linux-kernel - Re: [PATCH v6 27/29] x86/boot/compressed: Remove, discard, or assert for unwanted sections

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Message-ID: <20200821212828.GA1741495@rani.riverdale.lan>
Date:   Fri, 21 Aug 2020 17:28:28 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Kees Cook <keescook@...omium.org>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Ingo Molnar <mingo@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        James Morse <james.morse@....com>,
        Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>, x86@...nel.org,
        clang-built-linux@...glegroups.com, linux-arch@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 27/29] x86/boot/compressed: Remove, discard, or assert
 for unwanted sections

On Fri, Aug 21, 2020 at 02:21:34PM -0700, Kees Cook wrote:
> On Fri, Aug 21, 2020 at 04:01:59PM -0400, Arvind Sankar wrote:
> > On Fri, Aug 21, 2020 at 12:43:08PM -0700, Kees Cook wrote:
> > > In preparation for warning on orphan sections, stop the linker from
> > > generating the .eh_frame* sections, discard unwanted non-zero-sized
> > > generated sections, and enforce other expected-to-be-zero-sized sections
> > > (since discarding them might hide problems with them suddenly gaining
> > > unexpected entries).
> > > 
> > > Signed-off-by: Kees Cook <keescook@...omium.org>
> > >  	.rel.dyn : {
> > > -		*(.rel.*)
> > > +		*(.rel.*) *(.rel_*)
> > >  	}
> > >  	ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) detected!")
> > >  
> > >  	.rela.dyn : {
> > > -		*(.rela.*)
> > > +		*(.rela.*) *(.rela_*)
> > >  	}
> > >  	ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!")
> > >  }
> > > -- 
> > > 2.25.1
> > > 
> > 
> > When do you get .rela_?
> 
> i386 builds, IIRC. I can try to hunt that down if you want?
> 
> -- 
> Kees Cook

Nah, just curious.

Thanks.