linux-kernel - Re: [PATCH v3 0/7] crypto: x86: Fix indirect function call casts

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Date:   Thu, 9 May 2019 08:38:28 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Joao Moreira <jmoreira@...e.de>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
        linux-crypto <linux-crypto@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v3 0/7] crypto: x86: Fix indirect function call casts

On Wed, May 08, 2019 at 07:04:40PM -0700, Eric Biggers wrote:
> And I also asked whether indirect calls to asm code are even allowed
> with CFI. IIRC, the AOSP kernels have been patched to remove them from
> arm64

At least with clang, indirect calls to stand-alone assembly functions
trip CFI checks, which is why Android kernels use static inline stubs
to convert these to direct calls instead.

Sami