2009-12-14 22:24:32

by Steven J. Magnani

Subject: [PATCH v2] microblaze: nommu: Don't clobber R11 on syscalls

The noMMU syscall trap has a bug that causes R11 to be zero on return to
userland. Remove the extra "save" of R11 responsible for the bug, as well
as an unnecessary extra "load".

Signed-off-by: Steven J. Magnani <[email protected]>
---
diff -uprN a/arch/microblaze/kernel/entry-nommu.S b/arch/microblaze/kernel/entry-nommu.S
--- a/arch/microblaze/kernel/entry-nommu.S 2009-12-09 17:05:11.000000000 -0600
+++ b/arch/microblaze/kernel/entry-nommu.S 2009-12-14 11:29:37.000000000 -0600
@@ -208,8 +208,6 @@ ENTRY(_user_exception)
lwi r1, r1, TS_THREAD_INFO /* get the thread info */
/* calculate kernel stack pointer */
addik r1, r1, THREAD_SIZE - PT_SIZE
- swi r11, r0, PER_CPU(R11_SAVE) /* temporarily save r11 */
- lwi r11, r0, PER_CPU(KM) /* load mode indicator */
2:
swi r11, r1, PT_MODE /* store the mode */
lwi r11, r0, PER_CPU(R11_SAVE) /* reload r11 */

2009-12-15 07:24:43

by Michal Simek

Subject: Re: [PATCH v2] microblaze: nommu: Don't clobber R11 on syscalls

[email protected] wrote:
> The noMMU syscall trap has a bug that causes R11 to be zero on return to
> userland. Remove the extra "save" of R11 responsible for the bug, as well
> as an unnecessary extra "load".

It seems to me that this patch means that you tested it.
But anyway I was pretty sure that I am right that's why I did this
change myself. This patch is already in Linus tree.

Thanks for test,
Michal

>
> Signed-off-by: Steven J. Magnani <[email protected]>
> ---
> diff -uprN a/arch/microblaze/kernel/entry-nommu.S b/arch/microblaze/kernel/entry-nommu.S
> --- a/arch/microblaze/kernel/entry-nommu.S 2009-12-09 17:05:11.000000000 -0600
> +++ b/arch/microblaze/kernel/entry-nommu.S 2009-12-14 11:29:37.000000000 -0600
> @@ -208,8 +208,6 @@ ENTRY(_user_exception)
> lwi r1, r1, TS_THREAD_INFO /* get the thread info */
> /* calculate kernel stack pointer */
> addik r1, r1, THREAD_SIZE - PT_SIZE
> - swi r11, r0, PER_CPU(R11_SAVE) /* temporarily save r11 */
> - lwi r11, r0, PER_CPU(KM) /* load mode indicator */
> 2:
> swi r11, r1, PT_MODE /* store the mode */
> lwi r11, r0, PER_CPU(R11_SAVE) /* reload r11 */
>


--
Michal Simek, Ing. (M.Eng)
w: http://www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian