From: Michael Ellerman <mpe@ellerman.id.au>
To: Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe()
Date: Fri, 09 Jun 2023 23:06:11 +1000 [thread overview]
Message-ID: <874jnghjjw.fsf@mail.lhotse> (raw)
In-Reply-To: <CT5FZBY14ZM4.OYXBJNXQU9A2@wheely>
"Nicholas Piggin" <npiggin@gmail.com> writes:
> On Mon Jun 5, 2023 at 6:58 PM AEST, Christophe Leroy wrote:
>> Looking at generated code for handle_signal32() shows calls to a
>> function called __unsafe_save_user_regs.constprop.0 while user access
>> is open.
>>
>> And that __unsafe_save_user_regs.constprop.0 function has two nops at
>> the begining, allowing it to be traced, which is unexpected during
>> user access open window.
>>
>> The solution could be to mark __unsafe_save_user_regs() no trace, but
>> to be on the safe side the most efficient is to flag it __always_inline
>> as already done for function __unsafe_restore_general_regs(). The
>> function is relatively small and only called twice, so the size
>> increase will remain in the noise.
>>
>> Do the same with save_tm_user_regs_unsafe() as it may suffer the
>> same issue.
>
> Could you put a comment so someone doesn't uninline it later?
I think the "unsafe" in the name is probably sufficient to warn people
off, but you never know. Still I'd happily take a patch to add comments :)
> Marking it notrace as well would be sufficient for a comment, if that works.
I nearly did that when applying, but I'm not sure it won't change the
code generation, so I left it as-is.
cheers
WARNING: multiple messages have this Message-ID (diff)
From: Michael Ellerman <mpe@ellerman.id.au>
To: Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe()
Date: Fri, 09 Jun 2023 23:06:11 +1000 [thread overview]
Message-ID: <874jnghjjw.fsf@mail.lhotse> (raw)
In-Reply-To: <CT5FZBY14ZM4.OYXBJNXQU9A2@wheely>
"Nicholas Piggin" <npiggin@gmail.com> writes:
> On Mon Jun 5, 2023 at 6:58 PM AEST, Christophe Leroy wrote:
>> Looking at generated code for handle_signal32() shows calls to a
>> function called __unsafe_save_user_regs.constprop.0 while user access
>> is open.
>>
>> And that __unsafe_save_user_regs.constprop.0 function has two nops at
>> the begining, allowing it to be traced, which is unexpected during
>> user access open window.
>>
>> The solution could be to mark __unsafe_save_user_regs() no trace, but
>> to be on the safe side the most efficient is to flag it __always_inline
>> as already done for function __unsafe_restore_general_regs(). The
>> function is relatively small and only called twice, so the size
>> increase will remain in the noise.
>>
>> Do the same with save_tm_user_regs_unsafe() as it may suffer the
>> same issue.
>
> Could you put a comment so someone doesn't uninline it later?
I think the "unsafe" in the name is probably sufficient to warn people
off, but you never know. Still I'd happily take a patch to add comments :)
> Marking it notrace as well would be sufficient for a comment, if that works.
I nearly did that when applying, but I'm not sure it won't change the
code generation, so I left it as-is.
cheers
next prev parent reply other threads:[~2023-06-09 13:06 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-05 8:58 [PATCH] powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe() Christophe Leroy
2023-06-05 8:58 ` Christophe Leroy
2023-06-06 8:58 ` Nicholas Piggin
2023-06-06 8:58 ` Nicholas Piggin
2023-06-09 13:06 ` Michael Ellerman [this message]
2023-06-09 13:06 ` Michael Ellerman
2023-07-03 5:26 ` Michael Ellerman
2023-07-03 5:26 ` Michael Ellerman
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=874jnghjjw.fsf@mail.lhotse \
--to=mpe@ellerman.id.au \
--cc=christophe.leroy@csgroup.eu \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.