linux-kernel - Re: [RFC PATCH v2 1/4] arm64: Implement infrastructure for stack trace reliability checks

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Message-ID: <20210409115708.GB4499@sirena.org.uk>
Date:   Fri, 9 Apr 2021 12:57:08 +0100
From:   Mark Brown <broonie@...nel.org>
To:     "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
Cc:     mark.rutland@....com, jpoimboe@...hat.com, jthierry@...hat.com,
        catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 1/4] arm64: Implement infrastructure for stack
 trace reliability checks

On Thu, Apr 08, 2021 at 06:30:22PM -0500, Madhavan T. Venkataraman wrote:
> On 4/8/21 2:30 PM, Madhavan T. Venkataraman wrote:

> > 1. Create a common section (I will have to come up with an appropriate name) and put
> >    all such functions in that one section.

> > 2. Create one section for each logical type (exception section, ftrace section and
> >    kprobe section) or some such.

> For now, I will start with idea 2. I will create a special section for each class of
> functions (EL1 exception handlers, FTRACE trampolines, KPROBE trampolines). Instead of a
> special functions array, I will implement a special_sections array. The rest of the code
> should just fall into place.

> Let me know if you prefer something different.

It might be safer to start off by just putting all SYM_CODE into a
section then pulling bits we know to be safe out of the section as
needed - we know that anything that's SYM_CODE is doing something
non-standard and needs checking to verify that the unwinder will be
happy with it and I that should cover most if not all of the cases above
as well as anything else we didn't explicitly think of.

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