[1/3] <fd_to_filename.h>: Add type safety and port to Hurd
Commit Message
The new type struct fd_to_filename makes the allocation of the
backing storage explicit.
Hurd uses /dev/fd, not /proc/self/fd.
---
libio/freopen.c | 4 +-
libio/freopen64.c | 4 +-
misc/Makefile | 6 +-
misc/fd_to_filename.c | 104 +++++++++++++++++
misc/tst-fd_to_filename.c | 105 ++++++++++++++++++
sysdeps/generic/arch-fd_to_filename.h | 19 ++++
sysdeps/generic/fd_to_filename.h | 25 +++--
sysdeps/mach/hurd/arch-fd_to_filename.h | 19 ++++
...fd_to_filename.h => arch-fd_to_filename.h} | 22 +---
9 files changed, 275 insertions(+), 33 deletions(-)
create mode 100644 misc/fd_to_filename.c
create mode 100644 misc/tst-fd_to_filename.c
create mode 100644 sysdeps/generic/arch-fd_to_filename.h
create mode 100644 sysdeps/mach/hurd/arch-fd_to_filename.h
rename sysdeps/unix/sysv/linux/{fd_to_filename.h => arch-fd_to_filename.h} (58%)
Comments
Florian Weimer, le ven. 14 févr. 2020 19:11:09 +0100, a ecrit:
> The new type struct fd_to_filename makes the allocation of the
> backing storage explicit.
>
> Hurd uses /dev/fd, not /proc/self/fd.
Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Thanks!
> ---
> libio/freopen.c | 4 +-
> libio/freopen64.c | 4 +-
> misc/Makefile | 6 +-
> misc/fd_to_filename.c | 104 +++++++++++++++++
> misc/tst-fd_to_filename.c | 105 ++++++++++++++++++
> sysdeps/generic/arch-fd_to_filename.h | 19 ++++
> sysdeps/generic/fd_to_filename.h | 25 +++--
> sysdeps/mach/hurd/arch-fd_to_filename.h | 19 ++++
> ...fd_to_filename.h => arch-fd_to_filename.h} | 22 +---
> 9 files changed, 275 insertions(+), 33 deletions(-)
> create mode 100644 misc/fd_to_filename.c
> create mode 100644 misc/tst-fd_to_filename.c
> create mode 100644 sysdeps/generic/arch-fd_to_filename.h
> create mode 100644 sysdeps/mach/hurd/arch-fd_to_filename.h
> rename sysdeps/unix/sysv/linux/{fd_to_filename.h => arch-fd_to_filename.h} (58%)
>
> diff --git a/libio/freopen.c b/libio/freopen.c
> index bab3ba204a..884cdb2961 100644
> --- a/libio/freopen.c
> +++ b/libio/freopen.c
> @@ -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)
> diff --git a/libio/freopen64.c b/libio/freopen64.c
> index c0ce604e6e..0d2c5264c7 100644
> --- a/libio/freopen64.c
> +++ b/libio/freopen64.c
> @@ -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);
> diff --git a/misc/Makefile b/misc/Makefile
> index e0465980c7..b8fed5783d 100644
> --- a/misc/Makefile
> +++ b/misc/Makefile
> @@ -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
> diff --git a/misc/fd_to_filename.c b/misc/fd_to_filename.c
> new file mode 100644
> index 0000000000..911c22cf2b
> --- /dev/null
> +++ b/misc/fd_to_filename.c
> @@ -0,0 +1,104 @@
> +/* 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 <string.h>
> +
> +/* The split into groups of three digits is arbitrary, but it covers
> + the common case of descriptors less than 1000 fairly
> + efficiently. */
> +
> +/* Writes two digits to P. VALUE must be between 0 and 99
> + (inclusive). Returns the address after the written digits. */
> +static char *
> +digit2 (char *p, int value)
> +{
> + p[0] = '0' + (value / 10);
> + p[1] = '0' + (value % 10);
> + return p + 2;
> +}
> +
> +/* Writes three digits to P. VALUE must be between 0 and 999
> + (inclusive). Returns the address after the written digits. */
> +static char *
> +digit3 (char *p, int value)
> +{
> + p[0] = '0' + (value / 100);
> + p[1] = '0' + ((value / 10) % 10);
> + p[2] = '0' + (value % 10);
> + return p + 3;
> +}
> +
> +/* Writes one to three digits to P, depending on VALUE, which must be
> + less than 1000. Returns the address after the written digits. */
