On Tuesday 19 September 2017 03:30 PM, Michael Ellerman wrote:
Ravi Bangoria <[email protected]> writes:
Kernel crashes if power pmu is not registered and user tries to dump
regs with 'echo p > /proc/sysrq-trigger'. Sample log:
Unable to handle kernel paging request for data at address 0x00000008
Faulting instruction address: 0xc0000000000d52f0
NIP [c0000000000d52f0] perf_event_print_debug+0x10/0x230
LR [c00000000058a938] sysrq_handle_showregs+0x38/0x50
Call Trace:
printk+0x38/0x4c (unreliable)
__handle_sysrq+0xe4/0x270
write_sysrq_trigger+0x64/0x80
proc_reg_write+0x80/0xd0
__vfs_write+0x40/0x200
vfs_write+0xc8/0x240
SyS_write+0x60/0x110
system_call+0x58/0x6c
Thanks.
I added:
Fixes: 5f6d0380c640 ("powerpc/perf: Define perf_event_print_debug() to print PMU
register values")
But I don't think I'll Cc stable, I can't think why we'd ever *not* have
a ppmu registered. How did you hit it?
mpe,
We hit this in a compact mode setup where the distro kernel did not have
the
pmu support for the base pvr.
Maddy
cheers
