[PATCH v0 5/5] perf/x86/intel/pt: Add support for instruction trace filtering in PT

[Alexander Shishkin]

Newer versions of Intel PT support address ranges, which can be used to
define IP address range-based filters or TraceSTOP regions. Number of
ranges in enumerated via cpuid.

This patch implements pmu callbacks and related low-level code to allow
filter validation, configuration and programming into the hardware.

Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/intel_pt.h            |  30 ++++++-
 arch/x86/kernel/cpu/perf_event_intel_pt.c | 132 +++++++++++++++++++++++++++++-
 2 files changed, 159 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_pt.h b/arch/x86/kernel/cpu/intel_pt.h
index 6ce8cd20b9..1b36c8529d 100644
--- a/arch/x86/kernel/cpu/intel_pt.h
+++ b/arch/x86/kernel/cpu/intel_pt.h
@@ -105,13 +105,39 @@ struct pt_buffer {
 	struct topa_entry	*topa_index[0];
 };
 
+#define PT_FILTERS_NUM	4
+
+/**
+ * struct pt_filter - IP range filter configuration
+ * @msr_a:	range start, goes to RTIT_ADDRn_A
+ * @msr_b:	range end, goes to RTIT_ADDRn_B
+ * @config:	4-bit field in RTIT_CTL
+ */
+struct pt_filter {
+	unsigned long	msr_a;
+	unsigned long	msr_b;
+	unsigned long	config;
+};
+
+/**
+ * struct pt_filters - IP range filtering context
+ * @filter:	filters defined for this context
+ * @nr_filters:	number of defined filters in the @filter array
+ */
+struct pt_filters {
+	struct pt_filter	filter[PT_FILTERS_NUM];
+	unsigned int		nr_filters;
+};
+
 /**
  * struct pt - per-cpu pt context
- * @handle:	perf output handle
- * @handle_nmi:	do handle PT PMI on this cpu, there's an active event
+ * @handle:		perf output handle
+ * @filters:		last configured filters
+ * @handle_nmi:		do handle PT PMI on this cpu, there's an active event
  */
 struct pt {
 	struct perf_output_handle handle;
+	struct pt_filters	filters;
 	int			handle_nmi;
 };
 
diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c
index 2ec25581de..f531a2f0de 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_pt.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c
@@ -253,6 +253,73 @@ static bool pt_event_valid(struct perf_event *event)
  * These all are cpu affine and operate on a local PT
  */
 
+/* Address ranges and their corresponding msr configuration registers */
+static const struct pt_address_range {
+	unsigned long	msr_a;
+	unsigned long	msr_b;
+	unsigned int	reg_off;
+} pt_address_ranges[] = {
+	{
+		.msr_a	 = MSR_IA32_RTIT_ADDR0_A,
+		.msr_b	 = MSR_IA32_RTIT_ADDR0_B,
+		.reg_off = RTIT_CTL_ADDR0_OFFSET,
+	},
+	{
+		.msr_a	 = MSR_IA32_RTIT_ADDR1_A,
+		.msr_b	 = MSR_IA32_RTIT_ADDR1_B,
+		.reg_off = RTIT_CTL_ADDR1_OFFSET,
+	},
+	{
+		.msr_a	 = MSR_IA32_RTIT_ADDR2_A,
+		.msr_b	 = MSR_IA32_RTIT_ADDR2_B,
+		.reg_off = RTIT_CTL_ADDR2_OFFSET,
+	},
+	{
+		.msr_a	 = MSR_IA32_RTIT_ADDR3_A,
+		.msr_b	 = MSR_IA32_RTIT_ADDR3_B,
+		.reg_off = RTIT_CTL_ADDR3_OFFSET,
+	}
+};
+
+static u64 pt_config_filters(struct perf_event *event)
+{
+	struct pt_filters *filters = event->hw.itrace_filters;
+	struct pt *pt = this_cpu_ptr(&pt_ctx);
+	unsigned int range = 0;
+	u64 rtit_ctl = 0;
+
+	if (!filters)
+		return 0;
+
+	for (range = 0; range < filters->nr_filters; range++) {
+		struct pt_filter *filter = &filters->filter[range];
+
+		/*
+		 * Note, if the range has zero start/end addresses due
+		 * to its dynamic object not being loaded yet, we just
+		 * go ahead and program zeroed range, which will simply
+		 * produce no data. Note^2: if executable code at 0x0
+		 * is a concern, we can set up an "invalid" configuration
+		 * such as msr_b < msr_a.
+		 */
+
+		/* avoid redundant msr writes */
+		if (pt->filters.filter[range].msr_a != filter->msr_a) {
+			wrmsrl(pt_address_ranges[range].msr_a, filter->msr_a);
+			pt->filters.filter[range].msr_a = filter->msr_a;
+		}
+
+		if (pt->filters.filter[range].msr_b != filter->msr_b) {
+			wrmsrl(pt_address_ranges[range].msr_b, filter->msr_b);
+			pt->filters.filter[range].msr_b = filter->msr_b;
+		}
+
+		rtit_ctl |= filter->config << pt_address_ranges[range].reg_off;
+	}
+
+	return rtit_ctl;
+}
+
 static void pt_config(struct perf_event *event)
 {
 	u64 reg;
@@ -262,7 +329,8 @@ static void pt_config(struct perf_event *event)
 		wrmsrl(MSR_IA32_RTIT_STATUS, 0);
 	}
 
