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

Kaigai Kohei
2004-06-15T12:52:26Z

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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
> >

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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