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 <stddef.h>
18 #include <cstdarg>
19 #include <cstdio>
20 #include <cstdlib>
21 #include <cstring>
22
23 #include "absl/base/attributes.h"
24 #include "absl/base/config.h"
25 #include "absl/base/internal/atomic_hook.h"
26 #include "absl/base/log_severity.h"
27
28 // We know how to perform low-level writes to stderr in POSIX and Windows. For
29 // these platforms, we define the token ABSL_LOW_LEVEL_WRITE_SUPPORTED.
30 // Much of raw_logging.cc becomes a no-op when we can't output messages,
31 // although a FATAL ABSL_RAW_LOG message will still abort the process.
32
33 // ABSL_HAVE_POSIX_WRITE is defined when the platform provides posix write()
34 // (as from unistd.h)
35 //
36 // This preprocessor token is also defined in raw_io.cc. If you need to copy
37 // this, consider moving both to config.h instead.
38 #if defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || \
39 defined(__Fuchsia__) || defined(__native_client__) || \
40 defined(__EMSCRIPTEN__) || defined(__ASYLO__)
41
42 #include <unistd.h>
43
44 #define ABSL_HAVE_POSIX_WRITE 1
45 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
46 #else
47 #undef ABSL_HAVE_POSIX_WRITE
48 #endif
49
50 // ABSL_HAVE_SYSCALL_WRITE is defined when the platform provides the syscall
51 // syscall(SYS_write, /*int*/ fd, /*char* */ buf, /*size_t*/ len);
52 // for low level operations that want to avoid libc.
53 #if (defined(__linux__) || defined(__FreeBSD__)) && !defined(__ANDROID__)
54 #include <sys/syscall.h>
55 #define ABSL_HAVE_SYSCALL_WRITE 1
56 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
57 #else
58 #undef ABSL_HAVE_SYSCALL_WRITE
59 #endif
60
61 #ifdef _WIN32
62 #include <io.h>
63
64 #define ABSL_HAVE_RAW_IO 1
65 #define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
66 #else
67 #undef ABSL_HAVE_RAW_IO
68 #endif
69
70 // TODO(gfalcon): We want raw-logging to work on as many platforms as possible.
71 // Explicitly #error out when not ABSL_LOW_LEVEL_WRITE_SUPPORTED, except for a
72 // whitelisted set of platforms for which we expect not to be able to raw log.
73
74 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES static absl::base_internal::AtomicHook<
75 absl::raw_logging_internal::LogPrefixHook>
76 log_prefix_hook;
77 ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES static absl::base_internal::AtomicHook<
78 absl::raw_logging_internal::AbortHook>
79 abort_hook;
80
81 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
82 static const char kTruncated[] = " ... (message truncated)\n";
83
84 // sprintf the format to the buffer, adjusting *buf and *size to reflect the
85 // consumed bytes, and return whether the message fit without truncation. If
86 // truncation occurred, if possible leave room in the buffer for the message
87 // kTruncated[].
88 inline static bool VADoRawLog(char** buf, int* size, const char* format,
89 va_list ap) ABSL_PRINTF_ATTRIBUTE(3, 0);
VADoRawLog(char ** buf,int * size,const char * format,va_list ap)90 inline static bool VADoRawLog(char** buf, int* size,
91 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 static constexpr int kLogBufSize = 3000;
109
110 namespace {
111
112 // CAVEAT: vsnprintf called from *DoRawLog below has some (exotic) code paths
113 // that invoke malloc() and getenv() that might acquire some locks.
114
115 // Helper for RawLog below.
116 // *DoRawLog writes to *buf of *size and move them past the written portion.
117 // It returns true iff there was no overflow or error.
118 bool DoRawLog(char** buf, int* size, const char* format, ...)
