From b09100f8b79b77f613f5d68fd661e3cbaf1f5c86 Mon Sep 17 00:00:00 2001
From: Danny Holman <dholman@gymli.org>
Date: Mon, 24 Jun 2024 02:07:27 -0500
Subject: arch: i386: add a function that walks the stack

Add a function that will walk the stack and save the return addresses
into an array. This will allow the kernel to print out stack traces
during a panic or on demand inside a debugger.

Signed-off-by: Danny Holman <dholman@gymli.org>
---
 arch/i386/kernel/stack_trace.s | 31 +++++++++++++++++++++++++++++++
 arch/i386/make.config          |  1 +
 2 files changed, 32 insertions(+)
 create mode 100644 arch/i386/kernel/stack_trace.s

diff --git a/arch/i386/kernel/stack_trace.s b/arch/i386/kernel/stack_trace.s
new file mode 100644
index 0000000..fbd77ed
--- /dev/null
+++ b/arch/i386/kernel/stack_trace.s
@@ -0,0 +1,31 @@
+.section .text
+
+.global walk_stack
+.type walk_stack, @function
+walk_stack:
+        pushl %ebp
+        movl %esp, %ebp
+
+        pushl %edi
+        movl -4(%ebp), %edi
+        pushl %ebx
+        movl -8(%ebp), %ebx
+
+        xorl %eax, %eax
+        movl 8(%esp), %ebx
+        movl 16(%esp), %edi
+        movl 20(%esp), %ecx
+walk:
+        testl %ebx, %ebx
+        jz done
+        movl 4(%ebx), %edx
+        movl 0(%ebx), %ebx
+        movl %edx, (%edi)
+        addl $4, %edi
+        inc %eax
+        loop walk
+done:
+        popl %ebx
+        popl %edi
+        popl %ebp
+        ret
diff --git a/arch/i386/make.config b/arch/i386/make.config
index 82d0733..557f01a 100644
--- a/arch/i386/make.config
+++ b/arch/i386/make.config
@@ -7,6 +7,7 @@ KERNEL_ARCH_OBJS=$(ARCHDIR)/boot/boot.o \
                  $(ARCHDIR)/kernel/idt.o \
                  $(ARCHDIR)/kernel/gdt.o \
                  $(ARCHDIR)/kernel/isr.o \
+                 $(ARCHDIR)/kernel/stack_trace.o \
                  $(ARCHDIR)/kernel/multiboot.o \
                  $(ARCHDIR)/kernel/serial.o \
                  $(ARCHDIR)/kernel/pic.o \
-- 
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