forked from rpms/glibc
356 lines
9.5 KiB
Diff
356 lines
9.5 KiB
Diff
commit 5ad589d63bc2d9b1fc3d9f32144acaebb85e0803
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Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Date: Tue Aug 24 16:12:24 2021 -0300
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support: Add support_open_dev_null_range
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It returns a range of file descriptor referring to the '/dev/null'
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pathname. The function takes care of restarting the open range
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if a file descriptor is found within the specified range and
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also increases RLIMIT_NOFILE if required.
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Checked on x86_64-linux-gnu.
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(cherry picked from commit e814f4b04ee413a7bb3dfa43e74c8fb4abf58359)
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diff --git a/support/Makefile b/support/Makefile
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index ef2b1a980a407f8f..2a0731796fdb3f2d 100644
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--- a/support/Makefile
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+++ b/support/Makefile
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@@ -66,6 +66,7 @@ libsupport-routines = \
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support_path_support_time64 \
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support_process_state \
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support_ptrace \
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+ support-open-dev-null-range \
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support_openpty \
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support_paths \
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support_quote_blob \
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@@ -265,6 +266,7 @@ tests = \
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tst-support_capture_subprocess \
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tst-support_descriptors \
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tst-support_format_dns_packet \
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+ tst-support-open-dev-null-range \
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tst-support-process_state \
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tst-support_quote_blob \
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tst-support_quote_string \
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diff --git a/support/support-open-dev-null-range.c b/support/support-open-dev-null-range.c
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new file mode 100644
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index 0000000000000000..80d9dba50402ce12
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--- /dev/null
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+++ b/support/support-open-dev-null-range.c
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@@ -0,0 +1,134 @@
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+/* Return a range of open file descriptors.
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+ Copyright (C) 2021 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <https://www.gnu.org/licenses/>. */
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+
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+#include <errno.h>
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+#include <fcntl.h>
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+#include <support/support.h>
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+#include <support/check.h>
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+#include <support/xunistd.h>
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+#include <stdlib.h>
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+#include <sys/resource.h>
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+
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+static void
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+increase_nofile (void)
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+{
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+ struct rlimit rl;
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+ if (getrlimit (RLIMIT_NOFILE, &rl) == -1)
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+ FAIL_EXIT1 ("getrlimit (RLIMIT_NOFILE): %m");
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+
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+ rl.rlim_cur += 128;
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+
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+ if (setrlimit (RLIMIT_NOFILE, &rl) == 1)
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+ FAIL_EXIT1 ("setrlimit (RLIMIT_NOFILE): %m");
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+}
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+
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+static int
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+open_dev_null (int flags, mode_t mode)
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+{
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+ int fd = open64 ("/dev/null", flags, mode);
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+ if (fd > 0)
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+ return fd;
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+
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+ if (fd < 0 && errno != EMFILE)
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+ FAIL_EXIT1 ("open64 (\"/dev/null\", 0x%x, 0%o): %m", flags, mode);
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+
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+ increase_nofile ();
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+
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+ return xopen ("/dev/null", flags, mode);
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+}
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+
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+struct range
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+{
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+ int lowfd;
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+ size_t len;
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+};
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+
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+struct range_list
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+{
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+ size_t total;
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+ size_t used;
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+ struct range *ranges;
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+};
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+
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+static void
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+range_init (struct range_list *r)
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+{
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+ r->total = 8;
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+ r->used = 0;
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+ r->ranges = xmalloc (r->total * sizeof (struct range));
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+}
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+
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+static void
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+range_add (struct range_list *r, int lowfd, size_t len)
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+{
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+ if (r->used == r->total)
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+ {
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+ r->total *= 2;
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+ r->ranges = xrealloc (r->ranges, r->total * sizeof (struct range));
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+ }
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+ r->ranges[r->used].lowfd = lowfd;
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+ r->ranges[r->used].len = len;
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+ r->used++;
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+}
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+
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+static void
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+range_close (struct range_list *r)
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+{
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+ for (size_t i = 0; i < r->used; i++)
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+ {
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+ int minfd = r->ranges[i].lowfd;
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+ int maxfd = r->ranges[i].lowfd + r->ranges[i].len;
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+ for (int fd = minfd; fd < maxfd; fd++)
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+ xclose (fd);
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+ }
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+ free (r->ranges);
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+}
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+
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+int
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+support_open_dev_null_range (int num, int flags, mode_t mode)
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+{
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+ /* We keep track of the ranges that hit an already opened descriptor, so
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+ we close them after we get a working range. */
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+ struct range_list rl;
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+ range_init (&rl);
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+
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+ int lowfd = open_dev_null (flags, mode);
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+ int prevfd = lowfd;
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+ while (true)
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+ {
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+ int i = 1;
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+ for (; i < num; i++)
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+ {
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+ int fd = open_dev_null (flags, mode);
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+ if (fd != lowfd + i)
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+ {
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+ range_add (&rl, lowfd, prevfd - lowfd + 1);
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+
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+ prevfd = lowfd = fd;
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+ break;
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+ }
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+ prevfd = fd;
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+ }
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+ if (i == num)
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+ break;
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+ }
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+
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+ range_close (&rl);
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+
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+ return lowfd;
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+}
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diff --git a/support/support.h b/support/support.h
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index a5978b939af2fb41..c219e0d9d1aef046 100644
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--- a/support/support.h
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+++ b/support/support.h
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@@ -197,6 +197,14 @@ struct support_stack support_stack_alloc (size_t size);
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/* Deallocate the STACK. */
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void support_stack_free (struct support_stack *stack);
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+
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+/* Create a range of NUM opened '/dev/null' file descriptors using FLAGS and
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+ MODE. The function takes care of restarting the open range if a file
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+ descriptor is found within the specified range and also increases
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+ RLIMIT_NOFILE if required.
