linux-kernel - [PATCH 3.16.y-ckt 121/180] s390/hibernate: fix save and restore of kernel text section

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Date:	Thu,  7 May 2015 10:45:30 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 121/180] s390/hibernate: fix save and restore of kernel text section

3.16.7-ckt11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Heiko Carstens <heiko.carstens@...ibm.com>

commit d74419495633493c9cd3f2bbeb7f3529d0edded6 upstream.

Sebastian reported a crash caused by a jump label mismatch after resume.
This happens because we do not save the kernel text section during suspend
and therefore also do not restore it during resume, but use the kernel image
that restores the old system.

This means that after a suspend/resume cycle we lost all modifications done
to the kernel text section.
The reason for this is the pfn_is_nosave() function, which incorrectly
returns that read-only pages don't need to be saved. This is incorrect since
we mark the kernel text section read-only.
We still need to make sure to not save and restore pages contained within
NSS and DCSS segment.
To fix this add an extra case for the kernel text section and only save
those pages if they are not contained within an NSS segment.

Fixes the following crash (and the above bugs as well):

Jump label code mismatch at netif_receive_skb_internal+0x28/0xd0
Found:    c0 04 00 00 00 00
Expected: c0 f4 00 00 00 11
New:      c0 04 00 00 00 00
Kernel panic - not syncing: Corrupted kernel text
CPU: 0 PID: 9 Comm: migration/0 Not tainted 3.19.0-01975-gb1b096e70f23 #4
Call Trace:
  [<0000000000113972>] show_stack+0x72/0xf0
  [<000000000081f15e>] dump_stack+0x6e/0x90
  [<000000000081c4e8>] panic+0x108/0x2b0
  [<000000000081be64>] jump_label_bug.isra.2+0x104/0x108
  [<0000000000112176>] __jump_label_transform+0x9e/0xd0
  [<00000000001121e6>] __sm_arch_jump_label_transform+0x3e/0x50
  [<00000000001d1136>] multi_cpu_stop+0x12e/0x170
  [<00000000001d1472>] cpu_stopper_thread+0xb2/0x168
  [<000000000015d2ac>] smpboot_thread_fn+0x134/0x1b0
  [<0000000000158baa>] kthread+0x10a/0x110
  [<0000000000824a86>] kernel_thread_starter+0x6/0xc

Reported-and-tested-by: Sebastian Ott <sebott@...ux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 arch/s390/kernel/suspend.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/s390/kernel/suspend.c b/arch/s390/kernel/suspend.c
index 1c4c5accd220..d3236c9e226b 100644
--- a/arch/s390/kernel/suspend.c
+++ b/arch/s390/kernel/suspend.c
@@ -138,6 +138,8 @@ int pfn_is_nosave(unsigned long pfn)
 {
 	unsigned long nosave_begin_pfn = PFN_DOWN(__pa(&__nosave_begin));
 	unsigned long nosave_end_pfn = PFN_DOWN(__pa(&__nosave_end));
+	unsigned long eshared_pfn = PFN_DOWN(__pa(&_eshared)) - 1;
+	unsigned long stext_pfn = PFN_DOWN(__pa(&_stext));
 
 	/* Always save lowcore pages (LC protection might be enabled). */
 	if (pfn <= LC_PAGES)
@@ -145,6 +147,8 @@ int pfn_is_nosave(unsigned long pfn)
 	if (pfn >= nosave_begin_pfn && pfn < nosave_end_pfn)
 		return 1;
 	/* Skip memory holes and read-only pages (NSS, DCSS, ...). */
+	if (pfn >= stext_pfn && pfn <= eshared_pfn)
+		return ipl_info.type == IPL_TYPE_NSS ? 1 : 0;
 	if (tprot(PFN_PHYS(pfn)))
 		return 1;
 	return 0;
--
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