[PATCH v1 1/5] libcsupport: Added futimens() and utimensat()
Gedare Bloom
gedare at rtems.org
Wed May 5 18:55:56 UTC 2021
On Wed, May 5, 2021 at 11:03 AM Ryan Long <ryan.long at oarcorp.com> wrote:
>
> Reply is below.
>
> -----Original Message-----
> From: Gedare Bloom <gedare at rtems.org>
> Sent: Tuesday, May 4, 2021 11:27 AM
> To: Ryan Long <ryan.long at oarcorp.com>
> Cc: Sebastian Huber <sebastian.huber at embedded-brains.de>; devel at rtems.org
> Subject: Re: [PATCH v1 1/5] libcsupport: Added futimens() and utimensat()
>
> On Tue, May 4, 2021 at 10:04 AM Ryan Long <ryan.long at oarcorp.com> wrote:
> >
> >
> >
> > -----Original Message-----
> > From: Sebastian Huber <sebastian.huber at embedded-brains.de>
> > Sent: Tuesday, May 4, 2021 12:04 AM
> > To: Ryan Long <ryan.long at oarcorp.com>; devel at rtems.org
> > Subject: Re: [PATCH v1 1/5] libcsupport: Added futimens() and
> > utimensat()
> >
> > On 03/05/2021 15:40, Ryan Long wrote:
> >
> > > Created futimens.c and utimensat.c to add support for the POSIX
> > > methods futimens() and utimensat().
> > >
> > > utime() and utimes() are considered obsolote by POSIX, but RTEMS
> > > will continue to support them.
> > >
> > > Closes #4396
> > > ---
> > > cpukit/Makefile.am | 2 +
> > > cpukit/include/rtems/libio_.h | 61 +++++++++-
> > > cpukit/libcsupport/src/futimens.c | 91 +++++++++++++++
> > > cpukit/libcsupport/src/utimensat.c | 229 +++++++++++++++++++++++++++++++++++++
> > > spec/build/cpukit/librtemscpu.yml | 2 +
> > > 5 files changed, 384 insertions(+), 1 deletion(-)
> > > create mode 100644 cpukit/libcsupport/src/futimens.c
> > > create mode 100644 cpukit/libcsupport/src/utimensat.c
> > >
> > > diff --git a/cpukit/Makefile.am b/cpukit/Makefile.am index
> > > b0df610..29b4207 100644
> > > --- a/cpukit/Makefile.am
> > > +++ b/cpukit/Makefile.am
> > > @@ -262,6 +262,8 @@ librtemscpu_a_SOURCES += libcsupport/src/unmount.c
> > > librtemscpu_a_SOURCES += libcsupport/src/__usrenv.c
> > > librtemscpu_a_SOURCES += libcsupport/src/utime.c
> > > librtemscpu_a_SOURCES += libcsupport/src/utimes.c
> > > +librtemscpu_a_SOURCES += libcsupport/src/futimens.c
> > > +librtemscpu_a_SOURCES += libcsupport/src/utimensat.c
> > > librtemscpu_a_SOURCES += libcsupport/src/utsname.c
> > > librtemscpu_a_SOURCES += libcsupport/src/vprintk.c
> > > librtemscpu_a_SOURCES += libcsupport/src/write.c diff --git
> > > a/cpukit/include/rtems/libio_.h b/cpukit/include/rtems/libio_.h
> > > index
> > > e9eb462..fc7a1e4 100644
> > > --- a/cpukit/include/rtems/libio_.h
> > > +++ b/cpukit/include/rtems/libio_.h
> > > @@ -7,7 +7,7 @@
> > > */
> > >
> > > /*
> > > - * COPYRIGHT (c) 1989-2011.
> > > + * COPYRIGHT (c) 1989-2011, 2021.
> > > * On-Line Applications Research Corporation (OAR).
