1#include "cpuid.h"
2#include "sanitizer_common/sanitizer_common.h"
3#if !SANITIZER_FUCHSIA
4#include "sanitizer_common/sanitizer_posix.h"
5#endif
6#include "xray_defs.h"
7#include "xray_interface_internal.h"
8
9#if SANITIZER_FREEBSD || SANITIZER_NETBSD || SANITIZER_APPLE
10#include <sys/types.h>
11#include <sys/sysctl.h>
12#elif SANITIZER_FUCHSIA
13#include <zircon/syscalls.h>
14#endif
15
16#include <atomic>
17#include <cstdint>
18#include <errno.h>
19#include <fcntl.h>
20#include <iterator>
21#include <limits>
22#include <tuple>
23#include <unistd.h>
24
25namespace __xray {
26
27#if SANITIZER_LINUX
28static std::pair<ssize_t, bool>
29retryingReadSome(int Fd, char *Begin, char *End) XRAY_NEVER_INSTRUMENT {
30 auto BytesToRead = std::distance(first: Begin, last: End);
31 ssize_t BytesRead;
32 ssize_t TotalBytesRead = 0;
33 while (BytesToRead && (BytesRead = read(fd: Fd, buf: Begin, nbytes: BytesToRead))) {
34 if (BytesRead == -1) {
35 if (errno == EINTR)
36 continue;
37 Report(format: "Read error; errno = %d\n", errno);
38 return std::make_pair(x&: TotalBytesRead, y: false);
39 }
40
41 TotalBytesRead += BytesRead;
42 BytesToRead -= BytesRead;
43 Begin += BytesRead;
44 }
45 return std::make_pair(x&: TotalBytesRead, y: true);
46}
47
48static bool readValueFromFile(const char *Filename,
49 long long *Value) XRAY_NEVER_INSTRUMENT {
50 int Fd = open(file: Filename, O_RDONLY | O_CLOEXEC);
51 if (Fd == -1)
52 return false;
53 static constexpr size_t BufSize = 256;
54 char Line[BufSize] = {};
55 ssize_t BytesRead;
56 bool Success;
57 std::tie(args&: BytesRead, args&: Success) = retryingReadSome(Fd, Begin: Line, End: Line + BufSize);
58 close(fd: Fd);
59 if (!Success)
60 return false;
61 const char *End = nullptr;
62 long long Tmp = internal_simple_strtoll(nptr: Line, endptr: &End, base: 10);
63 bool Result = false;
64 if (Line[0] != '\0' && (*End == '\n' || *End == '\0')) {
65 *Value = Tmp;
66 Result = true;
67 }
68 return Result;
69}
70
71uint64_t getTSCFrequency() XRAY_NEVER_INSTRUMENT {
72 long long TSCFrequency = -1;
73 if (readValueFromFile(Filename: "/sys/devices/system/cpu/cpu0/tsc_freq_khz",
74 Value: &TSCFrequency)) {
75 TSCFrequency *= 1000;
76 } else if (readValueFromFile(
77 Filename: "/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq",
78 Value: &TSCFrequency)) {
79 TSCFrequency *= 1000;
80 } else {
81 Report(format: "Unable to determine CPU frequency for TSC accounting.\n");
82 }
83 return TSCFrequency == -1 ? 0 : static_cast<uint64_t>(TSCFrequency);
84}
85#elif SANITIZER_FREEBSD || SANITIZER_NETBSD || SANITIZER_APPLE
86uint64_t getTSCFrequency() XRAY_NEVER_INSTRUMENT {
87 long long TSCFrequency = -1;
88 size_t tscfreqsz = sizeof(TSCFrequency);
89#if SANITIZER_APPLE
90 if (internal_sysctlbyname("machdep.tsc.frequency", &TSCFrequency,
91 &tscfreqsz, NULL, 0) != -1) {
92
93#else
94 if (internal_sysctlbyname("machdep.tsc_freq", &TSCFrequency, &tscfreqsz,
95 NULL, 0) != -1) {
96#endif
97 return static_cast<uint64_t>(TSCFrequency);
98 } else {
99 Report("Unable to determine CPU frequency for TSC accounting.\n");
100 }
101
102 return 0;
103}
104#elif !SANITIZER_FUCHSIA
105uint64_t getTSCFrequency() XRAY_NEVER_INSTRUMENT {
106 /* Not supported */
107 return 0;
108}
109#endif
110
111static constexpr uint8_t CallOpCode = 0xe8;
112static constexpr uint16_t MovR10Seq = 0xba41;
113static constexpr uint16_t Jmp9Seq = 0x09eb;
114static constexpr uint16_t Jmp20Seq = 0x14eb;
115static constexpr uint16_t Jmp15Seq = 0x0feb;
116static constexpr uint8_t JmpOpCode = 0xe9;
117static constexpr uint8_t RetOpCode = 0xc3;
118static constexpr uint16_t NopwSeq = 0x9066;
119
120static constexpr int64_t MinOffset{std::numeric_limits<int32_t>::min()};
121static constexpr int64_t MaxOffset{std::numeric_limits<int32_t>::max()};
122
123bool patchFunctionEntry(const bool Enable, const uint32_t FuncId,
124 const XRaySledEntry &Sled,
125 void (*Trampoline)()) XRAY_NEVER_INSTRUMENT {
126 // Here we do the dance of replacing the following sled:
127 //
128 // xray_sled_n:
129 // jmp +9
130 // <9 byte nop>
131 //
132 // With the following:
133 //
134 // mov r10d, <function id>
135 // call <relative 32bit offset to entry trampoline>
136 //
137 // We need to do this in the following order:
138 //
139 // 1. Put the function id first, 2 bytes from the start of the sled (just
140 // after the 2-byte jmp instruction).
