From: Samuel Thibault <samuel.thibault@ens-lyon.org>
To: Florian Weimer <fweimer@redhat.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH 1/3] <fd_to_filename.h>: Add type safety and port to Hurd
Date: Fri, 14 Feb 2020 10:43:15 -0800 [thread overview]
Message-ID: <20200214184315.qdtxjb77collk6hc@function> (raw)
In-Reply-To: <c6b3a5e519cd3b0d7d77c7f2dfe35384b36cb39a.1581703185.git.fweimer@redhat.com>
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
>
>
--
Samuel
"2 + 2 = 5 pour d'assez grandes valeurs de 2"
next prev parent reply other threads:[~2020-02-14 18:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 18:10 [PATCH 0/3] <fd_to_filename.h> improvements Florian Weimer
2020-02-14 18:11 ` [PATCH 1/3] <fd_to_filename.h>: Add type safety and port to Hurd Florian Weimer
2020-02-14 18:43 ` Samuel Thibault [this message]
2020-02-14 19:08 ` Adhemerval Zanella
2020-02-14 20:21 ` Florian Weimer
2020-02-14 20:28 ` Paul Eggert
2020-02-15 13:16 ` Florian Weimer
2020-02-16 0:02 ` Paul Eggert
2020-02-17 15:18 ` Florian Weimer
2020-02-17 18:26 ` Paul Eggert
2020-02-17 18:59 ` Adhemerval Zanella
2020-02-17 19:14 ` Paul Eggert
2020-02-14 18:11 ` [PATCH 2/3] Linux: Port ttyname, ttyname_r to <fd_file_name.h> Florian Weimer
2020-02-14 18:11 ` [PATCH 3/3] Linux: Port fexecve to <fd_to_filename.h> Florian Weimer
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