GSOC: Introduction

[Dmitry V. Levin]

On Tue, Mar 14, 2017 at 12:40:46AM +0530, Abhishek Tiwari wrote:
> > Per-file summary is not in GNU change log format, please refer to
> > https://www.gnu.org/prep/standards/html_node/Style-of-Change-Logs.html .
> > Specifically, it lacks asterisks at the beginning of each new file
> > description and has excess spaces between file part and description,
> > otherwise looks fine.
> >
> > The patch wires up {,l}stat{,64}, fstatat/fstatat64 syscalls (used for obtaining
> > file status), ustat syscall (which is a deprecated way to get some FS
> > statistics) and some statfs syscalls (which are more contemporary way
> > obtaining FS statistics information). On the other side, at least
> > fstat/fstat64, fstatfs/fstatfs64, old{,f,l}stat, osf_{,f}statfs, and various
> > (mostly unsupported) syscalls with osf_, svr4_, sysv_, bsd43_, and posix_
> > prefixes, present on alpha and mips, are omitted. I'm not sure whether
> > it was intended.
> >
> > There are minor tabulation irregularities introduced (at least) for
> > newfstatat and fstatat64 syscall entries, it is better to avoid this.
> 
> I have fixed the commit entries.
> Now the patch includes all the stat-like syscalls that can be
> displayed by following command->

The idea is not to throw all syscalls that do some kind of stat into a
single class, but to create a class of syscalls that could be useful.
As Eugene already noted, there is little use of grouping syscalls that
stat files with those that stat filesystems.

Actually, there is a software project that could benefit from more
fine-grained classes, e.g. oldstat+stat+stat64, oldlstat+lstat+lstat64,
and newfstatat+fstatat64.

There may be some use of a class that groups all filesystem stat syscalls
like ustat and *statfs*.  This might appear to be easier for you to
implement, especially the part that tests it.

> grep -nr stat linux/*/syscallent*

btw, why do you pass -nr to this grep command?

> >> --- a/syscall.c
> >> +++ b/syscall.c
> >> @@ -77,6 +77,7 @@
> >>  #define TS TRACE_SIGNAL
> >>  #define TM TRACE_MEMORY
> >>  #define TSC TRACE_SCHED
> >> +#define TST  TRACE_STAT
> > Tabulation is used for separating macro declaration and definition, but
> > neighbouring lines utilise space for this purpose.
> 
> Please elaborate, i don't get what correction is intended here?

The rule of thumb is simple:
when patching a piece of code, follow its coding style.

If the code uses spaces, use spaces.  If it uses tabs, use tabs.
strace has a long history with a lot of contributors so the style
used in different parts might differ slightly.

> >> +++ b/tests/stat_like.test
> >> @@ -0,0 +1,58 @@
> >> +#!/bin/sh
> >> +
> >> +# Check how stat-like syscalls are traced.
> >> +#
> >> +# Copyright (c) 2017 The strace developers.
> >> +# All rights reserved.
> >> +#
> >> +# 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.
> >> +# 3. The name of the author may not be used to endorse or promote products
> >> +#    derived from this software without specific prior written permission.
> >> +#
> >> +# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
> >> +
> >> +STAT_TESTS='21 fstat
> >> +33 ustat
> >> +32 statx
> >> +17 statfs
> >> +21 oldfstat'
> >> +
> >> +NON_STAT_TESTS='11 fchdir
> >> +27 futex
> >> +10 fsync'
> >> +
> >> +. "${srcdir=.}/init.sh"
> >> +
> >> +echo "$STAT_TESTS" | while read w i
> >> +do
> >> +     run_prog ./$i > /dev/null
> >> +     run_strace -a$w -e%stat ./$i > "$EXP"
> >> +     match_diff "$LOG" "$EXP"
> >> +done
> >> +
> >> +echo '+++ exited with 0 +++' > "$EXP"
> >> +
> >> +echo "$NON_STAT_TESTS" | while read w i
> >> +do
> >> +     run_prog ./$i > /dev/null
> >> +     run_strace -a$w -e%stat ./$i > /dev/null
> >> +     match_diff "$LOG" "$EXP"
> >> +done
> >> +
> >> +rm "$EXP"
> > This test produces the following diagnostics:
> >
> >     1,2c1,2
> >     < fstat(0, 0x7f4dc9b2ffe0) = -1 EFAULT (Bad address)
> >     < fstat(0, {st_dev=makedev(9, 1), st_ino=8761399, st_mode=S_IFREG|0640, st_nlink=1, st_uid=1000, st_gid=1000, st_blksize=4096, st_blocks=0, st_size=43147718418, st_atime=1969-12-31T21:59:17+0100.000000135, st_mtime=1969-12-31T21:59:19+0100.000000246, st_ctime=2017-03-13T07:03:55+0100.962268762}) = 0
> >     ---
> >     > stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2246, ...}) = 0
> >     > stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2246, ...}) = 0
> >     stat_like.test: failed test: ../strace -a21 -e%stat ./fstat output mismatch
> >
> > It exits with status 0, however.
> 
> Please help me with this part, how can I run this test on my machine.

Do you ask about running this particular test?  I think it's as simple as
$ make check TESTS=stat_like VERBOSE=1


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