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1 /*
2  * Copyright (c) 2013 Luca Clementi <luca.clementi@gmail.com>
3  * Copyright (c) 2013-2018 The strace developers.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. The name of the author may not be used to endorse or promote products
14  *    derived from this software without specific prior written permission.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26  */
27 
28 #include "defs.h"
29 #include <limits.h>
30 
31 #include "largefile_wrappers.h"
32 #include "mmap_cache.h"
33 #include "mmap_notify.h"
34 #include "xstring.h"
35 
36 static unsigned int mmap_cache_generation;
37 
38 static void
mmap_cache_invalidate(struct tcb * tcp,void * unused)39 mmap_cache_invalidate(struct tcb *tcp, void *unused)
40 {
41 #if SUPPORTED_PERSONALITIES > 1
42 	if (tcp->currpers != DEFAULT_PERSONALITY) {
43 		/* disable stack trace */
44 		return;
45 	}
46 #endif
47 	mmap_cache_generation++;
48 	debug_func_msg("tgen=%u, ggen=%u, tcp=%p, cache=%p",
49 		       tcp->mmap_cache ? tcp->mmap_cache->generation : 0,
50 		       mmap_cache_generation, tcp,
51 		       tcp->mmap_cache ? tcp->mmap_cache->entry : 0);
52 }
53 
54 void
mmap_cache_enable(void)55 mmap_cache_enable(void)
56 {
57 	static bool use_mmap_cache;
58 
59 	if (!use_mmap_cache) {
60 		mmap_notify_register_client(mmap_cache_invalidate, NULL);
61 		use_mmap_cache = true;
62 	}
63 }
64 
65 /* deleting the cache */
66 static void
delete_mmap_cache(struct tcb * tcp,const char * caller)67 delete_mmap_cache(struct tcb *tcp, const char *caller)
68 {
69 	debug_func_msg("tgen=%u, ggen=%u, tcp=%p, cache=%p, caller=%s",
70 		       tcp->mmap_cache ? tcp->mmap_cache->generation : 0,
71 		       mmap_cache_generation, tcp,
72 		       tcp->mmap_cache ? tcp->mmap_cache->entry : 0, caller);
73 
74 	if (!tcp->mmap_cache)
75 		return;
76 
77 	while (tcp->mmap_cache->size) {
78 		unsigned int i = --tcp->mmap_cache->size;
79 		free(tcp->mmap_cache->entry[i].binary_filename);
80 		tcp->mmap_cache->entry[i].binary_filename = NULL;
81 	}
82 
83 	free(tcp->mmap_cache->entry);
84 	tcp->mmap_cache->entry = NULL;
85 
86 	free(tcp->mmap_cache);
87 	tcp->mmap_cache = NULL;
88 }
89 
90 /*
91  * caching of /proc/ID/maps for each process to speed up stack tracing
92  *
93  * The cache must be refreshed after syscalls that affect memory mappings,
94  * e.g. mmap, mprotect, munmap, execve.
95  */
96 extern enum mmap_cache_rebuild_result
mmap_cache_rebuild_if_invalid(struct tcb * tcp,const char * caller)97 mmap_cache_rebuild_if_invalid(struct tcb *tcp, const char *caller)
98 {
99 	if (tcp->mmap_cache
100 	    && tcp->mmap_cache->generation != mmap_cache_generation)
101 		delete_mmap_cache(tcp, caller);
102 
103 	if (tcp->mmap_cache)
104 		return MMAP_CACHE_REBUILD_READY;
105 
106 	char filename[sizeof("/proc/4294967296/maps")];
107 	xsprintf(filename, "/proc/%u/maps", tcp->pid);
108 
109 	FILE *fp = fopen_stream(filename, "r");
110 	if (!fp) {
111 		perror_msg("fopen: %s", filename);
112 		return MMAP_CACHE_REBUILD_NOCACHE;
113 	}
114 
115 	struct mmap_cache_t cache = {
116 		.free_fn = delete_mmap_cache,
117 		.generation = mmap_cache_generation
118 	};
119 
120 	/* start with a small dynamically-allocated array and then expand it */
121 	size_t allocated = 0;
122 	char buffer[PATH_MAX + 80];
123 
124 	while (fgets(buffer, sizeof(buffer), fp) != NULL) {
125 		unsigned long start_addr, end_addr, mmap_offset;
126 		char read_bit;
127 		char write_bit;
128 		char exec_bit;
129 		char shared_bit;
130 		unsigned long major, minor;
131 		char binary_path[sizeof(buffer)];
132 
133 		if (sscanf(buffer, "%lx-%lx %c%c%c%c %lx %lx:%lx %*d %[^\n]",
