* [PATCH] 8xx: fix user space TLB walk in dcbX fixup
@ 2010-01-08 16:46 Joakim Tjernlund
2010-01-12 2:40 ` Benjamin Herrenschmidt
0 siblings, 1 reply; 5+ messages in thread
From: Joakim Tjernlund @ 2010-01-08 16:46 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Scott Wood, linuxppc-dev@ozlabs•org,
Rex Feany
The newly added fixup for buggy dcbX insn's has
a bug that always trigger a kernel TLB walk so a user space
dcbX insn will cause a Kernel Machine Check if it hits DTLB error.
Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode•se>
---
I found this problem in 2.4 and forward ported it to 2.6. I
cannot test it so I cannot be 100% sure I got it right.
arch/powerpc/kernel/head_8xx.S | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index ce327c5..91bef6e 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -542,11 +542,11 @@ DARFixed:/* Return from dcbx instruction bug workaround, r10 holds value of DAR
FixupDAR:/* Entry point for dcbx workaround. */
/* fetch instruction from memory. */
mfspr r10, SPRN_SRR0
+ andis. r11, r10, 0x8000 /* Address >= 0x80000000 */
DO_8xx_CPU6(0x3780, r3)
mtspr SPRN_MD_EPN, r10
mfspr r11, SPRN_M_TWB /* Get level 1 table entry address */
- cmplwi cr0, r11, 0x0800
- blt- 3f /* Branch if user space */
+ beq- 3f /* Branch if user space */
lis r11, (swapper_pg_dir-PAGE_OFFSET)@h
ori r11, r11, (swapper_pg_dir-PAGE_OFFSET)@l
rlwimi r11, r10, 32-20, 0xffc /* r11 = r11&~0xffc|(r10>>20)&0xffc */
--
1.6.4.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] 8xx: fix user space TLB walk in dcbX fixup
2010-01-08 16:46 [PATCH] 8xx: fix user space TLB walk in dcbX fixup Joakim Tjernlund
@ 2010-01-12 2:40 ` Benjamin Herrenschmidt
2010-01-12 7:07 ` Joakim Tjernlund
0 siblings, 1 reply; 5+ messages in thread
From: Benjamin Herrenschmidt @ 2010-01-12 2:40 UTC (permalink / raw)
To: Joakim Tjernlund; +Cc: Scott Wood, linuxppc-dev@ozlabs•org, Rex Feany
On Fri, 2010-01-08 at 17:46 +0100, Joakim Tjernlund wrote:
> The newly added fixup for buggy dcbX insn's has
> a bug that always trigger a kernel TLB walk so a user space
> dcbX insn will cause a Kernel Machine Check if it hits DTLB error.
>
> Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode•se>
> ---
>
> I found this problem in 2.4 and forward ported it to 2.6. I
> cannot test it so I cannot be 100% sure I got it right.
>
> arch/powerpc/kernel/head_8xx.S | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
Do you have something to make sure that TASK_SIZE is never bigger than
2G ? Else userspace could be all the way to 0xbfffffff ...
Cheers,
Ben.
> diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
> index ce327c5..91bef6e 100644
> --- a/arch/powerpc/kernel/head_8xx.S
> +++ b/arch/powerpc/kernel/head_8xx.S
> @@ -542,11 +542,11 @@ DARFixed:/* Return from dcbx instruction bug workaround, r10 holds value of DAR
> FixupDAR:/* Entry point for dcbx workaround. */
> /* fetch instruction from memory. */
> mfspr r10, SPRN_SRR0
> + andis. r11, r10, 0x8000 /* Address >= 0x80000000 */
> DO_8xx_CPU6(0x3780, r3)
> mtspr SPRN_MD_EPN, r10
> mfspr r11, SPRN_M_TWB /* Get level 1 table entry address */
> - cmplwi cr0, r11, 0x0800
> - blt- 3f /* Branch if user space */
> + beq- 3f /* Branch if user space */
> lis r11, (swapper_pg_dir-PAGE_OFFSET)@h
> ori r11, r11, (swapper_pg_dir-PAGE_OFFSET)@l
> rlwimi r11, r10, 32-20, 0xffc /* r11 = r11&~0xffc|(r10>>20)&0xffc */
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] 8xx: fix user space TLB walk in dcbX fixup
2010-01-12 2:40 ` Benjamin Herrenschmidt
@ 2010-01-12 7:07 ` Joakim Tjernlund
2010-01-12 8:44 ` Benjamin Herrenschmidt
0 siblings, 1 reply; 5+ messages in thread
From: Joakim Tjernlund @ 2010-01-12 7:07 UTC (permalink / raw)
To: Benjamin Herrenschmidt; +Cc: Scott Wood, linuxppc-dev@ozlabs•org, Rex Feany
Benjamin Herrenschmidt <benh@kernel•crashing.org> wrote on 12/01/2010 03:40:45:
>
> On Fri, 2010-01-08 at 17:46 +0100, Joakim Tjernlund wrote:
> > The newly added fixup for buggy dcbX insn's has
> > a bug that always trigger a kernel TLB walk so a user space
> > dcbX insn will cause a Kernel Machine Check if it hits DTLB error.