> +static char *
> +digit123 (char *p, int value)
> +{
> + if (value < 10)
> + {
> + p[0] = '0' + value;
> + return p + 1;
> + }
> + else if (value < 100)
> + return digit2 (p, value);
> + else
> + return digit3 (p, value);
> +}
> +
> +char *
> +__fd_to_filename (int descriptor, struct fd_to_filename *storage)
> +{
> + char *p = mempcpy (storage->buffer, FD_TO_FILENAME_PREFIX,
> + strlen (FD_TO_FILENAME_PREFIX));
> + if (__glibc_likely (descriptor >= 0))
> + {
> + if (descriptor < 1000)
> + p = digit123 (p, descriptor);
> + else if (descriptor < 1000 * 1000)
> + {
> + p = digit123 (p, descriptor / 1000);
> + p = digit3 (p, descriptor % 1000);
> + }
> + else if (descriptor < 1000 * 1000 * 1000)
> + {
> + p = digit123 (p, descriptor / (1000 * 1000));
> + p = digit3 (p, (descriptor / 1000) % 1000);
> + p = digit3 (p, descriptor % 1000);
> + }
> + else
> + {
> + if (descriptor < 2000 * 1000 * 1000)
> + {
> + *p = '1';
> + descriptor -= 1000 * 1000 * 1000;
> + }
> + else
> + {
> + *p = '2';
> + descriptor -= 2000 * 1000 * 1000;
> + }
> + ++p;
> + p = digit3 (p, descriptor / (1000 * 1000));
> + p = digit3 (p, (descriptor / 1000) % 1000);
> + p = digit3 (p, descriptor % 1000);
> + }
> + }
> +
> + *p = '\0';
> + return storage->buffer;
> +}
> diff --git a/misc/tst-fd_to_filename.c b/misc/tst-fd_to_filename.c
> new file mode 100644
> index 0000000000..480f613dcf
> --- /dev/null
> +++ b/misc/tst-fd_to_filename.c
> @@ -0,0 +1,105 @@
> +/* 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 <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)
> +{
> + 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);
> +
> + if (value < 0)
> + /* Negative inputs are invalid, but the output should still be
> + deterministic. */
> + TEST_COMPARE_STRING (actual, FD_TO_FILENAME_PREFIX);
> + else
> + 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);
> + 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>
> diff --git a/sysdeps/generic/arch-fd_to_filename.h b/sysdeps/generic/arch-fd_to_filename.h
> new file mode 100644
> index 0000000000..ecaaa14dba
> --- /dev/null
> +++ b/sysdeps/generic/arch-fd_to_filename.h
> @@ -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"
> diff --git a/sysdeps/generic/fd_to_filename.h b/sysdeps/generic/fd_to_filename.h
> index eff6ca211b..7889db879c 100644
> --- a/sysdeps/generic/fd_to_filename.h
> +++ b/sysdeps/generic/fd_to_filename.h
> @@ -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 +16,21 @@
> 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>
> +
> +struct fd_to_filename
> {
> - return NULL;
> -}
> + /* A positive int value has at most 10 decimal digits. */
> + char buffer[sizeof (FD_TO_FILENAME_PREFIX) + 10];
> +};
> +
> +/* 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 */
> diff --git a/sysdeps/mach/hurd/arch-fd_to_filename.h b/sysdeps/mach/hurd/arch-fd_to_filename.h
> new file mode 100644
> index 0000000000..b45cd8d836
> --- /dev/null
> +++ b/sysdeps/mach/hurd/arch-fd_to_filename.h
> @@ -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/"
> diff --git a/sysdeps/unix/sysv/linux/fd_to_filename.h b/sysdeps/unix/sysv/linux/arch-fd_to_filename.h
> similarity index 58%
> rename from sysdeps/unix/sysv/linux/fd_to_filename.h
> rename to sysdeps/unix/sysv/linux/arch-fd_to_filename.h
> index 92a5e02976..b6017214c7 100644
> --- a/sysdeps/unix/sysv/linux/fd_to_filename.h
> +++ b/sysdeps/unix/sysv/linux/arch-fd_to_filename.h
> @@ -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/"
> --
> 2.24.1
>
>
On 14/02/2020 15:11, Florian Weimer wrote:
> The new type struct fd_to_filename makes the allocation of the
> backing storage explicit.