-	reg = RTIT_CTL_TOPA | RTIT_CTL_BRANCH_EN | RTIT_CTL_TRACEEN;
+	reg = pt_config_filters(event);
+	reg |= RTIT_CTL_TOPA | RTIT_CTL_BRANCH_EN | RTIT_CTL_TRACEEN;
 
 	if (!event->attr.exclude_kernel)
 		reg |= RTIT_CTL_OS;
@@ -907,6 +975,60 @@ static void pt_buffer_free_aux(void *data)
 	kfree(buf);
 }
 
+static int pt_itrace_filters_init(struct perf_event *event)
+{
+	struct pt_filters *filters;
+	int node = event->cpu == -1 ? -1 : cpu_to_node(event->cpu);
+
+	if (!pt_cap_get(PT_CAP_num_address_ranges))
+		return 0;
+
+	filters = kzalloc_node(sizeof(struct pt_filters), GFP_KERNEL, node);
+	if (!filters)
+		return -ENOMEM;
+
+	event->hw.itrace_filters = filters;
+
+	return 0;
+}
+
+static void pt_itrace_filters_fini(struct perf_event *event)
+{
+	kfree(event->hw.itrace_filters);
+	event->hw.itrace_filters = NULL;
+}
+
+static int pt_event_itrace_filter_setup(struct perf_event *event)
+{
+	struct pt_filters *filters = event->hw.itrace_filters;
+	struct perf_itrace_filter *filter;
+	int range = 0;
+
+	if (!filters)
+		return -EOPNOTSUPP;
+
+	list_for_each_entry_rcu(filter, &event->itrace_filters, entry) {
+		/* PT doesn't support single address triggers */
+		if (!filter->range)
+			return -EOPNOTSUPP;
+
+		if (filter->kernel && !kernel_ip(filter->offset))
+			return -EINVAL;
+
+		filters->filter[range].msr_a  = filter->start;
+		filters->filter[range].msr_b  = filter->end;
+		filters->filter[range].config = filter->filter ? 1 : 2;
+
+		if (++range > pt_cap_get(PT_CAP_num_address_ranges))
+			return -EOPNOTSUPP;
+	}
+
+	if (range)
+		filters->nr_filters = range - 1;
+
+	return 0;
+}
+
 /**
  * intel_pt_interrupt() - PT PMI handler
  */
@@ -1075,6 +1197,7 @@ static void pt_event_read(struct perf_event *event)
 
 static void pt_event_destroy(struct perf_event *event)
 {
+	pt_itrace_filters_fini(event);
 	x86_del_exclusive(x86_lbr_exclusive_pt);
 }
 
@@ -1089,6 +1212,11 @@ static int pt_event_init(struct perf_event *event)
 	if (x86_add_exclusive(x86_lbr_exclusive_pt))
 		return -EBUSY;
 
+	if (pt_itrace_filters_init(event)) {
+		x86_del_exclusive(x86_lbr_exclusive_pt);
+		return -ENOMEM;
+	}
+
 	event->destroy = pt_event_destroy;
 
 	return 0;
@@ -1152,6 +1280,8 @@ static __init int pt_init(void)
 	pt_pmu.pmu.read		= pt_event_read;
 	pt_pmu.pmu.setup_aux	= pt_buffer_setup_aux;
 	pt_pmu.pmu.free_aux	= pt_buffer_free_aux;
+	pt_pmu.pmu.itrace_filter_setup =
+		pt_event_itrace_filter_setup;
 	ret = perf_pmu_register(&pt_pmu.pmu, "intel_pt", -1);
 
 	return ret;
-- 
2.6.2

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