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From: Russell Currey <ruscur@russell.cc>
To: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/powernv/idle: Restore IAMR after idle
Date: Wed, 20 Feb 2019 22:25:15 +1100
Message-ID: <c9e2c03da5f2ccf351f5417b5a6deaf321699707.camel@russell.cc> (raw)
In-Reply-To: <20190220071503.GA4708@aks.ibm>

On Wed, 2019-02-20 at 12:45 +0530, Akshay Adiga wrote:
> On Wed, Feb 06, 2019 at 05:28:37PM +1100, Russell Currey wrote:
> > Without restoring the IAMR after idle, execution prevention on
> > POWER9
> > with Radix MMU is overwritten and the kernel can freely execute
> > userspace without
> > faulting.
> > 
> > This is necessary when returning from any stop state that modifies
> > user
> > state, as well as hypervisor state.
> > 
> > To test how this fails without this patch, load the lkdtm driver
> > and
> > do the following:
> > 
> >    echo EXEC_USERSPACE > /sys/kernel/debug/provoke-crash/DIRECT
> > 
> > which won't fault, then boot the kernel with powersave=off, where
> > it
> > will fault.  Applying this patch will fix this.
> > 
> > Fixes: 3b10d0095a1e ("powerpc/mm/radix: Prevent kernel execution of
> > user
> > space")
> > Cc: <stable@vger.kernel.org>
> > Signed-off-by: Russell Currey <ruscur@russell.cc>
> > ---
> >  arch/powerpc/include/asm/cpuidle.h |  1 +
> >  arch/powerpc/kernel/asm-offsets.c  |  1 +
> >  arch/powerpc/kernel/idle_book3s.S  | 20 ++++++++++++++++++++
> >  3 files changed, 22 insertions(+)
> > 
> > diff --git a/arch/powerpc/include/asm/cpuidle.h
> > b/arch/powerpc/include/asm/cpuidle.h
> > index 43e5f31fe64d..ad67dbe59498 100644
> > --- a/arch/powerpc/include/asm/cpuidle.h
> > +++ b/arch/powerpc/include/asm/cpuidle.h
> > @@ -77,6 +77,7 @@ struct stop_sprs {
> >  	u64 mmcr1;
> >  	u64 mmcr2;
> >  	u64 mmcra;
> > +	u64 iamr;
> >  };
> > 
> >  #define PNV_IDLE_NAME_LEN    16
> > diff --git a/arch/powerpc/kernel/asm-offsets.c
> > b/arch/powerpc/kernel/asm-offsets.c
> > index 9ffc72ded73a..10e0314c2b0d 100644
> > --- a/arch/powerpc/kernel/asm-offsets.c
> > +++ b/arch/powerpc/kernel/asm-offsets.c
> > @@ -774,6 +774,7 @@ int main(void)
> >  	STOP_SPR(STOP_MMCR1, mmcr1);
> >  	STOP_SPR(STOP_MMCR2, mmcr2);
> >  	STOP_SPR(STOP_MMCRA, mmcra);
> > +	STOP_SPR(STOP_IAMR, iamr);
> >  #endif
> > 
> >  	DEFINE(PPC_DBELL_SERVER, PPC_DBELL_SERVER);
> > diff --git a/arch/powerpc/kernel/idle_book3s.S
> > b/arch/powerpc/kernel/idle_book3s.S
> > index 7f5ac2e8581b..bb4f552f6c7e 100644
> > --- a/arch/powerpc/kernel/idle_book3s.S
> > +++ b/arch/powerpc/kernel/idle_book3s.S
> > @@ -200,6 +200,12 @@ pnv_powersave_common:
> >  	/* Continue saving state */
> >  	SAVE_GPR(2, r1)
> >  	SAVE_NVGPRS(r1)
> > +
> > +BEGIN_FTR_SECTION
> > +	mfspr	r5, SPRN_IAMR
> > +	std	r5, STOP_IAMR(r13)
> > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
> > +
> 
> Are we trying to add for both power8 and power9 ?
> power9 would be CPU_FTR_ARCH_300.
> 

If I recall correctly I had this at P9 only but for some reason I
changed it - the reason is probably just that I had it confused for
something else.  Michael can you confirm this should be P9 only?


  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-06  6:28 Russell Currey
2019-02-07  4:29 ` Michael Ellerman
2019-02-07  6:28   ` Russell Currey
2019-02-07  5:08 ` Nicholas Piggin
2019-02-07  6:33   ` Russell Currey
2019-02-07 16:37     ` Thiago Jung Bauermann
2019-02-07 22:38       ` Russell Currey
2019-02-08  1:04   ` Michael Ellerman
2019-02-19  4:21     ` Nicholas Piggin
2019-02-20  6:04       ` Akshay Adiga
2019-02-20 11:18         ` Russell Currey
2019-02-20  7:15 ` Akshay Adiga
2019-02-20 11:25   ` Russell Currey [this message]
2019-02-20  8:58 ` Akshay Adiga
2019-02-20 11:20   ` Russell Currey

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