>
> Hurd uses /dev/fd, not /proc/self/fd.
> ---
> libio/freopen.c | 4 +-
> libio/freopen64.c | 4 +-
> misc/Makefile | 6 +-
> misc/fd_to_filename.c | 104 +++++++++++++++++
> misc/tst-fd_to_filename.c | 105 ++++++++++++++++++
> sysdeps/generic/arch-fd_to_filename.h | 19 ++++
> sysdeps/generic/fd_to_filename.h | 25 +++--
> sysdeps/mach/hurd/arch-fd_to_filename.h | 19 ++++
> ...fd_to_filename.h => arch-fd_to_filename.h} | 22 +---
> 9 files changed, 275 insertions(+), 33 deletions(-)
> create mode 100644 misc/fd_to_filename.c
> create mode 100644 misc/tst-fd_to_filename.c
> create mode 100644 sysdeps/generic/arch-fd_to_filename.h
> create mode 100644 sysdeps/mach/hurd/arch-fd_to_filename.h
> rename sysdeps/unix/sysv/linux/{fd_to_filename.h => arch-fd_to_filename.h} (58%)
>
> diff --git a/libio/freopen.c b/libio/freopen.c
> index bab3ba204a..884cdb2961 100644
> --- a/libio/freopen.c
> +++ b/libio/freopen.c
> @@ -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)
> diff --git a/libio/freopen64.c b/libio/freopen64.c
> index c0ce604e6e..0d2c5264c7 100644
> --- a/libio/freopen64.c
> +++ b/libio/freopen64.c
> @@ -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);
> diff --git a/misc/Makefile b/misc/Makefile
> index e0465980c7..b8fed5783d 100644
> --- a/misc/Makefile
> +++ b/misc/Makefile
> @@ -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
> diff --git a/misc/fd_to_filename.c b/misc/fd_to_filename.c
> new file mode 100644
> index 0000000000..911c22cf2b
> --- /dev/null
> +++ b/misc/fd_to_filename.c
> @@ -0,0 +1,104 @@
> +/* 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 <string.h>
> +
> +/* The split into groups of three digits is arbitrary, but it covers
> + the common case of descriptors less than 1000 fairly
> + efficiently. */
> +
> +/* Writes two digits to P. VALUE must be between 0 and 99
> + (inclusive). Returns the address after the written digits. */
> +static char *
> +digit2 (char *p, int value)
> +{
> + p[0] = '0' + (value / 10);
> + p[1] = '0' + (value % 10);
> + return p + 2;
> +}
> +
> +/* Writes three digits to P. VALUE must be between 0 and 999
> + (inclusive). Returns the address after the written digits. */
> +static char *
> +digit3 (char *p, int value)
> +{
> + p[0] = '0' + (value / 100);
> + p[1] = '0' + ((value / 10) % 10);
> + p[2] = '0' + (value % 10);
> + return p + 3;
> +}
> +
> +/* Writes one to three digits to P, depending on VALUE, which must be
> + less than 1000. Returns the address after the written digits. */
> +static char *
> +digit123 (char *p, int value)
> +{
> + if (value < 10)
> + {
> + p[0] = '0' + value;
> + return p + 1;
> + }
> + else if (value < 100)
> + return digit2 (p, value);
> + else
> + return digit3 (p, value);
> +}
> +
> +char *
> +__fd_to_filename (int descriptor, struct fd_to_filename *storage)
> +{
> + char *p = mempcpy (storage->buffer, FD_TO_FILENAME_PREFIX,
> + strlen (FD_TO_FILENAME_PREFIX));
> + if (__glibc_likely (descriptor >= 0))
> + {
> + if (descriptor < 1000)
> + p = digit123 (p, descriptor);
> + else if (descriptor < 1000 * 1000)
> + {
> + p = digit123 (p, descriptor / 1000);
> + p = digit3 (p, descriptor % 1000);
> + }
> + else if (descriptor < 1000 * 1000 * 1000)
> + {
> + p = digit123 (p, descriptor / (1000 * 1000));
> + p = digit3 (p, (descriptor / 1000) % 1000);
> + p = digit3 (p, descriptor % 1000);
> + }
> + else
> + {
> + if (descriptor < 2000 * 1000 * 1000)
> + {
> + *p = '1';
> + descriptor -= 1000 * 1000 * 1000;
> + }
> + else
> + {
> + *p = '2';
> + descriptor -= 2000 * 1000 * 1000;
> + }
> + ++p;
> + p = digit3 (p, descriptor / (1000 * 1000));
> + p = digit3 (p, (descriptor / 1000) % 1000);
