From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCHv3] arm64: Rework valid_user_regs
Date: Tue, 1 Mar 2016 13:40:44 +0000 [thread overview]
Message-ID: <20160301134043.GA14022@arm.com> (raw)
In-Reply-To: <CAFEAcA9PmQYFYBw0GstA88MGHwGivB+VJdowBf6T1ggneZKihg@mail.gmail.com>
On Tue, Mar 01, 2016 at 01:08:33PM +0000, Peter Maydell wrote:
> On 1 March 2016 at 12:47, Mark Rutland <mark.rutland@arm•com> wrote:
> > On Tue, Feb 16, 2016 at 06:20:05PM +0000, Will Deacon wrote:
> >> > +static int valid_native_regs(struct user_pt_regs *regs)
> >> > +{
> >> > + regs->pstate &= ~SPSR_EL1_AARCH64_RES0_BITS;
> >> > +
> >> > + if (user_mode(regs) && !(regs->pstate & PSR_MODE32_BIT) &&
> >> > + (regs->pstate & PSR_D_BIT) == 0 &&
> >> > + (regs->pstate & PSR_A_BIT) == 0 &&
> >> > + (regs->pstate & PSR_I_BIT) == 0 &&
> >> > + (regs->pstate & PSR_F_BIT) == 0) {
> >> > + return 1;
> >> > + }
> >> > +
> >> > + /* Force PSR to a valid 64-bit EL0t */
> >> > + regs->pstate &= PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT;
> >>
> >> Can we not just zap the pstate to PSR_MODE_EL0t and be done with it?
> >
> > I'm worried that some userspace might be relying on these being
> > preserved.
>
> This function is called as part of signal-return, right?
> You clearly can't just zap the flag registers in that code
> path, because you'd then be corrupting the flags of the
> bit of userspace code that was interrupted by the signal.
> (Or am I missing something?)
Well, it would only occur if the signal handler had tried to set pstate
to an invalid value. That said, it is a change in behaviour, so we can
leave it as Mark has suggested.
Will
next prev parent reply other threads:[~2016-03-01 13:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-16 18:15 [PATCHv3] arm64: Rework valid_user_regs Mark Rutland
2016-02-16 18:20 ` Will Deacon
2016-02-29 19:08 ` Will Deacon
2016-03-01 12:47 ` Mark Rutland
2016-03-01 13:08 ` Peter Maydell
2016-03-01 13:40 ` Will Deacon [this message]
2016-03-01 14:01 ` Mark Rutland
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