From: "H.J. Lu" <hjl.tools@gmail.com>
To: Mark Brown <broonie@kernel.org>,
"dalias@libc.org" <dalias@libc.org>,
"Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
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Subject: Re: [musl] Re: [PATCH v8 00/38] arm64/gcs: Provide support for GCS in userspace
Date: Sat, 2 Mar 2024 07:05:49 -0800 [thread overview]
Message-ID: <CAMe9rOoVNZ+q0MAcpW-HDuptD8WDEDddZjOycy7G=P48nJ=DSA@mail.gmail.com> (raw)
In-Reply-To: <20240302145702.GD1884416@port70.net>
On Sat, Mar 2, 2024 at 6:57 AM Szabolcs Nagy <nsz@port70.net> wrote:
>
> * Mark Brown <broonie@kernel.org> [2024-02-21 17:36:12 +0000]:
>
> > On Wed, Feb 21, 2024 at 09:58:01AM -0500, dalias@libc.org wrote:
> > > On Wed, Feb 21, 2024 at 01:53:10PM +0000, Mark Brown wrote:
> > > > On Tue, Feb 20, 2024 at 08:27:37PM -0500, dalias@libc.org wrote:
> > > > > On Wed, Feb 21, 2024 at 12:35:48AM +0000, Edgecombe, Rick P wrote:
> >
> > > > > > (INCSSP, RSTORSSP, etc). These are a collection of instructions that
> > > > > > allow limited control of the SSP. When shadow stack gets disabled,
> > > > > > these suddenly turn into #UD generating instructions. So any other
> > > > > > threads executing those instructions when shadow stack got disabled
> > > > > > would be in for a nasty surprise.
> >
> > > > > This is the kernel's problem if that's happening. It should be
> > > > > trapping these and returning immediately like a NOP if shadow stack
> > > > > has been disabled, not generating SIGILL.
> >
> > > > I'm not sure that's going to work out well, all it takes is some code
> > > > that's looking at the shadow stack and expecting something to happen as
> > > > a result of the instructions it's executing and we run into trouble. A
> >
> > > I said NOP but there's no reason it strictly needs to be a NOP. It
> > > could instead do something reasonable to convey the state of racing
> > > with shadow stack being disabled.
> >
> > This feels like it's getting complicated and I fear it may be an uphill
> > struggle to get such code merged, at least for arm64. My instinct is
>
> the aarch64 behaviour is already nop
> for gcs instructions when gcs is disabled.
> the isa was designed so async disable is
> possible.
>
> only x86 linux would have to emulate this.
On Linux/x86, normal instructions are used to update SSP after
checking SHSTK is enabled. If SHSTK is disabled in between,
program behavior may be undefined.
--
H.J.
next prev parent reply other threads:[~2024-03-02 15:06 UTC|newest]
Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-03 12:25 [PATCH v8 00/38] arm64/gcs: Provide support for GCS in userspace Mark Brown
2024-02-03 12:25 ` [PATCH v8 01/38] arm64/mm: Restructure arch_validate_flags() for extensibility Mark Brown
2024-02-03 12:25 ` [PATCH v8 02/38] prctl: arch-agnostic prctl for shadow stack Mark Brown
2024-02-03 12:25 ` [PATCH v8 03/38] mman: Add map_shadow_stack() flags Mark Brown
2024-02-03 12:25 ` [PATCH v8 04/38] arm64: Document boot requirements for Guarded Control Stacks Mark Brown
2024-02-03 12:25 ` [PATCH v8 05/38] arm64/gcs: Document the ABI " Mark Brown
2024-02-03 12:25 ` [PATCH v8 06/38] arm64/sysreg: Add definitions for architected GCS caps Mark Brown
2024-02-03 12:25 ` [PATCH v8 07/38] arm64/gcs: Add manual encodings of GCS instructions Mark Brown
2024-02-03 12:25 ` [PATCH v8 08/38] arm64/gcs: Provide put_user_gcs() Mark Brown
2024-02-03 12:25 ` [PATCH v8 09/38] arm64/cpufeature: Runtime detection of Guarded Control Stack (GCS) Mark Brown
2024-02-03 12:25 ` [PATCH v8 10/38] arm64/mm: Allocate PIE slots for EL0 guarded control stack Mark Brown
2024-02-03 12:25 ` [PATCH v8 11/38] mm: Define VM_SHADOW_STACK for arm64 when we support GCS Mark Brown
2024-02-03 12:25 ` [PATCH v8 12/38] arm64/mm: Map pages for guarded control stack Mark Brown
2024-02-03 12:25 ` [PATCH v8 13/38] KVM: arm64: Manage GCS registers for guests Mark Brown
2024-02-05 9:46 ` Marc Zyngier
2024-02-05 12:35 ` Mark Brown
2024-02-05 15:34 ` Marc Zyngier
2024-02-05 16:58 ` Mark Brown
