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

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

/*
 * amd64 stack frame layout:
 *
 *  24(%rbp) ...
 *  16(%rbp) argument 7 (if applicable, args 1-6 are passed in registers)
 *   8(%rbp) caller %rip (after the call instruction, pushed by hardware)
 * ------------------------------------------------------------
 *    (%rbp) caller %rbp (pushed in callee prologue)
 *  -8(%rbp) local variable 1
 * -16(%rbp) local variable 2
 * -24(%rbp) ...
 */

__naked void ktrace_print(void)
{
	__asm__ volatile(
"	movq	%rbp, %rdi		\n"
"	jmp	ktrace_print_from	\n"
	);
}

void ktrace_print_from(void *frame)
{
	void **rbp = (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 (rbp >= (void **)image_start && rbp < (void **)image_end) {
		/* arch/x86/boot/setup64.S pushes two `nil's as the initial stack frame */
		if (rbp[1] == nil)
			break;
		/* Caller return address is immediately above the stack frame.
		 * XXX This prints the position *after* the call instruction. */
		kprintf("  %p\n", rbp[1]);
		if (rbp[1] >= isr_start && rbp[1] < isr_end)
			break;
		rbp = *rbp;
	}
}

__naked void *ktrace_return_addr(void)
{
	__asm__ volatile(
"	movq	8(%rbp), %rax	\n"
"	ret			\n"
	);
}