From: Josh Poimboeuf <jpoimboe@redhat.com>
To: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
Cc: Mark Brown <broonie@kernel.org>,
mark.rutland@arm.com, ardb@kernel.org, jthierry@redhat.com,
catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org,
pasha.tatashin@soleen.com, linux-arm-kernel@lists.infradead.org,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v4 1/2] arm64: Introduce stack trace reliability checks in the unwinder
Date: Fri, 21 May 2021 14:11:40 -0500 [thread overview]
Message-ID: <20210521191140.4aezpvm2kruztufi@treble> (raw)
In-Reply-To: <74d12457-7590-bca2-d1ce-5ff82d7ab0d8@linux.microsoft.com>
On Fri, May 21, 2021 at 01:59:16PM -0500, Madhavan T. Venkataraman wrote:
>
>
> On 5/21/21 1:48 PM, Josh Poimboeuf wrote:
> > On Fri, May 21, 2021 at 06:53:18PM +0100, Mark Brown wrote:
> >> On Fri, May 21, 2021 at 12:47:13PM -0500, Madhavan T. Venkataraman wrote:
> >>> On 5/21/21 12:42 PM, Mark Brown wrote:
> >>
> >>>> Like I say we may come up with some use for the flag in error cases in
> >>>> future so I'm not opposed to keeping the accounting there.
> >>
> >>> So, should I leave it the way it is now? Or should I not set reliable = false
> >>> for errors? Which one do you prefer?
> >>
> >>> Josh,
> >>
> >>> Are you OK with not flagging reliable = false for errors in unwind_frame()?
> >>
> >> I think it's fine to leave it as it is.
> >
> > Either way works for me, but if you remove those 'reliable = false'
> > statements for stack corruption then, IIRC, the caller would still have
> > some confusion between the end of stack error (-ENOENT) and the other
> > errors (-EINVAL).
> >
>
> I will leave it the way it is. That is, I will do reliable = false on errors
> like you suggested.
>
> > So the caller would have to know that -ENOENT really means success.
> > Which, to me, seems kind of flaky.
> >
>
> Actually, that is why -ENOENT was introduced - to indicate successful
> stack trace termination. A return value of 0 is for continuing with
> the stack trace. A non-zero value is for terminating the stack trace.
>
> So, either we return a positive value (say 1) to indicate successful
> termination. Or, we return -ENOENT to say no more stack frames left.
> I guess -ENOENT was chosen.
I see. So it's a tri-state return value, and frame->reliable is
intended to be a private interface not checked by the callers.
That makes sense, and probably fine, it's just perhaps a bit nonstandard
compared to most Linux interfaces.
--
Josh
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next prev parent reply other threads:[~2021-05-21 19:13 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <68eeda61b3e9579d65698a884b26c8632025e503>
2021-05-16 4:00 ` [RFC PATCH v4 0/2] arm64: Stack trace reliability checks in the unwinder madvenka
2021-05-16 4:00 ` [RFC PATCH v4 1/2] arm64: Introduce stack " madvenka
2021-05-21 16:11 ` Mark Brown
2021-05-21 17:23 ` Madhavan T. Venkataraman
2021-05-21 17:42 ` Mark Brown
2021-05-21 17:47 ` Madhavan T. Venkataraman
2021-05-21 17:53 ` Mark Brown
2021-05-21 18:48 ` Josh Poimboeuf
2021-05-21 18:59 ` Madhavan T. Venkataraman
2021-05-21 19:11 ` Josh Poimboeuf [this message]
2021-05-21 19:16 ` Josh Poimboeuf
2021-05-21 19:41 ` Madhavan T. Venkataraman
2021-05-21 20:08 ` Josh Poimboeuf
2021-05-25 21:44 ` Madhavan T. Venkataraman
2021-05-16 4:00 ` [RFC PATCH v4 2/2] arm64: Create a list of SYM_CODE functions, blacklist them " madvenka
2021-05-19 2:06 ` nobuta.keiya
2021-05-19 3:38 ` Madhavan T. Venkataraman
2021-05-19 19:27 ` Mark Brown
2021-05-20 2:00 ` Madhavan T. Venkataraman
2021-05-21 17:18 ` [RFC PATCH v4 0/2] arm64: Stack trace reliability checks " Mark Brown
2021-05-21 17:32 ` Madhavan T. Venkataraman
2021-05-21 17:47 ` Mark Brown
2021-05-21 17:48 ` Madhavan T. Venkataraman
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