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Date:      Mon, 22 Nov 2021 18:04:40 +0100
From:      =?UTF-8?Q?Micha=C5=82_G=C3=B3rny?= <mgorny@moritz.systems>
To:        Ed Maste <emaste@freebsd.org>
Cc:        FreeBSD Hackers <freebsd-hackers@freebsd.org>, John Baldwin <jhb@freebsd.org>, Peter Wemm <peter@freebsd.org>
Subject:   Re: Looking for rationale for the minidump format
Message-ID:  <1b140e6f5e3a44fe875820fd0a5a2d621ae23ae5.camel@moritz.systems>
In-Reply-To: <CAPyFy2Bhpj5MQK72b1A1X4=ez2okuuDo3rrx8Hn4BHk1OPtRKQ@mail.gmail.com>
References:  <305082d9f216bb8382773c074eaf7a5c3101cc13.camel@moritz.systems> <CAPyFy2Bhpj5MQK72b1A1X4=ez2okuuDo3rrx8Hn4BHk1OPtRKQ@mail.gmail.com>

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On Mon, 2021-11-22 at 10:26 -0500, Ed Maste wrote:
> On Sun, 21 Nov 2021 at 09:42, Michał Górny <mgorny@moritz.systems> wrote:
> > 
> > Hi, everyone.
> > 
> > As part of the work contracted by the FreeBSD Foundation, I'm working
> > on adding explicit minidump support to LLDB.  When discussing
> > the options with upstream, I've been asked why FreeBSD created their own
> > minidump format.
> > 
> > I did a bit of digging but TBH all the rationale I could get was to
> > create partial memory dumps.  However, unless I'm mistaken the ELF
> > format is perfectly capable of that -- e.g. via creating an explicit
> > segment for every continuous active region.
> 
> ELF can, indeed. One of my previous co-op students wrote a little tool
> to convert a minidump to ELF, see https://reviews.freebsd.org/D19253.
> That's what it does - creates a segment for each contiguous region. If
> we ended up going this way we could integrate D19253 into savecore.

Thank you for your reply.  I think this approach makes sense.  Do you
want us to pursue updating D19253 to build again (it's failing due to
libkvm API changes and -Werror) and moving it into savecore instead of
adding FreeBSD minidump support in LLDB?

-- 
Best regards,
Michał Górny




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