1 /* util.h
2 * Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
3 * Use of this source code is governed by a BSD-style license that can be
4 * found in the LICENSE file.
5 *
6 * Logging and other utility functions.
7 */
8
9 #ifndef _UTIL_H_
10 #define _UTIL_H_
11
12 #include <stdbool.h>
13 #include <stdio.h>
14 #include <stdlib.h>
15 #include <sys/types.h>
16 #include <syslog.h>
17 #include <unistd.h>
18
19 #include "libsyscalls.h"
20
21 #ifdef __cplusplus
22 extern "C" {
23 #endif
24
25 /*
26 * Silence compiler warnings for unused variables/functions.
27 *
28 * If the definition is actually used, the attribute should be removed, but if
29 * it's forgotten or left in place, it doesn't cause a problem.
30 *
31 * If the definition is actually unused, the compiler is free to remove it from
32 * the output so as to save size. If you want to make sure the definition is
33 * kept (e.g. for ABI compatibility), look at the "used" attribute instead.
34 */
35 #define attribute_unused __attribute__((__unused__))
36
37 /*
38 * Mark the symbol as "weak" in the ELF output. This provides a fallback symbol
39 * that may be overriden at link time. See this page for more details:
40 * https://en.wikipedia.org/wiki/Weak_symbol
41 */
42 #define attribute_weak __attribute__((__weak__))
43
44 /*
45 * Mark the function as a printf-style function.
46 * @format_idx The index in the function argument list where the format string
47 * is passed (where the first argument is "1").
48 * @check_idx The index in the function argument list where the first argument
49 * used in the format string is passed.
50 * Some examples:
51 * foo([1] const char *format, [2] ...): format=1 check=2
52 * foo([1] int, [2] const char *format, [3] ...): format=2 check=3
53 * foo([1] const char *format, [2] const char *, [3] ...): format=1 check=3
54 */
55 #define attribute_printf(format_idx, check_idx) \
56 __attribute__((__format__(__printf__, format_idx, check_idx)))
57
58 /* clang-format off */
59 #define die(_msg, ...) \
60 do_fatal_log(LOG_ERR, "libminijail[%d]: " _msg, getpid(), ## __VA_ARGS__)
61
62 #define pdie(_msg, ...) \
63 die(_msg ": %m", ## __VA_ARGS__)
64
65 #define warn(_msg, ...) \
66 do_log(LOG_WARNING, "libminijail[%d]: " _msg, getpid(), ## __VA_ARGS__)
67
68 #define pwarn(_msg, ...) \
69 warn(_msg ": %m", ## __VA_ARGS__)
70
71 #define info(_msg, ...) \
72 do_log(LOG_INFO, "libminijail[%d]: " _msg, getpid(), ## __VA_ARGS__)
73
74 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
75 /* clang-format on */
76
77 extern const char *log_syscalls[];
78 extern const size_t log_syscalls_len;
79
80 enum logging_system_t {
81 /* Log to syslog. This is the default. */
82 LOG_TO_SYSLOG = 0,
83
84 /* Log to a file descriptor. */
85 LOG_TO_FD,
86 };
87
88 /*
89 * Even though this function internally calls abort(2)/exit(2), it is
90 * intentionally not marked with the noreturn attribute. When marked as
91 * noreturn, clang coalesces several of the do_fatal_log() calls in methods that
92 * have a large number of such calls (like minijail_enter()), making it
93 * impossible for breakpad to correctly identify the line where it was called,
94 * making the backtrace somewhat useless.
95 */
96 extern void do_fatal_log(int priority, const char *format, ...)
97 attribute_printf(2, 3);
98
99 extern void do_log(int priority, const char *format, ...)
100 attribute_printf(2, 3);
101
is_android(void)102 static inline int is_android(void)
103 {
104 #if defined(__ANDROID__)
105 return 1;
106 #else
107 return 0;
108 #endif
109 }
110
compiled_with_asan(void)111 static inline bool compiled_with_asan(void)
112 {
113 #if defined(__SANITIZE_ADDRESS__)
114 /* For gcc. */
115 return true;
116 #elif defined(__has_feature)
117 /* For clang. */
118 return __has_feature(address_sanitizer) ||
119 __has_feature(hwaddress_sanitizer);
120 #else
121 return false;
122 #endif
123 }
124
125 void __asan_init(void) attribute_weak;
126 void __hwasan_init(void) attribute_weak;
127
running_with_asan(void)128 static inline bool running_with_asan(void)
129 {
130 /*
131 * There are some configurations under which ASan needs a dynamic (as
132 * opposed to compile-time) test. Some Android processes that start
133 * before /data is mounted run with non-instrumented libminijail.so, so
134 * the symbol-sniffing code must be present to make the right decision.
