<html><head></head><body dir="auto" style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="ApplePlainTextBody"><div class="ApplePlainTextBody"><br><br><blockquote type="cite">On 16-Jun-2021, at 11:56 AM, Christophe Leroy <christophe.leroy@csgroup.eu> wrote:<br><br><br><br>Le 16/06/2021 à 05:40, Athira Rajeev a écrit :<br><blockquote type="cite"><blockquote type="cite">On 16-Jun-2021, at 8:53 AM, Madhavan Srinivasan <maddy@linux.ibm.com> wrote:<br><br><br>On 6/15/21 8:35 PM, Christophe Leroy wrote:<br><blockquote type="cite">For your information, I'm getting the following Oops. Detected with 5.13-rc6, it also oopses on 5.12 and 5.11.<br>Runs ok on 5.10. I'm starting bisecting now.<br></blockquote><br><br>Thanks for reporting, got the issue. What has happened in this case is that, pmu device is not registered<br>and trying to access the instruction point which will land in perf_instruction_pointer(). And recently I have added<br>a workaround patch for power10 DD1 which has caused this breakage. My bad. We are working on a fix patch<br>for the same and will post it out. Sorry again.<br><br></blockquote>Hi Christophe,<br>Can you please try with below patch in your environment and test if it works for you.<br>From 55d3afc9369dfbe28a7152c8e9f856c11c7fe43d Mon Sep 17 00:00:00 2001<br>From: Athira Rajeev <atrajeev@linux.vnet.ibm.com><br>Date: Tue, 15 Jun 2021 22:28:11 -0400<br>Subject: [PATCH] powerpc/perf: Fix crash with 'perf_instruction_pointer' when<br> pmu is not set<br>On systems without any specific PMU driver support registered, running<br>perf record causes oops:<br>[ 38.841073] NIP [c00000000013af54] perf_instruction_pointer+0x24/0x100<br>[ 38.841079] LR [c0000000003c7358] perf_prepare_sample+0x4e8/0x820<br>[ 38.841085] --- interrupt: 300<br>[ 38.841088] [c00000001cf03440] [c0000000003c6ef8] perf_prepare_sample+0x88/0x820 (unreliable)<br>[ 38.841096] [c00000001cf034a0] [c0000000003c76d0] perf_event_output_forward+0x40/0xc0<br>[ 38.841104] [c00000001cf03520] [c0000000003b45e8] __perf_event_overflow+0x88/0x1b0<br>[ 38.841112] [c00000001cf03570] [c0000000003b480c] perf_swevent_hrtimer+0xfc/0x1a0<br>[ 38.841119] [c00000001cf03740] [c0000000002399cc] __hrtimer_run_queues+0x17c/0x380<br>[ 38.841127] [c00000001cf037c0] [c00000000023a5f8] hrtimer_interrupt+0x128/0x2f0<br>[ 38.841135] [c00000001cf03870] [c00000000002962c] timer_interrupt+0x13c/0x370<br>[ 38.841143i] [c00000001cf038d0] [c000000000009ba4] decrementer_common_virt+0x1a4/0x1b0<br>[ 38.841151] --- interrupt: 900 at copypage_power7+0xd4/0x1c0<br>During perf record session, perf_instruction_pointer() is called to<br>capture the sample ip. This function in core-book3s accesses ppmu->flags.<br>If a platform specific PMU driver is not registered, ppmu is set to NULL<br>and accessing its members results in a crash. Fix this crash by checking<br>if ppmu is set.<br>Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com><br>Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu><br></blockquote><br>Fixes: 2ca13a4cc56c ("powerpc/perf: Use regs->nip when SIAR is zero")<br>Cc: stable@vger.kernel.org<br>Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu><br></blockquote><br>Hi Christophe,<br><br>Thanks for testing with the change. I have a newer version where I have added braces around the check.<br>Can you please check once and can I add your tested-by for the below patch.<br><br>From 621cd0449c8503a016c0b1ae63639061aa5134a8 Mon Sep 17 00:00:00 2001<br>From: Athira Rajeev <atrajeev@linux.vnet.ibm.com><br>Date: Tue, 15 Jun 2021 22:28:11 -0400<br>Subject: [PATCH] powerpc/perf: Fix crash with 'perf_instruction_pointer' when<br> pmu is not set<br><br>On systems without any specific PMU driver support registered, running<br>perf record causes Oops.