linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jessica Yu <jeyu@kernel.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Nicholas Piggin" <npiggin@gmail.com>,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	"Michal Suchánek" <msuchanek@suse.de>
Subject: Re: [PATCH v4 1/2] module: add elf_check_module_arch for module specific elf arch checks
Date: Wed, 16 Jun 2021 15:49:54 +0200	[thread overview]
Message-ID: <YMoBgsVPMkzEAQxV@linux.fritz.box> (raw)
In-Reply-To: <87v96esffr.fsf@mpe.ellerman.id.au>

+++ Michael Ellerman [16/06/21 12:37 +1000]:
>Jessica Yu <jeyu@kernel.org> writes:
>> +++ Nicholas Piggin [15/06/21 12:05 +1000]:
>>>Excerpts from Jessica Yu's message of June 14, 2021 10:06 pm:
>>>> +++ Nicholas Piggin [11/06/21 19:39 +1000]:
>>>>>The elf_check_arch() function is used to test usermode binaries, but
>>>>>kernel modules may have more specific requirements. powerpc would like
>>>>>to test for ABI version compatibility.
>>>>>
>>>>>Add an arch-overridable function elf_check_module_arch() that defaults
>>>>>to elf_check_arch() and use it in elf_validity_check().
>>>>>
>>>>>Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
>>>>>[np: split patch, added changelog]
>>>>>Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
>>>>>---
>>>>> include/linux/moduleloader.h | 5 +++++
>>>>> kernel/module.c              | 2 +-
>>>>> 2 files changed, 6 insertions(+), 1 deletion(-)
>>>>>
>>>>>diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
>>>>>index 9e09d11ffe5b..fdc042a84562 100644
>>>>>--- a/include/linux/moduleloader.h
>>>>>+++ b/include/linux/moduleloader.h
>>>>>@@ -13,6 +13,11 @@
>>>>>  * must be implemented by each architecture.
>>>>>  */
>>>>>
>>>>>+// Allow arch to optionally do additional checking of module ELF header
>>>>>+#ifndef elf_check_module_arch
>>>>>+#define elf_check_module_arch elf_check_arch
>>>>>+#endif
>>>>
>>>> Hi Nicholas,
>>>>
>>>> Why not make elf_check_module_arch() consistent with the other
>>>> arch-specific functions? Please see module_frob_arch_sections(),
>>>> module_{init,exit}_section(), etc in moduleloader.h. That is, they are
>>>> all __weak functions that are overridable by arches. We can maybe make
>>>> elf_check_module_arch() a weak symbol, available for arches to
>>>> override if they want to perform additional elf checks. Then we don't
>>>> have to have this one-off #define.
>
>>>Like this? I like it. Good idea.
>>
>> Yeah! Also, maybe we can alternatively make elf_check_module_arch() a
>> separate check entirely so that the powerpc implementation doesn't
>> have to include that extra elf_check_arch() call. Something like this maybe?
>
>My thinking for making elf_check_module_arch() the only hook was that
>conceivably you might not want/need to call elf_check_arch() from
>elf_check_module_arch().
>
>So having a single module specific hook allows arch code to decide
>how to implement the check, which may or may not involve calling
>elf_check_arch(), but that becomes an arch implementation detail.

Thanks for the feedback! Yeah, that's fair too. Well, I ended up doing
it this way mostly to create less churn/change of behavior, since in
its current state elf_check_arch() is already being called for each
arch. Additionally I wanted to save the powerpc implementation of
elf_check_module_arch() an extra elf_check_arch() call. In any case I
have a slight preference for having a second hook to allow arches add
any extra checks in addition to elf_check_arch(). Thanks!

  reply	other threads:[~2021-06-16 13:50 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-11  9:39 [PATCH v4 0/2] powerpc/64: Option to use ELF V2 ABI for big-endian Nicholas Piggin
2021-06-11  9:39 ` [PATCH v4 1/2] module: add elf_check_module_arch for module specific elf arch checks Nicholas Piggin
2021-06-14 12:06   ` Jessica Yu
2021-06-15  2:05     ` Nicholas Piggin
2021-06-15 12:17       ` Jessica Yu
2021-06-15 12:50         ` Segher Boessenkool
2021-06-15 13:41           ` Jessica Yu
2021-06-15 14:30             ` Segher Boessenkool
2021-06-16  2:39               ` Michael Ellerman
2021-06-16  1:18         ` Nicholas Piggin
2021-06-16 12:54           ` Jessica Yu
2021-06-17  5:21             ` Nicholas Piggin
2021-06-16  2:37         ` Michael Ellerman
2021-06-16 13:49           ` Jessica Yu [this message]
2021-06-11  9:39 ` [PATCH v4 2/2] powerpc/64: Option to use ELF V2 ABI for big-endian kernels Nicholas Piggin
2021-06-11  9:58   ` Michal Suchánek
2021-06-11 10:20     ` Michal Suchánek

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=YMoBgsVPMkzEAQxV@linux.fritz.box \
    --to=jeyu@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mpe@ellerman.id.au \
    --cc=msuchanek@suse.de \
    --cc=npiggin@gmail.com \
    /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).