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+ The returned value is the lowest file descriptor number. */
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+int support_open_dev_null_range (int num, int flags, mode_t mode);
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+
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__END_DECLS
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#endif /* SUPPORT_H */
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diff --git a/support/tst-support-open-dev-null-range.c b/support/tst-support-open-dev-null-range.c
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new file mode 100644
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index 0000000000000000..8e29def1ce780629
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--- /dev/null
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+++ b/support/tst-support-open-dev-null-range.c
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@@ -0,0 +1,155 @@
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+/* Tests for support_open_dev_null_range.
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+ Copyright (C) 2021 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <https://www.gnu.org/licenses/>. */
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+
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+#include <errno.h>
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+#include <dirent.h>
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+#include <fcntl.h>
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+#include <limits.h>
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+#include <support/check.h>
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+#include <support/support.h>
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+#include <support/xunistd.h>
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+#include <sys/resource.h>
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+#include <stdlib.h>
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+
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+#ifndef PATH_MAX
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+# define PATH_MAX 1024
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+#endif
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+
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+#include <stdio.h>
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+
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+static void
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+check_path (int fd)
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+{
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+ char *proc_fd_path = xasprintf ("/proc/self/fd/%d", fd);
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+ char file_path[PATH_MAX];
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+ ssize_t file_path_length
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+ = readlink (proc_fd_path, file_path, sizeof (file_path));
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+ free (proc_fd_path);
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+ if (file_path_length < 0)
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+ FAIL_EXIT1 ("readlink (%s, %p, %zu)", proc_fd_path, file_path,
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+ sizeof (file_path));
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+ file_path[file_path_length] = '\0';
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+ TEST_COMPARE_STRING (file_path, "/dev/null");
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+}
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+
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+static int
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+number_of_opened_files (void)
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+{
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+ DIR *fds = opendir ("/proc/self/fd");
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+ if (fds == NULL)
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+ FAIL_EXIT1 ("opendir (\"/proc/self/fd\"): %m");
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+
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+ int r = 0;
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+ while (true)
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+ {
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+ errno = 0;
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+ struct dirent64 *e = readdir64 (fds);
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+ if (e == NULL)
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+ {
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+ if (errno != 0)
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+ FAIL_EXIT1 ("readdir: %m");
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+ break;
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+ }
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+
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+ if (e->d_name[0] == '.')
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+ continue;
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+
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+ char *endptr;
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+ long int fd = strtol (e->d_name, &endptr, 10);
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+ if (*endptr != '\0' || fd < 0 || fd > INT_MAX)
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+ FAIL_EXIT1 ("readdir: invalid file descriptor name: /proc/self/fd/%s",
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+ e->d_name);
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+
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+ /* Skip the descriptor which is used to enumerate the
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+ descriptors. */
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+ if (fd == dirfd (fds))
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+ continue;
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+
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+ r = r + 1;
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+ }
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+
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+ closedir (fds);
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+
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+ return r;
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+}
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+
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+static int
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+do_test (void)
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+{
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+ const int nfds1 = 8;
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+ int lowfd = support_open_dev_null_range (nfds1, O_RDONLY, 0600);
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+ for (int i = 0; i < nfds1; i++)
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+ {
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+ TEST_VERIFY (fcntl (lowfd + i, F_GETFL) > -1);
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+ check_path (lowfd + i);
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+ }
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+
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+ /* create some gaps. */
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+ xclose (lowfd + 1);
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+ xclose (lowfd + 5);
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+ xclose (lowfd + 6);
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+
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+ const int nfds2 = 16;
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+ int lowfd2 = support_open_dev_null_range (nfds2, O_RDONLY, 0600);
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+ for (int i = 0; i < nfds2; i++)
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+ {
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+ TEST_VERIFY (fcntl (lowfd2 + i, F_GETFL) > -1);
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+ check_path (lowfd2 + i);
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+ }
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+
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+ /* Decrease the maximum number of files. */
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+ {
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+ struct rlimit rl;
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+ if (getrlimit (RLIMIT_NOFILE, &rl) == -1)
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+ FAIL_EXIT1 ("getrlimit (RLIMIT_NOFILE): %m");
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+
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+ rl.rlim_cur = number_of_opened_files ();
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+
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+ if (setrlimit (RLIMIT_NOFILE, &rl) == 1)
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+ FAIL_EXIT1 ("setrlimit (RLIMIT_NOFILE): %m");
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+ }
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+
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+ const int nfds3 = 16;
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+ int lowfd3 = support_open_dev_null_range (nfds3, O_RDONLY, 0600);
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+ for (int i = 0; i < nfds3; i++)
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+ {
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+ TEST_VERIFY (fcntl (lowfd3 + i, F_GETFL) > -1);
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+ check_path (lowfd3 + i);
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+ }
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+
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+ /* create a lot of gaps to trigger the range extension. */
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+ xclose (lowfd3 + 1);
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+ xclose (lowfd3 + 3);
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+ xclose (lowfd3 + 5);
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+ xclose (lowfd3 + 7);
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+ xclose (lowfd3 + 9);
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+ xclose (lowfd3 + 11);
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+ xclose (lowfd3 + 13);
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+
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+ const int nfds4 = 16;
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+ int lowfd4 = support_open_dev_null_range (nfds4, O_RDONLY, 0600);
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+ for (int i = 0; i < nfds4; i++)
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+ {
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+ TEST_VERIFY (fcntl (lowfd4 + i, F_GETFL) > -1);
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+ check_path (lowfd4 + i);
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+ }
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+
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+ return 0;
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+}
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+
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+#include <support/test-driver.c>
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