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