libipt, ptdump: ignore unknown CFE packets

The current spec defines 12 types of CFE packets.  It reserves an
additional 18 types for future use.

CFE packets provide additional events, but are not strictly necessary for
decoding the trace, nor for understanding it.  It is therefore better to
ignore unknown CFE packets than to fail decode.

Signed-off-by: Markus Metzger <[email protected]>

Author: markus-metzger

libipt/src/pt_event_decoder.c

@@ -3566,7 +3566,27 @@ static int pt_evt_decode_cfe(struct pt_event_decoder *decoder,
 		return pt_evt_fetch_packet(decoder);
 	}
 
-	return -pte_bad_packet;
+	/* Decoding EVD is supposed to only enqueue supported CFE types. */
+	if (ev)
+		return -pte_internal;
+
+	/* Ignore unknown CFE types.
+	 *
+	 * They provide additional information but they are not essential for
+	 * decoding the trace.  It is better to continue without that
+	 * information than to fail.
+	 *
+	 * Since CFE may consume a subsequent FUP, we need to ignore that, too.
+	 */
+	if (packet->ip) {
+		ev = pt_evq_enqueue(&decoder->evq, evb_fup_bound);
+		if (!ev)
+			return -pte_nomem;
+
+		ev->type = ptev_ignore;
+	}
+
+	return 1;
 }
 
 static int pt_evt_decode_evd(struct pt_event_decoder *decoder,

ptdump/src/ptdump.c

@@ -1394,13 +1394,13 @@ static int print_packet(struct ptdump_buffer *buffer, uint64_t offset,
 		case pt_cfe_vmexit:
 		case pt_cfe_shutdown:
 		case pt_cfe_uiret:
-			print_field(buffer->payload.standard, "%u%s",
-				    packet->payload.cfe.type,
-				    packet->payload.cfe.ip ? ", ip" : "");
-			return 0;
+			break;
 		}
 
-		return diag("unknown cfe type", offset, -pte_bad_packet);
+		print_field(buffer->payload.standard, "%u%s",
+			    packet->payload.cfe.type,
+			    packet->payload.cfe.ip ? ", ip" : "");
+		return 0;
 
 	case ppt_evd:
 		print_field(buffer->opcode, "evd");

test/src/ptet.ptt

@@ -97,6 +97,10 @@ l12: nop
 ; @pt p45:  cfe(9: 14, ip)
 ; @pt p46:  fup(1: %l13)
 l13: nop
+; @pt p47:  cfe(31, ip)
+; @pt p48:  fup(1: %l14)
+l14: nop
+; @pt p49:  cfe(31)
 
 ; @pt .exp(ptdump)
 ;%0p0   psb
@@ -146,6 +150,9 @@ l13: nop
 ;%0p44  evd        31: 0
 ;%0p45  cfe        9: 14, ip
 ;%0p46  fup        1: %?l13.2
+;%0p47  cfe        31, ip
+;%0p48  fup        1: %?l14.2
+;%0p49  cfe        31
 
 
 ; @pt .exp(ptxed)