On 2020-03-27 18:41, Joel Sherrill wrote:
On Fri, Mar 27, 2020 at 12:12 PM Eshan Dhawan <eshandhawa...@gmail.com
<mailto:eshandhawa...@gmail.com>> wrote:
On Thu, Mar 26, 2020 at 11:18 AM Sebastian Huber
<sebastian.hu...@embedded-brains.de
<mailto:sebastian.hu...@embedded-brains.de>> wrote:
On 25/03/2020 20:33, Joel Sherrill wrote:
On Wed, Mar 25, 2020 at 12:17 AM Eshan Dhawan
<eshandhawa...@gmail.com <mailto:eshandhawa...@gmail.com>> wrote:
On Wed, Mar 25, 2020 at 4:01 AM Joel Sherrill
<j...@rtems.org <mailto:j...@rtems.org>> wrote:
On Tue, Mar 24, 2020 at 4:57 PM Eshan Dhawan
<eshandhawa...@gmail.com
<mailto:eshandhawa...@gmail.com>> wrote:
Hello everyone,
As @Vaibhav Gupta
<mailto:vaibhav.varo...@gmail.com> suggested I
have also added adding file descriptor functions
to my GSOC project.
I went through the mailing list archives for more
information.
RTEMS as its own file descriptor so the functions
need to be implemented from scratch.
I wanted to get more information related to it.
What's the set of functions you are proposing for
those not tracking your draft proposal?
Link:
https://docs.google.com/document/d/1n-JOFUbFn6V1kViAGWsEGbVHL9MxlMyKP0BbZhEA1Rs/edit?usp=sharing
I haven't searched about the functions in the list yet.
The list was made by Vaibhav, last year and he told me
that it could be added to proposal this year as well.
I read the archives that these need to be written from
scratch.
Maybe not. I found at least this implementation of renameat()
which was implemented on top of existing calls:
https://github.com/lattera/freebsd/blob/master/contrib/openbsm/bin/auditdistd/renameat.h
It should be in a C file but that shows it can be done. That
directory has a lot of these methods.
Adding the *at() functions with an RTEMS-specific
implementation would be nice (and not difficult). The generic
renameat() implementation for example changes the current
directory. One of the goals of this API is to avoid exactly
this. In glibc/Linux for example a system call is used:
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/renameat.c;h=901d61f37e10d0c2df245c01bb2ef980d00e8f52;hb=HEAD
https://github.com/torvalds/linux/blob/master/fs/namei.c#L4590
I'm not disagreeing that a generic implementation is undesirable
long-term but these methods have not been present for 30 years and no
one has complained about their absence. I would propose generic
implementations be added and a ticket filed to add RTEMS specific
implementations if someone complains about the performance.
I see adding them now as a higher effort task that brings little
value. These are for standards compliance and not performance critical.
I would prefer to have real implementations and not just a Potemkin
village. Changing the current working directory (there is only on in
RTEMS by default) can lead to hard to find bugs.
All these functions are probably easy to implement. With LIBIO_GET_IOP()
and LIBIO_GET_IOP_WITH_ACCESS() you get the iop from the file
descriptor. Then we have to add a variant of
rtems_filesystem_eval_path_start_with_root_and_current() which uses the
location of the iop as the initial currentloc. The root and current
global locations can be set to rtems_filesystem_global_location_null.
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