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c79a72aa AZ |
1 | /* Write data into multiple buffers. Base implementation for pwritev |
2 | and pwritev64. | |
6d7e8eda | 3 | Copyright (C) 2017-2023 Free Software Foundation, Inc. |
c79a72aa AZ |
4 | This file is part of the GNU C Library. |
5 | ||
6 | The GNU C Library is free software; you can redistribute it and/or | |
7 | modify it under the terms of the GNU Lesser General Public | |
8 | License as published by the Free Software Foundation; either | |
9 | version 2.1 of the License, or (at your option) any later version. | |
10 | ||
11 | The GNU C Library is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public | |
17 | License along with the GNU C Library; if not, see | |
5a82c748 | 18 | <https://www.gnu.org/licenses/>. */ |
c79a72aa AZ |
19 | |
20 | #include <unistd.h> | |
21 | #include <sys/uio.h> | |
22 | #include <sys/param.h> | |
23 | #include <errno.h> | |
24 | #include <malloc.h> | |
25 | ||
26 | #include <ldsodefs.h> | |
c45d78aa | 27 | #include <libc-pointer-arith.h> |
c79a72aa AZ |
28 | |
29 | /* Write data pointed by the buffers described by IOVEC, which is a | |
30 | vector of COUNT 'struct iovec's, to file descriptor FD at the given | |
31 | position OFFSET without change the file pointer. The data is | |
32 | written in the order specified. Operates just like 'write' (see | |
33 | <unistd.h>) except that the data are taken from IOVEC instead of a | |
34 | contiguous buffer. */ | |
35 | ssize_t | |
36 | PWRITEV (int fd, const struct iovec *vector, int count, OFF_T offset) | |
37 | { | |
38 | /* Find the total number of bytes to be read. */ | |
39 | size_t bytes = 0; | |
40 | for (int i = 0; i < count; ++i) | |
41 | { | |
42 | /* Check for ssize_t overflow. */ | |
43 | if (SSIZE_MAX - bytes < vector[i].iov_len) | |
44 | { | |
45 | __set_errno (EINVAL); | |
46 | return -1; | |
47 | } | |
48 | bytes += vector[i].iov_len; | |
49 | } | |
50 | ||
51 | /* Allocate a temporary buffer to hold the data. It could be done with a | |
52 | stack allocation, but due limitations on some system (Linux with | |
53 | O_DIRECT) it aligns the buffer to pagesize. A possible optimization | |
54 | would be querying if the syscall would impose any alignment constraint, | |
55 | but 1. it is system specific (not meant in generic implementation), and | |
56 | 2. it would make the implementation more complex, and 3. it will require | |
57 | another syscall (fcntl). */ | |
200fc24b | 58 | void *buffer = __mmap (NULL, bytes, PROT_READ | PROT_WRITE, |
c45d78aa AZ |
59 | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); |
60 | if (__glibc_unlikely (buffer == MAP_FAILED)) | |
c79a72aa AZ |
61 | return -1; |
62 | ||
63 | /* Copy the data from BUFFER into the memory specified by VECTOR. */ | |
64 | char *ptr = buffer; | |
65 | for (int i = 0; i < count; ++i) | |
66 | ptr = __mempcpy ((void *) ptr, (void *) vector[i].iov_base, | |
67 | vector[i].iov_len); | |
68 | ||
69 | ssize_t ret = PWRITE (fd, buffer, bytes, offset); | |
70 | ||
c45d78aa | 71 | __munmap (buffer, bytes); |
c79a72aa AZ |
72 | |
73 | return ret; | |
74 | } |