119 ABSL_PRINTF_ATTRIBUTE(3, 4);
DoRawLog(char ** buf,int * size,const char * format,...)120 bool DoRawLog(char** buf, int* size, const char* format, ...) {
121 va_list ap;
122 va_start(ap, format);
123 int n = vsnprintf(*buf, *size, format, ap);
124 va_end(ap);
125 if (n < 0 || n > *size) return false;
126 *size -= n;
127 *buf += n;
128 return true;
129 }
130
131 void RawLogVA(absl::LogSeverity severity, const char* file, int line,
132 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)133 void RawLogVA(absl::LogSeverity severity, const char* file, int line,
134 const char* format, va_list ap) {
135 char buffer[kLogBufSize];
136 char* buf = buffer;
137 int size = sizeof(buffer);
138 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
139 bool enabled = true;
140 #else
141 bool enabled = false;
142 #endif
143
144 #ifdef ABSL_MIN_LOG_LEVEL
145 if (severity < static_cast<absl::LogSeverity>(ABSL_MIN_LOG_LEVEL) &&
146 severity < absl::LogSeverity::kFatal) {
147 enabled = false;
148 }
149 #endif
150
151 auto log_prefix_hook_ptr = log_prefix_hook.Load();
152 if (log_prefix_hook_ptr) {
153 enabled = log_prefix_hook_ptr(severity, file, line, &buf, &size);
154 } else {
155 if (enabled) {
156 DoRawLog(&buf, &size, "[%s : %d] RAW: ", file, line);
157 }
158 }
159 const char* const prefix_end = buf;
160
161 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
162 if (enabled) {
163 bool no_chop = VADoRawLog(&buf, &size, format, ap);
164 if (no_chop) {
165 DoRawLog(&buf, &size, "\n");
166 } else {
167 DoRawLog(&buf, &size, "%s", kTruncated);
168 }
169 absl::raw_logging_internal::SafeWriteToStderr(buffer, strlen(buffer));
170 }
171 #else
172 static_cast<void>(format);
173 static_cast<void>(ap);
174 #endif
175
176 // Abort the process after logging a FATAL message, even if the output itself
177 // was suppressed.
178 if (severity == absl::LogSeverity::kFatal) {
179 abort_hook(file, line, buffer, prefix_end, buffer + kLogBufSize);
180 abort();
181 }
182 }
183
184 } // namespace
185
186 namespace absl {
187 ABSL_NAMESPACE_BEGIN
188 namespace raw_logging_internal {
SafeWriteToStderr(const char * s,size_t len)189 void SafeWriteToStderr(const char *s, size_t len) {
190 #if defined(ABSL_HAVE_SYSCALL_WRITE)
191 syscall(SYS_write, STDERR_FILENO, s, len);
192 #elif defined(ABSL_HAVE_POSIX_WRITE)
193 write(STDERR_FILENO, s, len);
194 #elif defined(ABSL_HAVE_RAW_IO)
195 _write(/* stderr */ 2, s, len);
196 #else
197 // stderr logging unsupported on this platform
198 (void) s;
199 (void) len;
200 #endif
201 }
202
203 void RawLog(absl::LogSeverity severity, const char* file, int line,
204 const char* format, ...) ABSL_PRINTF_ATTRIBUTE(4, 5);
RawLog(absl::LogSeverity severity,const char * file,int line,const char * format,...)205 void RawLog(absl::LogSeverity severity, const char* file, int line,
206 const char* format, ...) {
207 va_list ap;
208 va_start(ap, format);
209 RawLogVA(severity, file, line, format, ap);
210 va_end(ap);
211 }
212
213 // Non-formatting version of RawLog().
214 //
215 // TODO(gfalcon): When string_view no longer depends on base, change this
216 // interface to take its message as a string_view instead.
DefaultInternalLog(absl::LogSeverity severity,const char * file,int line,const std::string & message)217 static void DefaultInternalLog(absl::LogSeverity severity, const char* file,
218 int line, const std::string& message) {
219 RawLog(severity, file, line, "%s", message.c_str());
220 }
221
RawLoggingFullySupported()222 bool RawLoggingFullySupported() {
223 #ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
224 return true;
225 #else // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
226 return false;
227 #endif // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
228 }
229
230 ABSL_DLL ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
231 absl::base_internal::AtomicHook<InternalLogFunction>
232 internal_log_function(DefaultInternalLog);
233
RegisterInternalLogFunction(InternalLogFunction func)234 void RegisterInternalLogFunction(InternalLogFunction func) {
235 internal_log_function.Store(func);
236 }
237
238 } // namespace raw_logging_internal
239 ABSL_NAMESPACE_END
240 } // namespace absl
241