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b1e3441299
This line in tools/testing/selftests/proc/read.c was added to catch
oopses, not to verify lseek correctness:
(void)lseek(fd, 0, SEEK_SET);
Oh, well. Prevent more embarassement with simple test.
Link: https://lkml.kernel.org/r/aKTCfMuRXOpjBXxI@p183
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
69 lines
2.0 KiB
C
69 lines
2.0 KiB
C
/*
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* Copyright (c) 2025 Alexey Dobriyan <adobriyan@gmail.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#undef _GNU_SOURCE
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#define _GNU_SOURCE
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#undef NDEBUG
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <string.h>
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#include <unistd.h>
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#include <sched.h>
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/*
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* Test that lseek("/proc/net/dev/", 0, SEEK_SET)
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* a) works,
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* b) does what you think it does.
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*/
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int main(void)
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{
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/* /proc/net/dev output is deterministic in fresh netns only. */
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if (unshare(CLONE_NEWNET) == -1) {
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if (errno == ENOSYS || errno == EPERM) {
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return 4;
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}
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return 1;
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}
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const int fd = open("/proc/net/dev", O_RDONLY);
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assert(fd >= 0);
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char buf1[4096];
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const ssize_t rv1 = read(fd, buf1, sizeof(buf1));
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/*
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* Not "<=", this file can't be empty:
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* there is header, "lo" interface with some zeroes.
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*/
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assert(0 < rv1);
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assert(rv1 <= sizeof(buf1));
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/* Believe it or not, this line broke one day. */
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assert(lseek(fd, 0, SEEK_SET) == 0);
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char buf2[4096];
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const ssize_t rv2 = read(fd, buf2, sizeof(buf2));
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/* Not "<=", see above. */
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assert(0 < rv2);
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assert(rv2 <= sizeof(buf2));
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/* Test that lseek rewinds to the beginning of the file. */
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assert(rv1 == rv2);
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assert(memcmp(buf1, buf2, rv1) == 0);
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/* Contents of the file is not validated: this test is about lseek(). */
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return 0;
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}
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