1/*
2 * Copyright (c) 2002 Andi Kleen <ak@suse.de>
3 * Copyright (c) 2002 Michal Ludvig <mludvig@suse.cz>
4 * Copyright (c) 2002 Roland McGrath <roland@redhat.com>
5 * Copyright (c) 2008-2013 Denys Vlasenko <vda.linux@googlemail.com>
6 * Copyright (c) 2012 H.J. Lu <hongjiu.lu@intel.com>
7 * Copyright (c) 2010-2015 Dmitry V. Levin <ldv@altlinux.org>
8 * Copyright (c) 2015-2018 The strace developers.
9 * All rights reserved.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 *    notice, this list of conditions and the following disclaimer in the
18 *    documentation and/or other materials provided with the distribution.
19 * 3. The name of the author may not be used to endorse or promote products
20 *    derived from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34#ifdef X86_64
35# define X32_PERSONALITY_NUMBER 2
36#else
37# define X32_PERSONALITY_NUMBER 0
38#endif
39
40/* Return codes: 1 - ok, 0 - ignore, other - error. */
41static int
42arch_get_scno(struct tcb *tcp)
43{
44	kernel_ulong_t scno = 0;
45	unsigned int currpers;
46
47#ifndef __X32_SYSCALL_BIT
48# define __X32_SYSCALL_BIT	0x40000000
49#endif
50
51#if 1
52	/*
53	 * GETREGSET of NT_PRSTATUS tells us regset size,
54	 * which unambiguously detects i386.
55	 *
56	 * Linux kernel distinguishes x86-64 and x32 processes
57	 * solely by looking at __X32_SYSCALL_BIT:
58	 * arch/x86/include/asm/compat.h::is_x32_task():
59	 * if (task_pt_regs(current)->orig_ax & __X32_SYSCALL_BIT)
60	 *	return true;
61	 */
62	if (x86_io.iov_len == sizeof(i386_regs)) {
63		scno = i386_regs.orig_eax;
64		currpers = 1;
65	} else {
66		scno = x86_64_regs.orig_rax;
67		currpers = 0;
68		if (scno & __X32_SYSCALL_BIT) {
69			/*
70			 * Syscall number -1 requires special treatment:
71			 * it might be a side effect of SECCOMP_RET_ERRNO
72			 * filtering that sets orig_rax to -1
73			 * in some versions of linux kernel.
74			 * If that is the case, then
75			 * __X32_SYSCALL_BIT logic does not apply.
76			 */
77			if ((long long) x86_64_regs.orig_rax != -1) {
78				currpers = 2;
79			} else {
80# ifdef X32
81				currpers = 2;
82# endif
83			}
84		}
85	}
86
87#elif 0
88	/*
89	 * cs = 0x33 for long mode (native 64 bit and x32)
90	 * cs = 0x23 for compatibility mode (32 bit)
91	 * ds = 0x2b for x32 mode (x86-64 in 32 bit)
92	 */
93	scno = x86_64_regs.orig_rax;
94	switch (x86_64_regs.cs) {
95		case 0x23:
96			currpers = 1;
97			break;
98		case 0x33:
99			if (x86_64_regs.ds == 0x2b) {
100				currpers = 2;
101			} else
102				currpers = 0;
103			break;
104		default:
105			error_msg("Unknown value CS=0x%08X while "
106				  "detecting personality of process PID=%d",
107				  (int)x86_64_regs.cs, tcp->pid);
108			currpers = current_personality;
109			break;
110	}
111#elif 0
112	/*
113	 * This version analyzes the opcode of a syscall instruction.
114	 * (int 0x80 on i386 vs. syscall on x86-64)
115	 * It works, but is too complicated, and strictly speaking, unreliable.
116	 */
117	unsigned long call, rip = x86_64_regs.rip;
118	/* sizeof(syscall) == sizeof(int 0x80) == 2 */
119	rip -= 2;
120	errno = 0;
121	call = ptrace(PTRACE_PEEKTEXT, tcp->pid, (char *)rip, (char *)0);
122	if (errno)
123		perror_msg("ptrace_peektext failed");
124	switch (call & 0xffff) {
125		/* x86-64: syscall = 0x0f 0x05 */
126		case 0x050f:
127			currpers = 0;
128			break;
129		/* i386: int 0x80 = 0xcd 0x80 */
130		case 0x80cd:
131			currpers = 1;
132			break;
133		default:
134			currpers = current_personality;
135			error_msg("Unknown syscall opcode (0x%04X) while "
136				  "detecting personality of process PID=%d",
137				  (int)call, tcp->pid);
138			break;
139	}
140#endif
141
142#ifdef X32
143	/*
144	 * If we are built for a x32 system, then personality 0 is x32
145	 * (not x86_64), and stracing of x86_64 apps is not supported.
146	 * Stracing of i386 apps is still supported.
147	 */
148	if (currpers == 0) {
149		error_msg("syscall_%" PRI_klu "(...) in unsupported "
150			  "64-bit mode of process PID=%d", scno, tcp->pid);
151		return 0;
152	}
153	currpers &= ~2; /* map 2,1 to 0,1 */
154#endif /* X32 */
155
156	update_personality(tcp, currpers);
157	tcp->scno = scno;
158	return 1;
159}
160