141 // 2. Put the call opcode 6 bytes from the start of the sled.
142 // 3. Put the relative offset 7 bytes from the start of the sled.
143 // 4. Do an atomic write over the jmp instruction for the "mov r10d"
144 // opcode and first operand.
145 //
146 // Prerequisite is to compute the relative offset to the trampoline's address.
147 const uint64_t Address = Sled.address();
148 int64_t TrampolineOffset = reinterpret_cast<int64_t>(Trampoline) -
149 (static_cast<int64_t>(Address) + 11);
150 if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) {
151 Report(format: "XRay Entry trampoline (%p) too far from sled (%p)\n",
152 reinterpret_cast<void *>(Trampoline),
153 reinterpret_cast<void *>(Address));
154 return false;
155 }
156 if (Enable) {
157 *reinterpret_cast<uint32_t *>(Address + 2) = FuncId;
158 *reinterpret_cast<uint8_t *>(Address + 6) = CallOpCode;
159 *reinterpret_cast<uint32_t *>(Address + 7) = TrampolineOffset;
160 std::atomic_store_explicit(
161 a: reinterpret_cast<std::atomic<uint16_t> *>(Address), i: MovR10Seq,
162 m: std::memory_order_release);
163 } else {
164 std::atomic_store_explicit(
165 a: reinterpret_cast<std::atomic<uint16_t> *>(Address), i: Jmp9Seq,
166 m: std::memory_order_release);
167 // FIXME: Write out the nops still?
168 }
169 return true;
170}
171
172bool patchFunctionExit(const bool Enable, const uint32_t FuncId,
173 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
174 // Here we do the dance of replacing the following sled:
175 //
176 // xray_sled_n:
177 // ret
178 // <10 byte nop>
179 //
180 // With the following:
181 //
182 // mov r10d, <function id>
183 // jmp <relative 32bit offset to exit trampoline>
184 //
185 // 1. Put the function id first, 2 bytes from the start of the sled (just
186 // after the 1-byte ret instruction).
187 // 2. Put the jmp opcode 6 bytes from the start of the sled.
188 // 3. Put the relative offset 7 bytes from the start of the sled.
189 // 4. Do an atomic write over the jmp instruction for the "mov r10d"
190 // opcode and first operand.
191 //
192 // Prerequisite is to compute the relative offset fo the
193 // __xray_FunctionExit function's address.
194 const uint64_t Address = Sled.address();
195 int64_t TrampolineOffset = reinterpret_cast<int64_t>(__xray_FunctionExit) -
196 (static_cast<int64_t>(Address) + 11);
197 if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) {
198 Report(format: "XRay Exit trampoline (%p) too far from sled (%p)\n",
199 reinterpret_cast<void *>(__xray_FunctionExit),
200 reinterpret_cast<void *>(Address));
201 return false;
202 }
203 if (Enable) {
204 *reinterpret_cast<uint32_t *>(Address + 2) = FuncId;
205 *reinterpret_cast<uint8_t *>(Address + 6) = JmpOpCode;
206 *reinterpret_cast<uint32_t *>(Address + 7) = TrampolineOffset;
207 std::atomic_store_explicit(
208 a: reinterpret_cast<std::atomic<uint16_t> *>(Address), i: MovR10Seq,
209 m: std::memory_order_release);
210 } else {
211 std::atomic_store_explicit(
212 a: reinterpret_cast<std::atomic<uint8_t> *>(Address), i: RetOpCode,
213 m: std::memory_order_release);
214 // FIXME: Write out the nops still?
