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Date:   Fri, 29 Apr 2022 18:00:03 -0700
From:   Sami Tolvanen <>
To:     Peter Zijlstra <>
Cc:     LKML <>,
        Kees Cook <>,
        Josh Poimboeuf <>, X86 ML <>,
        Catalin Marinas <>,
        Will Deacon <>,
        Mark Rutland <>,
        Nathan Chancellor <>,
        Nick Desaulniers <>,
        Joao Moreira <>,
        Sedat Dilek <>,
        Steven Rostedt <>,,
        linux-arm-kernel <>,
Subject: Re: [RFC PATCH 16/21] objtool: Add support for CONFIG_CFI_CLANG

On Fri, Apr 29, 2022 at 4:30 PM Peter Zijlstra <> wrote:
> Urgh, what does this do for decode speed? This is a hash-lookup for
> every single instruction.

Two actually, since .kcfi_traps only contains compiler-emitted
locations and we also have to check for manual type annotations. I
haven't measured performance yet, but I also didn't notice a
significant impact here.

> Is that kcfi location array sorted by the compiler? Because then you can
> keep a running iterator and replace the whole lookup with a simple
> equality comparison.

The compiler generates a separate .kcfi_types section for each text
section and the entries are emitted in order, so this should be


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