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>

1 files changed, 31 insertions, 0 deletions

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