linux-kernel - Re: [PATCH 2/2] recordmcount: Handle sections with no non-weak symbols

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: <20220504130642.7b9a301d@rorschach.local.home>
Date:   Wed, 4 May 2022 13:06:42 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 2/2] recordmcount: Handle sections with no non-weak
 symbols

On Wed, 4 May 2022 16:50:58 +0000
Christophe Leroy <christophe.leroy@...roup.eu> wrote:

> In vmlinux, relocations are resolved, trampolines are installed for 
> unreachable destinations and you don't anymore have a section with all 
> the relocations to mcount. It means 'recordmcount' or whatever tool we 
> use will have to read the code to find all direct calls to mcount, then 
> find all trampolines to mcount then find all calls to those trampolines.

OK, so what you are saying is that in the object file, we can see the
site that calls mcount, but when it is linked, it may not call mcount,
but instead it will call a trampoline that will call mcount, thus the
tool will need to find these calls to the trampolines that call mcount
as well as the locations that call mcount directly.

Did I get that right?

-- Steve