215 }
216 return true;
217}
218
219bool patchFunctionTailExit(const bool Enable, const uint32_t FuncId,
220 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
221 // Here we do the dance of replacing the tail call sled with a similar
222 // sequence as the entry sled, but calls the tail exit sled instead.
223 const uint64_t Address = Sled.address();
224 int64_t TrampolineOffset =
225 reinterpret_cast<int64_t>(__xray_FunctionTailExit) -
226 (static_cast<int64_t>(Address) + 11);
227 if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) {
228 Report(format: "XRay Tail Exit trampoline (%p) too far from sled (%p)\n",
229 reinterpret_cast<void *>(__xray_FunctionTailExit),
230 reinterpret_cast<void *>(Address));
231 return false;
232 }
233 if (Enable) {
234 *reinterpret_cast<uint32_t *>(Address + 2) = FuncId;
235 *reinterpret_cast<uint8_t *>(Address + 6) = CallOpCode;
236 *reinterpret_cast<uint32_t *>(Address + 7) = TrampolineOffset;
237 std::atomic_store_explicit(
238 a: reinterpret_cast<std::atomic<uint16_t> *>(Address), i: MovR10Seq,
239 m: std::memory_order_release);
240 } else {
241 std::atomic_store_explicit(
242 a: reinterpret_cast<std::atomic<uint16_t> *>(Address), i: Jmp9Seq,
243 m: std::memory_order_release);
244 // FIXME: Write out the nops still?
245 }
246 return true;
247}
248
249bool patchCustomEvent(const bool Enable, const uint32_t FuncId,
250 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
251 // Here we do the dance of replacing the following sled:
252 //
253 // xray_sled_n:
254 // jmp +15 // 2 bytes
255 // ...
256 //
257 // With the following:
258 //
259 // nopw // 2 bytes*
260 // ...
261 //
262 //
263 // The "unpatch" should just turn the 'nopw' back to a 'jmp +15'.
264 const uint64_t Address = Sled.address();
265 if (Enable) {
266 std::atomic_store_explicit(
267 a: reinterpret_cast<std::atomic<uint16_t> *>(Address), i: NopwSeq,
268 m: std::memory_order_release);
269 } else {
270 std::atomic_store_explicit(
271 a: reinterpret_cast<std::atomic<uint16_t> *>(Address), i: Jmp15Seq,
272 m: std::memory_order_release);
273 }
274 return false;
275}
276
277bool patchTypedEvent(const bool Enable, const uint32_t FuncId,
278 const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
279 // Here we do the dance of replacing the following sled:
280 //
281 // xray_sled_n:
282 // jmp +20 // 2 byte instruction
283 // ...
284 //
285 // With the following:
286 //
287 // nopw // 2 bytes
288 // ...
289 //
290 //
291 // The "unpatch" should just turn the 'nopw' back to a 'jmp +20'.
292 // The 20 byte sled stashes three argument registers, calls the trampoline,
293 // unstashes the registers and returns. If the arguments are already in
294 // the correct registers, the stashing and unstashing become equivalently
295 // sized nops.
296 const uint64_t Address = Sled.address();
297 if (Enable) {
298 std::atomic_store_explicit(
299 a: reinterpret_cast<std::atomic<uint16_t> *>(Address), i: NopwSeq,
300 m: std::memory_order_release);
301 } else {
302 std::atomic_store_explicit(
303 a: reinterpret_cast<std::atomic<uint16_t> *>(Address), i: Jmp20Seq,
304 m: std::memory_order_release);
305 }
306 return false;
307}
308
309#if !SANITIZER_FUCHSIA
310// We determine whether the CPU we're running on has the correct features we
311// need. In x86_64 this will be rdtscp support.
312bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT {
313 unsigned int EAX, EBX, ECX, EDX;
314
315 // We check whether rdtscp support is enabled. According to the x86_64 manual,
316 // level should be set at 0x80000001, and we should have a look at bit 27 in
317 // EDX. That's 0x8000000 (or 1u << 27).
318 __asm__ __volatile__("cpuid" : "=a"(EAX), "=b"(EBX), "=c"(ECX), "=d"(EDX)
319 : "0"(0x80000001));
320 if (!(EDX & (1u << 27))) {
321 Report(format: "Missing rdtscp support.\n");
322 return false;
323 }
324 // Also check whether we can determine the CPU frequency, since if we cannot,
325 // we should use the emulated TSC instead.
326 if (!getTSCFrequency()) {
327 Report(format: "Unable to determine CPU frequency.\n");
328 return false;
329 }
330 return true;
331}
332#endif
333
334} // namespace __xray
335