2024-02-03 12:25 ` [PATCH v8 14/38] arm64/gcs: Allow GCS usage at EL0 and EL1 Mark Brown
2024-02-03 12:25 ` [PATCH v8 15/38] arm64/idreg: Add overrride for GCS Mark Brown
2024-02-03 12:25 ` [PATCH v8 16/38] arm64/hwcap: Add hwcap " Mark Brown
2024-02-03 12:25 ` [PATCH v8 17/38] arm64/traps: Handle GCS exceptions Mark Brown
2024-02-03 12:25 ` [PATCH v8 18/38] arm64/mm: Handle GCS data aborts Mark Brown
2024-02-03 12:25 ` [PATCH v8 19/38] arm64/gcs: Context switch GCS state for EL0 Mark Brown
2024-02-03 12:25 ` [PATCH v8 20/38] arm64/gcs: Ensure that new threads have a GCS Mark Brown
2024-02-20 2:02 ` Thiago Jung Bauermann
2024-02-21 18:16 ` Mark Brown
2024-02-03 12:25 ` [PATCH v8 21/38] arm64/gcs: Implement shadow stack prctl() interface Mark Brown
2024-02-03 12:25 ` [PATCH v8 22/38] arm64/mm: Implement map_shadow_stack() Mark Brown
2024-02-03 12:25 ` [PATCH v8 23/38] arm64/signal: Set up and restore the GCS context for signal handlers Mark Brown
2024-02-20 2:03 ` Thiago Jung Bauermann
2024-02-03 12:25 ` [PATCH v8 24/38] arm64/signal: Expose GCS state in signal frames Mark Brown
2024-02-03 12:25 ` [PATCH v8 25/38] arm64/ptrace: Expose GCS via ptrace and core files Mark Brown
2024-02-03 12:25 ` [PATCH v8 26/38] arm64: Add Kconfig for Guarded Control Stack (GCS) Mark Brown
2024-02-03 12:25 ` [PATCH v8 27/38] kselftest/arm64: Verify the GCS hwcap Mark Brown
2024-02-03 12:25 ` [PATCH v8 28/38] kselftest/arm64: Add GCS as a detected feature in the signal tests Mark Brown
2024-02-03 12:25 ` [PATCH v8 29/38] kselftest/arm64: Add framework support for GCS to signal handling tests Mark Brown
2024-02-03 12:25 ` [PATCH v8 30/38] kselftest/arm64: Allow signals tests to specify an expected si_code Mark Brown
2024-02-03 12:25 ` [PATCH v8 31/38] kselftest/arm64: Always run signals tests with GCS enabled Mark Brown
2024-02-03 12:25 ` [PATCH v8 32/38] kselftest/arm64: Add very basic GCS test program Mark Brown
2024-02-03 12:25 ` [PATCH v8 33/38] kselftest/arm64: Add a GCS test program built with the system libc Mark Brown
2024-02-20 2:15 ` Thiago Jung Bauermann
2024-02-21 19:20 ` Mark Brown
2024-02-22 19:11 ` Mark Brown
2024-02-23 2:24 ` Thiago Jung Bauermann
2024-02-27 16:14 ` Mark Brown
2024-02-27 19:08 ` Thiago Jung Bauermann
2024-02-29 21:45 ` Mark Brown
2024-02-29 22:13 ` Thiago Jung Bauermann
2024-02-03 12:26 ` [PATCH v8 34/38] kselftest/arm64: Add test coverage for GCS mode locking Mark Brown
2024-02-03 12:26 ` [PATCH v8 35/38] selftests/arm64: Add GCS signal tests Mark Brown
2024-02-20 2:17 ` Thiago Jung Bauermann
2024-02-03 12:26 ` [PATCH v8 36/38] kselftest/arm64: Add a GCS stress test Mark Brown
2024-02-03 12:26 ` [PATCH v8 37/38] kselftest/arm64: Enable GCS for the FP stress tests Mark Brown
2024-02-03 12:26 ` [PATCH v8 38/38] kselftest: Provide shadow stack enable helpers for arm64 Mark Brown
2024-02-20 2:00 ` [PATCH v8 00/38] arm64/gcs: Provide support for GCS in userspace Thiago Jung Bauermann
2024-02-20 16:36 ` Stefan O'Rear
2024-02-20 18:41 ` Edgecombe, Rick P
2024-02-20 18:57 ` [musl] " Rich Felker
2024-02-20 23:30 ` Edgecombe, Rick P
2024-02-20 23:54 ` dalias
2024-02-21 0:35 ` Edgecombe, Rick P
2024-02-21 0:44 ` Mark Brown
2024-02-21 1:27 ` dalias
2024-02-21 2:11 ` Edgecombe, Rick P
2024-02-21 4:18 ` Edgecombe, Rick P
2024-02-21 13:53 ` Mark Brown
2024-02-21 14:58 ` dalias
2024-02-21 17:36 ` Mark Brown
2024-02-21 17:57 ` dalias
2024-02-21 18:12 ` Edgecombe, Rick P
2024-02-21 18:30 ` dalias
2024-02-21 18:53 ` Edgecombe, Rick P
2024-02-21 19:06 ` dalias
2024-02-21 19:22 ` Edgecombe, Rick P
2024-02-21 20:18 ` H.J. Lu
2024-02-21 20:25 ` H.J. Lu
2024-02-21 21:12 ` H.J. Lu
2024-02-21 20:18 ` dalias
2024-02-22 13:57 ` Mark Brown
2024-02-21 18:32 ` Mark Brown
2024-02-21 19:10 ` dalias
2024-03-02 14:57 ` Szabolcs Nagy
2024-03-02 15:05 ` H.J. Lu [this message]
2024-03-14 14:03 ` Mark Brown
2024-02-20 23:59 ` Stefan O'Rear
2024-02-21 0:40 ` Mark Brown
2024-02-21 4:30 ` Edgecombe, Rick P
2024-02-20 20:14 ` Mark Brown
2024-02-20 23:30 ` Edgecombe, Rick P
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