[PATCH 2.5] r4k_switch task_struct/thread_info fixes

[PATCH 2.5] r4k_switch task_struct/thread_info fixes

[Vivien Chappelier]

Hi,

	This patch fixes an incorrect use of THREAD_FLAGS instead of
TI_FLAGS when clearing the TIF_USEDFPU flag of the current thread info,
and an incorrect assumption when using ST_OFF, that the stack is shared
with task_struct, whereas it is shared with thread_info in 2.5.

Vivien.

Index: arch/mips64/kernel/r4k_switch.S
===================================================================
RCS file: /home/cvs/linux/arch/mips64/kernel/r4k_switch.S,v
retrieving revision 1.22
diff -u -r1.22 r4k_switch.S
--- arch/mips64/kernel/r4k_switch.S	5 Nov 2002 19:51:47 -0000	1.22
+++ arch/mips64/kernel/r4k_switch.S	3 Feb 2003 22:05:26 -0000
@@ -24,6 +24,10 @@
 
 	.set	mips3
 
+/* 
+ * Offset to the current process status flags, the first 32 bytes of the
+ * stack are not used.
+ */
 #define ST_OFF (KERNEL_STACK_SIZE - 32 - PT_SIZE + PT_STATUS)
 
 /*
@@ -58,15 +62,15 @@
 	nor	t1, zero, t1
 
 	and	t0, t0, t1
-	sd	t0, TASK_FLAGS(t3)
+	sd	t0, TI_FLAGS(t3)
 
 	/*
 	 * clear saved user stack CU1 bit
 	 */
-	ld	t0, ST_OFF(a0)
+	ld	t0, ST_OFF(t3)
 	li	t1, ~ST0_CU1
 	and	t0, t0, t1
-	sd	t0, ST_OFF(a0)
+	sd	t0, ST_OFF(t3)
 
 	
 	sll	t2, t0, 5
Index: arch/mips/kernel/r4k_switch.S
===================================================================
RCS file: /home/cvs/linux/arch/mips/kernel/r4k_switch.S,v
retrieving revision 1.29
diff -u -r1.29 r4k_switch.S
--- arch/mips/kernel/r4k_switch.S	5 Nov 2002 19:51:47 -0000	1.29
+++ arch/mips/kernel/r4k_switch.S	3 Feb 2003 22:06:17 -0000
@@ -67,10 +67,10 @@
 	/*
 	 * clear saved user stack CU1 bit
 	 */
-	lw	t0, ST_OFF(a0)
+	lw	t0, ST_OFF(t3)
 	li	t1, ~ST0_CU1
 	and	t0, t0, t1
-	sw	t0, ST_OFF(a0)
+	sw	t0, ST_OFF(t3)
 
 	FPU_SAVE_DOUBLE(a0, t0)			# clobbers t0
 

Re: [PATCH 2.5] r4k_switch task_struct/thread_info fixes

[Ralf Baechle]

On Mon, Feb 03, 2003 at 11:21:50PM +0100, Vivien Chappelier wrote:

> 	This patch fixes an incorrect use of THREAD_FLAGS instead of
> TI_FLAGS when clearing the TIF_USEDFPU flag of the current thread info,
> and an incorrect assumption when using ST_OFF, that the stack is shared
> with task_struct, whereas it is shared with thread_info in 2.5.

Ok.  You missed r2300_switch.S though :)

  Ralf

Re: [PATCH 2.5] r4k_switch task_struct/thread_info fixes

[Jun Sun]

Actually the following hunks are not right.  ST_OFF
should be applied against the task_struct, which is a0,
not thread_info (t3).  Try to back off the change and see if things
are ok.

Also see my next email before you rush into trying :-)

Jun


On Mon, Feb 03, 2003 at 11:21:50PM +0100, Vivien Chappelier wrote:
<snip>
>  	/*
>  	 * clear saved user stack CU1 bit
>  	 */
> -	ld	t0, ST_OFF(a0)
> +	ld	t0, ST_OFF(t3)
>  	li	t1, ~ST0_CU1
>  	and	t0, t0, t1
> -	sd	t0, ST_OFF(a0)
> +	sd	t0, ST_OFF(t3)
>  
>  	
>  	sll	t2, t0, 5
> Index: arch/mips/kernel/r4k_switch.S
> ===================================================================
> RCS file: /home/cvs/linux/arch/mips/kernel/r4k_switch.S,v
> retrieving revision 1.29
> diff -u -r1.29 r4k_switch.S
> --- arch/mips/kernel/r4k_switch.S	5 Nov 2002 19:51:47 -0000	1.29
> +++ arch/mips/kernel/r4k_switch.S	3 Feb 2003 22:06:17 -0000
> @@ -67,10 +67,10 @@
>  	/*
>  	 * clear saved user stack CU1 bit
>  	 */
> -	lw	t0, ST_OFF(a0)
> +	lw	t0, ST_OFF(t3)
>  	li	t1, ~ST0_CU1
>  	and	t0, t0, t1
> -	sw	t0, ST_OFF(a0)
> +	sw	t0, ST_OFF(t3)
>  
>  	FPU_SAVE_DOUBLE(a0, t0)			# clobbers t0
>  
> 

Re: [PATCH 2.5] r4k_switch task_struct/thread_info fixes

[Vivien Chappelier]

On Thu, 6 Feb 2003, Jun Sun wrote:

> Actually the following hunks are not right.  ST_OFF
> should be applied against the task_struct, which is a0,
> not thread_info (t3).

In 2.4 yes, not in 2.5.

include/linux/sched.h:469
> union thread_union {
>         struct thread_info thread_info;
>         unsigned long stack[INIT_THREAD_SIZE/sizeof(long)];
> };

That means the top of the stack is actually at (task->thread_info +
KERNEL_STACK_SIZE) in 2.5. See for example arch/mips64/kernel/ptrace.c:107

> Also see my next email before you rush into trying :-)

Ok, I'll look at it later.

Vivien.

Re: [PATCH 2.5] r4k_switch task_struct/thread_info fixes

[Jun Sun]

On Fri, Feb 07, 2003 at 10:29:16AM +0100, Vivien Chappelier wrote:
> On Thu, 6 Feb 2003, Jun Sun wrote:
> 
> > Actually the following hunks are not right.  ST_OFF
> > should be applied against the task_struct, which is a0,
> > not thread_info (t3).
> 
> In 2.4 yes, not in 2.5.
> 

You are right.  I got misled.  I thought task struct has 2 page 
size and thread_info is allocated from slab.  It should be reverse.

> include/linux/sched.h:469
> > union thread_union {
> >         struct thread_info thread_info;
> >         unsigned long stack[INIT_THREAD_SIZE/sizeof(long)];
> > };
> 
> That means the top of the stack is actually at (task->thread_info +
> KERNEL_STACK_SIZE) in 2.5. See for example arch/mips64/kernel/ptrace.c:107
> 
> > Also see my next email before you rush into trying :-)
> 
> Ok, I'll look at it later.
>

It turns I made a rather stupid comment there as well.  See it there.  :-)

Jun