__init int intel_pmu_init(void)
{
	union cpuid10_edx edx;
	union cpuid10_eax eax;
	union cpuid10_ebx ebx;
	struct event_constraint *c;
	unsigned int unused;
	int version;

	if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
		switch (boot_cpu_data.x86) {
		case 0x6:
			return p6_pmu_init();
		case 0xb:
			return knc_pmu_init();
		case 0xf:
			return p4_pmu_init();
		}
		return -ENODEV;
	}

	/*
	 * Check whether the Architectural PerfMon supports
	 * Branch Misses Retired hw_event or not.
	 */
	cpuid(10, &eax.full, &ebx.full, &unused, &edx.full);
	if (eax.split.mask_length < ARCH_PERFMON_EVENTS_COUNT)
		return -ENODEV;

	version = eax.split.version_id;
	if (version < 2)
		x86_pmu = core_pmu;
	else
		x86_pmu = intel_pmu;

	x86_pmu.version			= version;
	x86_pmu.num_counters		= eax.split.num_counters;
	x86_pmu.cntval_bits		= eax.split.bit_width;
	x86_pmu.cntval_mask		= (1ULL << eax.split.bit_width) - 1;

	x86_pmu.events_maskl		= ebx.full;
	x86_pmu.events_mask_len		= eax.split.mask_length;

	x86_pmu.max_pebs_events		= min_t(unsigned, MAX_PEBS_EVENTS, x86_pmu.num_counters);

	/*
	 * Quirk: v2 perfmon does not report fixed-purpose events, so
	 * assume at least 3 events:
	 */
	if (version > 1)
		x86_pmu.num_counters_fixed = max((int)edx.split.num_counters_fixed, 3);

	/*
	 * v2 and above have a perf capabilities MSR
	 */
	if (version > 1) {
		u64 capabilities;

		rdmsrl(MSR_IA32_PERF_CAPABILITIES, capabilities);
		x86_pmu.intel_cap.capabilities = capabilities;
	}

	intel_ds_init();

	x86_add_quirk(intel_arch_events_quirk); /* Install first, so it runs last */

	/*
	 * Install the hw-cache-events table:
	 */
	switch (boot_cpu_data.x86_model) {
	case 14: /* 65 nm core solo/duo, "Yonah" */
		pr_cont("Core events, ");
		break;

	case 15: /* original 65 nm celeron/pentium/core2/xeon, "Merom"/"Conroe" */
		x86_add_quirk(intel_clovertown_quirk);
	case 22: /* single-core 65 nm celeron/core2solo "Merom-L"/"Conroe-L" */
	case 23: /* current 45 nm celeron/core2/xeon "Penryn"/"Wolfdale" */
	case 29: /* six-core 45 nm xeon "Dunnington" */
		memcpy(hw_cache_event_ids, core2_hw_cache_event_ids,
		       sizeof(hw_cache_event_ids));

		intel_pmu_lbr_init_core();

		x86_pmu.event_constraints = intel_core2_event_constraints;
		x86_pmu.pebs_constraints = intel_core2_pebs_event_constraints;
		pr_cont("Core2 events, ");
		break;

	case 26: /* 45 nm nehalem, "Bloomfield" */
	case 30: /* 45 nm nehalem, "Lynnfield" */
	case 46: /* 45 nm nehalem-ex, "Beckton" */
		memcpy(hw_cache_event_ids, nehalem_hw_cache_event_ids,
		       sizeof(hw_cache_event_ids));
		memcpy(hw_cache_extra_regs, nehalem_hw_cache_extra_regs,
		       sizeof(hw_cache_extra_regs));

		intel_pmu_lbr_init_nhm();

		x86_pmu.event_constraints = intel_nehalem_event_constraints;
		x86_pmu.pebs_constraints = intel_nehalem_pebs_event_constraints;
		x86_pmu.enable_all = intel_pmu_nhm_enable_all;
		x86_pmu.extra_regs = intel_nehalem_extra_regs;

		/* UOPS_ISSUED.STALLED_CYCLES */
		intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_FRONTEND] =
			X86_CONFIG(.event=0x0e, .umask=0x01, .inv=1, .cmask=1);
		/* UOPS_EXECUTED.CORE_ACTIVE_CYCLES,c=1,i=1 */
		intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_BACKEND] =
			X86_CONFIG(.event=0xb1, .umask=0x3f, .inv=1, .cmask=1);

		x86_add_quirk(intel_nehalem_quirk);

		pr_cont("Nehalem events, ");
		break;

	case 28: /* Atom */
	case 38: /* Lincroft */
	case 39: /* Penwell */
	case 53: /* Cloverview */
	case 54: /* Cedarview */
		memcpy(hw_cache_event_ids, atom_hw_cache_event_ids,
		       sizeof(hw_cache_event_ids));

		intel_pmu_lbr_init_atom();

		x86_pmu.event_constraints = intel_gen_event_constraints;
		x86_pmu.pebs_constraints = intel_atom_pebs_event_constraints;
		pr_cont("Atom events, ");
		break;

	case 37: /* 32 nm nehalem, "Clarkdale" */
	case 44: /* 32 nm nehalem, "Gulftown" */
	case 47: /* 32 nm Xeon E7 */
		memcpy(hw_cache_event_ids, westmere_hw_cache_event_ids,
		       sizeof(hw_cache_event_ids));
		memcpy(hw_cache_extra_regs, nehalem_hw_cache_extra_regs,
		       sizeof(hw_cache_extra_regs));

		intel_pmu_lbr_init_nhm();

		x86_pmu.event_constraints = intel_westmere_event_constraints;
		x86_pmu.enable_all = intel_pmu_nhm_enable_all;
		x86_pmu.pebs_constraints = intel_westmere_pebs_event_constraints;
		x86_pmu.extra_regs = intel_westmere_extra_regs;
		x86_pmu.er_flags |= ERF_HAS_RSP_1;

