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__)
41#include <unistd.h>
42
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
74ABSL_CONST_INIT static absl::base_internal::AtomicHook<
75 absl::raw_logging_internal::LogPrefixHook> log_prefix_hook;
76ABSL_CONST_INIT static absl::base_internal::AtomicHook<
77 absl::raw_logging_internal::AbortHook> abort_hook;
78
79#ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
80static const char kTruncated[] = " ... (message truncated)\n";
81
82// sprintf the format to the buffer, adjusting *buf and *size to reflect the
83// consumed bytes, and return whether the message fit without truncation. If
84// truncation occurred, if possible leave room in the buffer for the message
85// kTruncated[].
86inline static bool VADoRawLog(char** buf, int* size, const char* format,
87 va_list ap) ABSL_PRINTF_ATTRIBUTE(3, 0);
88inline static bool VADoRawLog(char** buf, int* size,
89 const char* format, va_list ap) {
90 int n = vsnprintf(*buf, *size, format, ap);
91 bool result = true;
92 if (n < 0 || n > *size) {
93 result = false;
94 if (static_cast<size_t>(*size) > sizeof(kTruncated)) {
95 n = *size - sizeof(kTruncated); // room for truncation message
96 } else {
97 n = 0; // no room for truncation message
98 }
99 }
100 *size -= n;
101 *buf += n;
102 return result;
103}
104#endif // ABSL_LOW_LEVEL_WRITE_SUPPORTED
105
106static constexpr int kLogBufSize = 3000;
107
108namespace {
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.
116bool DoRawLog(char** buf, int* size, const char* format, ...)
117 ABSL_PRINTF_ATTRIBUTE(3, 4);
118bool 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
129void RawLogVA(absl::LogSeverity severity, const char* file, int line,
130 const char* format, va_list ap) ABSL_PRINTF_ATTRIBUTE(4, 0);
131void RawLogVA(absl::LogSeverity severity, const char* file, int line,
132 const char* format, va_list ap) {
133 char buffer[kLogBufSize];
134 char* buf = buffer;
135 int size = sizeof(buffer);
136#ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
137 bool enabled = true;
138#else
139 bool enabled = false;
140#endif
141
142#ifdef ABSL_MIN_LOG_LEVEL
143 if (severity < static_cast<absl::LogSeverity>(ABSL_MIN_LOG_LEVEL) &&
144 severity < absl::LogSeverity::kFatal) {
145 enabled = false;
146 }
147#endif
148
149 auto log_prefix_hook_ptr = log_prefix_hook.Load();
150 if (log_prefix_hook_ptr) {
151 enabled = log_prefix_hook_ptr(severity, file, line, &buf, &size);
152 } else {
153 if (enabled) {
154 DoRawLog(&buf, &size, "[%s : %d] RAW: ", file, line);
155 }
156 }
157 const char* const prefix_end = buf;
158
159#ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
160 if (enabled) {
161 bool no_chop = VADoRawLog(&buf, &size, format, ap);
162 if (no_chop) {
163 DoRawLog(&buf, &size, "\n");
164 } else {
165 DoRawLog(&buf, &size, "%s", kTruncated);
166 }
167 absl::raw_logging_internal::SafeWriteToStderr(buffer, strlen(buffer));
168 }
169#else
170 static_cast<void>(format);
171 static_cast<void>(ap);
172#endif
173
174 // Abort the process after logging a FATAL message, even if the output itself
175 // was suppressed.
176 if (severity == absl::LogSeverity::kFatal) {
177 abort_hook(file, line, buffer, prefix_end, buffer + kLogBufSize);
178 abort();
179 }
180}
181
182} // namespace
183
184namespace absl {
185namespace raw_logging_internal {
186void SafeWriteToStderr(const char *s, size_t len) {
187#if defined(ABSL_HAVE_SYSCALL_WRITE)
188 syscall(SYS_write, STDERR_FILENO, s, len);
189#elif defined(ABSL_HAVE_POSIX_WRITE)
190 write(STDERR_FILENO, s, len);
191#elif defined(ABSL_HAVE_RAW_IO)
192 _write(/* stderr */ 2, s, len);
193#else
194 // stderr logging unsupported on this platform
195 (void) s;
196 (void) len;
197#endif
198}
199
200void RawLog(absl::LogSeverity severity, const char* file, int line,
201 const char* format, ...) ABSL_PRINTF_ATTRIBUTE(4, 5);
202void RawLog(absl::LogSeverity severity, const char* file, int line,
203 const char* format, ...) {
204 va_list ap;
205 va_start(ap, format);
206 RawLogVA(severity, file, line, format, ap);
207 va_end(ap);
208}
209
210// Non-formatting version of RawLog().
211//
212// TODO(gfalcon): When string_view no longer depends on base, change this
213// interface to take its message as a string_view instead.
214static void DefaultInternalLog(absl::LogSeverity severity, const char* file,
215 int line, const std::string& message) {
216 RawLog(severity, file, line, "%s", message.c_str());
217}
218
219bool RawLoggingFullySupported() {
220#ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
221 return true;
222#else // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
223 return false;
224#endif // !ABSL_LOW_LEVEL_WRITE_SUPPORTED
225}
226
227ABSL_CONST_INIT absl::base_internal::AtomicHook<InternalLogFunction>
228 internal_log_function(DefaultInternalLog);
229
230void RegisterInternalLogFunction(InternalLogFunction func) {
231 internal_log_function.Store(func);
232}
233
234} // namespace raw_logging_internal
235} // namespace absl
236