From: rabin@rab.in (Rabin Vincent)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] arm: use fixmap for text patching when text is RO
Date: Thu, 10 Apr 2014 21:34:46 +0200 [thread overview]
Message-ID: <20140410193433.GA22746@debian> (raw)
In-Reply-To: <1396879071.3654.43.camel@linaro1.home>
On Mon, Apr 07, 2014 at 02:57:51PM +0100, Jon Medhurst (Tixy) wrote:
> How does fixmap cope with cache colouring? Looking at the implementation
> it looks like it doesn't and so fixmap use on ARM is possibly buggy.
>
> For the text patching case where we know there are no writeable mappings
> [1] this should be OK if we used set_fixmap_nocache here, so long as we
> also invalidated the dcache later for the proper virtual address.
OK. The dcache invalidation for the proper virtual address is btw
already there via the call to flush_icache_range().
> [1] Can we know there are no writeable mappings though, the ftrace code
> modifying patches from Kees Cook have there own way of modifying text
> code permissions.
The ftrace patches does the modifications and the cache cleaning in
stop_machine(), so there should not be any dirty cache lines from those
writable mappings when we set up and write to these fixmaps. Do you
still see a problem?
WARNING: multiple messages have this Message-ID (diff)
From: Rabin Vincent <rabin@rab.in>
To: "Jon Medhurst (Tixy)" <tixy@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>,
Laura Abbott <lauraa@codeaurora.org>
Subject: Re: [PATCH 2/2] arm: use fixmap for text patching when text is RO
Date: Thu, 10 Apr 2014 21:34:46 +0200 [thread overview]
Message-ID: <20140410193433.GA22746@debian> (raw)
In-Reply-To: <1396879071.3654.43.camel@linaro1.home>
On Mon, Apr 07, 2014 at 02:57:51PM +0100, Jon Medhurst (Tixy) wrote:
> How does fixmap cope with cache colouring? Looking at the implementation
> it looks like it doesn't and so fixmap use on ARM is possibly buggy.
>
> For the text patching case where we know there are no writeable mappings
> [1] this should be OK if we used set_fixmap_nocache here, so long as we
> also invalidated the dcache later for the proper virtual address.
OK. The dcache invalidation for the proper virtual address is btw
already there via the call to flush_icache_range().
> [1] Can we know there are no writeable mappings though, the ftrace code
> modifying patches from Kees Cook have there own way of modifying text
> code permissions.
The ftrace patches does the modifications and the cache cleaning in
stop_machine(), so there should not be any dirty cache lines from those
writable mappings when we set up and write to these fixmaps. Do you
still see a problem?
next prev parent reply other threads:[~2014-04-10 19:34 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-04 21:27 [PATCH 1/2] arm: fixmap: implement __set_fixmap() Rabin Vincent
2014-04-04 21:27 ` Rabin Vincent
2014-04-04 21:27 ` [PATCH 2/2] arm: use fixmap for text patching when text is RO Rabin Vincent
2014-04-04 21:27 ` Rabin Vincent
2014-04-07 13:57 ` Jon Medhurst (Tixy)
2014-04-07 13:57 ` Jon Medhurst (Tixy)
2014-04-07 18:04 ` Kees Cook
2014-04-07 18:04 ` Kees Cook
2014-04-08 9:31 ` Jon Medhurst (Tixy)
2014-04-08 9:31 ` Jon Medhurst (Tixy)
2014-04-10 19:34 ` Rabin Vincent [this message]
2014-04-10 19:34 ` Rabin Vincent
2014-04-23 21:09 ` Kees Cook
2014-04-23 21:09 ` Kees Cook
2014-04-23 22:51 ` Doug Anderson
2014-04-23 22:51 ` Doug Anderson
2014-04-24 21:28 ` [PATCHv2 " Rabin Vincent
2014-04-24 21:28 ` Rabin Vincent
2014-04-25 0:52 ` [PATCH 1/2] arm: fixmap: implement __set_fixmap() Doug Anderson
2014-04-25 0:52 ` Doug Anderson
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