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From: Segher Boessenkool <segher@kernel.crashing.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, Paul Mackerras <paulus@samba.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/32: indirect function call use bctrl rather than blrl in ret_from_kernel_thread
Date: Fri, 20 Aug 2021 13:12:01 -0500	[thread overview]
Message-ID: <20210820181201.GT1583@gate.crashing.org> (raw)
In-Reply-To: <20210820171845.GS1583@gate.crashing.org>

On Fri, Aug 20, 2021 at 12:18:45PM -0500, Segher Boessenkool wrote:
> On Fri, Aug 20, 2021 at 10:15:11PM +1000, Michael Ellerman wrote:
> > Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> > > Copied from commit 89bbe4c798bc ("powerpc/64: indirect function call
> > > use bctrl rather than blrl in ret_from_kernel_thread")
> > >
> > > blrl is not recommended to use as an indirect function call, as it may
> > > corrupt the link stack predictor.
> > 
> > Do we know if any 32-bit CPUs have a link stack predictor or similar?
> 
> 74xx do.

7450 and later, that is.  Will I ever get that right, sigh.


Segher

WARNING: multiple messages have this Message-ID (diff)
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/32: indirect function call use bctrl rather than blrl in ret_from_kernel_thread
Date: Fri, 20 Aug 2021 13:12:01 -0500	[thread overview]
Message-ID: <20210820181201.GT1583@gate.crashing.org> (raw)
In-Reply-To: <20210820171845.GS1583@gate.crashing.org>

On Fri, Aug 20, 2021 at 12:18:45PM -0500, Segher Boessenkool wrote:
> On Fri, Aug 20, 2021 at 10:15:11PM +1000, Michael Ellerman wrote:
> > Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> > > Copied from commit 89bbe4c798bc ("powerpc/64: indirect function call
> > > use bctrl rather than blrl in ret_from_kernel_thread")
> > >
> > > blrl is not recommended to use as an indirect function call, as it may
> > > corrupt the link stack predictor.
> > 
> > Do we know if any 32-bit CPUs have a link stack predictor or similar?
> 
> 74xx do.

7450 and later, that is.  Will I ever get that right, sigh.


Segher

  reply	other threads:[~2021-08-20 18:14 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-20  5:16 [PATCH] powerpc/32: indirect function call use bctrl rather than blrl in ret_from_kernel_thread Christophe Leroy
2021-08-20  5:16 ` Christophe Leroy
2021-08-20 12:15 ` Michael Ellerman
2021-08-20 12:15   ` Michael Ellerman
2021-08-20 17:18   ` Segher Boessenkool
2021-08-20 17:18     ` Segher Boessenkool
2021-08-20 18:12     ` Segher Boessenkool [this message]
2021-08-20 18:12       ` Segher Boessenkool
2021-08-27 13:15 ` Michael Ellerman

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