[PATCH v6 10/21] perf arm_spe: Fixup top byte for data virtual address

[Leo Yan]

To establish a valid address from the address packet payload and finally
the address value can be used for parsing data symbol in DSO, current
code uses 0xff to replace the tag in the top byte of data virtual
address.

So far the code only fixups top byte for the memory layouts with 4KB
pages, it misses to support memory layouts with 64KB pages.

This patch adds the conditions for checking bits [55:52] are 0xf, if
detects the pattern it will fill 0xff into the top byte of the address,
also adds comment to explain the fixing up.

Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
---
 .../util/arm-spe-decoder/arm-spe-decoder.c    | 20 ++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
index 776b3e6628bb..cac2ef79c025 100644
--- a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
+++ b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
@@ -24,7 +24,7 @@
 
 static u64 arm_spe_calc_ip(int index, u64 payload)
 {
-	u64 ns, el;
+	u64 ns, el, val;
 
 	/* Instruction virtual address or Branch target address */
 	if (index == SPE_ADDR_PKT_HDR_INDEX_INS ||
@@ -45,8 +45,22 @@ static u64 arm_spe_calc_ip(int index, u64 payload)
 		/* Clean tags */
 		payload = SPE_ADDR_PKT_ADDR_GET_BYTES_0_6(payload);
 
-		/* Fill highest byte if bits [48..55] is 0xff */
-		if (SPE_ADDR_PKT_ADDR_GET_BYTE_6(payload) == 0xffULL)
+		/*
+		 * Armv8 ARM (ARM DDI 0487F.c), chapter "D10.2.1 Address packet"
+		 * defines the data virtual address payload format, the top byte
+		 * (bits [63:56]) is assigned as top-byte tag; so we only can
+		 * retrieve address value from bits [55:0].
+		 *
+		 * According to Documentation/arm64/memory.rst, if detects the
+		 * specific pattern in bits [55:52] of payload which falls in
+		 * the kernel space, should fixup the top byte and this allows
+		 * perf tool to parse DSO symbol for data address correctly.
+		 *
+		 * For this reason, if detects the bits [55:52] is 0xf, will
+		 * fill 0xff into the top byte.
+		 */
+		val = SPE_ADDR_PKT_ADDR_GET_BYTE_6(payload);
+		if ((val & 0xf0ULL) == 0xf0ULL)
 			payload |= 0xffULL << SPE_ADDR_PKT_ADDR_BYTE7_SHIFT;
 
 	/* Data access physical address */
-- 
2.17.1