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Re: ptrace PEEKTEXT IO error?!
On Wed, Oct 05, 2005 at 07:20:11PM +0100, David Lecomber wrote:
> On Wed, 2005-10-05 at 13:11 -0400, Daniel Jacobowitz wrote:
> > On Wed, Oct 05, 2005 at 06:04:00PM +0100, David Lecomber wrote:
> > > Dear all,
> > >
> > > I have a multithreaded code which is misbehaving in GDB (verified on
> > > latest CVS). After threads are created, the target suddenly seems to
> > > become unwriteable, and even unreadable in some bits.
> >
> > This usually means the thread is not stopped. Failing that, check with
> > your kernel.
>
> 'ps' says the processes is stopped - so I guess that makes it a kernel
> woe.
>
> I've knocked up a ptrace test code, and it also shows the same behaviour
> independently of GDB.
>
> It seems ok at reading memory from addresses on the heap and stack --
> but it barfs at reading memory from the text segment. Is there
> something that the user code (one of the libraries called by my
> program) could do to prevent access to memory by a ptracing program?
No, this is most likely a kernel bug. This is mapped code, right, not
some mmaped device file (which is not generally accessible by ptrace)?
--
Daniel Jacobowitz
CodeSourcery, LLC