		/* UOPS_ISSUED.STALLED_CYCLES */
		intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_FRONTEND] =
			X86_CONFIG(.event=0x0e, .umask=0x01, .inv=1, .cmask=1);
		/* UOPS_EXECUTED.CORE_ACTIVE_CYCLES,c=1,i=1 */
		intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_BACKEND] =
			X86_CONFIG(.event=0xb1, .umask=0x3f, .inv=1, .cmask=1);

		pr_cont("Westmere events, ");
		break;

	case 42: /* SandyBridge */
	case 45: /* SandyBridge, "Romely-EP" */
		x86_add_quirk(intel_sandybridge_quirk);
		memcpy(hw_cache_event_ids, snb_hw_cache_event_ids,
		       sizeof(hw_cache_event_ids));
		memcpy(hw_cache_extra_regs, snb_hw_cache_extra_regs,
		       sizeof(hw_cache_extra_regs));

		intel_pmu_lbr_init_snb();

 		x86_pmu.event_constraints = intel_snb_event_constraints;
 		x86_pmu.pebs_constraints = intel_snb_pebs_event_constraints;
 		x86_pmu.pebs_aliases = intel_pebs_aliases_snb;
		x86_pmu.extra_regs = intel_snb_extra_regs;
 		/* all extra regs are per-cpu when HT is on */
 		x86_pmu.er_flags |= ERF_HAS_RSP_1;
 		x86_pmu.er_flags |= ERF_NO_HT_SHARING;

		/* UOPS_ISSUED.ANY,c=1,i=1 to count stall cycles */
		intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_FRONTEND] =
			X86_CONFIG(.event=0x0e, .umask=0x01, .inv=1, .cmask=1);
		/* UOPS_DISPATCHED.THREAD,c=1,i=1 to count stall cycles*/
		intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_BACKEND] =
			X86_CONFIG(.event=0xb1, .umask=0x01, .inv=1, .cmask=1);

		pr_cont("SandyBridge events, ");
		break;
	case 58: /* IvyBridge */
	case 62: /* IvyBridge EP */
		memcpy(hw_cache_event_ids, snb_hw_cache_event_ids,
		       sizeof(hw_cache_event_ids));
		memcpy(hw_cache_extra_regs, snb_hw_cache_extra_regs,
		       sizeof(hw_cache_extra_regs));

		intel_pmu_lbr_init_snb();

 		x86_pmu.event_constraints = intel_ivb_event_constraints;
 		x86_pmu.pebs_constraints = intel_ivb_pebs_event_constraints;
 		x86_pmu.pebs_aliases = intel_pebs_aliases_snb;
		x86_pmu.extra_regs = intel_snb_extra_regs;
 		/* all extra regs are per-cpu when HT is on */
 		x86_pmu.er_flags |= ERF_HAS_RSP_1;
 		x86_pmu.er_flags |= ERF_NO_HT_SHARING;

		/* UOPS_ISSUED.ANY,c=1,i=1 to count stall cycles */
		intel_perfmon_event_map[PERF_COUNT_HW_STALLED_CYCLES_FRONTEND] =
			X86_CONFIG(.event=0x0e, .umask=0x01, .inv=1, .cmask=1);

		pr_cont("IvyBridge events, ");
		break;


	default:
		switch (x86_pmu.version) {
		case 1:
			x86_pmu.event_constraints = intel_v1_event_constraints;
			pr_cont("generic architected perfmon v1, ");
			break;
		default:
			/*
			 * default constraints for v2 and up
			 */
			x86_pmu.event_constraints = intel_gen_event_constraints;
			pr_cont("generic architected perfmon, ");
			break;
		}
	}

	if (x86_pmu.num_counters > INTEL_PMC_MAX_GENERIC) {
		WARN(1, KERN_ERR "hw perf events %d > max(%d), clipping!",
		     x86_pmu.num_counters, INTEL_PMC_MAX_GENERIC);
		x86_pmu.num_counters = INTEL_PMC_MAX_GENERIC;
	}
	x86_pmu.intel_ctrl = (1 << x86_pmu.num_counters) - 1;

	if (x86_pmu.num_counters_fixed > INTEL_PMC_MAX_FIXED) {
		WARN(1, KERN_ERR "hw perf events fixed %d > max(%d), clipping!",
		     x86_pmu.num_counters_fixed, INTEL_PMC_MAX_FIXED);
		x86_pmu.num_counters_fixed = INTEL_PMC_MAX_FIXED;
	}

	x86_pmu.intel_ctrl |=
		((1LL << x86_pmu.num_counters_fixed)-1) << INTEL_PMC_IDX_FIXED;

	if (x86_pmu.event_constraints) {
		/*
		 * event on fixed counter2 (REF_CYCLES) only works on this
		 * counter, so do not extend mask to generic counters
		 */
		for_each_event_constraint(c, x86_pmu.event_constraints) {
			if (c->cmask != X86_RAW_EVENT_MASK
			    || c->idxmsk64 == INTEL_PMC_MSK_FIXED_REF_CYCLES) {
				continue;
			}

			c->idxmsk64 |= (1ULL << x86_pmu.num_counters) - 1;
			c->weight += x86_pmu.num_counters;
		}
	}

	return 0;
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.