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<fd_to_filename.h>: Add type safety and port to Hurd

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The new type struct fd_to_filename makes the allocation of the
backing storage explicit.

Hurd uses /dev/fd, not /proc/self/fd.

Co-Authored-By: Paul Eggert <eggert@cs.ucla.edu>
This commit is contained in:
Florian Weimer 2020-02-18 13:02:37 +01:00
parent e4a3999213
commit fa185f0d45
9 changed files with 206 additions and 33 deletions
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4
libio/freopen.c
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@ -37,7 +37,7 @@ FILE *
freopen (const char *filename, const char *mode, FILE *fp)
{
FILE *result = NULL;
char fdfilename[FD_TO_FILENAME_SIZE];
struct fd_to_filename fdfilename;
CHECK_FILE (fp, NULL);
@ -50,7 +50,7 @@ freopen (const char *filename, const char *mode, FILE *fp)
int fd = _IO_fileno (fp);
const char *gfilename
= filename != NULL ? filename : fd_to_filename (fd, fdfilename);
= filename != NULL ? filename : __fd_to_filename (fd, &fdfilename);
fp->_flags2 |= _IO_FLAGS2_NOCLOSE;
#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)

4
libio/freopen64.c
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@ -36,7 +36,7 @@ FILE *
freopen64 (const char *filename, const char *mode, FILE *fp)
{
FILE *result = NULL;
char fdfilename[FD_TO_FILENAME_SIZE];
struct fd_to_filename fdfilename;
CHECK_FILE (fp, NULL);
@ -49,7 +49,7 @@ freopen64 (const char *filename, const char *mode, FILE *fp)
int fd = _IO_fileno (fp);
const char *gfilename
= filename != NULL ? filename : fd_to_filename (fd, fdfilename);
= filename != NULL ? filename : __fd_to_filename (fd, &fdfilename);
fp->_flags2 |= _IO_FLAGS2_NOCLOSE;
_IO_file_close_it (fp);

6
misc/Makefile
View File

@ -72,7 +72,7 @@ routines := brk sbrk sstk ioctl \
fgetxattr flistxattr fremovexattr fsetxattr getxattr \
listxattr lgetxattr llistxattr lremovexattr lsetxattr \
removexattr setxattr getauxval ifunc-impl-list makedev \
allocate_once
allocate_once fd_to_filename
generated += tst-error1.mtrace tst-error1-mem.out \
tst-allocate_once.mtrace tst-allocate_once-mem.out
@ -97,6 +97,10 @@ endif
tests-internal := tst-atomic tst-atomic-long tst-allocate_once
tests-static := tst-empty
# Test for the internal, non-exported __fd_to_filename function.
tests-internal += tst-fd_to_filename
tests-static += tst-fd_to_filename
ifeq ($(run-built-tests),yes)
tests-special += $(objpfx)tst-error1-mem.out \
$(objpfx)tst-allocate_once-mem.out

38
misc/fd_to_filename.c Normal file
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@ -0,0 +1,38 @@
/* Construct a pathname under /proc/self/fd (or /dev/fd for Hurd).
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <fd_to_filename.h>
#include <assert.h>
#include <string.h>
char *
__fd_to_filename (int descriptor, struct fd_to_filename *storage)
{
assert (descriptor >= 0);
char *p = mempcpy (storage->buffer, FD_TO_FILENAME_PREFIX,
strlen (FD_TO_FILENAME_PREFIX));
for (int d = descriptor; p++, (d /= 10) != 0; )
continue;
*p = '\0';
for (int d = descriptor; *--p = '0' + d % 10, (d /= 10) != 0; )
continue;
return storage->buffer;
}