<br><br>The relevant portion from call trace:<br><br>BUG: Kernel NULL pointer dereference on read at 0x00000040<br>Faulting instruction address: 0xc0021f0c<br>Oops: Kernel access of bad area, sig: 11 [#1]<br>BE PAGE_SIZE=4K PREEMPT CMPCPRO<br>SAF3000 DIE NOTIFICATION<br>CPU: 0 PID: 442 Comm: null_syscall Not tainted 5.13.0-rc6-s3k-dev-01645-g7649ee3d2957 #5164<br>NIP: c0021f0c LR: c00e8ad8 CTR: c00d8a5c<br>NIP [c0021f0c] perf_instruction_pointer+0x10/0x60<br>LR [c00e8ad8] perf_prepare_sample+0x344/0x674<br>Call Trace:<br>[e6775880] [c00e8810] perf_prepare_sample+0x7c/0x674 (unreliable)<br>[e67758c0] [c00e8e44] perf_event_output_forward+0x3c/0x94<br>[e6775910] [c00dea8c] __perf_event_overflow+0x74/0x14c<br>[e6775930] [c00dec5c] perf_swevent_hrtimer+0xf8/0x170<br>[e6775a40] [c008c8d0] __hrtimer_run_queues.constprop.0+0x160/0x318<br>[e6775a90] [c008d94c] hrtimer_interrupt+0x148/0x3b0<br>[e6775ae0] [c000c0c0] timer_interrupt+0xc4/0x22c<br>[e6775b10] [c00046f0] Decrementer_virt+0xb8/0xbc<br><br>During perf record session, perf_instruction_pointer() is called to<br>capture the sample ip. This function in core-book3s accesses ppmu->flags.<br>If a platform specific PMU driver is not registered, ppmu is set to NULL<br>and accessing its members results in a crash. Fix this crash by checking<br>if ppmu is set.<br><br>Fixes: 2ca13a4cc56c ("powerpc/perf: Use regs->nip when SIAR is zero")<br>Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com><br>Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu><br>---<br> arch/powerpc/perf/core-book3s.c | 2 +-<br> 1 file changed, 1 insertion(+), 1 deletion(-)<br><br>diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c<br>index 16d4d1b..5162241 100644<br>--- a/arch/powerpc/perf/core-book3s.c<br>+++ b/arch/powerpc/perf/core-book3s.c<br>@@ -2254,7 +2254,7 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs)<br> <span class="Apple-tab-span" style="white-space:pre"> </span>bool use_siar = regs_use_siar(regs);<br> <span class="Apple-tab-span" style="white-space:pre"> </span>unsigned long siar = mfspr(SPRN_SIAR);<br><br>-<span class="Apple-tab-span" style="white-space:pre"> </span>if (ppmu->flags & PPMU_P10_DD1) {<br>+<span class="Apple-tab-span" style="white-space:pre"> </span>if (ppmu && (ppmu->flags & PPMU_P10_DD1)) {<br> <span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span>if (siar)<br> <span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span>return siar;<br> <span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span>else<br>-- <br>1.8.3.1<br><br>Thanks<br>Athira<br><br><blockquote type="cite"><br><blockquote type="cite">---<br> arch/powerpc/perf/core-book3s.c | 2 +-<br> 1 file changed, 1 insertion(+), 1 deletion(-)<br>diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c<br>index 16d4d1b6a1ff..816756588cb7 100644<br>--- a/arch/powerpc/perf/core-book3s.c<br>+++ b/arch/powerpc/perf/core-book3s.c<br>@@ -2254,7 +2254,7 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs)<br> <span class="Apple-tab-span" style="white-space:pre"> </span>bool use_siar = regs_use_siar(regs);<br> <span class="Apple-tab-span" style="white-space:pre"> </span>unsigned long siar = mfspr(SPRN_SIAR);<br> -<span class="Apple-tab-span" style="white-space:pre"> </span>if (ppmu->flags & PPMU_P10_DD1) {<br>+<span class="Apple-tab-span" style="white-space:pre"> </span>if (ppmu && ppmu->flags & PPMU_P10_DD1) {<br> <span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span>if (siar)<br> <span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span>return siar;<br> <span class="Apple-tab-span" style="white-space:pre"> </span><span class="Apple-tab-span" style="white-space:pre"> </span>else<br></blockquote></blockquote><br></div></body></html>