1 /*
2 * Copyright 2006 The Android Open Source Project
3 *
4 * System utilities.
5 */
6 #include <stdlib.h>
7 #include <stdio.h>
8 #include <unistd.h>
9 #include <string.h>
10 #include <sys/mman.h>
11 #include <limits.h>
12 #include <errno.h>
13 #include <assert.h>
14
15 #define LOG_TAG "minzip"
16 #include "Log.h"
17 #include "SysUtil.h"
18
19 /*
20 * Having trouble finding a portable way to get this. sysconf(_SC_PAGE_SIZE)
21 * seems appropriate, but we don't have that on the device. Some systems
22 * have getpagesize(2), though the linux man page has some odd cautions.
23 */
24 #define DEFAULT_PAGE_SIZE 4096
25
26
27 /*
28 * Create an anonymous shared memory segment large enough to hold "length"
29 * bytes. The actual segment may be larger because mmap() operates on
30 * page boundaries (usually 4K).
31 */
sysCreateAnonShmem(size_t length)32 static void* sysCreateAnonShmem(size_t length)
33 {
34 void* ptr;
35
36 ptr = mmap(NULL, length, PROT_READ | PROT_WRITE,
37 MAP_SHARED | MAP_ANON, -1, 0);
38 if (ptr == MAP_FAILED) {
39 LOGW("mmap(%d, RW, SHARED|ANON) failed: %s\n", (int) length,
40 strerror(errno));
41 return NULL;
42 }
43
44 return ptr;
45 }
46
getFileStartAndLength(int fd,off_t * start_,size_t * length_)47 static int getFileStartAndLength(int fd, off_t *start_, size_t *length_)
48 {
49 off_t start, end;
50 size_t length;
51
52 assert(start_ != NULL);
53 assert(length_ != NULL);
54
55 start = lseek(fd, 0L, SEEK_CUR);
56 end = lseek(fd, 0L, SEEK_END);
57 (void) lseek(fd, start, SEEK_SET);
58
59 if (start == (off_t) -1 || end == (off_t) -1) {
60 LOGE("could not determine length of file\n");
61 return -1;
62 }
63
64 length = end - start;
65 if (length == 0) {
66 LOGE("file is empty\n");
67 return -1;
68 }
69
70 *start_ = start;
71 *length_ = length;
72
73 return 0;
74 }
75
76 /*
77 * Pull the contents of a file into an new shared memory segment. We grab
78 * everything from fd's current offset on.
79 *
80 * We need to know the length ahead of time so we can allocate a segment
81 * of sufficient size.
82 */
sysLoadFileInShmem(int fd,MemMapping * pMap)83 int sysLoadFileInShmem(int fd, MemMapping* pMap)
84 {
85 off_t start;
86 size_t length, actual;
87 void* memPtr;
88
89 assert(pMap != NULL);
90
91 if (getFileStartAndLength(fd, &start, &length) < 0)
92 return -1;
93
94 memPtr = sysCreateAnonShmem(length);
95 if (memPtr == NULL)
96 return -1;
97
98 pMap->baseAddr = pMap->addr = memPtr;
99 pMap->baseLength = pMap->length = length;
100
101 actual = TEMP_FAILURE_RETRY(read(fd, memPtr, length));
102 if (actual != length) {
103 LOGE("only read %d of %d bytes\n", (int) actual, (int) length);
104 sysReleaseShmem(pMap);
105 return -1;
106 }
107
108 return 0;
109 }
110
111 /*
112 * Map a file (from fd's current offset) into a shared, read-only memory
113 * segment. The file offset must be a multiple of the page size.
114 *
115 * On success, returns 0 and fills out "pMap". On failure, returns a nonzero
116 * value and does not disturb "pMap".
117 */
sysMapFileInShmem(int fd,MemMapping * pMap)118 int sysMapFileInShmem(int fd, MemMapping* pMap)
119 {
120 off_t start;
121 size_t length;
122 void* memPtr;
123
124 assert(pMap != NULL);
125
126 if (getFileStartAndLength(fd, &start, &length) < 0)
127 return -1;
128
129 memPtr = mmap(NULL, length, PROT_READ, MAP_FILE | MAP_SHARED, fd, start);
130 if (memPtr == MAP_FAILED) {
131 LOGW("mmap(%d, R, FILE|SHARED, %d, %d) failed: %s\n", (int) length,
132 fd, (int) start, strerror(errno));
133 return -1;
134 }
135
136 pMap->baseAddr = pMap->addr = memPtr;
137 pMap->baseLength = pMap->length = length;
138
139 return 0;
140 }
141
142 /*
143 * Map part of a file (from fd's current offset) into a shared, read-only
144 * memory segment.
145 *
146 * On success, returns 0 and fills out "pMap". On failure, returns a nonzero
147 * value and does not disturb "pMap".
148 */
sysMapFileSegmentInShmem(int fd,off_t start,long length,MemMapping * pMap)149 int sysMapFileSegmentInShmem(int fd, off_t start, long length,
150 MemMapping* pMap)
151 {
152 off_t dummy;
153 size_t fileLength, actualLength;
154 off_t actualStart;
155 int adjust;
156 void* memPtr;
157
158 assert(pMap != NULL);
159
160 if (getFileStartAndLength(fd, &dummy, &fileLength) < 0)
161 return -1;
162
163 if (start + length > (long)fileLength) {
164 LOGW("bad segment: st=%d len=%ld flen=%d\n",
165 (int) start, length, (int) fileLength);
166 return -1;
167 }
168
169 /* adjust to be page-aligned */
170 adjust = start % DEFAULT_PAGE_SIZE;
171 actualStart = start - adjust;
172 actualLength = length + adjust;
173
174 memPtr = mmap(NULL, actualLength, PROT_READ, MAP_FILE | MAP_SHARED,
175 fd, actualStart);
176 if (memPtr == MAP_FAILED) {
177 LOGW("mmap(%d, R, FILE|SHARED, %d, %d) failed: %s\n",
178 (int) actualLength, fd, (int) actualStart, strerror(errno));
179 return -1;
180 }
181
182 pMap->baseAddr = memPtr;
183 pMap->baseLength = actualLength;
184 pMap->addr = (char*)memPtr + adjust;
185 pMap->length = length;
186
187 LOGVV("mmap seg (st=%d ln=%d): bp=%p bl=%d ad=%p ln=%d\n",
188 (int) start, (int) length,
189 pMap->baseAddr, (int) pMap->baseLength,
190 pMap->addr, (int) pMap->length);
191
192 return 0;
193 }
194
195 /*
196 * Release a memory mapping.
197 */
sysReleaseShmem(MemMapping * pMap)198 void sysReleaseShmem(MemMapping* pMap)
199 {
200 if (pMap->baseAddr == NULL && pMap->baseLength == 0)
201 return;
202
203 if (munmap(pMap->baseAddr, pMap->baseLength) < 0) {
204 LOGW("munmap(%p, %d) failed: %s\n",
205 pMap->baseAddr, (int)pMap->baseLength, strerror(errno));
206 } else {
207 LOGV("munmap(%p, %d) succeeded\n", pMap->baseAddr, pMap->baseLength);
208 pMap->baseAddr = NULL;
209 pMap->baseLength = 0;
210 }
211 }
212
213