> + p = digit3 (p, descriptor % 1000);
> + }
> + }
> +
> + *p = '\0';
> + return storage->buffer;
> +}
Do we really such optimization which results in somewhat complicate
code? Couldn't we use something simple as:
char *
__fd_to_filename (int descriptor, struct fd_to_filename *storage)
{
char *buf = storage->buffer;
int i, j;
for (i = 0; (buf[i] = FD_TO_FILENAME_PREFIX[i]); i++);
if (descriptor == 0)
{
buf[i] = '0';
buf[i+1] = '\0';
return storage->buffer;
}
for (j = descriptor; j != 0; j /= 10, i++);
buf[i] = '\0';
for (; descriptor != 0; descriptor /= 10)
buf[--i] = '0' + descriptor % 10;
return storage->buffer;
}
> diff --git a/misc/tst-fd_to_filename.c b/misc/tst-fd_to_filename.c
> new file mode 100644
> index 0000000000..480f613dcf
> --- /dev/null
> +++ b/misc/tst-fd_to_filename.c
> @@ -0,0 +1,105 @@
> +/* 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 <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)
> +{
> + 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);
> +
> + if (value < 0)
> + /* Negative inputs are invalid, but the output should still be
> + deterministic. */
> + TEST_COMPARE_STRING (actual, FD_TO_FILENAME_PREFIX);
> + else
> + 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);
> + 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>
> diff --git a/sysdeps/generic/arch-fd_to_filename.h b/sysdeps/generic/arch-fd_to_filename.h
> new file mode 100644
> index 0000000000..ecaaa14dba
> --- /dev/null
> +++ b/sysdeps/generic/arch-fd_to_filename.h
> @@ -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"
> diff --git a/sysdeps/generic/fd_to_filename.h b/sysdeps/generic/fd_to_filename.h
> index eff6ca211b..7889db879c 100644
> --- a/sysdeps/generic/fd_to_filename.h
> +++ b/sysdeps/generic/fd_to_filename.h
> @@ -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 +16,21 @@
> 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>
> +
> +struct fd_to_filename
> {
> - return NULL;
> -}
> + /* A positive int value has at most 10 decimal digits. */
> + char buffer[sizeof (FD_TO_FILENAME_PREFIX) + 10];
> +};
> +
> +/* 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 */
> diff --git a/sysdeps/mach/hurd/arch-fd_to_filename.h b/sysdeps/mach/hurd/arch-fd_to_filename.h
> new file mode 100644
> index 0000000000..b45cd8d836
> --- /dev/null
> +++ b/sysdeps/mach/hurd/arch-fd_to_filename.h
> @@ -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/"
> diff --git a/sysdeps/unix/sysv/linux/fd_to_filename.h b/sysdeps/unix/sysv/linux/arch-fd_to_filename.h
> similarity index 58%
> rename from sysdeps/unix/sysv/linux/fd_to_filename.h
> rename to sysdeps/unix/sysv/linux/arch-fd_to_filename.h
> index 92a5e02976..b6017214c7 100644
> --- a/sysdeps/unix/sysv/linux/fd_to_filename.h
> +++ b/sysdeps/unix/sysv/linux/arch-fd_to_filename.h
> @@ -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/"
>
* Adhemerval Zanella:
> Do we really such optimization which results in somewhat complicate
> code? Couldn't we use something simple as:
>
> char *
> __fd_to_filename (int descriptor, struct fd_to_filename *storage)
> {
> char *buf = storage->buffer;
> int i, j;
>
> for (i = 0; (buf[i] = FD_TO_FILENAME_PREFIX[i]); i++);
> if (descriptor == 0)
> {
> buf[i] = '0';
> buf[i+1] = '\0';
> return storage->buffer;
> }
>
> for (j = descriptor; j != 0; j /= 10, i++);
> buf[i] = '\0';
> for (; descriptor != 0; descriptor /= 10)
> buf[--i] = '0' + descriptor % 10;
>
> return storage->buffer;
> }
I don't have a strong opinion about this (but I think we should probably
keep the mempcpy). Most descriptors will be fairly small, so the
smaller code size is probably more important.
