Fwd: vdso

[vijay nag <vijunag@gmail.com>]

---------- Forwarded message ----------
From: vijay nag <vijunag@gmail.com>
Date: Fri, Jul 5, 2013 at 11:38 AM
Subject: Re: vdso
To: Jan Kratochvil <jan.kratochvil@redhat.com>


On Thu, Jul 4, 2013 at 11:40 AM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> On Wed, 03 Jul 2013 17:23:39 +0200, vijay nag wrote:
>> On Wednesday, July 3, 2013, Jan Kratochvil <jan.kratochvil@redhat.com> wrote:
>> > This warning is tracked as:
>> >         http://sourceware.org/bugzilla/show_bug.cgi?id=14466
>> >
>> > and it is harmless, it should not affect functionality/symbols of GDB.
>> >
>> >
>> > Jan
>> >
>> Are you suggesting me that it could be a problem with glibc ?
>
> No.
>
>
> Jan

The function linux_proc_xfer_partial() is returning result zero when
trying to pread64 /proc/<pid>/mem and errno is set to -EIO.
Does that mean kernel doesn't support pread64 on /proc/xxx/mem files ?

gdb) l
4392
4393      /* We could keep this file open and cache it - possibly one per
4394         thread.  That requires some juggling, but is even faster.  */
4395      sprintf (filename, "/proc/%d/mem", PIDGET (inferior_ptid));
4396      fd = open (filename, O_RDONLY | O_LARGEFILE);
4397      if (fd == -1)
4398        return 0;
4399
4400      /* If pread64 is available, use it.  It's faster if the kernel
4401         supports it (only one syscall), and it's 64-bit safe even on
(gdb) l
4402         32-bit platforms (for instance, SPARC debugging a SPARC64
4403         application).  */
4404    #ifdef HAVE_PREAD64
4405      if (pread64 (fd, readbuf, len, offset) != len)
4406    #else
4407      if (lseek (fd, offset, SEEK_SET) == -1 || read (fd, readbuf,
len) != len)
4408    #endif
4409        ret = 0;
4410      else
4411        ret = len;
(gdb) p *__errno_location()
$18 = 5
(gdb)