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1 /*
2  * Copyright 2019 Intel Corporation
3  * SPDX-License-Identifier: MIT
4  */
5 
6 #include "os_file.h"
7 #include "detect_os.h"
8 
9 #include <errno.h>
10 #include <fcntl.h>
11 #include <stdlib.h>
12 #include <sys/stat.h>
13 
14 #if DETECT_OS_WINDOWS
15 #include <io.h>
16 #define open _open
17 #define fdopen _fdopen
18 #define O_CREAT _O_CREAT
19 #define O_EXCL _O_EXCL
20 #define O_WRONLY _O_WRONLY
21 #else
22 #include <unistd.h>
23 #ifndef F_DUPFD_CLOEXEC
24 #define F_DUPFD_CLOEXEC 1030
25 #endif
26 #endif
27 
28 
29 FILE *
os_file_create_unique(const char * filename,int filemode)30 os_file_create_unique(const char *filename, int filemode)
31 {
32    int fd = open(filename, O_CREAT | O_EXCL | O_WRONLY, filemode);
33    if (fd == -1)
34       return NULL;
35    return fdopen(fd, "w");
36 }
37 
38 
39 #if DETECT_OS_WINDOWS
40 int
os_dupfd_cloexec(int fd)41 os_dupfd_cloexec(int fd)
42 {
43    /*
44     * On Windows child processes don't inherit handles by default:
45     * https://devblogs.microsoft.com/oldnewthing/20111216-00/?p=8873
46     */
47    return dup(fd);
48 }
49 #else
50 int
os_dupfd_cloexec(int fd)51 os_dupfd_cloexec(int fd)
52 {
53    int minfd = 3;
54    int newfd = fcntl(fd, F_DUPFD_CLOEXEC, minfd);
55 
56    if (newfd >= 0)
57       return newfd;
58 
59    if (errno != EINVAL)
60       return -1;
61 
62    newfd = fcntl(fd, F_DUPFD, minfd);
63 
64    if (newfd < 0)
65       return -1;
66 
67    long flags = fcntl(newfd, F_GETFD);
68    if (flags == -1) {
69       close(newfd);
70       return -1;
71    }
72 
73    if (fcntl(newfd, F_SETFD, flags | FD_CLOEXEC) == -1) {
74       close(newfd);
75       return -1;
76    }
77 
78    return newfd;
79 }
80 #endif
81 
82 
83 #if DETECT_OS_LINUX
84 
85 #include <fcntl.h>
86 #include <sys/stat.h>
87 #include <sys/syscall.h>
88 #include <unistd.h>
89 
90 /* copied from <linux/kcmp.h> */
91 #define KCMP_FILE 0
92 
93 static ssize_t
readN(int fd,char * buf,size_t len)94 readN(int fd, char *buf, size_t len)
95 {
96    int err = -ENODATA;
97    size_t total = 0;
98    do {
99       ssize_t ret = read(fd, buf + total, len - total);
100 
101       if (ret < 0)
102          ret = -errno;
103 
104       if (ret == -EINTR || ret == -EAGAIN)
105          continue;
106 
107       if (ret <= 0) {
108          err = ret;
109          break;
110       }
111 
112       total += ret;
113    } while (total != len);
114 
115    return total ? (ssize_t)total : err;
116 }
117 
118 char *
os_read_file(const char * filename,size_t * size)119 os_read_file(const char *filename, size_t *size)
120 {
121    /* Note that this also serves as a slight margin to avoid a 2x grow when
122     * the file is just a few bytes larger when we read it than when we
123     * fstat'ed it.
124     * The string's NULL terminator is also included in here.
125     */
126    size_t len = 64;
127 
128    int fd = open(filename, O_RDONLY);
129    if (fd == -1) {
130       /* errno set by open() */
131       return NULL;
132    }
133 
134    /* Pre-allocate a buffer at least the size of the file if we can read
135     * that information.
136     */
137    struct stat stat;
138    if (fstat(fd, &stat) == 0)
139       len += stat.st_size;
140 
141    char *buf = malloc(len);
142    if (!buf) {
143       close(fd);
144       errno = -ENOMEM;
145       return NULL;
146    }
147 
148    ssize_t actually_read;
149    size_t offset = 0, remaining = len - 1;
150    while ((actually_read = readN(fd, buf + offset, remaining)) == (ssize_t)remaining) {
151       char *newbuf = realloc(buf, 2 * len);
152       if (!newbuf) {
153          free(buf);
154          close(fd);
155          errno = -ENOMEM;
156          return NULL;
157       }
158 
159       buf = newbuf;
160       len *= 2;
161       offset += actually_read;
162       remaining = len - offset - 1;
163    }
164 
165    close(fd);
166 
167    if (actually_read > 0)
168       offset += actually_read;
169 
170    /* Final resize to actual size */
171    len = offset + 1;
172    char *newbuf = realloc(buf, len);
173    if (!newbuf) {
174       free(buf);
175       errno = -ENOMEM;
176       return NULL;
177    }
178    buf = newbuf;
179 
180    buf[offset] = '\0';
181 
182    if (size)
183       *size = offset;
184 
185    return buf;
186 }
187 
188 int
os_same_file_description(int fd1,int fd2)189 os_same_file_description(int fd1, int fd2)
190 {
191    pid_t pid = getpid();
192 
193    /* Same file descriptor trivially implies same file description */
194    if (fd1 == fd2)
195       return 0;
196 
197    return syscall(SYS_kcmp, pid, pid, KCMP_FILE, fd1, fd2);
198 }
199 
200 #else
201 
202 #include "u_debug.h"
203 
204 char *
os_read_file(const char * filename,size_t * size)205 os_read_file(const char *filename, size_t *size)
206 {
207    errno = -ENOSYS;
208    return NULL;
209 }
210 
211 int
os_same_file_description(int fd1,int fd2)212 os_same_file_description(int fd1, int fd2)
213 {
214    /* Same file descriptor trivially implies same file description */
215    if (fd1 == fd2)
216       return 0;
217 
218    /* Otherwise we can't tell */
219    return -1;
220 }
221 
222 #endif
223