Function db_backtrace

freebsd/i386/i386/db_trace.c:435–592

}

static int
db_backtrace(struct thread *td, struct trapframe *tf, struct i386_frame *frame,
    db_addr_t pc, register_t sp, int count)
{
	struct i386_frame *actframe;
#define MAXNARG	16
	char *argnames[MAXNARG], **argnp = NULL;
	const char *name;
	int *argp;
	db_expr_t offset;
	c_db_sym_t sym;
	int instr, narg;
	bool first;

	if (db_segsize(tf) == 16) {
		db_printf(
"--- 16-bit%s, cs:eip = %#x:%#x, ss:esp = %#x:%#x, ebp = %#x, tf = %p ---\n",
		    (tf->tf_eflags & PSL_VM) ? " (vm86)" : "",
		    tf->tf_cs, tf->tf_eip,
		    TF_HAS_STACKREGS(tf) ? tf->tf_ss : rss(),
		    TF_HAS_STACKREGS(tf) ? tf->tf_esp : (intptr_t)&tf->tf_esp,
		    tf->tf_ebp, tf);
		return (0);
	}

	/* 'frame' can be null initially.  Just print the pc then. */
	if (frame == NULL)
		goto out;

	/*
	 * If an indirect call via an invalid pointer caused a trap,
	 * %pc contains the invalid address while the return address
	 * of the unlucky caller has been saved by CPU on the stack
	 * just before the trap frame.  In this case, try to recover
	 * the caller's address so that the first frame is assigned
	 * to the right spot in the right function, for that is where
	 * the failure actually happened.
	 *
	 * This trick depends on the fault address stashed in tf_err
	 * by trap_fatal() before entering KDB.
	 */
	if (kdb_frame && pc == kdb_frame->tf_err) {
		/*
		 * Find where the trap frame actually ends.
		 * It won't contain tf_esp or tf_ss unless crossing rings.
		 */
		if (TF_HAS_STACKREGS(kdb_frame))
			instr = (int)(kdb_frame + 1);
		else
			instr = (int)&kdb_frame->tf_esp;
		pc = db_get_value(instr, 4, false);
	}

	if (count == -1)
		count = 1024;

	first = true;
	while (count-- && !db_pager_quit) {