From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 30 Jul 1999 15:24:26 +1000 Message-Id: <199907300524.PAA03967@tango.anu.edu.au> From: Paul Mackerras To: drow@false.org CC: linuxppc-dev@lists.linuxppc.org In-reply-to: <19990730011819.A364@them.org> (message from Daniel Jacobowitz on Fri, 30 Jul 1999 01:18:20 -0400) Subject: Re: Vger broken w.r.t. gdb Reply-to: Paul.Mackerras@cs.anu.edu.au References: <19990728222617.A636@them.org> <199907290400.OAA02618@tango.anu.edu.au> <19990729013842.A1209@them.org> <199907290548.PAA02760@tango.anu.edu.au> <19990730011819.A364@them.org> Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: Daniel Jacobowitz wrote: > Now I'm really confused. > > >From my readings it appears that we should only reach this point if a > trap instruction was encountered. But from what I can see no trap > instruction exists at that address. At A common thing that gdb does is to put trap instructions into the memory image of a process being debugged. It sounds to me as though, with all the page cache and memory management changes that have gone on in 2.3, we now have the undesirable situation that a trap instruction put in by gdb hasn't stayed confined to the process being debugged but has leaked into the copy of the page that is being used by other processes. > Perhaps something having to do with instruction caching by the > processor? This is a completely wild guess, but if a trap instruction > was encountered, and then gdb cleared it, and the instruction cache was > not flushed... Well, whatever the problem is, it's something new in 2.3, it's not a long-standing omission of some cache flushing stuff. It's far more likely to be something in the ptrace syscall code which hasn't been correctly updated to cope with the recent page cache and VM changes. Paul. [[ This message was sent via the linuxppc-dev mailing list. Replies are ]] [[ not forced back to the list, so be sure to Cc linuxppc-dev if your ]] [[ reply is of general interest. Please check http://lists.linuxppc.org/ ]] [[ and http://www.linuxppc.org/ for useful information before posting. ]]