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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 /* Return codes: 1 - ok, 0 - ignore, other - error. */
34 static int
arch_get_scno(struct tcb * tcp)35 arch_get_scno(struct tcb *tcp)
36 {
37 	long scno = 0;
38 	unsigned int currpers;
39 
40 #ifndef __X32_SYSCALL_BIT
41 # define __X32_SYSCALL_BIT	0x40000000
42 #endif
43 
44 #if 1
45 	/*
46 	 * GETREGSET of NT_PRSTATUS tells us regset size,
47 	 * which unambiguously detects i386.
48 	 *
49 	 * Linux kernel distinguishes x86-64 and x32 processes
50 	 * solely by looking at __X32_SYSCALL_BIT:
51 	 * arch/x86/include/asm/compat.h::is_x32_task():
52 	 * if (task_pt_regs(current)->orig_ax & __X32_SYSCALL_BIT)
53 	 *         return true;
54 	 */
55 	if (x86_io.iov_len == sizeof(i386_regs)) {
56 		scno = i386_regs.orig_eax;
57 		currpers = 1;
58 	} else {
59 		scno = x86_64_regs.orig_rax;
60 		currpers = 0;
61 		if (scno & __X32_SYSCALL_BIT) {
62 			/*
63 			 * Syscall number -1 requires special treatment:
64 			 * it might be a side effect of SECCOMP_RET_ERRNO
65 			 * filtering that sets orig_rax to -1
66 			 * in some versions of linux kernel.
67 			 * If that is the case, then
68 			 * __X32_SYSCALL_BIT logic does not apply.
69 			 */
70 			if ((long long) x86_64_regs.orig_rax != -1) {
71 				scno -= __X32_SYSCALL_BIT;
72 				currpers = 2;
73 			} else {
74 # ifdef X32
75 				currpers = 2;
76 # endif
77 			}
78 		}
79 	}
80 
81 #elif 0
82 	/*
83 	 * cs = 0x33 for long mode (native 64 bit and x32)
84 	 * cs = 0x23 for compatibility mode (32 bit)
85 	 * ds = 0x2b for x32 mode (x86-64 in 32 bit)
86 	 */
87 	scno = x86_64_regs.orig_rax;
88 	switch (x86_64_regs.cs) {
89 		case 0x23: currpers = 1; break;
90 		case 0x33:
91 			if (x86_64_regs.ds == 0x2b) {
92 				currpers = 2;
93 				scno &= ~__X32_SYSCALL_BIT;
94 			} else
95 				currpers = 0;
96 			break;
97 		default:
98 			error_msg("Unknown value CS=0x%08X while "
99 				  "detecting personality of process PID=%d",
100 				  (int)x86_64_regs.cs, tcp->pid);
101 			currpers = current_personality;
102 			break;
103 	}
104 #elif 0
105 	/*
106 	 * This version analyzes the opcode of a syscall instruction.
107 	 * (int 0x80 on i386 vs. syscall on x86-64)
108 	 * It works, but is too complicated, and strictly speaking, unreliable.
109 	 */
110 	unsigned long call, rip = x86_64_regs.rip;
111 	/* sizeof(syscall) == sizeof(int 0x80) == 2 */
112 	rip -= 2;
113 	errno = 0;
114 	call = ptrace(PTRACE_PEEKTEXT, tcp->pid, (char *)rip, (char *)0);
115 	if (errno)
116 		perror_msg("ptrace_peektext failed");
117 	switch (call & 0xffff) {
118 		/* x86-64: syscall = 0x0f 0x05 */
119 		case 0x050f: currpers = 0; break;
120 		/* i386: int 0x80 = 0xcd 0x80 */
121 		case 0x80cd: currpers = 1; break;
122 		default:
123 			currpers = current_personality;
124 			error_msg("Unknown syscall opcode (0x%04X) while "
125 				  "detecting personality of process PID=%d",
126 				  (int)call, tcp->pid);
127 			break;
128 	}
129 #endif
130 
131 #ifdef X32
132 	/*
133 	 * If we are built for a x32 system, then personality 0 is x32
134 	 * (not x86_64), and stracing of x86_64 apps is not supported.
135 	 * Stracing of i386 apps is still supported.
136 	 */
137 	if (currpers == 0) {
138 		error_msg("syscall_%lu(...) in unsupported "
139 			  "64-bit mode of process PID=%d", scno, tcp->pid);
140 		return 0;
141 	}
142 	currpers &= ~2; /* map 2,1 to 0,1 */
143 #endif /* X32 */
144 
145 	update_personality(tcp, currpers);
146 	tcp->scno = scno;
147 	return 1;
148 }
149