIVATE, 0, true)))
         return err(ENOMEM);
 
-    guard.deactivate();
+    // Stack overflow guard page, remains unmapped.
+    if (!TRY(space->test_and_alloc_region(THREAD_STACK_BASE - ARCH_PAGE_SIZE, 1, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS,
+                                          0, 0, true)))
+        return err(ENOMEM);
+
+    TRY(MemoryManager::alloc_at_zeroed(THREAD_STACK_BASE, DEFAULT_USER_STACK_PAGES,
+                                       MMU::ReadWrite | MMU::NoExecute | MMU::User));
 
     user_stack = { THREAD_STACK_BASE, DEFAULT_USER_STACK_SIZE };
 

ports/gcc/PACKAGE

@@ -17,7 +17,7 @@ do_patch()
 
 do_configure()
 {
-    $srcdir/configure --prefix=/usr --target=$LUNA_ARCH-luna --host=$LUNA_ARCH-luna --disable-nls --with-build-sysroot=$BUILD_SYSROOT --enable-languages=c,c++
+    $srcdir/configure --prefix=/usr --target=$LUNA_ARCH-luna --host=$LUNA_ARCH-luna --disable-nls --with-build-sysroot=$LUNA_BASE --enable-languages=c,c++ --enable-checking
 }
 
 do_build()