[PATCH 15/16] perf intel-pt: Enable decoder to handle TIP.PGD with missing IP

[Adrian Hunter]

When address filters are used, the decoder must detect the end of a filter
region (or a branch into a tracestop region) by matching Packet Generation
Disabled (TIP.PGD) packets against the object code using the IP given in
the packet. However, due to errata SKL014 "Intel PT TIP.PGD May Not Have
Target IP Payload", that IP may not be present.

Enable the decoder to handle that by adding a new callback function
'pgd_ip()' which indicates whether the IP is not traced, in which case that
is the point where the trace was disabled.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
 .../perf/util/intel-pt-decoder/intel-pt-decoder.c  | 30 ++++++++++++++++++++++
 .../perf/util/intel-pt-decoder/intel-pt-decoder.h  |  1 +
 2 files changed, 31 insertions(+)

diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index 8ff6c6a61291..7591a0c37473 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -80,6 +80,7 @@ struct intel_pt_decoder {
 	int (*walk_insn)(struct intel_pt_insn *intel_pt_insn,
 			 uint64_t *insn_cnt_ptr, uint64_t *ip, uint64_t to_ip,
 			 uint64_t max_insn_cnt, void *data);
+	bool (*pgd_ip)(uint64_t ip, void *data);
 	void *data;
 	struct intel_pt_state state;
 	const unsigned char *buf;
@@ -186,6 +187,7 @@ struct intel_pt_decoder *intel_pt_decoder_new(struct intel_pt_params *params)
 
 	decoder->get_trace          = params->get_trace;
 	decoder->walk_insn          = params->walk_insn;
+	decoder->pgd_ip             = params->pgd_ip;
 	decoder->data               = params->data;
 	decoder->return_compression = params->return_compression;
 
@@ -1008,6 +1010,19 @@ static int intel_pt_walk_tip(struct intel_pt_decoder *decoder)
 	int err;
 
 	err = intel_pt_walk_insn(decoder, &intel_pt_insn, 0);
+	if (err == INTEL_PT_RETURN &&
+	    decoder->pgd_ip &&
+	    decoder->pkt_state == INTEL_PT_STATE_TIP_PGD &&
+	    (decoder->state.type & INTEL_PT_BRANCH) &&
+	    decoder->pgd_ip(decoder->state.to_ip, decoder->data)) {
+		/* Unconditional branch leaving filter region */
+		decoder->no_progress = 0;
+		decoder->pge = false;
+		decoder->continuous_period = false;
+		decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
+		decoder->state.to_ip = 0;
+		return 0;
+	}
 	if (err == INTEL_PT_RETURN)
 		return 0;
 	if (err)
@@ -1036,6 +1051,21 @@ static int intel_pt_walk_tip(struct intel_pt_decoder *decoder)
 	}
 
 	if (intel_pt_insn.branch == INTEL_PT_BR_CONDITIONAL) {
+		uint64_t to_ip = decoder->ip + intel_pt_insn.length +
+				 intel_pt_insn.rel;
+
+		if (decoder->pgd_ip &&
+		    decoder->pkt_state == INTEL_PT_STATE_TIP_PGD &&
+		    decoder->pgd_ip(to_ip, decoder->data)) {
+			/* Conditional branch leaving filter region */
+			decoder->pge = false;
+			decoder->continuous_period = false;
+			decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
+			decoder->ip = to_ip;
+			decoder->state.from_ip = decoder->ip;
+			decoder->state.to_ip = 0;
+			return 0;
+		}
 		intel_pt_log_at("ERROR: Conditional branch when expecting indirect branch",
 				decoder->ip);
 		decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.h b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.h
index 02c38fec1c37..89399985fa4d 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.h
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.h
@@ -83,6 +83,7 @@ struct intel_pt_params {
 	int (*walk_insn)(struct intel_pt_insn *intel_pt_insn,
 			 uint64_t *insn_cnt_ptr, uint64_t *ip, uint64_t to_ip,
 			 uint64_t max_insn_cnt, void *data);
+	bool (*pgd_ip)(uint64_t ip, void *data);
 	void *data;
 	bool return_compression;
 	uint64_t period;
-- 
1.9.1