From: Michael Ellerman <mpe@ellerman•id.au>
To: Kamalesh Babulal <kamalesh@linux•vnet.ibm.com>
Cc: Kamalesh Babulal <kamalesh@linux•vnet.ibm.com>,
Balbir Singh <bsingharora@gmail•com>,
"Naveen N . Rao" <naveen.n.rao@linux•vnet.ibm.com>,
linuxppc-dev@lists•ozlabs.org
Subject: Re: [PATCH] powerpc/livepatch: Fix livepatch stack access
Date: Thu, 21 Sep 2017 20:02:52 +1000 [thread overview]
Message-ID: <87d16kcqsz.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <1505902791-26383-1-git-send-email-kamalesh@linux.vnet.ibm.com>
Kamalesh Babulal <kamalesh@linux•vnet.ibm.com> writes:
> While running stress test with livepatch module loaded, kernel
> bug was triggered.
>
> cpu 0x5: Vector: 400 (Instruction Access) at [c0000000eb9d3b60]
> pc: c0000000eb9d3e30
> lr: c0000000eb9d3e30
> sp: c0000000eb9d3de0
> msr: 800000001280b033
> current = 0xc0000000dbd38700
> paca = 0xc00000000fe01400 softe: 0 irq_happened: 0x01
> pid = 8618, comm = make
> Linux version 4.13.0+ (root@ubuntu) (gcc version 6.3.0 20170406 (Ubuntu 6.3.0-12ubuntu2)) #1 SMP Wed Sep 13 03:49:27 EDT 2017
>
> 5:mon> t
> [c0000000eb9d3de0] c0000000eb9d3e30 (unreliable)
> [c0000000eb9d3e30] c000000000008ab4 hardware_interrupt_common+0x114/0x120
> --- Exception: 501 (Hardware Interrupt) at c000000000053040 livepatch_handler+0x4c/0x74
> [c0000000eb9d4120] 0000000057ac6e9d (unreliable)
> [d0000000089d9f78] 2e0965747962382e
> SP (965747962342e09) is in userspace
>
> When an interrupt is served in between the livepatch_handler execution,
> there are chances of the livepatch_stack/task task getting corrupted.
Ouch. That's pretty broken by me.
> Fix the corruption by using r11 register for livepatch stack manipulation,
> instead of shuffling task stack and livepatch stack into r1 register.
> Using r11 register also avoids disabling/enabling irq's while setting
> up the livepatch stack.
I'm trying to think if there's some reason I didn't use r11. But I can't
remember anything specific. I suspect I just didn't check the ABI
closely enough, and knew I could use r0 and r12 so stuck with them.
cheers
next prev parent reply other threads:[~2017-09-21 10:02 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-20 10:19 [PATCH] powerpc/livepatch: Fix livepatch stack access Kamalesh Babulal
2017-09-20 11:11 ` Naveen N . Rao
2017-09-29 11:47 ` Balbir Singh
2017-09-21 10:02 ` Michael Ellerman [this message]
2017-09-21 11:00 ` Balbir Singh
2017-09-21 11:53 ` Kamalesh Babulal
2017-09-21 16:55 ` Naveen N . Rao
2017-09-22 5:16 ` Kamalesh Babulal
2017-10-12 0:20 ` Michael Ellerman
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