From: Charles Mirabile <cmirabil@redhat.com>
To: cmirabil@redhat.com
Cc: Liam.Howlett@oracle.com, a.hindborg@kernel.org,
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Subject: Re: [PATCH v19 00/27] riscv control-flow integrity for usermode
Date: Fri, 26 Sep 2025 15:52:24 -0400 [thread overview]
Message-ID: <20250926195224.351862-1-cmirabil@redhat.com> (raw)
In-Reply-To: <20250926192919.349578-1-cmirabil@redhat.com>
Hi -
Sorry for my previous email, I realized I was mistaken...
On Fri, Sep 26, 2025 at 03:29:19PM -0400, Charles Mirabile wrote:
> Hi -
>
> Hoping that I got everything right with git-send-email so that this is
> delivered alright...
>
> Wanted to jump in to head off a potential talking past one another /
> miscommunication situation I see here.
>
> On Wed, Sep 24, 2025 at 08:36:11AM -0600, Paul Walmsley wrote:
> > Hi,
> >
> > On Thu, 31 Jul 2025, Deepak Gupta wrote:
> >
> > [ ... ]
> >
> > > vDSO related Opens (in the flux)
> > > =================================
> > >
> > > I am listing these opens for laying out plan and what to expect in future
> > > patch sets. And of course for the sake of discussion.
> > >
> >
> > [ ... ]
> >
> > > How many vDSOs
> > > ---------------
> > > Shadow stack instructions are carved out of zimop (may be operations) and if CPU
> > > doesn't implement zimop, they're illegal instructions. Kernel could be running on
> > > a CPU which may or may not implement zimop. And thus kernel will have to carry 2
> > > different vDSOs and expose the appropriate one depending on whether CPU implements
> > > zimop or not.
> >
> > If we merge this series without this, then when CFI is enabled in the
> > Kconfig, we'll wind up with a non-portable kernel that won't run on older
> > hardware. We go to great lengths to enable kernel binary portability
> > across the presence or absence of other RISC-V extensions, and I think
> > these CFI extensions should be no different.
>
> That is not true, this series does not contain the VDSO changes so it can
> be merged as is.
Oops... no sorry, it looks like it does. See 19/27. I was misled by the
cover letter which said to pick that patch separately. I completely agree
that that needs to not be included if this is to be merged.
>
> >
> > So before considering this for merging, I'd like to see at least an
> > attempt to implement the dual-vDSO approach (or something equivalent)
> > where the same kernel binary with CFI enabled can run on both pre-Zimop
> > and post-Zimop hardware, with the existing userspaces that are common
> > today.
>
> I agree that when the VDSO patches are submitted for inclusion they should
> be written in a way that avoids limiting the entire kernel to either
> pre-Zimop or post-Zimop hardware based on the config, but I think it
> should be quite possible to perform e.g. runtime patching of the VDSO
> to replace the Zimop instructions with nops if the config is enabled but
> the hardware does not support Zimop.
>
> However, that concern should not hold up this patch series. Raise it again
> when the VDSO patches are posted.
@Deepak, would it be possible to just resend this without the VDSO patch?
Or to rework as I had alluded to to check for the presense of the extension
and remove the instructions from the VDSO at boot if it is not found?
>
> >
> > thanks Deepak,
> >
> > - Paul
>
> Best - Charlie
>
Best - Charlie
next prev parent reply other threads:[~2025-09-26 19:52 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-31 23:19 Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 01/27] mm: VM_SHADOW_STACK definition for riscv Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 02/27] dt-bindings: riscv: zicfilp and zicfiss in dt-bindings (extensions.yaml) Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 03/27] riscv: zicfiss / zicfilp enumeration Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 04/27] riscv: zicfiss / zicfilp extension csr and bit definitions Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 05/27] riscv: usercfi state for task and save/restore of CSR_SSP on trap entry/exit Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 06/27] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 07/27] riscv/mm: manufacture shadow stack pte Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 08/27] riscv/mm: teach pte_mkwrite to manufacture shadow stack PTEs Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 09/27] riscv/mm: write protect and shadow stack Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 10/27] riscv/mm: Implement map_shadow_stack() syscall Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 11/27] riscv/shstk: If needed allocate a new shadow stack on clone Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 12/27] riscv: Implements arch agnostic shadow stack prctls Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 13/27] prctl: arch-agnostic prctl for indirect branch tracking Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 14/27] riscv: Implements arch agnostic indirect branch tracking prctls Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 15/27] riscv/traps: Introduce software check exception and uprobe handling Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 16/27] riscv: signal: abstract header saving for setup_sigcontext Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 17/27] riscv/signal: save and restore of shadow stack for signal Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 18/27] riscv/kernel: update __show_regs to print shadow stack register Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 19/27] riscv/ptrace: riscv cfi status and state via ptrace and in core files Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 20/27] riscv/hwprobe: zicfilp / zicfiss enumeration in hwprobe Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 21/27] riscv: kernel command line option to opt out of user cfi Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 22/27] riscv: enable kernel access to shadow stack memory via FWFT sbi call Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 23/27] arch/riscv: compile vdso with landing pad and shadow stack note Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 24/27] riscv: create a config for shadow stack and landing pad instr support Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 25/27] riscv: Documentation for landing pad / indirect branch tracking Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 26/27] riscv: Documentation for shadow stack on riscv Deepak Gupta
2025-07-31 23:19 ` [PATCH v19 27/27] kselftest/riscv: kselftest for user mode cfi Deepak Gupta
2025-08-01 1:09 ` [PATCH v19 00/27] riscv control-flow integrity for usermode Benjamin LaHaise
2025-08-06 17:15 ` patchwork-bot+linux-riscv
2025-08-07 12:28 ` Mark Brown
2025-08-08 8:23 ` Deepak Gupta
2025-08-08 11:48 ` Mark Brown
2025-08-08 17:20 ` Deepak Gupta
2025-09-24 14:36 ` Paul Walmsley
2025-09-24 18:40 ` Deepak Gupta
2025-09-24 21:41 ` Heinrich Schuchardt
2025-09-25 12:30 ` Andy Chiu
2025-09-25 14:30 ` Deepak Gupta
2025-09-30 11:15 ` Florian Weimer
2025-10-01 0:13 ` Deepak Gupta
2025-09-26 19:29 ` Charles Mirabile
2025-09-26 19:52 ` Charles Mirabile [this message]
2025-09-26 20:03 ` Deepak Gupta
2025-09-26 19:57 ` Deepak Gupta
2025-09-26 20:28 ` Charles Mirabile
2025-09-26 21:07 ` Deepak Gupta
2025-09-30 9:20 ` Florian Weimer
2025-09-30 23:48 ` Deepak Gupta
2025-10-02 11:45 ` Florian Weimer
2025-10-02 16:45 ` Deepak Gupta
2025-10-13 14:30 ` Florian Weimer
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