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Ravi Bangoria f41d84dddc powerpc/perf: Dereference BHRB entries safely 
It's theoretically possible that branch instructions recorded in
BHRB (Branch History Rolling Buffer) entries have already been
unmapped before they are processed by the kernel. Hence, trying to
dereference such memory location will result in a crash. eg:

    Unable to handle kernel paging request for data at address 0xd000000019c41764
    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 it by deferefencing the addresses safely.

Fixes: 691231846c ("powerpc/perf: Fix setting of "to" addresses for BHRB")
Cc: stable@vger.kernel.org # v3.10+
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>
[mpe: Use probe_kernel_read() which is clearer, tweak change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
 		2017-12-13 20:29:20 +11:00
..
alpha treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
arc ARC updates for 4.15-rc1 2017-11-25 08:21:54 -10:00
arm Merge branch 'fixes' of git://git.armlinux.org.uk/~rmk/linux-arm 2017-12-03 10:51:08 -05:00
arm64 arm64 fixes: 2017-12-01 19:37:03 -05:00
blackfin treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
c6x Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
cris pci-v4.15-changes 2017-11-15 15:01:28 -08:00
frv Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
h8300 mm, arch: remove empty_bad_page* 2017-11-15 18:21:03 -08:00
hexagon Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
ia64 arch/ia64/include/asm/topology.h: remove unused parent_node() macro 2017-11-17 16:10:04 -08:00
m32r m32r: fix endianness constraints 2017-11-15 18:21:00 -08:00
m68k m68k/macboing: Fix missed timer callback assignment 2017-11-24 16:19:40 +01:00
metag DeviceTree for 4.15: 2017-11-14 18:25:40 -08:00
microblaze Microblaze patch for 4.15-rc2 2017-11-29 14:19:22 -08:00
mips * x86 bugfixes: APIC, nested virtualization, IOAPIC 2017-11-30 08:15:19 -08:00
mn10300 bug: define the "cut here" string in a single place 2017-11-17 16:10:01 -08:00
nios2 DeviceTree for 4.15: 2017-11-14 18:25:40 -08:00
openrisc kmemcheck: remove annotations 2017-11-15 18:21:04 -08:00
parisc treewide: Switch DEFINE_TIMER callbacks to struct timer_list * 2017-11-21 15:57:05 -08:00
powerpc powerpc/perf: Dereference BHRB entries safely 2017-12-13 20:29:20 +11:00
riscv RISC-V: Fixes for clean allmodconfig build 2017-12-01 13:31:31 -08:00
s390 * x86 bugfixes: APIC, nested virtualization, IOAPIC 2017-11-30 08:15:19 -08:00
score License cleanup: add SPDX license identifier to uapi header files with no license 2017-11-02 11:19:54 +01:00
sh treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
sparc Merge branch 'akpm' (patches from Andrew) 2017-11-29 19:12:44 -08:00
tile mm: switch to 'define pmd_write' instead of __HAVE_ARCH_PMD_WRITE 2017-11-29 18:40:42 -08:00
um This pull request contains the following core changes: 2017-11-22 20:46:06 -10:00
unicore32 kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK 2017-11-15 18:21:04 -08:00
x86 * x86 bugfixes: APIC, nested virtualization, IOAPIC 2017-11-30 08:15:19 -08:00
xtensa libnvdimm for 4.15 2017-11-17 09:51:57 -08:00
.gitignore
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Kconfig bpf: Revert bpf_overrid_function() helper changes. 2017-11-11 18:24:55 +09:00