> >
> > Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode•se>
> > ---
> >
> > I found this problem in 2.4 and forward ported it to 2.6. I
> > cannot test it so I cannot be 100% sure I got it right.
> >
> > arch/powerpc/kernel/head_8xx.S | 4 ++--
> > 1 files changed, 2 insertions(+), 2 deletions(-)
>
> Do you have something to make sure that TASK_SIZE is never bigger than
> 2G ? Else userspace could be all the way to 0xbfffffff ...
No, but this is 8xx :) The TLB handlers has the same "limitation" and has always
been so.
Jocke
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] 8xx: fix user space TLB walk in dcbX fixup
2010-01-12 7:07 ` Joakim Tjernlund
@ 2010-01-12 8:44 ` Benjamin Herrenschmidt
2010-01-12 9:17 ` Joakim Tjernlund
0 siblings, 1 reply; 5+ messages in thread
From: Benjamin Herrenschmidt @ 2010-01-12 8:44 UTC (permalink / raw)
To: Joakim Tjernlund; +Cc: Scott Wood, linuxppc-dev@ozlabs•org, Rex Feany
On Tue, 2010-01-12 at 08:07 +0100, Joakim Tjernlund wrote:
> Benjamin Herrenschmidt <benh@kernel•crashing.org> wrote on 12/01/2010 03:40:45:
> >
> > On Fri, 2010-01-08 at 17:46 +0100, Joakim Tjernlund wrote:
> > > The newly added fixup for buggy dcbX insn's has
> > > a bug that always trigger a kernel TLB walk so a user space
> > > dcbX insn will cause a Kernel Machine Check if it hits DTLB error.
> > >
> > > Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode•se>
> > > ---
> > >
> > > I found this problem in 2.4 and forward ported it to 2.6. I
> > > cannot test it so I cannot be 100% sure I got it right.
> > >
> > > arch/powerpc/kernel/head_8xx.S | 4 ++--
> > > 1 files changed, 2 insertions(+), 2 deletions(-)
> >
> > Do you have something to make sure that TASK_SIZE is never bigger than
> > 2G ? Else userspace could be all the way to 0xbfffffff ...
>
> No, but this is 8xx :) The TLB handlers has the same "limitation" and has always
> been so.
You should send a patch to express that limitation in KConfig :-)
Cheers,
Ben.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] 8xx: fix user space TLB walk in dcbX fixup
2010-01-12 8:44 ` Benjamin Herrenschmidt
@ 2010-01-12 9:17 ` Joakim Tjernlund
0 siblings, 0 replies; 5+ messages in thread
From: Joakim Tjernlund @ 2010-01-12 9:17 UTC (permalink / raw)
To: Benjamin Herrenschmidt; +Cc: Scott Wood, linuxppc-dev@ozlabs•org, Rex Feany
Benjamin Herrenschmidt <benh@kernel•crashing.org> wrote on 12/01/2010 09:44:09:
>
> On Tue, 2010-01-12 at 08:07 +0100, Joakim Tjernlund wrote:
> > Benjamin Herrenschmidt <benh@kernel•crashing.org> wrote on 12/01/2010 03:40:45:
> > >
> > > On Fri, 2010-01-08 at 17:46 +0100, Joakim Tjernlund wrote:
> > > > The newly added fixup for buggy dcbX insn's has
> > > > a bug that always trigger a kernel TLB walk so a user space
> > > > dcbX insn will cause a Kernel Machine Check if it hits DTLB error.
> > > >
> > > > Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode•se>
> > > > ---
> > > >
> > > > I found this problem in 2.4 and forward ported it to 2.6. I
> > > > cannot test it so I cannot be 100% sure I got it right.
> > > >
> > > > arch/powerpc/kernel/head_8xx.S | 4 ++--
> > > > 1 files changed, 2 insertions(+), 2 deletions(-)
> > >
> > > Do you have something to make sure that TASK_SIZE is never bigger than
> > > 2G ? Else userspace could be all the way to 0xbfffffff ...
> >
> > No, but this is 8xx :) The TLB handlers has the same "limitation" and has always
> > been so.
>
> You should send a patch to express that limitation in KConfig :-)
Yeah, but this is nothing new to 8xx users.
The TLB handlers (and possible other parts too) has always had this limitation.
I don't think anyone cares since this is a small embedded CPU.
Jocke
^ permalink raw reply [flat|nested] 5+ messages in thread
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2010-01-08 16:46 [PATCH] 8xx: fix user space TLB walk in dcbX fixup Joakim Tjernlund
2010-01-12 2:40 ` Benjamin Herrenschmidt
2010-01-12 7:07 ` Joakim Tjernlund
2010-01-12 8:44 ` Benjamin Herrenschmidt
2010-01-12 9:17 ` Joakim Tjernlund
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