[PATCH] powerpc/perf: Fix crash with 'perf_instruction_pointer' when pmu is not set

[Michael Ellerman]

On Thu, 17 Jun 2021 13:55:06 -0400, Athira Rajeev wrote:
> On systems without any specific PMU driver support registered, running
> perf record causes Oops.
> 
> The relevant portion from call trace:
> 
> BUG: Kernel NULL pointer dereference on read at 0x00000040
> Faulting instruction address: 0xc0021f0c
> Oops: Kernel access of bad area, sig: 11 [#1]
> BE PAGE_SIZE=4K PREEMPT CMPCPRO
> SAF3000 DIE NOTIFICATION
> CPU: 0 PID: 442 Comm: null_syscall Not tainted 5.13.0-rc6-s3k-dev-01645-g7649ee3d2957 #5164
> NIP:  c0021f0c LR: c00e8ad8 CTR: c00d8a5c
> NIP [c0021f0c] perf_instruction_pointer+0x10/0x60
> LR [c00e8ad8] perf_prepare_sample+0x344/0x674
> Call Trace:
> [e6775880] [c00e8810] perf_prepare_sample+0x7c/0x674 (unreliable)
> [e67758c0] [c00e8e44] perf_event_output_forward+0x3c/0x94
> [e6775910] [c00dea8c] __perf_event_overflow+0x74/0x14c
> [e6775930] [c00dec5c] perf_swevent_hrtimer+0xf8/0x170
> [e6775a40] [c008c8d0] __hrtimer_run_queues.constprop.0+0x160/0x318
> [e6775a90] [c008d94c] hrtimer_interrupt+0x148/0x3b0
> [e6775ae0] [c000c0c0] timer_interrupt+0xc4/0x22c
> [e6775b10] [c00046f0] Decrementer_virt+0xb8/0xbc
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/perf: Fix crash with 'perf_instruction_pointer' when pmu is not set
      https://git.kernel.org/powerpc/c/60b7ed54a41b550d50caf7f2418db4a7e75b5bdc

cheers