linux-kernel - Re: [PATCH] powerpc:Don't print raw EIP/LR hex values in dump_stack() and show

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Message-ID: <20201221163130.GZ2672@gate.crashing.org>
Date:   Mon, 21 Dec 2020 10:31:30 -0600
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Xiaoming Ni <nixiaoming@...wei.com>, linux-kernel@...r.kernel.org,
        benh@...nel.crashing.org, mpe@...erman.id.au, paulus@...ba.org,
        linuxppc-dev@...ts.ozlabs.org, yanaijie@...wei.com,
        npiggin@...il.com, ravi.bangoria@...ux.ibm.com, mikey@...ling.org,
        aneesh.kumar@...ux.ibm.com, haren@...ux.ibm.com, wangle6@...wei.com
Subject: Re: [PATCH] powerpc:Don't print raw EIP/LR hex values in dump_stack() and show_regs()

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.


Segher