Reimplement backtrace() in terms of _Unwind_Backtrace().

Remove get_frame_pointer() entirely as it is now obsolete.

Kernel/CMakeLists.txt

@@ -15,7 +15,6 @@ set(PLATFORM_AGNOSTIC_SOURCE_FILES
     "include/generic_interrupt_dispatcher.hpp"
     "include/generic_interrupt_handler.hpp"
     "include/simple_device_interrupt_handler.hpp"
-    "include/get_frame_pointer.h"
     "include/halt.h"
     "include/inout.h"
     "include/interrupt_asm.h"
@@ -145,7 +144,6 @@ if(CMAKE_CROSSCOMPILING)
     GenerateSourceFromTemplate("${PROJECT_SOURCE_DIR}/Kernel/src/${CMAKE_SYSTEM_PROCESSOR}/isr_wrapper_asm.S.erb"
                                "${CMAKE_CURRENT_BINARY_DIR}/isr_wrapper_asm.S")
     list(APPEND PLATFORM_SPECIFIC_SOURCE_FILES
-         "src/${BUILD_ARCH}/get_frame_pointer.S"
          "src/${BUILD_ARCH}/halt.S"
          "src/${BUILD_ARCH}/inout.S"
          "src/${BUILD_ARCH}/interrupt_asm.S"
@@ -155,7 +153,6 @@ else(CMAKE_CROSSCOMPILING)
     GenerateSourceFromTemplate("${PROJECT_SOURCE_DIR}/Kernel/src/host/isr_wrapper.c.erb"
                                "${CMAKE_CURRENT_BINARY_DIR}/isr_wrapper.c")
     list(APPEND PLATFORM_SPECIFIC_SOURCE_FILES
-         "src/host/get_frame_pointer.c"
          "src/host/halt.c"
          "src/host/inout.c"
          "src/host/interrupt.c"

Kernel/include/backtrace.hpp

@@ -1,38 +1,14 @@
 #ifndef FLAPJACKOS_KERNEL_INCLUDE_BACKTRACE_HPP
 #define FLAPJACKOS_KERNEL_INCLUDE_BACKTRACE_HPP
 
-#include <common/text_terminal.hpp>
-#include <get_frame_pointer.h>
+#include <unwind.h> // for _Unwind_* symbols
 
-template<typename Function>
-void enumerate_stack_frames(Function&& function)
-{
-    constexpr size_t MAXFRAMES = 16;
-    size_t frame;
-    uintptr_t* frame_pointer;
+class StackWalker {
+public:
+    virtual ~StackWalker() = default;
+    virtual void trace(void* ip) = 0;
+};
 
-    frame_pointer = get_frame_pointer();
-
-    for (frame = 0; frame < MAXFRAMES; ++frame) {
-        uintptr_t return_address;
-
-        if(frame_pointer == nullptr) {
-            // We set ebp to zero at the root stack frame.
-            break;
-        }
-
-        return_address = frame_pointer[1];
-
-        if(return_address == 0) {
-            // No return address?
-            break;
-        }
-
-        frame_pointer = (uintptr_t *)(frame_pointer[0]);
-        function(return_address);
-    }
-}
-
-void backtrace(TextTerminal &term);
+void backtrace(StackWalker& stack_walker);
 
 #endif // FLAPJACKOS_KERNEL_INCLUDE_BACKTRACE_HPP

Kernel/src/backtrace.cpp

@@ -1,14 +1,17 @@
 #include <backtrace.hpp>
-#include <common/logger.hpp>
 
-void backtrace(TextTerminal &term)
+static _Unwind_Reason_Code backtrace_trace(struct _Unwind_Context* context, void* param)
 {
-    TRACE("begin");
-    term.printf("Back Trace:\n");
-    enumerate_stack_frames([&](uintptr_t instruction_pointer){
-        TRACE("[%p]", reinterpret_cast<void*>(instruction_pointer));
-        term.printf("[%p]\n", reinterpret_cast<void*>(instruction_pointer));
-    });
-    TRACE("end");
-    term.printf("\n");
+    void* ip = reinterpret_cast<void*>(_Unwind_GetIP(context));
+    if (ip) {
+        reinterpret_cast<StackWalker*>(param)->trace(ip);
+        return _URC_NO_REASON;
+    } else {
+        return _URC_END_OF_STACK;
+    }
+}
+
+void backtrace(StackWalker& stack_walker)
+{
+    _Unwind_Backtrace(backtrace_trace, reinterpret_cast<void*>(&stack_walker));
 }

Kernel/src/platform/i386/panic.cpp

@@ -4,14 +4,12 @@
 #include <common/text_terminal.hpp>
 #include <halt.h>
 #include <interrupt_asm.h>
-#include <unwind.h> // for _Unwind_* symbols
+#include <backtrace.hpp>
 
 #include <cstdio>
 #include <cstdarg>
 
-static _Unwind_Reason_Code trace(struct _Unwind_Context* context, void* param);
-
-class PanicKernel : private KernelPolicy {
+class PanicKernel : public StackWalker, private KernelPolicy {
 public:
     virtual ~PanicKernel() = default;
 
@@ -41,22 +39,16 @@ class PanicKernel : private KernelPolicy {
     void backtrace()
     {
         puts("Back Trace:\n");
-        _Unwind_Backtrace(::trace, reinterpret_cast<void*>(this));
+        ::backtrace(*this);
         puts("End Back Trace\n");
     }
 
-    _Unwind_Reason_Code trace(struct _Unwind_Context* context)
+    void trace(void *ip) override
     {
-        void* ip = reinterpret_cast<void*>(_Unwind_GetIP(context));
-        if (ip) {
-            char buffer[32] = {0};
-            snprintf(buffer, sizeof(buffer), "[%p]\n",
-                    reinterpret_cast<void*>(ip));
-            puts(buffer);
-            return _URC_NO_REASON;
-        } else {
-            return _URC_END_OF_STACK;
-        }
+        char buffer[32] = {0};
+        snprintf(buffer, sizeof(buffer), "[%p]\n",
+                reinterpret_cast<void*>(ip));
+        puts(buffer);
     }
 
     __attribute__((noreturn)) void interrupt() noexcept
@@ -75,11 +67,6 @@ class PanicKernel : private KernelPolicy {
     LoggerTextOutputStream logger_;
 };
 
-static _Unwind_Reason_Code trace(struct _Unwind_Context* context, void* param)
-{
-    return reinterpret_cast<PanicKernel*>(param)->trace(context);
-}
-
 static PanicKernel* g_panic_kernel;
 
 // Prints a message to the screen and halts forever.