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 #include "absl/base/attributes.h"
25 #include "absl/base/config.h"
26 #include "absl/base/internal/atomic_hook.h"
27 #include "absl/base/internal/errno_saver.h"
28 #include "absl/base/log_severity.h"
29
30 // We know how to perform low-level writes to stderr in POSIX and Windows. For
31 // these platforms, we define the token ABSL_LOW_LEVEL_WRITE_SUPPORTED.
32 // Much of raw_logging.cc becomes a no-op when we can't output messages,
33 // although a FATAL ABSL_RAW_LOG message will still abort the process.
34
35 // ABSL_HAVE_POSIX_WRITE is defined when the platform provides posix write()
36 // (as from unistd.h)
37 //
38 // This preprocessor token is also defined in raw_io.cc. If you need to copy
39 // this, consider moving both to config.h instead.
40 #if defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || \
41 defined(__Fuchsia__) || defined(__native_client__) || \
42 defined(__OpenBSD__) || defined(__EMSCRIPTEN__) || defined(__ASYLO__)
43
44 #include <unistd.h>
45
46 #define ABSL_HAVE_POSIX_WRITE 1
47 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
48 #else
49 #undef ABSL_HAVE_POSIX_WRITE
50 #endif
51
52 // ABSL_HAVE_SYSCALL_WRITE is defined when the platform provides the syscall
53 // syscall(SYS_write, /*int*/ fd, /*char* */ buf, /*size_t*/ len);
54 // for low level operations that want to avoid libc.
55 #if (defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__)) && \
56 !defined(__ANDROID__)
57 #include <sys/syscall.h>
58 #define ABSL_HAVE_SYSCALL_WRITE 1
59 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
60 #else
61 #undef ABSL_HAVE_SYSCALL_WRITE
62 #endif
63
64 #ifdef _WIN32
65 #include <io.h>
66
67 #define ABSL_HAVE_RAW_IO 1
68 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
69 #else
70 #undef ABSL_HAVE_RAW_IO
71 #endif
72
73 namespace absl {
74 ABSL_NAMESPACE_BEGIN
75 namespace raw_logging_internal {
76 namespace {
77
78 // TODO(gfalcon): We want raw-logging to work on as many platforms as possible.
79 // Explicitly `#error` out when not `ABSL_LOW_LEVEL_WRITE_SUPPORTED`, except for
80 // a selected set of platforms for which we expect not to be able to raw log.
81
82 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
83 constexpr char kTruncated[] = " ... (message truncated)\n";
84
85 // sprintf the format to the buffer, adjusting *buf and *size to reflect the
86 // consumed bytes, and return whether the message fit without truncation. If
87 // truncation occurred, if possible leave room in the buffer for the message
88 // kTruncated[].
89 bool VADoRawLog(char** buf, int* size, const char* format, va_list ap)
90 ABSL_PRINTF_ATTRIBUTE(3, 0);
VADoRawLog(char ** buf,int * size,const char * format,va_list ap)91 bool VADoRawLog(char** buf, int* size, const char* format, va_list ap) {
92 int n = vsnprintf(*buf, *size, format, ap);
93 bool result = true;
94 if (n < 0 || n > *size) {
95 result = false;
96 if (static_cast<size_t>(*size) > sizeof(kTruncated)) {
97 n = *size - sizeof(kTruncated); // room for truncation message
98 } else {
99 n = 0; // no room for truncation message
100 }
101 }
102 *size -= n;
103 *buf += n;
104 return result;
105 }
106 #endif // ABSL_LOW_LEVEL_WRITE_SUPPORTED
107
108 constexpr int kLogBufSize = 3000;
109
110 // CAVEAT: vsnprintf called from *DoRawLog below has some (exotic) code paths
111 // that invoke malloc() and getenv() that might acquire some locks.
112
113 // Helper for RawLog below.
114 // *DoRawLog writes to *buf of *size and move them past the written portion.
115 // It returns true iff there was no overflow or error.
116 bool DoRawLog(char** buf, int* size, const char* format, ...)