> > > *
> > > * Modifications to support reference counting in the file system
> > > are @@ -357,6 +357,65 @@ static inline void rtems_filesystem_instance_unlock(
> > > (*mt_entry->ops->unlock_h)( mt_entry );
> > > }
> > >
> > > +/* Prototypes for functions used between utimensat() and futimens()
> > > +*/
> > > +
> > > +/**
> > > + * @brief Checks the tv_sec member of a timespec struct
> > > + *
> > > + * @param[in] time The timespec struct to be validated
> > > + *
> > > + * Ensures that the value in the tv_sec member is non-negative.
> > > + *
> > > + * @retval true If the tv_sec member is a valid value
> > > + * @retval false If the tv_sec member is not a valid value */ bool
> > > +rtems_filesystem_utime_tv_sec_valid( struct timespec time );
> > > +
> > > +/**
> > > + * @brief Checks the tv_nsec member of a timespec struct
> > > + *
> > > + * Ensures that the value in the tv_nsec member is equal to either
> > > + * UTIME_NOW, UTIME_OMIT, or a value greater-than or equal to zero
> > > + * and less than a billion.
> > > + *
> > > + * @param[in] time The timespec struct to be validated
> > > + *
> > > + * @retval true If the tv_nsec member is a valid value
> > > + * @retval false If the tv_nsec member is not a valid value */
> > > +bool rtems_filesystem_utime_tv_nsec_valid( struct timespec time );
> >
> > Are these two functions ever used individually? Do they modify the time?
> > Maybe we should add a standard phase for boolean type returns:
> >
> > @return Returns true, if the X is valid, otherwise false.
> >
> > [Ryan Long] These functions are only used in rtems_filesystem_utime_check_times(). They don't modify the time, they just ensure that the members of the timespec struct are valid values. Should the arguments for those functions be changed to be a const since they're not being modified? And sure, I can consolidate the @retval statements like that.
> >
> > > +
> > > +/**
> > > + * @brief Determines if the process has write permissions to a file
> > > + *
> > > + * Checks that the process has the same userID as the file and
> > > +whether the
> > > + * file has write permissions.
> > > + *
> > > + * @param[in] currentloc The current location to a file
> > > + * @param[in] fstat_h The file handler of @currentloc
> > Why is this an extra parameter?
> > [Ryan Long] This was Joel's suggestion, but I didn't think about just using the currentloc argument. I'll change that in V2.
> > > + *
> > > + * @retval 0 If the process has write permissions
> > > + * @retval -1 If the process does not have write permissions
> > Why 0 and -1, what about errno? Is it set by the function or not?
> > [Ryan Long] It's 0 and -1 because it uses the rtems_set_errno_and_return_minus_one() macro.
> > > + */
> > > +int rtems_filesystem_utime_check_permissions(
> > > + const rtems_filesystem_location_info_t *currentloc,
> > > + rtems_filesystem_fstat_t fstat_h
> > > +);
> > > +
> > > +/**
> > > + * @brief Checks @times and updates @new_times
> > > + *
> > > + * @param[in] times The timespec struct to be checked
> > > + * @param[in,out] new_times The timespec struct to contain the
> > > +updated time
> > > + *
> > > + * @retval 0 If the time was able to be updated
> > > + * @retval -1 If the time was not able to be updated */ int
> > > +rtems_filesystem_utime_check_times(
> > > + const struct timespec times[2],
> > > + struct timespec new_times[2]
> > > +);
> > > +
> > > /*
> > > * File Descriptor Routine Prototypes
> > > */
> > > diff --git a/cpukit/libcsupport/src/futimens.c
> > > b/cpukit/libcsupport/src/futimens.c
> > > new file mode 100644
> > > index 0000000..33ae469
> > > --- /dev/null
> > > +++ b/cpukit/libcsupport/src/futimens.c
> > > @@ -0,0 +1,91 @@
> > > +/* SPDX-License-Identifier: BSD-2-Clause */
> > > +
> > > +/**
> > > + * @file
> > > + *
> > > + * @ingroup libcsupport
> > > + *
> > > + * @brief Set file access and modification times based on file
> > > +descriptor in
> > > + * nanoseconds.
