* [PATCH] arc: enable unaligned access in kernel mode
@ 2016-12-21 11:40 Alexey Brodkin
2016-12-23 1:00 ` Vineet Gupta
0 siblings, 1 reply; 2+ messages in thread
From: Alexey Brodkin @ 2016-12-21 11:40 UTC (permalink / raw)
To: linux-snps-arc; +Cc: linux-kernel, Vineet Gupta, Alexey Brodkin, John Crispin
This enables misaligned access handling even in kernel mode.
Some wireless drivers (ath9k-htc and mt7601u) use misaligned accesses
here and there and to cope with that without fixing stuff in the drivers
we're just gracefully handling it on ARC.
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: John Crispin <john@phrozen.org>
---
arch/arc/kernel/unaligned.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/arc/kernel/unaligned.c b/arch/arc/kernel/unaligned.c
index abd961f3e763..58b7415e47ca 100644
--- a/arch/arc/kernel/unaligned.c
+++ b/arch/arc/kernel/unaligned.c
@@ -205,8 +205,8 @@ int misaligned_fixup(unsigned long address, struct pt_regs *regs,
struct disasm_state state;
char buf[TASK_COMM_LEN];
- /* handle user mode only and only if enabled by sysadmin */
- if (!user_mode(regs) || !unaligned_enabled)
+ /* handle only if enabled by sysadmin */
+ if (!unaligned_enabled)
return 1;
if (no_unaligned_warning) {
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] arc: enable unaligned access in kernel mode
2016-12-21 11:40 [PATCH] arc: enable unaligned access in kernel mode Alexey Brodkin
@ 2016-12-23 1:00 ` Vineet Gupta
0 siblings, 0 replies; 2+ messages in thread
From: Vineet Gupta @ 2016-12-23 1:00 UTC (permalink / raw)
To: Alexey Brodkin, linux-snps-arc; +Cc: linux-kernel, John Crispin
On 12/21/2016 03:40 AM, Alexey Brodkin wrote:
> This enables misaligned access handling even in kernel mode.
> Some wireless drivers (ath9k-htc and mt7601u) use misaligned accesses
> here and there and to cope with that without fixing stuff in the drivers
> we're just gracefully handling it on ARC.
>
> Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
> Cc: John Crispin <john@phrozen.org>
> ---
> arch/arc/kernel/unaligned.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arc/kernel/unaligned.c b/arch/arc/kernel/unaligned.c
> index abd961f3e763..58b7415e47ca 100644
> --- a/arch/arc/kernel/unaligned.c
> +++ b/arch/arc/kernel/unaligned.c
> @@ -205,8 +205,8 @@ int misaligned_fixup(unsigned long address, struct pt_regs *regs,
> struct disasm_state state;
> char buf[TASK_COMM_LEN];
>
> - /* handle user mode only and only if enabled by sysadmin */
> - if (!user_mode(regs) || !unaligned_enabled)
> + /* handle only if enabled by sysadmin */
> + if (!unaligned_enabled)
This in theory seems OK but AFAIKR we discussed this internally for STAR
9000974739- [openwrt/AXS101] unaligned access on connection of the first wireless
client
One of the crash logs had Interrupt Active while failing to emulate unaligned
access - despite this patch.
> [ECR ]: 0x00230400 => Misaligned r/w from 0x9e67a22b
> [ 51.630000] [EFA ]: 0x9e67a22b
> [ 51.630000] [BLINK ]: br_multicast_add_group+0x246/0x284
> [ 51.630000] [ERET ]: br_multicast_add_group+0xae/0x284
> [ 51.650000] [STAT32]: 0x0000020e : K A1 E2 E1
^^^^
It seemed to me at the time that allowing this from kernel mode might require more
things - like not allowing preemption or disabling further interrupts ? I looked
in CRM but can't find more details - do u remember !
Can we try and reproduce that new-issue-after-patch or perhaps just add this patch
as it is and deal with any fallouts later ?
-Vineet
> return 1;
>
> if (no_unaligned_warning) {
>
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