linux-kernel - Re: [PATCH v2] recordmcount: support >64k sections

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Message-ID: <202006161101.34B26E6@keescook>
Date:   Tue, 16 Jun 2020 11:03:18 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Matt Helsley <mhelsley@...are.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Kristen Carlson Accardi <kristen@...ux.intel.com>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] recordmcount: support >64k sections

On Fri, Apr 24, 2020 at 03:22:14PM -0700, Matt Helsley wrote:
> On Fri, Apr 24, 2020 at 12:30:46PM -0700, Sami Tolvanen wrote:
> > When compiling a kernel with Clang and LTO, we need to run
> > recordmcount on vmlinux.o with a large number of sections, which
> > currently fails as the program doesn't understand extended
> > section indexes. This change adds support for processing binaries
> > with >64k sections.
> > 
> > Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> 
> Feel free to add
> 
> Reviewed-by: Matt Helsley <mhelsley@...are.com>

Hi!

Can this patch please be applied and sent before -rc2? FGKASLR, LTO, and
link time improvements[1] all depend on this fix, and I'd really like
them all to be able to sanely rebase for the development window.

Thanks!

-Kees

[1] https://lore.kernel.org/lkml/CAK7LNARbZhoaA=Nnuw0=gBrkuKbr_4Ng_Ei57uafujZf7Xazgw@mail.gmail.com/

> 
> > ---
> > Changes in v2:
> >  - Switched to unsigned int for (old|new)_shnum in append_func.
> >  - Added set_shnum and find_symtab helper functions and moved
> >    the new logic there.
> > 
> > ---
> >  scripts/recordmcount.h | 98 +++++++++++++++++++++++++++++++++++++++---
> >  1 file changed, 92 insertions(+), 6 deletions(-)
> 
> <snip>

-- 
Kees Cook