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
40 int (*dtrace_pid_probe_ptr)(arm_saved_state_t *);
41 int (*dtrace_return_probe_ptr) (arm_saved_state_t *);
42
43 kern_return_t
44 dtrace_user_probe(arm_saved_state_t *);
45
46 kern_return_t
dtrace_user_probe(arm_saved_state_t * regs)47 dtrace_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 struct proc *p = current_proc();
58 int is_fasttrap = 0;
59
60 thread_t thread = current_thread();
61 uthread_t uthread = current_uthread();
62
63 kauth_cred_thread_update(thread, p);
64
65 uint32_t pc;
66 if (copyin((user_addr_t)saved_state64(regs)->pc, &pc, sizeof(uint32_t))) {
67 return KERN_FAILURE;
68 }
69 is_fasttrap = (pc == FASTTRAP_ARM64_RET_INSTR);
70
71 if (is_fasttrap) {
72 uint8_t step = uthread->t_dtrace_step;
73 uint8_t ret = uthread->t_dtrace_ret;
74 user_addr_t npc = uthread->t_dtrace_npc;
75
76 if (uthread->t_dtrace_ast) {
77 printf("dtrace_user_probe() should be calling aston()\n");
78 // aston(thread);
79 // uthread->t_sig_check = 1;
80 }
81
82 /*
83 * Clear all user tracing flags.
84 */
85 uthread->t_dtrace_ft = 0;
86
87 /*
88 * If we weren't expecting a quick return to the kernel, just kill
89 * the process as though it had just executed an unassigned
90 * trap instruction.
91 */
92 if (step == 0) {
93 /*
94 * APPLE NOTE: We're returning KERN_FAILURE, which causes
95 * the generic signal handling code to take over, which will effectively
96 * deliver a EXC_BAD_INSTRUCTION to the user process.
97 */
98 return KERN_FAILURE;
99 }
100
101 /*
102 * If we hit this trap unrelated to a return probe, we're
103 * here to either:
104 *
105 * 1. Reset the AST flag, since we deferred a signal
106 * until after we logically single-stepped the instruction we
107 * copied out.
108 *
109 * 2. Just return to normal execution (required for U64).
110 */
111 if (ret == 0) {
112 set_saved_state_pc(regs, npc);
113 return KERN_SUCCESS;
114 }
115
116 /*
117 * We need to wait until after we've called the
118 * dtrace_return_probe_ptr function pointer to step the pc.
119 */
120 rwp = &CPU->cpu_ft_lock;
121 lck_rw_lock_shared(rwp);
122
123 if (dtrace_return_probe_ptr != NULL) {
124 (void) (*dtrace_return_probe_ptr)(regs);
125 }
126 lck_rw_unlock_shared(rwp);
127
128 set_saved_state_pc(regs, npc);
129
130 return KERN_SUCCESS;
131 } else {
132 rwp = &CPU->cpu_ft_lock;
133
134 /*
135 * The DTrace fasttrap provider uses a trap,
136 * FASTTRAP_{ARM,THUMB}_INSTR. We let
137 * DTrace take the first crack at handling
138 * this trap; if it's not a probe that DTrace knows about,
139 * we call into the trap() routine to handle it like a
140 * breakpoint placed by a conventional debugger.
141 */
142
143 /*
144 * APPLE NOTE: I believe the purpose of the reader/writers lock
145 * is thus: There are times which dtrace needs to prevent calling
146 * dtrace_pid_probe_ptr(). Sun's original impl grabbed a plain
147 * mutex here. However, that serialized all probe calls, and
148 * destroyed MP behavior. So now they use a RW lock, with probes
149 * as readers, and the top level synchronization as a writer.
150 */
151 lck_rw_lock_shared(rwp);
152 if (dtrace_pid_probe_ptr != NULL &&
153 (*dtrace_pid_probe_ptr)(regs) == 0) {
154 lck_rw_unlock_shared(rwp);
155 return KERN_SUCCESS;
156 }
157 lck_rw_unlock_shared(rwp);
158
159 /*
160 * If the instruction that caused the breakpoint trap doesn't
161 * look like our trap anymore, it may be that this tracepoint
162 * was removed just after the user thread executed it. In
163 * that case, return to user land to retry the instuction.
164 *
165 * Note that the PC points to the instruction that caused the fault.
166 */
167 uint32_t instr;
168 if (fuword32(saved_state64(regs)->pc, &instr) == 0 && instr != FASTTRAP_ARM64_INSTR) {
169 return KERN_SUCCESS;
170 }
171 }
172
173 return KERN_FAILURE;
174 }
175