Kernel: Don't get rbp from internal context switch structures

This has been broken on x86_64 since its introduction, as it features
more registers to be saved, and we never held up the "rbp has to be the
last pushed register" there.

Instead, just copy rbp from the thread structure, which is now properly
updated since the last commit.

1 files changed, 1 insertions, 13 deletions

diff --git a/Kernel/Arch/x86_64/Processor.cpp b/Kernel/Arch/x86_64/Processor.cpp
index 4bb7c09963..67c73eac9c 100644
--- a/Kernel/Arch/x86_64/Processor.cpp
+++ b/Kernel/Arch/x86_64/Processor.cpp
@@ -863,23 +863,11 @@ ErrorOr<Vector<FlatPtr, 32>> Processor::capture_stack_trace(Thread& thread, size
         case Thread::State::Blocked:
         case Thread::State::Dying:
         case Thread::State::Dead: {
-            // We need to retrieve ebp from what was last pushed to the kernel
-            // stack. Before switching out of that thread, it switch_context
-            // pushed the callee-saved registers, and the last of them happens
-            // to be ebp.
             ScopedAddressSpaceSwitcher switcher(thread.process());
             auto& regs = thread.regs();
-            auto* stack_top = reinterpret_cast<FlatPtr*>(regs.sp());
-            if (Memory::is_user_range(VirtualAddress(stack_top), sizeof(FlatPtr))) {
-                if (copy_from_user(&frame_ptr, &((FlatPtr*)stack_top)[0]).is_error())
-                    frame_ptr = 0;
-            } else {
-                void* fault_at;
-                if (!safe_memcpy(&frame_ptr, &((FlatPtr*)stack_top)[0], sizeof(FlatPtr), fault_at))
-                    frame_ptr = 0;
-            }
 
             ip = regs.ip();
+            frame_ptr = regs.rbp;
 
             // TODO: We need to leave the scheduler lock here, but we also
             //       need to prevent the target thread from being run while