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From: Kees Cook <keescook@chromium.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	x86@kernel.org, joao@overdrivepizza.com, hjl.tools@gmail.com,
	andrew.cooper3@citrix.com, linux-kernel@vger.kernel.org,
	ndesaulniers@google.com, samitolvanen@google.com
Subject: Re: [RFC][PATCH 6/6] objtool: Add IBT validation / fixups
Date: Tue, 8 Feb 2022 15:43:27 -0800	[thread overview]
Message-ID: <202202081542.F685EC23@keescook> (raw)
In-Reply-To: <20211124193037.nu7q4pa3sianzqtc@treble>

On Wed, Nov 24, 2021 at 11:30:37AM -0800, Josh Poimboeuf wrote:
> On Mon, Nov 22, 2021 at 06:03:07PM +0100, Peter Zijlstra wrote:
> > +static int validate_ibt_reloc(struct objtool_file *file, struct reloc *reloc, char **name)
> > +{
> > +	struct instruction *dest;
> > +	struct section *sec;
> > +	unsigned long off;
> > +
> > +	sec = reloc->sym->sec;
> > +	off = reloc->sym->offset + reloc->addend;
> > +
> > +	dest = find_insn(file, sec, off);
> > +	if (!dest)
> > +		return 0;
> > +
> > +	if (name && dest->func)
> > +		*name = dest->func->name;
> 
> I think these checks can be further narrowed down by only looking for
> X86_64_64 relocs.
> 
> > +	list_for_each_entry(insn, &file->endbr_list, call_node) {
> > +		if (ibt_seal) {
> > +			elf_write_insn(file->elf, insn->sec,
> > +				       insn->offset, insn->len,
> > +				       arch_nop_insn(insn->len));
> > +		}
> 
> Like the retpoline rewriting, I'd much rather have objtool create
> annotations which the kernel can then read and patch itself.
> 
> e.g. have '.ibt.direct_call_sites' and '.ibt.unused_endbr_insns'
> sections.

Why have the kernel do that work at every boot when it can be known at
link time?

-- 
Kees Cook

  reply	other threads:[~2022-02-08 23:43 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-22 17:03 [RFC][PATCH 0/6] x86: Kernel IBT beginnings Peter Zijlstra
2021-11-22 17:03 ` [RFC][PATCH 1/6] x86: Annotate _THIS_IP_ Peter Zijlstra
2021-11-23 13:53   ` Mark Rutland
2021-11-23 14:14     ` Peter Zijlstra
2021-11-24 18:18       ` Josh Poimboeuf
2021-11-22 17:03 ` [RFC][PATCH 2/6] x86: Base IBT bits Peter Zijlstra
2022-02-08 23:32   ` Kees Cook
2021-11-22 17:03 ` [RFC][PATCH 3/6] x86: Add ENDBR to IRET-to-Self Peter Zijlstra
2021-11-22 18:09   ` Peter Zijlstra
2022-02-08 23:33     ` Kees Cook
2021-11-22 17:03 ` [RFC][PATCH 4/6] objtool: Read the _THIS_IP_ hints Peter Zijlstra
2021-11-22 17:03 ` [RFC][PATCH 5/6] x86: Sprinkle ENDBR dust Peter Zijlstra
2021-11-23 14:00   ` Mark Rutland
2021-11-23 14:21     ` Peter Zijlstra
2022-02-08 23:38     ` Kees Cook
2021-11-22 17:03 ` [RFC][PATCH 6/6] objtool: Add IBT validation / fixups Peter Zijlstra
2021-11-24 19:30   ` Josh Poimboeuf
2022-02-08 23:43     ` Kees Cook [this message]
2022-02-09  5:09       ` Josh Poimboeuf
2022-02-09 11:41       ` Peter Zijlstra
2022-02-09 11:45         ` Peter Zijlstra
2021-12-24  2:05   ` joao
2022-02-08 23:42     ` Kees Cook
2022-02-09  2:21       ` Joao Moreira
2022-02-09  4:05         ` Kees Cook
2022-02-09  5:18           ` Joao Moreira
2022-02-11 13:38             ` Peter Zijlstra
2022-02-14 21:38               ` Sami Tolvanen
2022-02-14 22:25                 ` Peter Zijlstra
2022-02-15 16:56                   ` Sami Tolvanen
2022-02-15 20:03                     ` Kees Cook
2022-02-15 21:05                       ` Peter Zijlstra
2022-02-15 23:05                         ` Kees Cook
2022-02-15 23:38                           ` Joao Moreira
2022-02-16 12:24                         ` Peter Zijlstra
2022-02-15 20:53                     ` Peter Zijlstra
2022-02-15 22:45               ` Joao Moreira
2022-02-16  0:57               ` Andrew Cooper
2022-03-02  3:06               ` Peter Collingbourne
2022-03-02  3:32                 ` Joao Moreira
2022-06-08 17:53                 ` Fāng-ruì Sòng
2022-06-09  0:05                   ` Sami Tolvanen
2021-11-23  7:58 ` [RFC][PATCH 0/6] x86: Kernel IBT beginnings Christoph Hellwig
2021-11-23  9:02   ` Peter Zijlstra
2022-02-08 23:48 ` Kees Cook
2022-02-09  0:09 ` Nick Desaulniers

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