1 // Copyright 2017 The Abseil Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include "absl/base/internal/raw_logging.h"
16
17 #include <cstdarg>
18 #include <cstddef>
19 #include <cstdio>
20 #include <cstdlib>
21 #include <cstring>
22 #include <string>
23
24 #ifdef __EMSCRIPTEN__
25 #include <emscripten/console.h>
26 #endif
27
28 #include "absl/base/attributes.h"
29 #include "absl/base/config.h"
30 #include "absl/base/internal/atomic_hook.h"
31 #include "absl/base/internal/errno_saver.h"
32 #include "absl/base/log_severity.h"
33
34 // We know how to perform low-level writes to stderr in POSIX and Windows. For
35 // these platforms, we define the token ABSL_LOW_LEVEL_WRITE_SUPPORTED.
36 // Much of raw_logging.cc becomes a no-op when we can't output messages,
37 // although a FATAL ABSL_RAW_LOG message will still abort the process.
38
39 // ABSL_HAVE_POSIX_WRITE is defined when the platform provides posix write()
40 // (as from unistd.h)
41 //
42 // This preprocessor token is also defined in raw_io.cc. If you need to copy
43 // this, consider moving both to config.h instead.
44 #if defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || \
45 defined(__hexagon__) || defined(__Fuchsia__) || \
46 defined(__native_client__) || defined(__OpenBSD__) || \
47 defined(__EMSCRIPTEN__) || defined(__ASYLO__)
48
49 #include <unistd.h>
50
51 #define ABSL_HAVE_POSIX_WRITE 1
52 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
53 #else
54 #undef ABSL_HAVE_POSIX_WRITE
55 #endif
56
57 // ABSL_HAVE_SYSCALL_WRITE is defined when the platform provides the syscall
58 // syscall(SYS_write, /*int*/ fd, /*char* */ buf, /*size_t*/ len);
59 // for low level operations that want to avoid libc.
60 #if (defined(__linux__) || defined(__FreeBSD__)) && !defined(__ANDROID__)
61 #include <sys/syscall.h>
62 #define ABSL_HAVE_SYSCALL_WRITE 1
63 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
64 #else
65 #undef ABSL_HAVE_SYSCALL_WRITE
66 #endif
67
68 #ifdef _WIN32
69 #include <io.h>
70
71 #define ABSL_HAVE_RAW_IO 1
72 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
73 #else
74 #undef ABSL_HAVE_RAW_IO
75 #endif
76
77 namespace absl {
78 ABSL_NAMESPACE_BEGIN
79 namespace raw_log_internal {
80 namespace {
81
82 // TODO(gfalcon): We want raw-logging to work on as many platforms as possible.
83 // Explicitly `#error` out when not `ABSL_LOW_LEVEL_WRITE_SUPPORTED`, except for
84 // a selected set of platforms for which we expect not to be able to raw log.
85
86 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
87 constexpr char kTruncated[] = " ... (message truncated)\n";
88
89 // sprintf the format to the buffer, adjusting *buf and *size to reflect the
90 // consumed bytes, and return whether the message fit without truncation. If
91 // truncation occurred, if possible leave room in the buffer for the message
92 // kTruncated[].
93 bool VADoRawLog(char** buf, int* size, const char* format, va_list ap)
94 ABSL_PRINTF_ATTRIBUTE(3, 0);
VADoRawLog(char ** buf,int * size,const char * format,va_list ap)95 bool VADoRawLog(char** buf, int* size, const char* format, va_list ap) {
96 if (*size < 0) return false;
97 int n = vsnprintf(*buf, static_cast<size_t>(*size), format, ap);
98 bool result = true;
99 if (n < 0 || n > *size) {
100 result = false;
101 if (static_cast<size_t>(*size) > sizeof(kTruncated)) {
102 n = *size - static_cast<int>(sizeof(kTruncated));
103 } else {
104 n = 0; // no room for truncation message
105 }
106 }
107 *size -= n;
108 *buf += n;
109 return result;
110 }
111 #endif // ABSL_LOW_LEVEL_WRITE_SUPPORTED
112
113 constexpr int kLogBufSize = 3000;
114
115 // CAVEAT: vsnprintf called from *DoRawLog below has some (exotic) code paths
116 // that invoke malloc() and getenv() that might acquire some locks.
117
118 // Helper for RawLog below.
119 // *DoRawLog writes to *buf of *size and move them past the written portion.
120 // It returns true iff there was no overflow or error.
121 bool DoRawLog(char** buf, int* size, const char* format, ...)
