linux-kernel - Re: [PATCH] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S

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Date:   Mon, 13 Jan 2020 14:43:06 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Arvind Sankar <nivedita@...m.mit.edu>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Thomas Lendacky <Thomas.Lendacky@....com>,
        Michael Matz <matz@...e.de>
Subject: Re: [PATCH] x86/tools/relocs: Add _etext and __end_of_kernel_reserve
 to S_REL

On Sat, Jan 11, 2020 at 12:20:48PM -0500, Arvind Sankar wrote:
> I'm not sure if that's the same issue. The root cause for the one I
> reported is described in more detail in [1], and the change that makes
> these symbols no longer absolute is commit d2667025dd30 in binutils-gdb
> (sourceware.org seems to be taking too long to respond from here so I
> don't have the web link).

My binutils guy says that the proper fix should be to make those two
symbols section-relative, i.e., move _etext at the end of the .text
section and so on.

Please check whether this fixes the build issue too because if it does,
it would be The RightThing(tm).

> I'm running gentoo, but building the kernel using binutils-2.21.1
> compiled from the GNU source tarball, and gcc-4.6.4 again compiled from
> source. (It's not something I normally need but I was investigating
> something else to see what exactly happens with older toolchains.)
> 
> I used the below to compile the kernel (I added in
> readelf/objdump/objcopy just now, and it does build until the relocs
> error). The config is x86-64 defconfig with CONFIG_RETPOLINE overridden
> to n (since gcc 4.6.4 doesn't support retpoline).
> 
> make O=~/kernel64 -j LD=~/old/bin/ld AS=~/old/bin/as READELF=~/old/bin/readelf \
> 	OBJDUMP=~/old/bin/objdump OBJCOPY=~/old/bin/objcopy GCC=~/old/bin/gcc

Make this all part of your commit message because it explains in detail
how exactly you've triggered it so that anyone else reading this can
reproduce her/himself.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette