bsd/dev/arm64/dtrace_subr_arm.c

   1 /*
   2  *  Copyright (c) 2007 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 /*
  31  * #pragma ident        "@(#)dtrace_subr.c      1.12    05/06/08 SMI"
  32  */
  33
  34 #include <sys/dtrace.h>
  35 #include <sys/dtrace_glue.h>
  36 #include <sys/dtrace_impl.h>
  37 #include <sys/fasttrap.h>
  38 #include <sys/vm.h>
  39 #include <sys/user.h>
  40 #include <sys/kauth.h>
  41 #include <kern/debug.h>
  42 #include <arm/proc_reg.h>
  43
  44 int             (*dtrace_pid_probe_ptr)(arm_saved_state_t *);
  45 int             (*dtrace_return_probe_ptr) (arm_saved_state_t *);
  46
  47 kern_return_t
  48 dtrace_user_probe(arm_saved_state_t *);
  49
  50 kern_return_t
  51 dtrace_user_probe(arm_saved_state_t *regs)
  52 {
  53         /*
  54          * FIXME
  55          *
  56          * The only call path into this method is always a user trap.
  57          * We don't need to test for user trap, but should assert it.
  58          */
  59
  60         lck_rw_t *rwp;
  61         struct proc *p = current_proc();
  62         int is_fasttrap = 0;
  63
  64         uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());
  65
  66         kauth_cred_uthread_update(uthread, p);
  67
  68         if (is_saved_state32(regs)) {
  69                 if (saved_state32(regs)->cpsr & PSR_TF) {
  70                         uint16_t pc;
  71                         if (copyin((user_addr_t)saved_state32(regs)->pc, &pc, sizeof(uint16_t))) {
  72                                 return KERN_FAILURE;
  73                         }
  74                         is_fasttrap = (pc == FASTTRAP_THUMB32_RET_INSTR);
  75                 } else {
  76                         uint32_t pc;
  77                         if (copyin((user_addr_t)saved_state32(regs)->pc, &pc, sizeof(uint32_t))) {
  78                                 return KERN_FAILURE;
  79                         }
  80                         is_fasttrap = (pc == FASTTRAP_ARM32_RET_INSTR);
  81                 }
  82         } else {
  83                 uint32_t pc;
  84                 if (copyin((user_addr_t)saved_state64(regs)->pc, &pc, sizeof(uint32_t))) {
  85                         return KERN_FAILURE;
  86                 }
  87                 is_fasttrap = (pc == FASTTRAP_ARM64_RET_INSTR);
  88         }
  89
  90         if (is_fasttrap) {
  91                 uint8_t step = uthread->t_dtrace_step;
  92                 uint8_t ret = uthread->t_dtrace_ret;
  93                 user_addr_t npc = uthread->t_dtrace_npc;
  94
  95                 if (uthread->t_dtrace_ast) {
  96                         printf("dtrace_user_probe() should be calling aston()\n");
  97                         // aston(thread);
  98                         // uthread->t_sig_check = 1;
  99                 }
 100
 101                 /*
 102                  * Clear all user tracing flags.
 103                  */
 104                 uthread->t_dtrace_ft = 0;
 105
 106                 /*
 107                  * If we weren't expecting a quick return to the kernel, just kill
 108                  * the process as though it had just executed an unassigned
 109                  * trap instruction.
 110                  */
 111                 if (step == 0) {
 112                         /*
 113                          * APPLE NOTE: We're returning KERN_FAILURE, which causes
 114                          * the generic signal handling code to take over, which will effectively
 115                          * deliver a EXC_BAD_INSTRUCTION to the user process.
 116                          */
 117                         return KERN_FAILURE;
 118                 }
 119
 120                 /*
 121                  * If we hit this trap unrelated to a return probe, we're
 122                  * here to either:
 123                  *
 124                  * 1.  Reset the AST flag, since we deferred a signal
 125                  * until after we logically single-stepped the instruction we
 126                  * copied out.
 127                  *
 128                  * 2.  Just return to normal execution (required for U64).
 129                  */
 130                 if (ret == 0) {
 131                         set_saved_state_pc(regs, npc);
 132                         return KERN_SUCCESS;
 133                 }
 134
 135                 /*
 136                  * We need to wait until after we've called the
 137                  * dtrace_return_probe_ptr function pointer to step the pc.
 138                  */
 139                 rwp = &CPU->cpu_ft_lock;
 140                 lck_rw_lock_shared(rwp);
 141
 142                 if (dtrace_return_probe_ptr != NULL) {
 143                         (void) (*dtrace_return_probe_ptr)(regs);
 144                 }
 145                 lck_rw_unlock_shared(rwp);
 146
 147                 set_saved_state_pc(regs, npc);
 148
 149                 return KERN_SUCCESS;
 150         } else {
 151                 rwp = &CPU->cpu_ft_lock;
 152
 153                 /*
 154                  * The DTrace fasttrap provider uses a trap,
 155                  * FASTTRAP_{ARM,THUMB}_INSTR. We let
 156                  * DTrace take the first crack at handling
 157                  * this trap; if it's not a probe that DTrace knows about,
 158                  * we call into the trap() routine to handle it like a
 159                  * breakpoint placed by a conventional debugger.
 160                  */
 161
 162                 /*
 163                  * APPLE NOTE: I believe the purpose of the reader/writers lock
 164                  * is thus: There are times which dtrace needs to prevent calling
 165                  * dtrace_pid_probe_ptr(). Sun's original impl grabbed a plain
 166                  * mutex here. However, that serialized all probe calls, and
 167                  * destroyed MP behavior. So now they use a RW lock, with probes
 168                  * as readers, and the top level synchronization as a writer.
 169                  */
 170                 lck_rw_lock_shared(rwp);
 171                 if (dtrace_pid_probe_ptr != NULL &&
 172                     (*dtrace_pid_probe_ptr)(regs) == 0) {
 173                         lck_rw_unlock_shared(rwp);
 174                         return KERN_SUCCESS;
 175                 }
 176                 lck_rw_unlock_shared(rwp);
 177
 178                 /*
 179                  * If the instruction that caused the breakpoint trap doesn't
 180                  * look like our trap anymore, it may be that this tracepoint
 181                  * was removed just after the user thread executed it. In
 182                  * that case, return to user land to retry the instuction.
 183                  *
 184                  * Note that the PC points to the instruction that caused the fault.
 185                  */
 186                 if (is_saved_state32(regs)) {
 187                         if (saved_state32(regs)->cpsr & PSR_TF) {
 188                                 uint16_t instr;
 189                                 if (fuword16(saved_state32(regs)->pc, &instr) == 0 && instr != FASTTRAP_THUMB32_INSTR) {
 190                                         return KERN_SUCCESS;
 191                                 }
 192                         } else {
 193                                 uint32_t instr;
 194                                 if (fuword32(saved_state32(regs)->pc, &instr) == 0 && instr != FASTTRAP_ARM32_INSTR) {
 195                                         return KERN_SUCCESS;
 196                                 }
 197                         }
 198                 } else {
 199                         uint32_t instr;
 200                         if (fuword32(saved_state64(regs)->pc, &instr) == 0 && instr != FASTTRAP_ARM64_INSTR) {
 201                                 return KERN_SUCCESS;
 202                         }
 203                 }
 204         }
 205
 206         return KERN_FAILURE;
 207 }
 208
 209 void
 210 dtrace_safe_synchronous_signal(void)
 211 {
 212         /* Not implemented */
 213 }
 214
 215 int
 216 dtrace_safe_defer_signal(void)
 217 {
 218         /* Not implemented */
 219         return 0;
 220 }