Thanks,
Florian
On 2/14/20 10:11 AM, Florian Weimer wrote:
> + /* A positive int value has at most 10 decimal digits. */
> + char buffer[sizeof (FD_TO_FILENAME_PREFIX) + 10];
This should use 'INT_STRLEN_BOUND (int)' rather than '10', where
INT_STRLEN_BOUND is taken from intprops.h. Then you don't need the
comment (and the code won't break on future ILP64 platforms :-).
> +char *
> +__fd_to_filename (int descriptor, struct fd_to_filename *storage)
> +{
> + char *p = mempcpy (storage->buffer, FD_TO_FILENAME_PREFIX,
> + strlen (FD_TO_FILENAME_PREFIX));
> + if (__glibc_likely (descriptor >= 0))
> + {
> + if (descriptor < 1000)
> + p = digit123 (p, descriptor);
> + else if (descriptor < 1000 * 1000) ...
It's not clear what that "descriptor >= 0" test is doing. I assume that
a precondition is that DESCRIPTOR is nonnegative; if so, this should be
mentioned and the test removed. If it's not a precondition, the code
should do the right thing if DESCRIPTOR is negative (I suppose, return a
filename that cannot be opened, though it doesn't do that currently) --
which should also be documented but I think this'd be overkill.
As Adhemerval writes, there's no need for special cases for powers of
1000 etc. Something like the following should do (this is a bit shorter
than Adhemerval's version):
/* Convert nonnegative DESCRIPTOR to a file name. */
char *
__fd_to_filename (int descriptor, struct fd_to_filename *storage)
{
char *p = mempcpy (storage->buffer, FD_TO_FILENAME_PREFIX,
strlen (FD_TO_FILENAME_PREFIX) - 1);
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;
}
GCC turns those divisions and remainders into the usual
multiply+shift+add and this should be good enough.
* Paul Eggert:
> On 2/14/20 10:11 AM, Florian Weimer wrote:
>> + /* A positive int value has at most 10 decimal digits. */
>> + char buffer[sizeof (FD_TO_FILENAME_PREFIX) + 10];
>
> This should use 'INT_STRLEN_BOUND (int)' rather than '10', where
> INT_STRLEN_BOUND is taken from intprops.h. Then you don't need the
> comment (and the code won't break on future ILP64 platforms :-).
But INT_STRLEN_BOUND is 11, right?
>> +char *
>> +__fd_to_filename (int descriptor, struct fd_to_filename *storage)
>> +{
>> + char *p = mempcpy (storage->buffer, FD_TO_FILENAME_PREFIX,
>> + strlen (FD_TO_FILENAME_PREFIX));
>> + if (__glibc_likely (descriptor >= 0))
>> + {
>> + if (descriptor < 1000)
>> + p = digit123 (p, descriptor);
>> + else if (descriptor < 1000 * 1000) ...
>
> It's not clear what that "descriptor >= 0" test is doing. I assume
> that a precondition is that DESCRIPTOR is nonnegative; if so, this
> should be mentioned and the test removed. If it's not a precondition,
> the code should do the right thing if DESCRIPTOR is negative (I
> suppose, return a filename that cannot be opened, though it doesn't do
> that currently) -- which should also be documented but I think this'd
> be overkill.
The problem is when an application passes an invalid descriptor to some
libc function and that ends up with __fd_to_filename. We should not
make matters worse in that case.
Maybe we should use an assert?
Thanks,
Florian
On 2/15/20 5:16 AM, Florian Weimer wrote:
> INT_STRLEN_BOUND is 11, right?
Yes, it's a bound on the string length of a printed int, and that's 11 in the
typical case of 32-bit int because the int might be negative. I didn't lose
sleep over the wasted byte, but if we want a tighter bound then we could use
INT_STRLEN_BOUND (int) - 1 instead. However, it might be better to leave it
alone so that we can use the code below.
> The problem is when an application passes an invalid descriptor to some
> libc function and that ends up with __fd_to_filename. We should not
> make matters worse in that case.
