linux-kernel - Re: [RESEND PATCH 2/6] x86/traps: add a system interrupt table for system interrupt dispatch

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Date:   Thu, 10 Nov 2022 14:12:53 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     "Li, Xin3" <xin3.li@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, llvm@...ts.linux.dev,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [RESEND PATCH 2/6] x86/traps: add a system interrupt table for
 system interrupt dispatch

On Thu, Nov 10, 2022 at 08:36:30PM +0000, Li, Xin3 wrote:
> > > > +#pragma GCC diagnostic push
> > > > +#pragma GCC diagnostic ignored "-Wcast-function-type"
> > >
> > > How does this not break CFI ?
> > 
> > I wasn't aware of it, will check.
> 
> CFI needs $(cc-option,-fsanitize=kcfi), which, reported on LWN on Jun, 2002,
> had not yet landed in the LLVM mainline (I'm using GCC).  So looks we are
> replying on people keeping an eye on it to make sure it's not broken?

Well, the entire point of the warning that you are disabling here is to
catch potential CFI failures at compile time, rather than run time :)

Clang also has -Wcast-function-type-strict, which Gustavo and Kees are
working on getting enabled, so that even more CFI failures can be caught
at compile time.

https://github.com/ClangBuiltLinux/linux/issues/1724
https://lore.kernel.org/all/?q=-Wcast-function-type-strict

Cheers,
Nathan