kernel-hardening.lists.openwall.com archive mirror
 help / color / mirror / Atom feed
From: Thomas Gleixner <tglx@linutronix.de>
To: Kristen Carlson Accardi <kristen@linux.intel.com>,
	keescook@chromium.org, mingo@redhat.com, bp@alien8.de
Cc: arjan@linux.intel.com, x86@kernel.org,
	linux-kernel@vger.kernel.org,
	kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com,
	Kristen Carlson Accardi <kristen@linux.intel.com>
Subject: Re: [PATCH v2 0/9] Function Granular KASLR
Date: Fri, 22 May 2020 00:26:30 +0200	[thread overview]
Message-ID: <87367sudpl.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com>

Kristen,

Kristen Carlson Accardi <kristen@linux.intel.com> writes:

sorry for not following this work and a maybe stupid question.

> Proposed Improvement
> --------------------
> This patch set proposes adding function reordering on top of the existing
> KASLR base address randomization. The over-arching objective is incremental
> improvement over what we already have. It is designed to work in combination
> with the existing solution. The implementation is really pretty simple, and
> there are 2 main area where changes occur:
>
> * Build time
>
> GCC has had an option to place functions into individual .text sections for
> many years now. This option can be used to implement function reordering at
> load time. The final compiled vmlinux retains all the section headers, which
> can be used to help find the address ranges of each function. Using this
> information and an expanded table of relocation addresses, individual text
> sections can be suffled immediately after decompression. Some data tables
> inside the kernel that have assumptions about order require re-sorting
> after being updated when applying relocations. In order to modify these tables,
> a few key symbols are excluded from the objcopy symbol stripping process for
> use after shuffling the text segments.

I understand how this is supposed to work, but I fail to find an
explanation how all of this is preserving the text subsections we have,
i.e. .kprobes.text, .entry.text ...?

I assume that the functions in these subsections are reshuffled within
their own randomized address space so that __xxx_text_start and
__xxx_text_end markers still make sense, right?

I'm surely too tired to figure it out from the patches, but you really
want to explain that very detailed for mere mortals who are not deep
into this magic as you are.

Thanks,

        tglx

  parent reply	other threads:[~2020-05-21 22:27 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21 16:56 [PATCH v2 0/9] Function Granular KASLR Kristen Carlson Accardi
2020-05-21 16:56 ` [PATCH v2 1/9] objtool: Do not assume order of parent/child functions Kristen Carlson Accardi
2020-05-21 16:56 ` [PATCH v2 2/9] x86: tools/relocs: Support >64K section headers Kristen Carlson Accardi
2020-05-21 16:56 ` [PATCH v2 3/9] x86/boot: Allow a "silent" kaslr random byte fetch Kristen Carlson Accardi
2020-05-21 16:56 ` [PATCH v2 4/9] x86: Makefile: Add build and config option for CONFIG_FG_KASLR Kristen Carlson Accardi
2020-05-21 20:00   ` Kees Cook
2020-05-21 16:56 ` [PATCH v2 5/9] x86: Make sure _etext includes function sections Kristen Carlson Accardi
2020-05-21 18:11   ` Kees Cook
2020-05-21 16:56 ` [PATCH v2 6/9] x86/tools: Add relative relocs for randomized functions Kristen Carlson Accardi
2020-05-21 19:54   ` Kees Cook
2020-05-21 16:56 ` [PATCH v2 7/9] x86: Add support for function granular KASLR Kristen Carlson Accardi
2020-05-21 21:08   ` Kees Cook
2020-05-21 21:42     ` Kristen Carlson Accardi
2020-06-04 17:27     ` Kristen Carlson Accardi
2020-06-04 22:37       ` Kees Cook
2020-05-21 16:56 ` [PATCH v2 8/9] kallsyms: Hide layout Kristen Carlson Accardi
2020-05-21 21:14   ` Kees Cook
2020-05-21 16:56 ` [PATCH v2 9/9] module: Reorder functions Kristen Carlson Accardi
2020-05-21 21:33   ` Kees Cook
2020-06-09 20:14     ` Kristen Carlson Accardi
2020-06-09 20:42       ` Kees Cook
2020-06-09 20:59         ` Kristen Carlson Accardi
2020-05-21 21:54 ` [PATCH v2 0/9] Function Granular KASLR Kees Cook
2020-05-21 22:26 ` Thomas Gleixner [this message]
2020-05-21 23:30   ` Kees Cook
2020-05-21 23:43     ` Thomas Gleixner
2020-05-21 23:44     ` Kristen Carlson Accardi

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87367sudpl.fsf@nanos.tec.linutronix.de \
    --to=tglx@linutronix.de \
    --cc=arjan@linux.intel.com \
    --cc=bp@alien8.de \
    --cc=keescook@chromium.org \
    --cc=kernel-hardening@lists.openwall.com \
    --cc=kristen@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=rick.p.edgecombe@intel.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).