[PATCH] powerpc:Don't print raw EIP/LR hex values in dump_stack() and show_regs()

[David Laight]

From: Segher Boessenkool
> Sent: 21 December 2020 16:32
> 
> On Mon, Dec 21, 2020 at 04:17:21PM +0100, Christophe Leroy wrote:
> > Le 21/12/2020 à 04:27, Xiaoming Ni a écrit :
> > >Since the commit 2b0e86cc5de6 ("powerpc/fsl_booke/32: implement KASLR
> > >infrastructure"), the powerpc system is ready to support KASLR.
> > >To reduces the risk of invalidating address randomization, don't print the
> > >EIP/LR hex values in dump_stack() and show_regs().
> 
> > I think your change is not enough to hide EIP address, see below a dump
> > with you patch, you get "Faulting instruction address: 0xc03a0c14"
> 
> As far as I can see the patch does nothing to the GPR printout.  Often
> GPRs contain code addresses.  As one example, the LR is moved via a GPR
> (often GPR0, but not always) for storing on the stack.
> 
> So this needs more work.

If the dump_stack() is from an oops you need the real EIP value
on order to stand any chance of making headway.

Otherwise you might just as well just print 'borked - tough luck'.

	David

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