linux-kernel - Re: [RFC PATCH v2 0/4] arm64: Implement stack trace reliability checks

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Message-ID: <e8367fe9-6fd0-f962-422d-daa4548cc3b7@linux.microsoft.com>
Date:   Fri, 16 Apr 2021 09:43:48 -0500
From:   "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Mark Rutland <mark.rutland@....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,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC PATCH v2 0/4] arm64: Implement stack trace reliability
 checks

On 4/14/21 5:23 AM, Madhavan T. Venkataraman wrote:
> In any case, I have absolutely no problems in implementing your section idea. I will
> make an attempt to do that in version 3 of my patch series.

So, I attempted a patch with just declaring all .entry.text functions as unreliable
by checking just the section bounds. It does work for EL1 exceptions. But there
are other functions that are actually reliable that show up as unreliable.
The example in my test is el0_sync() which is at the base of all system call stacks.

How would you prefer I handle this? Should I place all SYM_CODE functions that
are actually safe for the unwinder in a separate section? I could just take
some approach and solve this. But I would like to get your opinion and Mark
Rutland's opinion so we are all on the same page.

Please let me know.

Madhavan