135 */
136 return compiled_with_asan() || &__asan_init != 0 || &__hwasan_init != 0;
137 }
138
debug_logging_allowed(void)139 static inline bool debug_logging_allowed(void) {
140 #if defined(ALLOW_DEBUG_LOGGING)
141 return true;
142 #else
143 return false;
144 #endif
145 }
146
get_num_syscalls(void)147 static inline size_t get_num_syscalls(void)
148 {
149 return syscall_table_size;
150 }
151
152 int lookup_syscall(const char *name, size_t *ind);
153 const char *lookup_syscall_name(int nr);
154
155 long int parse_single_constant(char *constant_str, char **endptr);
156 long int parse_constant(char *constant_str, char **endptr);
157 int parse_size(size_t *size, const char *sizespec);
158
159 char *strip(char *s);
160
161 /*
162 * tokenize: locate the next token in @stringp using the @delim
163 * @stringp A pointer to the string to scan for tokens
164 * @delim The delimiter to split by
165 *
166 * Note that, unlike strtok, @delim is not a set of characters, but the full
167 * delimiter. e.g. "a,;b,;c" with a delim of ",;" will yield ["a","b","c"].
168 *
169 * Note that, unlike strtok, this may return an empty token. e.g. "a,,b" with
170 * strtok will yield ["a","b"], but this will yield ["a","","b"].
171 */
172 char *tokenize(char **stringp, const char *delim);
173
174 char *path_join(const char *external_path, const char *internal_path);
175
176 /*
177 * consumebytes: consumes @length bytes from a buffer @buf of length @buflength
178 * @length Number of bytes to consume
179 * @buf Buffer to consume from
180 * @buflength Size of @buf
181 *
182 * Returns a pointer to the base of the bytes, or NULL for errors.
183 */
184 void *consumebytes(size_t length, char **buf, size_t *buflength);
185
186 /*
187 * consumestr: consumes a C string from a buffer @buf of length @length
188 * @buf Buffer to consume
189 * @length Length of buffer
190 *
191 * Returns a pointer to the base of the string, or NULL for errors.
192 */
193 char *consumestr(char **buf, size_t *buflength);
194
195 /*
196 * init_logging: initializes the module-wide logging.
197 * @logger The logging system to use.
198 * @fd The file descriptor to log into. Ignored unless
199 * @logger = LOG_TO_FD.
200 * @min_priority The minimum priority to display. Corresponds to syslog's
201 priority parameter. Ignored unless @logger = LOG_TO_FD.
202 */
203 void init_logging(enum logging_system_t logger, int fd, int min_priority);
204
205 /*
206 * minjail_free_env: Frees an environment array plus the environment strings it
207 * points to. The environment and its constituent strings must have been
208 * allocated (as opposed to pointing to static data), e.g. by using
209 * minijail_copy_env() and minijail_setenv().
210 *
211 * @env The environment to free.
212 */
213 void minijail_free_env(char **env);
214
215 /*
216 * minjail_copy_env: Copy an environment array (such as passed to execve),
217 * duplicating the environment strings and the array pointing at them.
218 *
219 * @env The environment to copy.
220 *
221 * Returns a pointer to the copied environment or NULL on memory allocation
222 * failure.
223 */
224 char **minijail_copy_env(char *const *env);
225
226 /*
227 * minjail_setenv: Set an environment variable in @env. Semantics match the
228 * standard setenv() function, but this operates on @env, not the global
229 * environment. @env must be dynamically allocated (as opposed to pointing to
230 * static data), e.g. via minijail_copy_env(). @name and @value get copied into
231 * newly-allocated memory.
232 *
233 * @env Address of the environment to modify. Might be re-allocated to
234 * make room for the new entry.
235 * @name Name of the key to set.
236 * @value The value to set.
237 * @overwrite Whether to replace the existing value for @name. If non-zero and
238 * the entry is already present, no changes will be made.
239 *
240 * Returns 0 and modifies *@env on success, returns an error code otherwise.
241 */
242 int minijail_setenv(char ***env, const char *name, const char *value,
243 int overwrite);
244
245 #ifdef __cplusplus
246 }; /* extern "C" */
247 #endif
248
249 #endif /* _UTIL_H_ */
250