From: Arvind Sankar <nivedita@alum.mit.edu>
To: Borislav Petkov <bp@alien8.de>
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Kees Cook <keescook@chromium.org>,
Thomas Lendacky <Thomas.Lendacky@amd.com>,
Michael Matz <matz@suse.de>
Subject: Re: [PATCH] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S_REL
Date: Mon, 13 Jan 2020 23:08:13 -0500 [thread overview]
Message-ID: <20200114040812.GB2536335@rani.riverdale.lan> (raw)
In-Reply-To: <20200113163855.GK13310@zn.tnic>
On Mon, Jan 13, 2020 at 05:38:55PM +0100, Borislav Petkov wrote:
> On Mon, Jan 13, 2020 at 11:13:10AM -0500, Arvind Sankar wrote:
> > I will note that the purpose of S_REL in relocs.c was originally to
> > handle exactly this case of symbols defined outside output sections:
>
> And we should try not to do hacks, if it can be fixed properly, as
> binutils expects symbols to be usually relative to a section.
>
I've poked around a bit more, and all the hacks in relocs.c in S_REL,
other than init_per_cpu__.*, are only there to work around old and/or
buggy binutils versions from the 2.21-2.22 days.
The current code is *not* broken for binutils-2.23+, where none of these
symbols are marked as absolute. IOW, the current code is perfectly fine
and generates relative symbols for any binutils not of 2.21-2.22
vintage.
So we have the following choices:
* bump minimum supported binutils version to 2.23, and remove all the
hacks for earlier versions.
* add a couple of hacks to relocs.c to account for new symbols, as in v2
* complicate regular code, as in v3, which Kees says might break new
code [1] and Tom says is bad for future kernel hackers [2]
[1] https://lore.kernel.org/lkml/202001131750.C1B8468@keescook/
[2] https://lore.kernel.org/lkml/3e46154d-6e5e-1c16-90fe-f2c5daa44b60@amd.com/
next prev parent reply other threads:[~2020-01-14 4:09 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 20:23 [PATCH] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S_REL Arvind Sankar
2020-01-10 20:38 ` Borislav Petkov
2020-01-10 20:50 ` Arvind Sankar
2020-01-10 21:50 ` [PATCH v2] " Arvind Sankar
2020-01-10 21:52 ` Arvind Sankar
2020-01-11 13:02 ` [PATCH] " Borislav Petkov
2020-01-11 17:20 ` Arvind Sankar
2020-01-11 17:32 ` Arvind Sankar
2020-01-13 13:43 ` Borislav Petkov
2020-01-13 16:13 ` Arvind Sankar
2020-01-13 16:38 ` Borislav Petkov
2020-01-13 17:59 ` Arvind Sankar
2020-01-13 18:08 ` Borislav Petkov
2020-01-14 4:17 ` Arvind Sankar
2020-01-14 11:25 ` Borislav Petkov
2020-01-14 16:32 ` Arvind Sankar
2020-01-14 4:08 ` Arvind Sankar [this message]
2020-01-13 19:53 ` [PATCH v3] x86/vmlinux: Fix vmlinux.lds.S with pre-2.23 binutils Arvind Sankar
2020-01-13 21:46 ` Tom Lendacky
2020-01-13 23:06 ` Arvind Sankar
2020-01-14 1:53 ` Kees Cook
2020-01-14 1:57 ` H. Peter Anvin
2020-01-14 2:20 ` Kees Cook
2020-01-14 3:58 ` Arvind Sankar
2020-01-14 5:05 ` hpa
2020-01-14 16:51 ` Borislav Petkov
2020-01-14 21:50 ` hpa
2020-01-15 0:21 ` Arvind Sankar
2020-01-15 12:24 ` Borislav Petkov
2020-03-16 16:02 ` [PATCH] Documentation/changes: Raise minimum supported binutils version to 2.23 Borislav Petkov
2020-03-16 20:54 ` Kees Cook
2020-03-23 20:44 ` Jason A. Donenfeld
2020-03-23 20:51 ` Kees Cook
2020-03-23 21:11 ` Jason A. Donenfeld
2020-03-25 17:33 ` David Laight
2020-03-24 9:02 ` Masahiro Yamada
2020-03-24 9:12 ` Masahiro Yamada
2020-03-24 15:38 ` Arvind Sankar
2020-03-24 17:31 ` Masahiro Yamada
2020-03-24 21:36 ` Arvind Sankar
2020-03-24 9:14 ` Borislav Petkov
2020-03-24 9:40 ` Masahiro Yamada
2020-03-24 12:00 ` Borislav Petkov
2020-03-24 16:22 ` Jason A. Donenfeld
2020-03-24 16:28 ` Borislav Petkov
2020-03-24 16:37 ` Linus Torvalds
2020-03-24 16:48 ` Borislav Petkov
2020-03-24 21:42 ` Arvind Sankar
2020-03-24 22:01 ` Arvind Sankar
2020-03-24 22:14 ` Linus Torvalds
2020-03-24 23:49 ` Arvind Sankar
2020-03-24 17:53 ` Kees Cook
2020-03-23 20:50 ` [PATCH] Documentation/changes: Raise minimum supported binutilsa " Nick Desaulniers
2020-01-13 23:38 ` [PATCH] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S_REL Arvind Sankar
2020-01-10 20:56 ` Kees Cook
[not found] ` <CAEQFVGa4fksPRtiLtBckSgbJY_JSHr07hoy5+5w-pAYym16YVg@mail.gmail.com>
2020-01-11 19:40 ` Fwd: " Mauro Rossi
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