If it's not a precondition that the descriptor is nonnegative, we can't simply
return a copy of FD_TO_FILENAME_PREFIX as that's an existing filename. Instead,
how about the following? It uses a randomish garbage filename beginning with "-"
which should be good enough, and it doesn't cost a conditional branch to handle
negative descriptors.
char *
__fd_to_filename (int descriptor, struct fd_to_filename *storage)
{
char *p = mempcpy (storage->buffer, FD_TO_FILENAME_PREFIX,
strlen (FD_TO_FILENAME_PREFIX) - 1);
/* If DESCRIPTOR is negative, arrange for the filename to not exist
by prepending any byte other than '/', '.', '\0' or an ASCII digit.
The rest of the filename will be gibberish that fits. */
*p = '-';
p += descriptor < 0;
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;
}
@@ -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)
@@ -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);
@@ -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
new file mode 100644
@@ -0,0 +1,104 @@
+/* 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 <string.h>
+
+/* The split into groups of three digits is arbitrary, but it covers
+ the common case of descriptors less than 1000 fairly
+ efficiently. */
+
+/* Writes two digits to P. VALUE must be between 0 and 99
+ (inclusive). Returns the address after the written digits. */
+static char *
+digit2 (char *p, int value)
+{
+ p[0] = '0' + (value / 10);
+ p[1] = '0' + (value % 10);
+ return p + 2;
+}
+
+/* Writes three digits to P. VALUE must be between 0 and 999
+ (inclusive). Returns the address after the written digits. */
+static char *
+digit3 (char *p, int value)
+{
+ p[0] = '0' + (value / 100);
+ p[1] = '0' + ((value / 10) % 10);
+ p[2] = '0' + (value % 10);
+ return p + 3;
+}
+
+/* Writes one to three digits to P, depending on VALUE, which must be
+ less than 1000. Returns the address after the written digits. */
+static char *
+digit123 (char *p, int value)
+{
+ if (value < 10)
+ {
+ p[0] = '0' + value;
+ return p + 1;
+ }
+ else if (value < 100)
+ return digit2 (p, value);
+ else
+ return digit3 (p, value);
+}
+
+char *
+__fd_to_filename (int descriptor, struct fd_to_filename *storage)
+{
+ char *p = mempcpy (storage->buffer, FD_TO_FILENAME_PREFIX,
+ strlen (FD_TO_FILENAME_PREFIX));
+ if (__glibc_likely (descriptor >= 0))
+ {
+ if (descriptor < 1000)
+ p = digit123 (p, descriptor);
+ else if (descriptor < 1000 * 1000)
+ {
+ p = digit123 (p, descriptor / 1000);
+ p = digit3 (p, descriptor % 1000);
+ }
+ else if (descriptor < 1000 * 1000 * 1000)
+ {
+ p = digit123 (p, descriptor / (1000 * 1000));
+ p = digit3 (p, (descriptor / 1000) % 1000);
+ p = digit3 (p, descriptor % 1000);
+ }
+ else
+ {
+ if (descriptor < 2000 * 1000 * 1000)
+ {
+ *p = '1';
+ descriptor -= 1000 * 1000 * 1000;
+ }
+ else
+ {
+ *p = '2';
+ descriptor -= 2000 * 1000 * 1000;
+ }
+ ++p;
+ p = digit3 (p, descriptor / (1000 * 1000));
+ p = digit3 (p, (descriptor / 1000) % 1000);
+ p = digit3 (p, descriptor % 1000);
+ }
+ }
+
+ *p = '\0';
+ return storage->buffer;
+}
new file mode 100644
@@ -0,0 +1,105 @@
+/* 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 <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)
+{
+ 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);
+
+ if (value < 0)
+ /* Negative inputs are invalid, but the output should still be
+ deterministic. */
+ TEST_COMPARE_STRING (actual, FD_TO_FILENAME_PREFIX);
+ else
+ 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);
+ 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>
new file mode 100644
@@ -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"
@@ -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 +16,21 @@
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>
+
+struct fd_to_filename
{
- return NULL;
-}
+ /* A positive int value has at most 10 decimal digits. */
+ char buffer[sizeof (FD_TO_FILENAME_PREFIX) + 10];
+};
+
+/* 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 */
new file mode 100644
@@ -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/"
similarity index 58%
rename from sysdeps/unix/sysv/linux/fd_to_filename.h
rename to sysdeps/unix/sysv/linux/arch-fd_to_filename.h
@@ -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/"