linux-kernel - [PATCH v4 10/21] perf arm_spe: Fixup top byte for data virtual address

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Message-Id: <20201027030917.15404-11-leo.yan@linaro.org>
Date:   Tue, 27 Oct 2020 11:09:06 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Andre Przywara <andre.przywara@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Wei Li <liwei391@...wei.com>,
        James Clark <james.clark@....com>, Al Grant <Al.Grant@....com>,
        Dave Martin <Dave.Martin@....com>, linux-kernel@...r.kernel.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v4 10/21] perf arm_spe: Fixup top byte for data virtual address

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 [55:48] are 0xf0 or
0xfd, if detects the patterns 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@...aro.org>
---
 .../util/arm-spe-decoder/arm-spe-decoder.c    | 24 ++++++++++++++++---
 1 file changed, 21 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..e135ac01d94a 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 +45,26 @@ 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 [55:48] 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 [55:48] is one of
+		 * following values, will fill 0xff into the top byte:
+		 *
+		 *   - 0xff (for most kernel memory regions);
+		 *   - 0xf0 (for kernel logical memory map with 64KB pages);
+		 *   - 0xfd (for kasan shadow region with 64KB pages).
+		 */
+		val = SPE_ADDR_PKT_ADDR_GET_BYTE_6(payload);
+		if (val == 0xffULL || val == 0xf0ULL || val == 0xfdULL)
 			payload |= 0xffULL << SPE_ADDR_PKT_ADDR_BYTE7_SHIFT;
 
 	/* Data access physical address */
-- 
2.17.1