/* Copyright (C) 2021,2022 fef <owo@fef.moe>.  All rights reserved. */

#include <gay/kprintf.h>
#include <gay/ktrace.h>
#include <gay/linker.h>

/*
 * i386 stack frame layout:
 *
 *  12(%ebp) ...
 *   8(%ebp) argument 1 (if applicable)
 *   4(%ebp) caller %eip (after the call instruction, pushed by hardware)
 * ------------------------------------------------------------
 *    (%ebp) caller %ebp (pushed in callee prologue)
 *  -4(%ebp) local variable 1
 *  -8(%ebp) local variable 2
 * -12(%ebp) ...
 */

__naked void ktrace_print(void)
{
	__asm__ volatile(
"	pushl	%ebp			\n"
"	call	ktrace_print_from	\n"
"	ret				\n"
	);
}

void ktrace_print_from(void *frame)
{
	void **ebp = (void **)frame;
	kprintf("Stack trace:\n");

	/* XXX Rather than spitting out raw addresses, parse the kernel image's
	 *     ELF sections to figure out what the address actually belongs to */
	while (ebp >= (void **)image_start && ebp < (void **)image_end) {
		/* arch/x86/boot/setup32.S pushes two `nil's as the initial stack frame */
		if (ebp[1] == nil)
			break;
		/* caller return address is immediately above the stack frame */
		kprintf("  %p\n", ebp[1]);
		if (ebp[1] >= isr_start && ebp[1] < isr_end)
			break;
		ebp = *ebp;
	}
}

__naked void *ktrace_return_addr(void)
{
	__asm__ volatile(
"	movl	4(%ebp), %eax	\n"
"	ret			\n"
	);
}