arch/arm/lib/cmd_boot.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * (C) Copyright 2008-2011
 * Graeme Russ, <graeme.russ@gmail.com>
 *
 * (C) Copyright 2002
 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
 *
 * (C) Copyright 2002
 * Wolfgang Denk, DENX Software Engineering, <wd@denx.de>
 *
 * (C) Copyright 2002
 * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
 * Marius Groeger <mgroeger@sysgo.de>
 *
 * Copyright 2015 ATS Advanced Telematics Systems GmbH
 * Copyright 2015 Konsulko Group, Matt Porter <mporter@konsulko.com>
 */

#include <command.h>

/*
 * ARMv7M does not support ARM instruction mode. However, the
 * interworking BLX and BX instructions do encode the ARM/Thumb
 * field in bit 0. This means that when executing any Branch
 * and eXchange instruction we must set bit 0 to one to guarantee
 * that we keep the processor in Thumb instruction mode. From The
 * ARMv7-M Instruction Set A4.1.1:
 *   "ARMv7-M only supports the Thumb instruction execution state,
 *    therefore the value of address bit [0] must be 1 in interworking
 *    instructions, otherwise a fault occurs."
 */
unsigned long do_go_exec(ulong (*entry)(int, char * const []),
			 int argc, char *const argv[])
{
	ulong addr = (ulong)entry | 1;
	entry = (void *)addr;

	return entry(argc, argv);
}