122 ABSL_PRINTF_ATTRIBUTE(3, 4);
DoRawLog(char ** buf,int * size,const char * format,...)123 bool DoRawLog(char** buf, int* size, const char* format, ...) {
124 if (*size < 0) return false;
125 va_list ap;
126 va_start(ap, format);
127 int n = vsnprintf(*buf, static_cast<size_t>(*size), format, ap);
128 va_end(ap);
129 if (n < 0 || n > *size) return false;
130 *size -= n;
131 *buf += n;
132 return true;
133 }
134
DefaultLogFilterAndPrefix(absl::LogSeverity,const char * file,int line,char ** buf,int * buf_size)135 bool DefaultLogFilterAndPrefix(absl::LogSeverity, const char* file, int line,
136 char** buf, int* buf_size) {
137 DoRawLog(buf, buf_size, "[%s : %d] RAW: ", file, line);
138 return true;
139 }
140
141 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
142 absl::base_internal::AtomicHook<LogFilterAndPrefixHook>
143 log_filter_and_prefix_hook(DefaultLogFilterAndPrefix);
144 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
145 absl::base_internal::AtomicHook<AbortHook> abort_hook;
146
147 void RawLogVA(absl::LogSeverity severity, const char* file, int line,
148 const char* format, va_list ap) ABSL_PRINTF_ATTRIBUTE(4, 0);
RawLogVA(absl::LogSeverity severity,const char * file,int line,const char * format,va_list ap)149 void RawLogVA(absl::LogSeverity severity, const char* file, int line,
150 const char* format, va_list ap) {
151 char buffer[kLogBufSize];
152 char* buf = buffer;
153 int size = sizeof(buffer);
154 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
155 bool enabled = true;
156 #else
157 bool enabled = false;
158 #endif
159
160 #ifdef ABSL_MIN_LOG_LEVEL
161 if (severity < static_cast<absl::LogSeverity>(ABSL_MIN_LOG_LEVEL) &&
162 severity < absl::LogSeverity::kFatal) {
163 enabled = false;
164 }
165 #endif
166
167 enabled = log_filter_and_prefix_hook(severity, file, line, &buf, &size);
168 const char* const prefix_end = buf;
169
170 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
171 if (enabled) {
172 bool no_chop = VADoRawLog(&buf, &size, format, ap);
173 if (no_chop) {
174 DoRawLog(&buf, &size, "\n");
175 } else {
176 DoRawLog(&buf, &size, "%s", kTruncated);
177 }
178 AsyncSignalSafeWriteError(buffer, strlen(buffer));
179 }
180 #else
181 static_cast<void>(format);
182 static_cast<void>(ap);
183 static_cast<void>(enabled);
184 #endif
185
186 // Abort the process after logging a FATAL message, even if the output itself
187 // was suppressed.
188 if (severity == absl::LogSeverity::kFatal) {
189 abort_hook(file, line, buffer, prefix_end, buffer + kLogBufSize);
190 abort();
191 }
192 }
193
194 // Non-formatting version of RawLog().
195 //
196 // TODO(gfalcon): When string_view no longer depends on base, change this
197 // interface to take its message as a string_view instead.
DefaultInternalLog(absl::LogSeverity severity,const char * file,int line,const std::string & message)198 void DefaultInternalLog(absl::LogSeverity severity, const char* file, int line,
199 const std::string& message) {
200 RawLog(severity, file, line, "%.*s", static_cast<int>(message.size()),
201 message.data());
202 }
203
204 } // namespace
205
AsyncSignalSafeWriteError(const char * s,size_t len)206 void AsyncSignalSafeWriteError(const char* s, size_t len) {
207 if (!len) return;
208 absl::base_internal::ErrnoSaver errno_saver;
209 #if defined(__EMSCRIPTEN__)
210 // In WebAssembly, bypass filesystem emulation via fwrite.
211 if (s[len - 1] == '\n') {
212 // Skip a trailing newline character as emscripten_errn adds one itself.
213 len--;
214 }
215 // emscripten_errn was introduced in 3.1.41 but broken in standalone mode
216 // until 3.1.43.
217 #if ABSL_INTERNAL_EMSCRIPTEN_VERSION >= 3001043
218 emscripten_errn(s, len);
219 #else
220 char buf[kLogBufSize];
221 if (len >= kLogBufSize) {
222 len = kLogBufSize - 1;
223 constexpr size_t trunc_len = sizeof(kTruncated) - 2;
224 memcpy(buf + len - trunc_len, kTruncated, trunc_len);
225 buf[len] = '\0';
226 len -= trunc_len;
227 } else {
228 buf[len] = '\0';
229 }
230 memcpy(buf, s, len);
231 _emscripten_err(buf);
232 #endif
233 #elif defined(ABSL_HAVE_SYSCALL_WRITE)
234 // We prefer calling write via `syscall` to minimize the risk of libc doing
235 // something "helpful".
236 syscall(SYS_write, STDERR_FILENO, s, len);
237 #elif defined(ABSL_HAVE_POSIX_WRITE)
238 write(STDERR_FILENO, s, len);
239 #elif defined(ABSL_HAVE_RAW_IO)
240 _write(/* stderr */ 2, s, static_cast<unsigned>(len));
241 #else
242 // stderr logging unsupported on this platform
243 (void)s;
244 (void)len;
245 #endif
246 }
247
RawLog(absl::LogSeverity severity,const char * file,int line,const char * format,...)248 void RawLog(absl::LogSeverity severity, const char* file, int line,
249 const char* format, ...) {
250 va_list ap;
251 va_start(ap, format);
252 RawLogVA(severity, file, line, format, ap);
253 va_end(ap);
254 }
255
RawLoggingFullySupported()256 bool RawLoggingFullySupported() {
257 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
258 return true;
259 #else // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
260 return false;
261 #endif // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
262 }
263
264 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES ABSL_DLL
265 absl::base_internal::AtomicHook<InternalLogFunction>
266 internal_log_function(DefaultInternalLog);
267
RegisterLogFilterAndPrefixHook(LogFilterAndPrefixHook func)268 void RegisterLogFilterAndPrefixHook(LogFilterAndPrefixHook func) {
269 log_filter_and_prefix_hook.Store(func);
270 }
271
RegisterAbortHook(AbortHook func)272 void RegisterAbortHook(AbortHook func) { abort_hook.Store(func); }
273
RegisterInternalLogFunction(InternalLogFunction func)274 void RegisterInternalLogFunction(InternalLogFunction func) {
275 internal_log_function.Store(func);
276 }
277
278 } // namespace raw_log_internal
279 ABSL_NAMESPACE_END
280 } // namespace absl
281