[igt-dev] [PATCH i-g-t 2/2] tests/panfrost: Add a test for accessing a purged buffer

[Neil Roberts]

The test creates a buffer, sets it as DONTNEED via madvise, tries to
trigger a purge of buffers and then accesses the buffer via a user-space
mapping. This should generate a bus error, but due to a bug in the
kernel driver it fails to invalidate the mapping when the buffer is
purged.

Signed-off-by: Neil Roberts <nroberts at igalia.com>
---
 tests/meson.build         |   1 +
 tests/panfrost_purgemap.c | 146 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 147 insertions(+)
 create mode 100644 tests/panfrost_purgemap.c

diff --git a/tests/meson.build b/tests/meson.build
index 825e0183..af24427a 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -82,6 +82,7 @@ test_progs = [
 	'panfrost_get_param',
 	'panfrost_gem_new',
 	'panfrost_prime',
+	'panfrost_purgemap',
 	'panfrost_submit',
 	'prime_busy',
 	'prime_mmap',
diff --git a/tests/panfrost_purgemap.c b/tests/panfrost_purgemap.c
new file mode 100644
index 00000000..096fb95a
--- /dev/null
+++ b/tests/panfrost_purgemap.c
@@ -0,0 +1,146 @@
+/*
+ * Copyright © 2021 Igalia
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "igt.h"
+#include "igt_panfrost.h"
+#include "igt_syncobj.h"
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <setjmp.h>
+#include <signal.h>
+#include "panfrost-job.h"
+#include "panfrost_drm.h"
+
+IGT_TEST_DESCRIPTION("Checks that accessing an mmapping of a buffer that has "
+		     "been purged causes a bus fault signal.");
+
+#define BUF_SIZE (32 * 1024 * 1024)
+
+struct buf_link {
+	struct panfrost_bo *bo;
+	struct buf_link *next;
+};
+
+static jmp_buf jmp;
+
+__noreturn static void sigtrap(int sig)
+{
+	siglongjmp(jmp, sig);
+}
+
+static void
+try_writing_to_mmap(uint8_t *ptr)
+{
+	sighandler_t old_sigsegv, old_sigbus;
+
+	old_sigsegv = signal(SIGSEGV, sigtrap);
+	old_sigbus = signal(SIGBUS, sigtrap);
+
+	switch (sigsetjmp(jmp, SIGBUS | SIGSEGV)) {
+	case SIGBUS:
+		break;
+	case 0:
+		*ptr = 0;
+	default:
+		igt_assert(!"reached");
+		break;
+	}
+
+	signal(SIGBUS, old_sigsegv);
+	signal(SIGSEGV, old_sigbus);
+}
+
+static void
+trigger_purge(int fd, struct panfrost_bo *madv_bo)
+{
+	struct buf_link *buf_list = NULL, *next, *buf;
+	bool retained;
+
+	/* Try to trigger a purge by allocating buffers until the main
+	 * buffer is no longer retained. This should probably be
+	 * replaced with a more reliable way to do this such as a
+	 * debugfs trigger.
+	 */
+
+	while (true) {
+		/* Mark the buffer as purgeable */
+		retained = igt_panfrost_bo_madvise(fd,
+						   madv_bo,
+						   PANFROST_MADV_DONTNEED);
+		igt_assert(retained);
+
+		buf = malloc(sizeof(*buf));
+		buf->bo = igt_panfrost_gem_new(fd, BUF_SIZE);
+		buf->next = buf_list;
+		buf_list = buf;
+
+		/* Check if that caused the buffer to be purged */
+		retained = igt_panfrost_bo_madvise(fd,
+						   madv_bo,
+						   PANFROST_MADV_WILLNEED);
+
+		if (!retained)
+			break;
+	}
+
+	/* Free all the temporary buffers that we created */
+	for (buf = buf_list; buf; buf = next) {
+		next = buf->next;
+		igt_panfrost_free_bo(fd, buf->bo);
+		free(buf);
+	}
+}
+
+igt_simple_main
+{
+	int fd;
+	struct panfrost_bo *bo;
+
+	fd = drm_open_driver(DRIVER_PANFROST);
+
+	bo = igt_panfrost_gem_new(fd, BUF_SIZE);
+
+	igt_panfrost_bo_mmap(fd, bo);
+
+	/* Write to the buffer to make sure the first page is
+	 * paged in
+	 */
+	memset(bo->map, 42, 64);
+
+	/* Try to cause the buffer to be purged */
+	trigger_purge(fd, bo);
+
+	/* Write through the mapping. This should cause a bus fault. */
+	try_writing_to_mmap(bo->map);
+
+	igt_panfrost_free_bo(fd, bo);
+
+	close(fd);
+}
-- 
2.29.2