From 972a35bdefc5d1f8d27cd43edb802a81bd9cc129 Mon Sep 17 00:00:00 2001
From: "Justin C. Miller" <justin@devjustinian.com>
Date: Thu, 15 Jul 2021 23:34:35 -0700
Subject: [PATCH] [kernel] Add get_grandcaller debug function

This should probably be replaced with a function taking the number of
steps back, but this is quick and useful.
---
 src/kernel/debug.h | 1 +
 src/kernel/debug.s | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/src/kernel/debug.h b/src/kernel/debug.h
index 7bcdc82..58e62ad 100644
--- a/src/kernel/debug.h
+++ b/src/kernel/debug.h
@@ -10,6 +10,7 @@ extern "C" {
 	uintptr_t get_rsp();
 	uintptr_t get_rip();
 	uintptr_t get_caller();
+	uintptr_t get_grandcaller();
 	uintptr_t get_frame(int frame);
 	uintptr_t get_gsbase();
 	void _halt();
diff --git a/src/kernel/debug.s b/src/kernel/debug.s
index 421695c..f86130b 100644
--- a/src/kernel/debug.s
+++ b/src/kernel/debug.s
@@ -14,6 +14,13 @@ get_caller:
 	mov rax, [rbp+8]
 	ret
 
+global get_grandcaller
+get_grandcaller:
+	; No prelude - don't touch rsp or rbp
+	mov rax, [rbp]
+	mov rax, [rax+8]
+	ret
+
 global get_gsbase
 get_gsbase:
 	rdgsbase rax