From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "Lutomirski, Andy" <luto@kernel.org>,
"alexander.shishkin@linux.intel.com"
<alexander.shishkin@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
"Mehta, Sohil" <sohil.mehta@intel.com>
Subject: Re: [PATCH v3 03/12] x86/alternatives: Disable LASS when patching kernel alternatives
Date: Tue, 1 Aug 2023 21:50:14 +0000 [thread overview]
Message-ID: <1432878a512dbb361c0fb9f303fda33a7cf68c9b.camel@intel.com> (raw)
In-Reply-To: <a947a270-dad6-5486-2e11-feb288aa9210@intel.com>
On Tue, 2023-08-01 at 14:10 -0700, Sohil Mehta wrote:
> > Why not do stac/clac in a single place inside __text_poke()?
>
> It would mostly look something like this:
> > diff --git a/arch/x86/kernel/alternative.c
> > b/arch/x86/kernel/alternative.c
> > index 0fbf8a631306..02ef08e2575d 100644
> > --- a/arch/x86/kernel/alternative.c
> > +++ b/arch/x86/kernel/alternative.c
> > @@ -1781,7 +1781,9 @@ static void *__text_poke(text_poke_f func,
> > void *addr, const void *src, size_t l
> > prev = use_temporary_mm(poking_mm);
> >
> > kasan_disable_current();
> > + stac();
> > func((u8 *)poking_addr + offset_in_page(addr), src, len);
> > + clac();
> > kasan_enable_current();
> >
> > /*
>
> Since, __text_poke() uses a dynamic function to call into
> text_poke_memcpy() and text_poke_memset(), objtool would still
> complain.
>
> > arch/x86/kernel/alternative.o: warning: objtool: __text_poke+0x259:
> > call to {dynamic}() with UACCESS enabled
>
> We could change __text_poke() to not use the dynamic func but it
> might
> be a bit heavy handed to save a couple of lines of stac/clac calls.
> The
> current trade-off seems reasonable to me.
>
> Did you have something different in mind?
I wondered if it might be something like that. Yes, seems like an ok
tradeoff.
next prev parent reply other threads:[~2023-08-01 21:50 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 18:36 [PATCH v3 00/12] Enable Linear Address Space Separation support Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 01/12] x86/cpu: Enumerate the LASS feature bits Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 02/12] x86/asm: Introduce inline memcpy and memset Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 03/12] x86/alternatives: Disable LASS when patching kernel alternatives Alexander Shishkin
2023-07-31 22:41 ` Edgecombe, Rick P
2023-08-01 21:10 ` Sohil Mehta
2023-08-01 21:50 ` Edgecombe, Rick P [this message]
2023-06-09 18:36 ` [PATCH v3 04/12] x86/cpu: Enable LASS during CPU initialization Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 05/12] x86/cpu: Remove redundant comment during feature setup Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 06/12] x86/vsyscall: Reorganize the #PF emulation code Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 07/12] x86/traps: Consolidate user fixups in exc_general_protection() Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 08/12] x86/vsyscall: Add vsyscall emulation for #GP Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 09/12] x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 10/12] x86/vsyscall: Document the fact that vsyscall=emulate disables LASS Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 11/12] x86/cpu: Set LASS CR4 bit as pinning sensitive Alexander Shishkin
2023-06-09 18:36 ` [RFC v3 12/12] x86/efi: Disable LASS enforcement when switching to EFI MM Alexander Shishkin
2023-07-31 18:00 ` [PATCH v3 00/12] Enable Linear Address Space Separation support Alexander Shishkin
2023-07-31 22:36 ` Edgecombe, Rick P
2023-08-01 19:50 ` Sohil Mehta
2023-08-01 20:38 ` Edgecombe, Rick P
2023-08-04 23:52 ` Edgecombe, Rick P
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