101
misc/tst-fd_to_filename.c Normal file
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@ -0,0 +1,101 @@
/* Test for /proc/self/fd (or /dev/fd) pathname construction.
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <fcntl.h>
#include <fd_to_filename.h>
#include <stdio.h>
#include <support/check.h>
#include <support/xunistd.h>
/* Run a check on one value. */
static void
check (int value)
{
if (value < 0)
/* Negative descriptor values violate the precondition. */
return;
struct fd_to_filename storage;
char *actual = __fd_to_filename (value, &storage);
char expected[100];
snprintf (expected, sizeof (expected), FD_TO_FILENAME_PREFIX "%d", value);
TEST_COMPARE_STRING (actual, expected);
}
/* Check various ranges constructed around powers. */
static void
check_ranges (int base)
{
unsigned int power = 1;
do
{
for (int factor = 1; factor < base; ++factor)
for (int shift = -1000; shift <= 1000; ++shift)
check (factor * power + shift);
}
while (!__builtin_mul_overflow (power, base, &power));
}
/* Check that it is actually possible to use a the constructed
name. */
static void
check_open (void)
{
int pipes[2];
xpipe (pipes);
struct fd_to_filename storage;
int read_alias = xopen (__fd_to_filename (pipes[0], &storage), O_RDONLY, 0);
int write_alias = xopen (__fd_to_filename (pipes[1], &storage), O_WRONLY, 0);
/* Ensure that all the descriptor numbers are different. */
TEST_VERIFY (pipes[0] < pipes[1]);
TEST_VERIFY (pipes[1] < read_alias);
TEST_VERIFY (read_alias < write_alias);
xwrite (write_alias, "1", 1);
char buf[16];
TEST_COMPARE_BLOB ("1", 1, buf, read (pipes[0], buf, sizeof (buf)));
xwrite (pipes[1], "2", 1);
TEST_COMPARE_BLOB ("2", 1, buf, read (read_alias, buf, sizeof (buf)));
xwrite (write_alias, "3", 1);
TEST_COMPARE_BLOB ("3", 1, buf, read (read_alias, buf, sizeof (buf)));
xwrite (pipes[1], "4", 1);
TEST_COMPARE_BLOB ("4", 1, buf, read (pipes[0], buf, sizeof (buf)));
xclose (write_alias);
xclose (read_alias);
xclose (pipes[1]);
xclose (pipes[0]);
}
static int
do_test (void)
{
check_ranges (2);
check_ranges (10);
check_open ();
return 0;
}
#include <support/test-driver.c>

19
sysdeps/generic/arch-fd_to_filename.h Normal file
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@ -0,0 +1,19 @@
/* Query filename corresponding to an open FD. Generic stub.
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#error "<arch-fd_to_filename.h> must be ported to this architecture"

26
sysdeps/generic/fd_to_filename.h
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@ -1,4 +1,4 @@
/* Query filename corresponding to an open FD. Generic version.
/* Query filename corresponding to an open FD.
Copyright (C) 2001-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
@ -16,12 +16,22 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#define FD_TO_FILENAME_SIZE 0
#ifndef _FD_TO_FILENAME_H
#define _FD_TO_FILENAME_H
/* In general there is no generic way to query filename for an open
file descriptor. */
static inline const char *
fd_to_filename (int fd, char *buf)
#include <arch-fd_to_filename.h>
#include <intprops.h>
struct fd_to_filename
{
return NULL;
}
/* A positive int value has at most 10 decimal digits. */
char buffer[sizeof (FD_TO_FILENAME_PREFIX) + INT_STRLEN_BOUND (int)];
};
/* Writes a /proc/self/fd-style path for DESCRIPTOR to *STORAGE and
returns a pointer to the start of the string. DESCRIPTOR must be
non-negative. */
char *__fd_to_filename (int descriptor, struct fd_to_filename *storage)
attribute_hidden;
#endif /* _FD_TO_FILENAME_H */

19
sysdeps/mach/hurd/arch-fd_to_filename.h Normal file
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@ -0,0 +1,19 @@
/* Query filename corresponding to an open FD. Hurd version.
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#define FD_TO_FILENAME_PREFIX "/dev/fd/"

22
sysdeps/unix/sysv/linux/fd_to_filename.h → sysdeps/unix/sysv/linux/arch-fd_to_filename.h
View File

@ -1,5 +1,5 @@
/* Query filename corresponding to an open FD. Linux version.
Copyright (C) 2001-2020 Free Software Foundation, Inc.
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@ -16,22 +16,4 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sys/stat.h>
#include <string.h>
#include <_itoa.h>
#define FD_TO_FILENAME_SIZE ((sizeof ("/proc/self/fd/") - 1) \
+ (sizeof ("4294967295") - 1) + 1)
static inline const char *
fd_to_filename (unsigned int fd, char *buf)
{
*_fitoa_word (fd, __stpcpy (buf, "/proc/self/fd/"), 10, 0) = '\0';
/* We must make sure the file exists. */
struct stat64 st;
if (__lxstat64 (_STAT_VER, buf, &st) < 0)
/* /proc is not mounted or something else happened. */
return NULL;
return buf;
}
#define FD_TO_FILENAME_PREFIX "/proc/self/fd/"