> > > + */
> > > +
> > > +/*
> > > + * COPYRIGHT (c) 1989-2009, 2021.
> > > + * On-Line Applications Research Corporation (OAR).
> > > + *
> > > + * Redistribution and use in source and binary forms, with or
> > > +without
> > > + * modification, are permitted provided that the following
> > > +conditions
> > > + * are met:
> > > + * 1. Redistributions of source code must retain the above copyright
> > > + * notice, this list of conditions and the following disclaimer.
> > > + * 2. Redistributions in binary form must reproduce the above copyright
> > > + * notice, this list of conditions and the following disclaimer in the
> > > + * documentation and/or other materials provided with the distribution.
> > > + *
> > > + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
> > > + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> > > +LIMITED TO, THE
> > > + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
> > > +PARTICULAR PURPOSE
> > > + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
> > > +CONTRIBUTORS BE
> > > + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
> > > +OR
> > > + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
> > > +PROCUREMENT OF
> > > + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
> > > +BUSINESS
> > > + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
> > > +WHETHER IN
> > > + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
> > > +OTHERWISE)
> > > + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
> > > +ADVISED OF THE
> > > + * POSSIBILITY OF SUCH DAMAGE.
> > > + */
> > > +
> > > +#ifdef HAVE_CONFIG_H
> > > +#include "config.h"
> > > +#endif
> > > +
> > > +#include <sys/stat.h>
> > > +#include <rtems/libio_.h>
> > > +
> > > +#include <fcntl.h>
> > > +#include <stdlib.h>
> > > +#include <string.h>
> > > +
> > > +/**
> > > + *
> > > +https://pubs.opengroup.org/onlinepubs/9699919799.2008edition/functi
> > > +on
> > > +s/futimens.html
> > > + *
> > > + * Set file access and modification times */ int futimens(
> > > + int fd,
> > > + const struct timespec times[2]
> > > +)
> > > +{
> > > + int rv;
> > > + rtems_libio_t *iop;
> > > + struct timespec new_times[2];
> > > + const rtems_filesystem_location_info_t *currentloc = NULL;
> > > +
> > > + LIBIO_GET_IOP_WITH_ACCESS( fd, iop, LIBIO_FLAGS_READ, EBADF );
> > > +
> > > + currentloc = &iop->pathinfo;
> > > +
> > > + rv = rtems_filesystem_utime_check_permissions(
> > > + currentloc,
> > > + (*currentloc->handlers->fstat_h) ); if( rv == -1 ) {
> >
> > Which coding style should this file and the other new files have?
> >
> > [...]
> >
> > > +}
> > > +
> > > +/* Determine whether the access and modified timestamps can be
> > > +updated */ int rtems_filesystem_utime_check_permissions(
> > > + const rtems_filesystem_location_info_t * currentloc,
> > > + rtems_filesystem_fstat_t fstat_h
> > > +)
> > > +{
> > > + struct stat st;
> > > + volatile int rv;
> > volatile?
> > [Ryan Long] Forgot to take this out after debugging. Will be removed in V2.
> > > + bool write_access;
> > > +
> > > + memset( &st, 0, sizeof(st) );
> > > +
> > > + rv = (*fstat_h)( currentloc, &st ); if( rv != 0 ) {
> > > + rtems_set_errno_and_return_minus_one( ENOENT ); }
> > > +
> > > + /*
> > > + * Check that the user ID and the user ID of the file match
> > > + */
> > > + if( geteuid() != st.st_uid ) {
> > > + rtems_set_errno_and_return_minus_one( EACCES ); }
> > Is this really what POSIX specified?
> > [Ryan Long] Yes, on https://pubs.opengroup.org/onlinepubs/9699919799.2008edition/functions/futimens.html they said return this if 'the effective user ID of the process does not match the owner of the file and write access is denied.'
> > > +
>
> But you haven't checked write access yet. I think you haven't parsed the specification correctly.
