1/*
2 * Copyright (c) 2007-2018 Apple Inc. All rights reserved.
3 */
4/*
5 * CDDL HEADER START
6 *
7 * The contents of this file are subject to the terms of the
8 * Common Development and Distribution License, Version 1.0 only
9 * (the "License"). You may not use this file except in compliance
10 * with the License.
11 *
12 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
13 * or http://www.opensolaris.org/os/licensing.
14 * See the License for the specific language governing permissions
15 * and limitations under the License.
16 *
17 * When distributing Covered Code, include this CDDL HEADER in each
18 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
19 * If applicable, add the following below this CDDL HEADER, with the
20 * fields enclosed by brackets "[]" replaced with your own identifying
21 * information: Portions Copyright [yyyy] [name of copyright owner]
22 *
23 * CDDL HEADER END
24 */
25/*
26 * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
27 * Use is subject to license terms.
28 */
29
30#include <sys/dtrace.h>
31#include <sys/dtrace_glue.h>
32#include <sys/dtrace_impl.h>
33#include <sys/fasttrap.h>
34#include <sys/vm.h>
35#include <sys/user.h>
36#include <sys/kauth.h>
37#include <kern/debug.h>
38#include <arm64/proc_reg.h>
39
40int (*dtrace_pid_probe_ptr)(arm_saved_state_t *);
41int (*dtrace_return_probe_ptr) (arm_saved_state_t *);
42
43kern_return_t
44dtrace_user_probe(arm_saved_state_t *);
45
46kern_return_t
47dtrace_user_probe(arm_saved_state_t *regs)
48{
49 /*
50 * FIXME
51 *
52 * The only call path into this method is always a user trap.
53 * We don't need to test for user trap, but should assert it.
54 */
55
56 lck_rw_t *rwp;
57 int is_fasttrap = 0;
58 uthread_t uthread = current_uthread();
59
60 current_cached_proc_cred_update();
61
62 uint32_t pc;
63 if (copyin((user_addr_t)saved_state64(regs)->pc, &pc, sizeof(uint32_t))) {
64 return KERN_FAILURE;
65 }
66 is_fasttrap = (pc == FASTTRAP_ARM64_RET_INSTR);
67
68 if (is_fasttrap) {
69 uint8_t step = uthread->t_dtrace_step;
70 uint8_t ret = uthread->t_dtrace_ret;
71 user_addr_t npc = uthread->t_dtrace_npc;
72
73 if (uthread->t_dtrace_ast) {
74 printf("dtrace_user_probe() should be calling aston()\n");
75 // aston(thread);
76 // uthread->t_sig_check = 1;
77 }
78
79 /*
80 * Clear all user tracing flags.
81 */
82 uthread->t_dtrace_ft = 0;
83
84 /*
85 * If we weren't expecting a quick return to the kernel, just kill
86 * the process as though it had just executed an unassigned
87 * trap instruction.
88 */
89 if (step == 0) {
90 /*
91 * APPLE NOTE: We're returning KERN_FAILURE, which causes
92 * the generic signal handling code to take over, which will effectively
93 * deliver a EXC_BAD_INSTRUCTION to the user process.
94 */
95 return KERN_FAILURE;
96 }
97
98 /*
99 * If we hit this trap unrelated to a return probe, we're
100 * here to either:
101 *
102 * 1. Reset the AST flag, since we deferred a signal
103 * until after we logically single-stepped the instruction we
104 * copied out.
105 *
106 * 2. Just return to normal execution (required for U64).
107 */
108 if (ret == 0) {
109 set_saved_state_pc(regs, pc: npc);
110 return KERN_SUCCESS;
111 }
112
113 /*
114 * We need to wait until after we've called the
115 * dtrace_return_probe_ptr function pointer to step the pc.
116 */
117 rwp = &CPU->cpu_ft_lock;
118 lck_rw_lock_shared(lck: rwp);
119
120 if (dtrace_return_probe_ptr != NULL) {
121 (void) (*dtrace_return_probe_ptr)(regs);
122 }
123 lck_rw_unlock_shared(lck: rwp);
124
125 set_saved_state_pc(regs, pc: npc);
126
127 return KERN_SUCCESS;
128 } else {
129 rwp = &CPU->cpu_ft_lock;
130
131 /*
132 * The DTrace fasttrap provider uses a trap,
133 * FASTTRAP_{ARM,THUMB}_INSTR. We let
134 * DTrace take the first crack at handling
135 * this trap; if it's not a probe that DTrace knows about,
136 * we call into the trap() routine to handle it like a
137 * breakpoint placed by a conventional debugger.
138 */
139
140 /*
141 * APPLE NOTE: I believe the purpose of the reader/writers lock
142 * is thus: There are times which dtrace needs to prevent calling
143 * dtrace_pid_probe_ptr(). Sun's original impl grabbed a plain
144 * mutex here. However, that serialized all probe calls, and
145 * destroyed MP behavior. So now they use a RW lock, with probes
146 * as readers, and the top level synchronization as a writer.
147 */
148 lck_rw_lock_shared(lck: rwp);
149 if (dtrace_pid_probe_ptr != NULL &&
150 (*dtrace_pid_probe_ptr)(regs) == 0) {
151 lck_rw_unlock_shared(lck: rwp);
152 return KERN_SUCCESS;
153 }
154 lck_rw_unlock_shared(lck: rwp);
155
156 /*
157 * If the instruction that caused the breakpoint trap doesn't
158 * look like our trap anymore, it may be that this tracepoint
159 * was removed just after the user thread executed it. In
160 * that case, return to user land to retry the instuction.
161 *
162 * Note that the PC points to the instruction that caused the fault.
163 */
164 uint32_t instr;
165 if (fuword32(saved_state64(regs)->pc, &instr) == 0 && instr != FASTTRAP_ARM64_INSTR) {
166 return KERN_SUCCESS;
167 }
168 }
169
170 return KERN_FAILURE;
171}
172