117 ABSL_PRINTF_ATTRIBUTE(3, 4);
DoRawLog(char ** buf,int * size,const char * format,...)118 bool DoRawLog(char** buf, int* size, const char* format, ...) {
119 va_list ap;
120 va_start(ap, format);
121 int n = vsnprintf(*buf, *size, format, ap);
122 va_end(ap);
123 if (n < 0 || n > *size) return false;
124 *size -= n;
125 *buf += n;
126 return true;
127 }
128
DefaultLogFilterAndPrefix(absl::LogSeverity,const char * file,int line,char ** buf,int * buf_size)129 bool DefaultLogFilterAndPrefix(absl::LogSeverity, const char* file, int line,
130 char** buf, int* buf_size) {
131 DoRawLog(buf, buf_size, "[%s : %d] RAW: ", file, line);
132 return true;
133 }
134
135 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
136 absl::base_internal::AtomicHook<LogFilterAndPrefixHook>
137 log_filter_and_prefix_hook(DefaultLogFilterAndPrefix);
138 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
139 absl::base_internal::AtomicHook<AbortHook> abort_hook;
140
141 void RawLogVA(absl::LogSeverity severity, const char* file, int line,
142 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)143 void RawLogVA(absl::LogSeverity severity, const char* file, int line,
144 const char* format, va_list ap) {
145 char buffer[kLogBufSize];
146 char* buf = buffer;
147 int size = sizeof(buffer);
148 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
149 bool enabled = true;
150 #else
151 bool enabled = false;
152 #endif
153
154 #ifdef ABSL_MIN_LOG_LEVEL
155 if (severity < static_cast<absl::LogSeverity>(ABSL_MIN_LOG_LEVEL) &&
156 severity < absl::LogSeverity::kFatal) {
157 enabled = false;
158 }
159 #endif
160
161 enabled = log_filter_and_prefix_hook(severity, file, line, &buf, &size);
162 const char* const prefix_end = buf;
163
164 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
165 if (enabled) {
166 bool no_chop = VADoRawLog(&buf, &size, format, ap);
167 if (no_chop) {
168 DoRawLog(&buf, &size, "\n");
169 } else {
170 DoRawLog(&buf, &size, "%s", kTruncated);
171 }
172 AsyncSignalSafeWriteToStderr(buffer, strlen(buffer));
173 }
174 #else
175 static_cast<void>(format);
176 static_cast<void>(ap);
177 static_cast<void>(enabled);
178 #endif
179
180 // Abort the process after logging a FATAL message, even if the output itself
181 // was suppressed.
182 if (severity == absl::LogSeverity::kFatal) {
183 abort_hook(file, line, buffer, prefix_end, buffer + kLogBufSize);
184 abort();
185 }
186 }
187
188 // Non-formatting version of RawLog().
189 //
190 // TODO(gfalcon): When string_view no longer depends on base, change this
191 // interface to take its message as a string_view instead.
DefaultInternalLog(absl::LogSeverity severity,const char * file,int line,const std::string & message)192 void DefaultInternalLog(absl::LogSeverity severity, const char* file, int line,
193 const std::string& message) {
194 RawLog(severity, file, line, "%.*s", static_cast<int>(message.size()),
195 message.data());
196 }
197
198 } // namespace
199
AsyncSignalSafeWriteToStderr(const char * s,size_t len)200 void AsyncSignalSafeWriteToStderr(const char* s, size_t len) {
201 absl::base_internal::ErrnoSaver errno_saver;
202 #if defined(ABSL_HAVE_SYSCALL_WRITE)
203 // We prefer calling write via `syscall` to minimize the risk of libc doing
204 // something "helpful".
205 syscall(SYS_write, STDERR_FILENO, s, len);
206 #elif defined(ABSL_HAVE_POSIX_WRITE)
207 write(STDERR_FILENO, s, len);
208 #elif defined(ABSL_HAVE_RAW_IO)
209 _write(/* stderr */ 2, s, len);
210 #else
211 // stderr logging unsupported on this platform
212 (void) s;
213 (void) len;
214 #endif
215 }
216
RawLog(absl::LogSeverity severity,const char * file,int line,const char * format,...)217 void RawLog(absl::LogSeverity severity, const char* file, int line,
218 const char* format, ...) {
219 va_list ap;
220 va_start(ap, format);
221 RawLogVA(severity, file, line, format, ap);
222 va_end(ap);
223 }
224
RawLoggingFullySupported()225 bool RawLoggingFullySupported() {
226 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
227 return true;
228 #else // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
229 return false;
230 #endif // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
231 }
232
233 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES ABSL_DLL
234 absl::base_internal::AtomicHook<InternalLogFunction>
235 internal_log_function(DefaultInternalLog);
236
RegisterLogFilterAndPrefixHook(LogFilterAndPrefixHook func)237 void RegisterLogFilterAndPrefixHook(LogFilterAndPrefixHook func) {
238 log_filter_and_prefix_hook.Store(func);
239 }
240
RegisterAbortHook(AbortHook func)241 void RegisterAbortHook(AbortHook func) { abort_hook.Store(func); }
242
RegisterInternalLogFunction(InternalLogFunction func)243 void RegisterInternalLogFunction(InternalLogFunction func) {
244 internal_log_function.Store(func);
245 }
246
247 } // namespace raw_logging_internal
248 ABSL_NAMESPACE_END
249 } // namespace absl
250