Re: Fwd: Re: libc/5055 - [BUG] getpt() does not detect /dev/pts due towrong statfs()

[Sreeji K Das]

Hi Wolfram

thx for ur sample code. I had similar piece of code
for my testing & it always produced the o/p
fstat.f_type = 7366766

I had been testing my sample script from within a
clearcase view ! Now I accidentally ran it outside the
view & boom ! it worked ! So it looks like clearcase
was the culprit (more specific, I think the mvfs
driver loaded by clarcase has hijacked statfs() ! I
need to debug this further !)

thanks
Sreeji

 --- Wolfram Gloger <address@hidden>
wrote: > > 2) Then the following code is executed:
> > if (fd != -1)
> > {
> >   struct statfs fsbuf;
> >   static int devpts_mounted;
> > 
> >   /* Check that the /dev/pts filesystem is mounted
> >    or if /dev is a devfs filesystem (this implies
> > /dev/pts).  */
> >    if (devpts_mounted
> >        || (__statfs (_PATH_DEVPTS, &fsbuf) == 0
> >         && fsbuf.f_type == DEVPTS_SUPER_MAGIC)
> >        || (__statfs (_PATH_DEV, &fsbuf) == 0
> >        && fsbuf.f_type == DEVFS_SUPER_MAGIC))
> > 
> > In the above, _PATH_DEVPTS is defined as :
> > #define _PATH_DEVPTS _PATH_DEV "pts"
> > ie. "/dev/pts"
> > So the above statfs() stats "/dev/pts", which is a
> > directory in the filesystem.
> > On my system:
> >  $ mount|grep pts
> >   none on /dev/pts type devpts (rw,gid=5,mode=620)
> >  $ ls -ld /dev/pts
> >  drwxr-xr-x    2 root     root            0 Jun 10
> > 16:07 /dev/pts/
> > 
> > Due to the above (/dev/ is not devfs and /dev/pts
> is a
> > directory), the magic is not what's expected.
> 
> Hold it there -- statfs should definitely work on a
> directory too.
> The appended program yields on my 2.4.21 system:
> 
> f_type=1cd1 PTS_MAGIC=1cd1
> 
> If it doesn't on your's, there may be a kernel bug
> in the statfs
> syscall.
> 
> Regards,
> Wolfram.
> 
> #include <stdio.h>
> #include <sys/vfs.h>
> #define DEVPTS_SUPER_MAGIC 0x1cd1
> int main()
> {
>     struct statfs sf;
> 
>     if (statfs("/dev/pts", &sf) == 0) {
>       printf("f_type=%lx PTS_MAGIC=%lx\n", sf.f_type,
> DEVPTS_SUPER_MAGIC);
>     }
>     return 0;
> } 

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