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From: Peter Zijlstra <peterz@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: "Christopher M. Riedl" <cmr@codefail.de>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/8] powerpc: Mark functions called inside uaccess blocks w/ 'notrace'
Date: Fri, 16 Oct 2020 11:41:32 +0200	[thread overview]
Message-ID: <20201016094132.GI2611@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201016065616.GB9343@infradead.org>

On Fri, Oct 16, 2020 at 07:56:16AM +0100, Christoph Hellwig wrote:
> On Thu, Oct 15, 2020 at 10:01:54AM -0500, Christopher M. Riedl wrote:
> > Functions called between user_*_access_begin() and user_*_access_end()
> > should be either inlined or marked 'notrace' to prevent leaving
> > userspace access exposed. Mark any such functions relevant to signal
> > handling so that subsequent patches can call them inside uaccess blocks.
> 
> I don't think running this much code with uaccess enabled is a good
> idea.  Please refactor the code to reduce the criticial sections with
> uaccess enabled.
> 
> Btw, does powerpc already have the objtool validation that we don't
> accidentally jump out of unsafe uaccess critical sections?

It does not, there was some effort on that a while ago, but I suspect
they're waiting for the ARM64 effort to land and build on that.

WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	"Christopher M. Riedl" <cmr@codefail.de>
Subject: Re: [PATCH 3/8] powerpc: Mark functions called inside uaccess blocks w/ 'notrace'
Date: Fri, 16 Oct 2020 11:41:32 +0200	[thread overview]
Message-ID: <20201016094132.GI2611@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201016065616.GB9343@infradead.org>

On Fri, Oct 16, 2020 at 07:56:16AM +0100, Christoph Hellwig wrote:
> On Thu, Oct 15, 2020 at 10:01:54AM -0500, Christopher M. Riedl wrote:
> > Functions called between user_*_access_begin() and user_*_access_end()
> > should be either inlined or marked 'notrace' to prevent leaving
> > userspace access exposed. Mark any such functions relevant to signal
> > handling so that subsequent patches can call them inside uaccess blocks.
> 
> I don't think running this much code with uaccess enabled is a good
> idea.  Please refactor the code to reduce the criticial sections with
> uaccess enabled.
> 
> Btw, does powerpc already have the objtool validation that we don't
> accidentally jump out of unsafe uaccess critical sections?

It does not, there was some effort on that a while ago, but I suspect
they're waiting for the ARM64 effort to land and build on that.

  reply	other threads:[~2020-10-16  9:41 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-15 15:01 [PATCH 0/8] Improve signal performance on PPC64 with KUAP Christopher M. Riedl
2020-10-15 15:01 ` [PATCH 1/8] powerpc/uaccess: Add unsafe_copy_from_user Christopher M. Riedl
2020-10-16  6:54   ` Christoph Hellwig
2020-10-16 13:18     ` Christophe Leroy
2020-10-16 13:17   ` Christophe Leroy
2020-10-20  3:00     ` Christopher M. Riedl
2020-10-15 15:01 ` [PATCH 2/8] powerpc/signal: Add unsafe_copy_{vsx,fpr}_from_user() Christopher M. Riedl
2020-10-16 13:48   ` [PATCH 2/8] powerpc/signal: Add unsafe_copy_{vsx, fpr}_from_user() Christophe Leroy
2020-10-20  2:01     ` [PATCH 2/8] powerpc/signal: Add unsafe_copy_{vsx,fpr}_from_user() Christopher M. Riedl
2021-02-06 16:32       ` [PATCH 2/8] powerpc/signal: Add unsafe_copy_{vsx, fpr}_from_user() Christophe Leroy
2021-02-06 17:39         ` [PATCH 2/8] powerpc/signal: Add unsafe_copy_{vsx,fpr}_from_user() Christopher M. Riedl
2021-02-07 10:12           ` [PATCH 2/8] powerpc/signal: Add unsafe_copy_{vsx, fpr}_from_user() Christophe Leroy
2021-02-08 17:14             ` [PATCH 2/8] powerpc/signal: Add unsafe_copy_{vsx,fpr}_from_user() Christopher M. Riedl
2021-02-08 17:18               ` [PATCH 2/8] powerpc/signal: Add unsafe_copy_{vsx, fpr}_from_user() Christophe Leroy
2020-10-15 15:01 ` [PATCH 3/8] powerpc: Mark functions called inside uaccess blocks w/ 'notrace' Christopher M. Riedl
2020-10-16  6:56   ` Christoph Hellwig
2020-10-16  6:56     ` Christoph Hellwig
2020-10-16  9:41     ` Peter Zijlstra [this message]
2020-10-16  9:41       ` Peter Zijlstra
2020-10-20  7:34       ` Michael Ellerman
2020-10-16  7:02   ` Christophe Leroy
2020-10-20  1:59     ` Christopher M. Riedl
2020-10-15 15:01 ` [PATCH 4/8] powerpc/signal64: Replace setup_sigcontext() w/ unsafe_setup_sigcontext() Christopher M. Riedl
2020-10-15 15:01 ` [PATCH 5/8] powerpc/signal64: Replace restore_sigcontext() w/ unsafe_restore_sigcontext() Christopher M. Riedl
2020-10-15 15:01 ` [PATCH 6/8] powerpc/signal64: Replace setup_trampoline() w/ unsafe_setup_trampoline() Christopher M. Riedl
2020-10-16 13:56   ` Christophe Leroy
2020-10-20  2:42     ` Christopher M. Riedl
2020-10-20  5:02       ` Christophe Leroy
2020-10-15 15:01 ` [PATCH 7/8] powerpc/signal64: Rewrite handle_rt_signal64() to minimise uaccess switches Christopher M. Riedl
2020-10-16 14:00   ` Christophe Leroy
2020-10-20  2:44     ` Christopher M. Riedl
2020-10-15 15:01 ` [PATCH 8/8] powerpc/signal64: Rewrite rt_sigreturn() " Christopher M. Riedl
2020-10-16 14:07   ` Christophe Leroy
2020-10-20  2:45     ` Christopher M. Riedl

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