[PATCH v3 13/14] perf tests: Check CoreSight abort entry and exit

[Leo Yan]

Add page_fault_loop to repeatedly discard an anonymous page with
MADV_DONTNEED and read it again. Each demand fault is resolved without
signal delivery, so the load must be retried at the same PC.

For example, an expected int/iret pair is:

  int            5ccadc => ffff800080010c00 insn: 00 00 40 39
  ...
  iret ffff800080012284 =>           5ccadc insn: e0 03 9f d6

The LDRB W0, [X0] at 0x5ccadc faults before completing. After resolving
the page fault, the kernel returns via ERET to the same PC to retry it.

Reviewed-by: James Clark <james.clark at linaro.org>
Signed-off-by: Leo Yan <leo.yan at arm.com>
---
 tools/perf/tests/builtin-test.c                    |  1 +
 .../perf/tests/shell/coresight/abort_entry_exit.sh | 32 +++++++++++++++++++
 tools/perf/tests/tests.h                           |  1 +
 tools/perf/tests/workloads/Build                   |  2 ++
 tools/perf/tests/workloads/page_fault_loop.c       | 37 ++++++++++++++++++++++
 5 files changed, 73 insertions(+)

diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 24e095d4d20cee6a6aae7cfda364fb237ef74b30..86698b86657f45b094755583800062c37e16ca8b 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -192,6 +192,7 @@ static struct test_workload *workloads[] = {
 	&workload__landlock,
 	&workload__traploop,
 	&workload__branch_not_taken_loop,
+	&workload__page_fault_loop,
 	&workload__inlineloop,
 	&workload__jitdump,
 	&workload__context_switch_loop,
diff --git a/tools/perf/tests/shell/coresight/abort_entry_exit.sh b/tools/perf/tests/shell/coresight/abort_entry_exit.sh
new file mode 100755
index 0000000000000000000000000000000000000000..98aeb2b1068e9847d87e3b25aeabf6da114c6ae2
--- /dev/null
+++ b/tools/perf/tests/shell/coresight/abort_entry_exit.sh
@@ -0,0 +1,32 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# CoreSight abort entry and exit (exclusive)
+
+. "$(dirname "$0")/../lib/coresight_exception.sh"
+
+test_abort_entry_exit()
+{
+	local attempt result
+
+	# A demand page fault retries the load at the same PC after resolution.
+	for attempt in 1 2 3; do
+		echo "Recording page faults (attempt $attempt/3)"
+		if ! record_trace page_fault_loop; then
+			cat "$tmpdir/record.log"
+			echo "Failed to record the page fault workload"
+			return 1
+		fi
+		decode_trace || return 1
+		check_exception_pairs "int" "iret" 0
+		result=$?
+		if [ "$result" -ne 2 ]; then
+			return "$result"
+		fi
+	done
+
+	echo "FAIL: No complete abort pair after three recordings"
+	return 1
+}
+
+setup_exception_test || exit $?
+test_abort_entry_exit
diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
index 989208fcd417a676d03e2372e8a71ecf2059b9c6..8c399840a735910d4344eba928075e3ec6b1f81c 100644
--- a/tools/perf/tests/tests.h
+++ b/tools/perf/tests/tests.h
@@ -265,6 +265,7 @@ DECLARE_WORKLOAD(datasym);
 DECLARE_WORKLOAD(landlock);
 DECLARE_WORKLOAD(traploop);
 DECLARE_WORKLOAD(branch_not_taken_loop);
+DECLARE_WORKLOAD(page_fault_loop);
 DECLARE_WORKLOAD(inlineloop);
 DECLARE_WORKLOAD(jitdump);
 DECLARE_WORKLOAD(context_switch_loop);
diff --git a/tools/perf/tests/workloads/Build b/tools/perf/tests/workloads/Build
index d3030bd9c0752a5bc8743a4539a0ac365d215719..43cc4da6fb0786de8bb5c52717c2ad5fdbaa639c 100644
--- a/tools/perf/tests/workloads/Build
+++ b/tools/perf/tests/workloads/Build
@@ -10,6 +10,7 @@ perf-test-y += datasym.o
 perf-test-y += landlock.o
 perf-test-y += traploop.o
 perf-test-y += branch_not_taken_loop.o
+perf-test-y += page_fault_loop.o
 perf-test-y += inlineloop.o
 perf-test-y += jitdump.o
 perf-test-y += context_switch_loop.o
@@ -28,6 +29,7 @@ CFLAGS_brstack.o          = -g -O0 -fno-inline -U_FORTIFY_SOURCE
 CFLAGS_datasym.o          = -g -O0 -fno-inline -U_FORTIFY_SOURCE
 CFLAGS_traploop.o         = -g -O0 -fno-inline -U_FORTIFY_SOURCE
 CFLAGS_branch_not_taken_loop.o = -g -O0 -fno-inline -U_FORTIFY_SOURCE
+CFLAGS_page_fault_loop.o  = -g -O0 -fno-inline -U_FORTIFY_SOURCE
 CFLAGS_inlineloop.o       = -g -O2
 CFLAGS_deterministic.o    = -g -O0 -fno-inline -U_FORTIFY_SOURCE
 CFLAGS_named_threads.o    = -g -O0 -fno-inline -U_FORTIFY_SOURCE
diff --git a/tools/perf/tests/workloads/page_fault_loop.c b/tools/perf/tests/workloads/page_fault_loop.c
new file mode 100644
index 0000000000000000000000000000000000000000..4afbc4ab0a55400360facdc3a99ea5a5a9d52596
--- /dev/null
+++ b/tools/perf/tests/workloads/page_fault_loop.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compiler.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include "../tests.h"
+
+static int page_fault_loop(int argc __maybe_unused, const char **argv __maybe_unused)
+{
+	size_t size = getpagesize();
+	char *page;
+	int ret = 1;
+
+	page = mmap(NULL, size, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (page == MAP_FAILED) {
+		perror("mmap");
+		return 1;
+	}
+
+	for (int i = 0; i < 256; i++) {
+		/* Drop the PTE so the kernel must resolve a fault on each read. */
+		if (madvise(page, size, MADV_DONTNEED)) {
+			perror("madvise");
+			goto out;
+		}
+		if (READ_ONCE(*page)) {
+			fprintf(stderr, "Anonymous page is not zero-filled\n");
+			goto out;
+		}
+	}
+	ret = 0;
+out:
+	munmap(page, size);
+	return ret;
+}
+
+DEFINE_WORKLOAD(page_fault_loop);

-- 
2.34.1