linux-kernel - Re: [PATCH 1/2] x86/boot: robustify calling startup

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Message-Id: <20221101153834.975871-1-alexandr.lobakin@intel.com>
Date:   Tue,  1 Nov 2022 16:38:34 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Jiri Slaby <jirislaby@...nel.org>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Tony Luck <tony.luck@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Masahiro Yamada <masahiroy@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] x86/boot: robustify calling startup_{32,64}() from the decompressor code

From: Jiri Slaby <jirislaby@...nel.org>
Date: Tue, 1 Nov 2022 07:50:04 +0100

> On 01. 11. 22, 7:47, Jiri Slaby wrote:
> > Tested-by: Jiri Slaby <jirislaby@...nel.org>
> 
> FWIW that means: tested with gcc-lto which deliberately stores 
> startup_64() randomly, not to the beginning of vmlinux.

Yeah, you never know. After rebasing on top of 6.1-rc1 my FG-KASLR
series stopped booting, I found out that the combo of that
head-object-list.txt + -ffunction-sections (but for Asm) also made
startup_64() appear in random parts of .head.text.

Re head removal -- that would be awesome, but currently from what
I've tried during the development, there's a lot of stuff to be
redone, the compressor code sometimes just doesn't want to work
if you play with .head.text too much. Will see.

> 
> -- 
> js
> suse labs

Thanks,
Olek