Re: [PATCH] Kernel panic on IA-64 Linux with SELinux

["Kaigai Kohei" <kaigai@ak.jp.nec.com>]

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I'm sorry the patch attached with the previous mail was wrong.
Please ignore it. orz

The patch attached with this mail is the latest version.

------------------------------------
Dear David

The attached patch moves the current of cpu_idle from region 7 to region 5.

The init_task can be viewed from either region 5 or 7.
But the current(r13) of cpu_idle was a region 7 address while &init_task
referes to a region 5 address. Thus, some bad effects occurred.
(This problem came to the front first time by enabling SELinux.)


Signed-off-by: Kazuto MIYOSHI <k-miyoshi@cb.jp.nec.com>
Signed-off-by: Takayoshi Kochi <t-kochi@bq.jp.nec.com>
Signed-off-by: Kaigai Kohei <kaigai@ak.jp.nec.com>
------------------------------------

> Dear David
> 
> The attached patch moves the current of cpu_idle from region 7 to region 5.
> 
> The init_task can be viewed from either region 5 or 7.
> But the current(r13) of cpu_idle was a region 7 address while &init_task
> referes to a region 5 address. Thus, some bad effects occurred.
> (This problem came to the front first time by enabling SELinux.)
> 
> 
> Signed-off-by: Kazuto MIYOSHI <k-miyoshi@cb.jp.nec.com>
> Signed-off-by: Takayoshi Kochi <t-kochi@bq.jp.nec.com>
> Signed-off-by: Kaigai Kohei <kaigai@ak.jp.nec.com>
> 
> Thanks, so much.
> --------
> Kaigai Kohei, Linux Promotion Center, NEC
> E-mail: kaigai@ak.jp.nec.com
> 
> 
> > Hi Kaigai,
> > 
> > Thanks for looking into this issue.
> > 
> > >>>>> On Tue, 15 Jun 2004 11:28:14 +0900, "Kaigai Kohei" <kaigai@ak.jp.nec.com> said:
> > 
> >   Kaigai> I have applied this patch to 2.6.6 kernel, and system stall
> >   Kaigai> occurred while booting up. The problem is in
> >   Kaigai> init_mount_tree().  The init_mount_tree() function uses
> >   Kaigai> do_each_thread() macro defined as follows:
> > 
> >   Kaigai> #define do_each_thread(g, t) \
> >   Kaigai>   for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do
> > 
> > Yeah, that'd do it.
> > 
> >   Kaigai> There are several solutions against this problem.
> > 
> >   Kaigai> (1) Initializing only wait_chldexit as my first patch.
> > 
> >   Kaigai> (2) Moving current of swapper from region 7 to region 5 as
> >   Kaigai> Miyoshi's second patch.
> > 
> >   Kaigai> (3) Replacing &init_task with task_t *p_init_task which
> >   Kaigai> refers to init_task in region 7, and refers to init_task
> >   Kaigai> directly on other archtectures.
> > 
> >   Kaigai> (1) is easy but ad hoc. (3) needs to correct generic code.
> >   Kaigai> (2) is consistent on &init_task is in region 5 and
> >   Kaigai> current(r13) for cpu_idle refers to region 5. But the number
> >   Kaigai> of steps in switch_to() macro will increase.  This overhead
> >   Kaigai> is not a big problem, I guess.
> > 
> >   Kaigai> For reasons already stated I prefer (2). What do you think?
> > 
> > I agree, (2) seems to best solution so far.  It maintains the
> > invariant that static data will be in region 5.  The extra
> > instructions should be pretty much free since it should be possible to
> > schedule them into existing stalls.
> > 
> > Can you resend the tested patch with proper changelog and "Signed-off-by"
> > trailer?
> > 
> > Thanks,
> > 
> > --david
> >

[-- Attachment #2: migrate.init_task.2.6.7-rc3.040615.patch --]
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diff -rNU2 linux-2.6.7-rc3/arch/ia64/kernel/entry.S linux-2.6.7-rc3.selinux/arch/ia64/kernel/entry.S
--- linux-2.6.7-rc3/arch/ia64/kernel/entry.S	2004-06-08 04:14:02.000000000 +0900
+++ linux-2.6.7-rc3.selinux/arch/ia64/kernel/entry.S	2004-06-15 19:29:47.981929427 +0900
@@ -178,5 +178,9 @@
 	DO_SAVE_SWITCH_STACK
 	.body
-
+	
+	movl r25=init_task
+	;;
+	cmp.eq p7,p6=r25,in0
+	
 	adds r22=IA64_TASK_THREAD_KSP_OFFSET,r13
 	mov r27=IA64_KR(CURRENT_STACK)
@@ -190,5 +194,5 @@
 	 * If we've already mapped this task's page, we can skip doing it again.
 	 */
-	cmp.eq p7,p6=r26,r27
+(p6)	cmp.eq p7,p6=r26,r27
 (p6)	br.cond.dpnt .map
 	;;
diff -rNU2 linux-2.6.7-rc3/arch/ia64/kernel/head.S linux-2.6.7-rc3.selinux/arch/ia64/kernel/head.S
--- linux-2.6.7-rc3/arch/ia64/kernel/head.S	2004-06-08 04:14:42.000000000 +0900
+++ linux-2.6.7-rc3.selinux/arch/ia64/kernel/head.S	2004-06-15 19:26:26.912398427 +0900
@@ -155,4 +155,7 @@
 	;;
 	tpa r3=r2		// r3 == phys addr of task struct
+	;;
+	shr.u r16=r3,IA64_GRANULE_SHIFT
+	(isBP) br.cond.dpnt .load_current // BP stack is on region 5 and no need to map it
 	// load mapping for stack (virtaddr in r2, physaddr in r3)
 	rsm psr.ic
@@ -166,5 +169,4 @@
 	;;
 	mov r17=rr[r2]
-	shr.u r16=r3,IA64_GRANULE_SHIFT
 	;;
 	dep r17=0,r17,8,24
@@ -181,4 +183,5 @@
   	;;
 
+.load_current:
 	// load the "current" pointer (r13) and ar.k6 with the current task
 	mov IA64_KR(CURRENT)=r2		// virtual address