libsyscall/wrappers/kdebug_trace.c

   1 /*
   2  * Copyright (c) 2014 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 #include <stdint.h>
  25 #include <stdbool.h>
  26 #include <stdlib.h>
  27 #include <stdatomic.h>
  28 #include <machine/cpu_capabilities.h>
  29 #include <sys/kdebug.h>
  30 #include <sys/kdebug_signpost.h>
  31 #include <sys/errno.h>
  32 #include <sys/param.h>
  33 #include <sys/sysctl.h>
  34 #include <mach/mach.h>
  35 #include <mach/mach_vm.h>
  36
  37 extern int __kdebug_typefilter(void** addr, size_t* size);
  38 extern int __kdebug_trace64(uint32_t code, uint64_t arg1, uint64_t arg2,
  39         uint64_t arg3, uint64_t arg4);
  40 extern uint64_t __kdebug_trace_string(uint32_t debugid, uint64_t str_id,
  41         const char *str);
  42
  43 static int kdebug_signpost_internal(uint32_t debugid, uintptr_t arg1,
  44         uintptr_t arg2, uintptr_t arg3, uintptr_t arg4);
  45
  46 /*
  47  * GENERAL API DESIGN NOTE!
  48  *
  49  * Trace API's are expected to avoid performing checks until tracing has
  50  * been enabled. This includes checks that might cause error codes to be
  51  * returned.
  52  *
  53  * Trace invocations via wrapper and syscall must have the same behavior.
  54  *
  55  * Note that the userspace API is chosing to optimize fastpath, non-error
  56  * performance by eliding validation of each debugid. This means that error
  57  * cases which could have been caught in userspace will make a syscall
  58  * before returning with the correct error code. This tradeoff in performance
  59  * is intentional.
  60  */
  61
  62 void *
  63 kdebug_typefilter(void)
  64 {
  65         static void* typefilter;
  66
  67         /* We expect kdebug_typefilter_bitmap to be valid (the if is not executed) */
  68         if (__builtin_expect(!typefilter, 0)) {
  69                 // Map the typefilter if it can be mapped.
  70                 void* ptr = NULL;
  71                 size_t ptr_size = 0;
  72
  73                 if (__kdebug_typefilter(&ptr, &ptr_size) == 0) {
  74                         void* old_value = NULL;
  75                         if (ptr && !atomic_compare_exchange_strong((void* _Atomic volatile *)&typefilter, &old_value, ptr)) {
  76                                 mach_vm_deallocate(mach_task_self(), (mach_vm_offset_t)ptr, KDBG_TYPEFILTER_BITMAP_SIZE);
  77                         }
  78                 }
  79         }
  80
  81         return typefilter;
  82 }
  83
  84 bool
  85 kdebug_is_enabled(uint32_t debugid)
  86 {
  87         uint32_t state = *((volatile uint32_t *)(uintptr_t)(_COMM_PAGE_KDEBUG_ENABLE));
  88
  89         if (state == 0) {
  90                 return FALSE;
  91         }
  92
  93         if ((state & KDEBUG_COMMPAGE_ENABLE_TYPEFILTER) > 0) {
  94                 /*
  95                  * Typefilter rules...
  96                  *
  97                  * If no typefilter is available (even if due to error),
  98                  * debugids are allowed.
  99                  *
 100                  * The typefilter will always allow DBG_TRACE; this is a kernel
 101                  * invariant. There is no need for an explicit check here.
 102                  *
 103                  * NOTE: The typefilter will always allow DBG_TRACE, but
 104                  * it is not legal to inject DBG_TRACE via kdebug_trace.
 105                  * Attempts to do so will not be detected here, but will be
 106                  * detected in the kernel, and an error will be returned. Per
 107                  * the API design note at the top of this file, this is a
 108                  * deliberate choice.
 109                  */
 110                 uint8_t* typefilter = kdebug_typefilter();
 111                 if (typefilter && isset(typefilter, KDBG_EXTRACT_CSC(debugid)) == 0) {
 112                         return FALSE;
 113                 }
 114         }
 115
 116         return TRUE;
 117 }
 118
 119 int
 120 kdebug_trace(uint32_t debugid, uint64_t arg1, uint64_t arg2, uint64_t arg3,
 121              uint64_t arg4)
 122 {
 123         if (!kdebug_is_enabled(debugid)) {
 124                 return 0;
 125         }
 126
 127         return __kdebug_trace64(debugid, arg1, arg2, arg3, arg4);
 128 }
 129
 130 uint64_t
 131 kdebug_trace_string(uint32_t debugid, uint64_t str_id, const char *str)
 132 {
 133         if (!kdebug_is_enabled(debugid)) {
 134                 return 0;
 135         }
 136
 137         if ((int64_t)str_id == -1) {
 138                 errno = EINVAL;
 139                 return (uint64_t)-1;
 140         }
 141
 142         if (str_id == 0 && str == NULL) {
 143                 errno = EINVAL;
 144                 return (uint64_t)-1;
 145         }
 146
 147         return __kdebug_trace_string(debugid, str_id, str);
 148 }
 149
 150 static int
 151 kdebug_signpost_internal(uint32_t debugid, uintptr_t arg1, uintptr_t arg2, uintptr_t arg3, uintptr_t arg4)
 152 {
 153         if (KDBG_EXTRACT_CSC(debugid) != 0) {
 154                 errno = EINVAL;
 155                 return -1;
 156         }
 157
 158         debugid |= APPSDBG_CODE(DBG_APP_SIGNPOST, 0);
 159
 160         return kdebug_trace(debugid, arg1, arg2, arg3, arg4);
 161 }
 162
 163 int
 164 kdebug_signpost(uint32_t code, uintptr_t arg1, uintptr_t arg2, uintptr_t arg3, uintptr_t arg4)
 165 {
 166         return kdebug_signpost_internal(code << KDBG_CODE_OFFSET, arg1, arg2, arg3, arg4);
 167 }
 168
 169 int
 170 kdebug_signpost_start(uint32_t code, uintptr_t arg1, uintptr_t arg2, uintptr_t arg3, uintptr_t arg4)
 171 {
 172         return kdebug_signpost_internal((code << KDBG_CODE_OFFSET) | DBG_FUNC_START, arg1, arg2, arg3, arg4);
 173 }
 174
 175 int
 176 kdebug_signpost_end(uint32_t code, uintptr_t arg1, uintptr_t arg2, uintptr_t arg3, uintptr_t arg4)
 177 {
 178         return kdebug_signpost_internal((code << KDBG_CODE_OFFSET) | DBG_FUNC_END, arg1, arg2, arg3, arg4);
 179 }