/*
 * Copyright (c) 2013 Denys Vlasenko <vda.linux@googlemail.com>
 * Copyright (c) 2013-2015 Dmitry V. Levin <ldv@altlinux.org>
 * Copyright (c) 2015-2017 The strace developers.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * PTRACE_GETREGSET was added to the kernel in v2.6.25,
 * a PTRACE_GETREGS based fallback is provided for old kernels.
 */
static int
getregs_old(struct tcb *tcp)
{
	/* Use old method, with unreliable heuristical detection of 32-bitness. */
	long r = ptrace(PTRACE_GETREGS, tcp->pid, NULL, &x86_64_regs);
	if (r)
		return r;

	if (x86_64_regs.cs == 0x23) {
		x86_io.iov_len = sizeof(i386_regs);
		/*
		 * The order is important: i386_regs and x86_64_regs
		 * are overlaid in memory!
		 */
		i386_regs.ebx = x86_64_regs.rbx;
		i386_regs.ecx = x86_64_regs.rcx;
		i386_regs.edx = x86_64_regs.rdx;
		i386_regs.esi = x86_64_regs.rsi;
		i386_regs.edi = x86_64_regs.rdi;
		i386_regs.ebp = x86_64_regs.rbp;
		i386_regs.eax = x86_64_regs.rax;
		/* i386_regs.xds = x86_64_regs.ds; unused by strace */
		/* i386_regs.xes = x86_64_regs.es; ditto... */
		/* i386_regs.xfs = x86_64_regs.fs; */
		/* i386_regs.xgs = x86_64_regs.gs; */
		i386_regs.orig_eax = x86_64_regs.orig_rax;
		i386_regs.eip = x86_64_regs.rip;
		/* i386_regs.xcs = x86_64_regs.cs; */
		/* i386_regs.eflags = x86_64_regs.eflags; */
		i386_regs.esp = x86_64_regs.rsp;
		/* i386_regs.xss = x86_64_regs.ss; */
	} else {
		x86_io.iov_len = sizeof(x86_64_regs);
	}
	return 0;
}