On 16 May 2016 at 13:41, Meelis Roos <mr...@linux.ee> wrote: > Not sure if this is a genuine warning or a false positive but since some > UBSAN warnings have been real and google does not find report about this > specific warning, I'll send it in anyway. > > I have seen similar amd pmu warnings from UBSAN but I do not have any > amd machines from that time frame online for now, so p6 only. > > [ 0.150000] Performance Events: p6 PMU driver. > [ 0.150000] > ================================================================================ > [ 0.150000] UBSAN: Undefined behaviour in arch/x86/events/intel/p6.c:115:29 > [ 0.150000] index 8 is out of range for type 'u64 [8]' > [ 0.150000] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0 #21 > [ 0.150000] Hardware name: Dell Computer Corporation PowerEdge 1550/933 > , BIOS A09 12/10/2004 > [ 0.150000] 00000000 c13a4bcc 00000046 f605de88 00000008 c13d5188 > c17ddfd4 c13d5725 > [ 0.150000] c176ae8c f605de8c c17ddfec 00000202 00000038 00752101 > 00000002 00000000 > [ 0.150000] 00000000 00000297 000000c2 c17d2b60 00000000 c102b14f > 00000008 00000000 > [ 0.150000] Call Trace: > [ 0.150000] [<c13a4bcc>] ? dump_stack+0x45/0x69 > [ 0.150000] [<c13d5188>] ? ubsan_epilogue+0x8/0x30 > [ 0.150000] [<c13d5725>] ? __ubsan_handle_out_of_bounds+0x55/0x60 > [ 0.150000] [<c102b14f>] ? __register_nmi_handler+0xbf/0x300 > [ 0.150000] [<c10183d0>] ? p4_pmu_schedule_events+0x740/0x740 > [ 0.150000] [<c101840d>] ? p6_pmu_event_map+0x3d/0x50 > [ 0.150000] [<c10183d0>] ? p4_pmu_schedule_events+0x740/0x740 > [ 0.150000] [<c1af0c78>] ? init_hw_perf_events+0x493/0x688 > [ 0.150000] [<c1af07e5>] ? merge_attr+0x1d5/0x1d5 > [ 0.150000] [<c1000412>] ? do_one_initcall+0x82/0x230 > [ 0.150000] [<c10e27ef>] ? vprintk_default+0xf/0x20 > [ 0.150000] [<c116de67>] ? printk+0x11/0x12 > [ 0.150000] [<c103bf46>] ? print_cpu_info+0x86/0x130 > [ 0.150000] [<c1b00754>] ? native_smp_prepare_cpus+0x40e/0x453 > [ 0.150000] [<c1aefd87>] ? kernel_init_freeable+0x117/0x2fd > [ 0.150000] [<c16a10e6>] ? kernel_init+0x6/0x100 > [ 0.150000] [<c16a9949>] ? ret_from_kernel_thread+0x21/0x38 > [ 0.150000] [<c16a10e0>] ? rest_init+0x60/0x60 > [ 0.150000] > ================================================================================ > [ 0.150000] > ================================================================================ > [ 0.150000] UBSAN: Undefined behaviour in arch/x86/events/intel/p6.c:115:9 > [ 0.150000] load of address c16adf20 with insufficient space > [ 0.150000] for an object of type 'const u64' > [ 0.150000] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0 #21 > [ 0.150000] Hardware name: Dell Computer Corporation PowerEdge 1550/933 > , BIOS A09 12/10/2004 > [ 0.150000] 00000000 c13a4bcc 00000046 f605deb4 c16adf20 c13d5188 > c17ddfac c13d5229 > [ 0.150000] c176a901 c17ddfc8 c176aca4 c176a95e c16adf20 00000202 > 00000008 00000000 > [ 0.150000] c101841d 00000008 c10183d0 00000008 c1af0c78 c17d2c00 > f605df08 00000001 > [ 0.150000] Call Trace: > [ 0.150000] [<c13a4bcc>] ? dump_stack+0x45/0x69 > [ 0.150000] [<c13d5188>] ? ubsan_epilogue+0x8/0x30 > [ 0.150000] [<c13d5229>] ? __ubsan_handle_type_mismatch+0x79/0x150 > [ 0.150000] [<c101841d>] ? p6_pmu_event_map+0x4d/0x50 > [ 0.150000] [<c10183d0>] ? p4_pmu_schedule_events+0x740/0x740 > [ 0.150000] [<c1af0c78>] ? init_hw_perf_events+0x493/0x688 > [ 0.150000] [<c1af07e5>] ? merge_attr+0x1d5/0x1d5 > [ 0.150000] [<c1000412>] ? do_one_initcall+0x82/0x230 > [ 0.150000] [<c10e27ef>] ? vprintk_default+0xf/0x20 > [ 0.150000] [<c116de67>] ? printk+0x11/0x12 > [ 0.150000] [<c103bf46>] ? print_cpu_info+0x86/0x130 > [ 0.150000] [<c1b00754>] ? native_smp_prepare_cpus+0x40e/0x453 > [ 0.150000] [<c1aefd87>] ? kernel_init_freeable+0x117/0x2fd > [ 0.150000] [<c16a10e6>] ? kernel_init+0x6/0x100 > [ 0.150000] [<c16a9949>] ? ret_from_kernel_thread+0x21/0x38 > [ 0.150000] [<c16a10e0>] ? rest_init+0x60/0x60 > [ 0.150000] > ================================================================================ > [ 0.150000] ... version: 0 > [ 0.150000] ... bit width: 32 > [ 0.150000] ... generic registers: 2 > [ 0.150000] ... value mask: 00000000ffffffff > [ 0.150000] ... max period: 000000007fffffff > [ 0.150000] ... fixed-purpose events: 0 > [ 0.150000] ... event mask: 0000000000000003 >
I think UBSAN has correctly identified a bug. I looked at the code in v4.6. In file arch/x86/events/core.c, in the function filter_events(), there is a loop starting at line 1554 that should go over 10 event counters. But in file arch/x86/events/intel/p6.c, only 8 event counters have been declared at line 9. I have a fix but do not for sure if its reasonable. I think we should pass on the max_events for the pmu to filter_events() function and change the loop condition accordingly. Can you apply the patch below and test again? It compiles, but I have not tested it. diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 041e442..3fd33e6 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -1544,14 +1544,14 @@ static struct attribute_group x86_pmu_format_group = { * Remove all undefined events (x86_pmu.event_map(id) == 0) * out of events_attr attributes. */ -static void __init filter_events(struct attribute **attrs) +static void __init filter_events(struct attribute **attrs, int max_events) { struct device_attribute *d; struct perf_pmu_events_attr *pmu_attr; int offset = 0; int i, j; - for (i = 0; attrs[i]; i++) { + for (i = 0; i < max_events && attrs[i]; i++) { d = (struct device_attribute *)attrs[i]; pmu_attr = container_of(d, struct perf_pmu_events_attr, attr); /* str trumps id */ @@ -1740,7 +1740,7 @@ static int __init init_hw_perf_events(void) if (!x86_pmu.events_sysfs_show) x86_pmu_events_group.attrs = &empty_attrs; else - filter_events(x86_pmu_events_group.attrs); + filter_events(x86_pmu_events_group.attrs, x86_pmu.max_events); if (x86_pmu.cpu_events) { struct attribute **tmp; -- Nilay