linux-kernel - Re: [RFC] Objtool toolchain proposal: -fannotate-{jump-table,noreturn}

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Message-ID: <20220914001205.ygvmwya5wcawcodj@treble>
Date:   Wed, 14 Sep 2022 01:12:05 +0100
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Indu Bhagat <indu.bhagat@...cle.com>
Cc:     linux-toolchains@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org, "Jose E. Marchesi" <jemarch@....org>,
        Miroslav Benes <mbenes@...e.cz>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>, x86@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Chen Zhongjin <chenzhongjin@...wei.com>,
        Sathvika Vasireddy <sv@...ux.ibm.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [RFC] Objtool toolchain proposal:
 -fannotate-{jump-table,noreturn}

On Tue, Sep 13, 2022 at 03:51:44PM -0700, Indu Bhagat wrote:
> Curious to know what all features of objtool rely on the need to reverse
> engineer the control flow graph. Is it a larger set or it is only for ORC
> generation ?

Objtool features which rely on the CFG:

- Frame pointer rule validation (when using
  CONFIG_UNWINDER_FRAME_POINTER)

- ORC metadata generation

- Intel SMAP rule validation - ensures EFLAGS #AC is only set during
  usercopy

- "noinstr" rule validation - ensures no instrumentation/tracing
  functions are called in certain critical sections

-- 
Josh