From: Athira Rajeev atrajeev@linux.vnet.ibm.com
[ Upstream commit f75e7d73bdf73f07b0701a6d21c111ef5d9021dd ]
On systems without any specific PMU driver support registered, running 'perf record' with —intr-regs will crash ( perf record -I <workload> ).
The relevant portion from crash logs and Call Trace:
Unable to handle kernel paging request for data at address 0x00000068 Faulting instruction address: 0xc00000000013eb18 Oops: Kernel access of bad area, sig: 11 [#1] CPU: 2 PID: 13435 Comm: kill Kdump: loaded Not tainted 4.18.0-193.el8.ppc64le #1 NIP: c00000000013eb18 LR: c000000000139f2c CTR: c000000000393d80 REGS: c0000004a07ab4f0 TRAP: 0300 Not tainted (4.18.0-193.el8.ppc64le) NIP [c00000000013eb18] is_sier_available+0x18/0x30 LR [c000000000139f2c] perf_reg_value+0x6c/0xb0 Call Trace: [c0000004a07ab770] [c0000004a07ab7c8] 0xc0000004a07ab7c8 (unreliable) [c0000004a07ab7a0] [c0000000003aa77c] perf_output_sample+0x60c/0xac0 [c0000004a07ab840] [c0000000003ab3f0] perf_event_output_forward+0x70/0xb0 [c0000004a07ab8c0] [c00000000039e208] __perf_event_overflow+0x88/0x1a0 [c0000004a07ab910] [c00000000039e42c] perf_swevent_hrtimer+0x10c/0x1d0 [c0000004a07abc50] [c000000000228b9c] __hrtimer_run_queues+0x17c/0x480 [c0000004a07abcf0] [c00000000022aaf4] hrtimer_interrupt+0x144/0x520 [c0000004a07abdd0] [c00000000002a864] timer_interrupt+0x104/0x2f0 [c0000004a07abe30] [c0000000000091c4] decrementer_common+0x114/0x120
When perf record session is started with "-I" option, capturing registers on each sample calls is_sier_available() to check for the SIER (Sample Instruction Event Register) availability in the platform. This function in core-book3s accesses 'ppmu->flags'. If a platform specific PMU driver is not registered, ppmu is set to NULL and accessing its members results in a crash. Fix the crash by returning false in is_sier_available() if ppmu is not set.
Fixes: 333804dc3b7a ("powerpc/perf: Update perf_regs structure to include SIER") Reported-by: Sachin Sant sachinp@linux.vnet.ibm.com Signed-off-by: Athira Rajeev atrajeev@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/1606185640-1720-1-git-send-email-atrajeev@linux.vn... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/perf/core-book3s.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c index f582aa2d98078..7bf1adcdfdaa1 100644 --- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -133,6 +133,9 @@ static void pmao_restore_workaround(bool ebb) { }
bool is_sier_available(void) { + if (!ppmu) + return false; + if (ppmu->flags & PPMU_HAS_SIER) return true;