From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: mpe@ellerman.id.au, Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: benh@kernel.crashing.org, kamalesh@linux.vnet.ibm.com,
kan.liang@intel.com, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, maddy@linux.vnet.ibm.com,
paulus@samba.org, tglx@linutronix.de
Subject: Re: [PATCH] powerpc/perf: Dereference bhrb entries safely
Date: Tue, 12 Dec 2017 21:09:26 +0530 [thread overview]
Message-ID: <1513093135.p9uc48ls6m.naveen@linux.ibm.com> (raw)
In-Reply-To: <20171212122915.20338-1-ravi.bangoria@linux.vnet.ibm.com>
Ravi Bangoria wrote:
> It may very well happen that branch instructions recorded by
> bhrb entries already get unmapped before they get processed by
> the kernel. Hence, trying to dereference such memory location
> will endup in a crash. Ex,
>=20
> Unable to handle kernel paging request for data at address 0xc0080000=
19c41764
> Faulting instruction address: 0xc000000000084a14
> NIP [c000000000084a14] branch_target+0x4/0x70
> LR [c0000000000eb828] record_and_restart+0x568/0x5c0
> Call Trace:
> [c0000000000eb3b4] record_and_restart+0xf4/0x5c0 (unreliable)
> [c0000000000ec378] perf_event_interrupt+0x298/0x460
> [c000000000027964] performance_monitor_exception+0x54/0x70
> [c000000000009ba4] performance_monitor_common+0x114/0x120
>=20
> Fix this by deferefencing them safely.
>=20
> Suggested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
- Naveen
=
next prev parent reply other threads:[~2017-12-12 15:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-12 12:29 [PATCH] powerpc/perf: Dereference bhrb entries safely Ravi Bangoria
2017-12-12 15:39 ` Naveen N. Rao [this message]
2017-12-14 12:24 ` Balbir Singh
2017-12-19 7:23 ` Ravi Bangoria
2017-12-19 9:55 ` Balbir Singh
2017-12-19 10:23 ` Michael Ellerman
2017-12-22 4:43 ` Michael Ellerman
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