linux-kernel - Re: [PATCH 7/7] DWARF: add the config option

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMe9rOriibRLb4rEsVcWjq8Soe3RQ6QKtSc2TJg+ztbOFdbsjA@mail.gmail.com>
Date:   Wed, 10 May 2017 09:23:33 -0700
From:   "H.J. Lu" <hjl.tools@...il.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Jiri Slaby <jslaby@...e.cz>, "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        live-patching@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Jiri Kosina <jikos@...nel.org>
Subject: Re: [PATCH 7/7] DWARF: add the config option

On Wed, May 10, 2017 at 6:09 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> On Wed, May 10, 2017 at 10:15:09AM +0200, Jiri Slaby wrote:
>> > I'm, ahem, highly skeptical to creating our own unwinding data
>> > format unless there is *documented, supported, and tested* way to
>> > force the compiler to *automatically* fall back to frame pointers
>> > any time there may be complexity involved,
>>
>> I second this. Inventing a new format like this mostly ends up with
>> using the standard one after several iterations. One cannot think of all
>> the consequences and needs while proposing a new one.
>>
>> The memory footprint is ~2M for average vmlinux. And people who need to
>> access:
>> * either need it frequently -- those do not need performance (LOCKDEP,
>> KASAN, or other debug builds)
>> * or are in the middle of WARNING, BUG, crash, panic or such and this is
>> not that often...
>>
>> And we would need *both*. The limited proprietary one in some sort of
>> .kernel_eh_frame, and DWARF cfis in .debug_frame for tools like crash,
>> gdb and so on.
>
> I don't think so.  DWARF CFI is optimized for size.  My proposal is to
> take the same data (or some subset of it) and reformat it to optimize
> for simplicity.
>
> If, for some reason, we ended up needing *all* the original DWARF data,
> we could still have it in the simpler format.  In that case it might end
> up being 8M instead of 2M :-) But I don't see that being possible.

There is a compact EH for MIPS:

https://github.com/itanium-cxx-abi/cxx-abi/blob/master/MIPSCompactEH.pdf

It can be extended to other targets.

-- 
H.J.