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From:   Sami Tolvanen <samitolvanen@google.com>
Date:   Thu, 5 May 2022 09:51:39 -0700
Message-ID: <CABCJKue6c0FMpKXysdoT0Lc+RBqGFhp52iM03tttWwRv7CZr5w@mail.gmail.com>
Subject: Re: [RFC PATCH 10/21] treewide: Drop function_nocfi
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>, X86 ML <x86@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Joao Moreira <joao@overdrivepizza.com>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-hardening@vger.kernel.org,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
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On Thu, May 5, 2022 at 9:30 AM Mark Rutland <mark.rutland@arm.com> wrote:
> I also believe that in most cases we can drop the __nocfi annotation on callers
> now that we can mark the called assembly function with SYM_TYPED_FUNC_START().

Good point, thanks for pointing that out. I'll add these to the next
version of the series.

> There' a latent bug here with the existing CFI scheme, since
> `kpti_install_ng_mappings` isn't marked with __nocfi, and should explode when
> calling `idmap_kpti_install_ng_mappings` via the idmap.

The CONFIG_UNMAP_KERNEL_AT_EL0 version of kpti_install_ng_mappings is
marked __nocfi

> There' a latent bug here with the existing CFI scheme, since
> `machine_kexec` isn't marked with __nocfi, and should explode when calling
> `cpu_soft_restart` via the idmap.

But it's indeed missing from this one.

Sami