134 			   &start_addr, &end_addr,
135 			   &read_bit, &write_bit, &exec_bit, &shared_bit,
136 			   &mmap_offset,
137 			   &major, &minor,
138 			   binary_path) != 10)
139 			continue;
140 
141 		/* skip mappings that have unknown protection */
142 		if (!(read_bit == '-' || read_bit == 'r'))
143 			continue;
144 		if (!(write_bit == '-' || write_bit == 'w'))
145 			continue;
146 		if (!(exec_bit == '-' || exec_bit == 'x'))
147 			continue;
148 		if (!(shared_bit == 'p' || shared_bit == 's'))
149 			continue;
150 
151 		if (end_addr < start_addr) {
152 			error_msg("%s: unrecognized file format", filename);
153 			break;
154 		}
155 
156 		struct mmap_cache_entry_t *entry;
157 		/*
158 		 * sanity check to make sure that we're storing
159 		 * non-overlapping regions in ascending order
160 		 */
161 		if (cache.size > 0) {
162 			entry = &cache.entry[cache.size - 1];
163 			if (entry->start_addr == start_addr &&
164 			    entry->end_addr == end_addr) {
165 				/* duplicate entry, e.g. [vsyscall] */
166 				continue;
167 			}
168 			if (start_addr <= entry->start_addr ||
169 			    start_addr < entry->end_addr) {
170 				debug_msg("%s: overlapping memory region: "
171 					  "\"%s\" [%08lx-%08lx] overlaps with "
172 					  "\"%s\" [%08lx-%08lx]",
173 					  filename, binary_path, start_addr,
174 					  end_addr, entry->binary_filename,
175 					  entry->start_addr, entry->end_addr);
176 				continue;
177 			}
178 		}
179 
180 		if (cache.size >= allocated)
181 			cache.entry = xgrowarray(cache.entry, &allocated,
182 						 sizeof(*cache.entry));
183 
184 		entry = &cache.entry[cache.size];
185 		entry->start_addr = start_addr;
186 		entry->end_addr = end_addr;
187 		entry->mmap_offset = mmap_offset;
188 		entry->protections = (
189 			0
190 			| ((read_bit   == 'r')? MMAP_CACHE_PROT_READABLE  : 0)
191 			| ((write_bit  == 'w')? MMAP_CACHE_PROT_WRITABLE  : 0)
192 			| ((exec_bit   == 'x')? MMAP_CACHE_PROT_EXECUTABLE: 0)
193 			| ((shared_bit == 's')? MMAP_CACHE_PROT_SHARED    : 0)
194 			);
195 		entry->major = major;
196 		entry->minor = minor;
197 		entry->binary_filename = xstrdup(binary_path);
198 		cache.size++;
199 	}
200 	fclose(fp);
201 
202 	if (!cache.size)
203 		return MMAP_CACHE_REBUILD_NOCACHE;
204 
205 	tcp->mmap_cache = xmalloc(sizeof(*tcp->mmap_cache));
206 	memcpy(tcp->mmap_cache, &cache, sizeof(cache));
207 
208 	debug_func_msg("tgen=%u, ggen=%u, tcp=%p, cache=%p, caller=%s",
209 		       tcp->mmap_cache->generation, mmap_cache_generation,
210 		       tcp, tcp->mmap_cache->entry, caller);
211 
212 	return MMAP_CACHE_REBUILD_RENEWED;
213 }
214 
215 struct mmap_cache_entry_t *
mmap_cache_search(struct tcb * tcp,unsigned long ip)216 mmap_cache_search(struct tcb *tcp, unsigned long ip)
217 {
218 	if (!tcp->mmap_cache)
219 		return NULL;
220 
221 	int lower = 0;
222 	int upper = (int) tcp->mmap_cache->size - 1;
223 
224 	while (lower <= upper) {
225 		int mid = (upper + lower) / 2;
226 		struct mmap_cache_entry_t *entry = &tcp->mmap_cache->entry[mid];
227 
228 		if (ip >= entry->start_addr &&
229 		    ip < entry->end_addr)
230 			return entry;
231 		else if (ip < entry->start_addr)
232 			upper = mid - 1;
233 		else
234 			lower = mid + 1;
235 	}
236 	return NULL;
237 }
238 
239 struct mmap_cache_entry_t *
mmap_cache_search_custom(struct tcb * tcp,mmap_cache_search_fn fn,void * data)240 mmap_cache_search_custom(struct tcb *tcp, mmap_cache_search_fn fn, void *data)
241 {
242 	for (unsigned int i = 0; i < tcp->mmap_cache->size; i++) {
243 		if (fn(tcp->mmap_cache->entry + i, data))
244 			return tcp->mmap_cache->entry + i;
245 	}
246 	return NULL;
247 }
248