lkml.org 
[lkml]   [2017]   [Dec]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] powerpc/perf: Dereference bhrb entries safely
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,
>
> Unable to handle kernel paging request for data at address 0xc008000019c41764
> 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
>
> Fix this by deferefencing them safely.
>
> 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


\
 
 \ /
  Last update: 2017-12-12 16:40    [W:0.078 / U:0.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site