> [Ryan Long] So I should move the assignment of write_access above this check, and change the check to be this?
>
yep. Other cases might be missing or conflicting though, so you'll
need to check through all the logic, e.g., EPERM.
> if( geteuid() != st.st_uid) {
> if( !write_access) {
> rtems_set_errno_and_return_minus_one( EACCES );
> }
> }
>
> > > + write_access = rtems_filesystem_check_access(
> > > + RTEMS_FS_PERMS_WRITE,
> > > + st.st_mode,
> > > + st.st_uid,
> > > + st.st_gid
> > > + );
> > > + if( !write_access ) {
> > > + rtems_set_errno_and_return_minus_one( EACCES ); }
> > > +
> > > + return 0;
> > > +}
> >
> > > [...]
> > > +
> > > +
> > > +/**
> > > + *
> > > +https://pubs.opengroup.org/onlinepubs/9699919799.2008edition/functi
> > > +ons/futimens.html
> > > + *
> > > + * Set file access and modification times */ int utimensat(
> > > + int fd,
> > > + const char *path,
> > > + const struct timespec times[2],
> > > + int flag
> > > +)
> > > +{
> > > + int rv = 0;
> > > + rtems_filesystem_eval_path_context_t ctx;
> > > + int eval_flags = RTEMS_FS_FOLLOW_LINK;
> > > + const rtems_filesystem_location_info_t *currentloc = NULL;
> > > + struct timespec new_times[2];
> > > +
> > > + /*
> > > + * RTEMS does not currently support operating on a real file descriptor
> > > + */
> > > + if( fd != AT_FDCWD ) {
> > > + rtems_set_errno_and_return_minus_one( ENOSYS ); }
> > > +
> > > + /*
> > > + * RTEMS does not currently support AT_SYMLINK_NOFOLLOW
> > > + */
> > > + if( flag != 0 ) {
> > > + rtems_set_errno_and_return_minus_one( ENOSYS ); }
> > > +
> > > + currentloc = rtems_filesystem_eval_path_start( &ctx, path,
> > > + eval_flags );
> > > +
> > > + rv = rtems_filesystem_utime_check_permissions(
> > > + currentloc,
> > > + (*currentloc->handlers->fstat_h) ); if( rv == -1 ) {
> > Better use the success code, for example rv != 0.
> > > + rtems_filesystem_eval_path_cleanup( &ctx );
> > > + return rv;
> > > + }
> > > +
> > > + rv = rtems_filesystem_utime_check_times( times, new_times); if(
> > > + rv == -1 ) {
> > > + rtems_filesystem_eval_path_cleanup( &ctx );
> > > + return rv;
> > > + }
> > > +
> > > + rv = (*currentloc->mt_entry->ops->utimens_h)(
> > > + currentloc,
> > > + new_times
> > > + );
> > > +
> > > + rtems_filesystem_eval_path_cleanup( &ctx );
> > > +
> > > + return rv;
> > > +}
> > > diff --git a/spec/build/cpukit/librtemscpu.yml
> > > b/spec/build/cpukit/librtemscpu.yml
> > > index a3a9ee4..9639051 100644
> > > --- a/spec/build/cpukit/librtemscpu.yml
> > > +++ b/spec/build/cpukit/librtemscpu.yml
> > > @@ -761,6 +761,8 @@ source:
> > > - cpukit/libcsupport/src/unmount.c
> > > - cpukit/libcsupport/src/utime.c
> > > - cpukit/libcsupport/src/utimes.c
> > > +- cpukit/libcsupport/src/futimens.c
> > > +- cpukit/libcsupport/src/utimensat.c
> > > - cpukit/libcsupport/src/utsname.c
> > > - cpukit/libcsupport/src/vprintk.c
> > > - cpukit/libcsupport/src/write.c
> >
> > --
> > embedded brains GmbH
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> > Germany
> > email: sebastian.huber at embedded-brains.de
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> >
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