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From:   Peter Xu <peterx@redhat.com>
To:     linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc:     Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Andrea Arcangeli <aarcange@redhat.com>, peterx@redhat.com,
        Leonardo Bras Soares Passos <lsoaresp@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Hildenbrand <david@redhat.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Nadav Amit <nadav.amit@gmail.com>
Subject: [PATCH 27/29] selftests/mm: Allow uffd test to skip properly with no privilege
Date:   Thu, 30 Mar 2023 12:08:35 -0400
Message-Id: <20230330160835.3107613-1-peterx@redhat.com>
In-Reply-To: <20230330155707.3106228-1-peterx@redhat.com>
References: <20230330155707.3106228-1-peterx@redhat.com>
MIME-Version: 1.0
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Allow skip a unit test properly due to no privilege (e.g. sigbus and events
tests).

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tools/testing/selftests/mm/uffd-common.c     | 27 ++++++++++++--------
 tools/testing/selftests/mm/uffd-common.h     |  4 +--
 tools/testing/selftests/mm/uffd-stress.c     |  6 +++--
 tools/testing/selftests/mm/uffd-unit-tests.c | 10 +++++---
 4 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c
index 95ad619d0df4..964fa57b710a 100644
--- a/tools/testing/selftests/mm/uffd-common.c
+++ b/tools/testing/selftests/mm/uffd-common.c
@@ -225,7 +225,7 @@ void uffd_stats_report(struct uffd_stats *stats, int n_cpus)
 	printf("\n");
 }
 
-void userfaultfd_open(uint64_t *features)
+int userfaultfd_open(uint64_t *features)
 {
 	struct uffdio_api uffdio_api;
 
@@ -234,18 +234,19 @@ void userfaultfd_open(uint64_t *features)
 	else
 		uffd = uffd_open_sys(UFFD_FLAGS);
 	if (uffd < 0)
-		err("uffd open failed (dev=%d)", test_dev_userfaultfd);
+		return -1;
 	uffd_flags = fcntl(uffd, F_GETFD, NULL);
 
 	uffdio_api.api = UFFD_API;
 	uffdio_api.features = *features;
 	if (ioctl(uffd, UFFDIO_API, &uffdio_api))
-		err("UFFDIO_API failed.\nPlease make sure to "
-		    "run with either root or ptrace capability.");
+		/* Probably lack of CAP_PTRACE? */
+		return -1;
 	if (uffdio_api.api != UFFD_API)
 		err("UFFDIO_API error: %" PRIu64, (uint64_t)uffdio_api.api);
 
 	*features = uffdio_api.features;
+	return 0;
 }
 
 static inline void munmap_area(void **area)
@@ -288,7 +289,7 @@ static void uffd_test_ctx_clear(void)
 	munmap_area((void **)&area_remap);
 }
 
-int uffd_test_ctx_init(uint64_t features)
+int uffd_test_ctx_init(uint64_t features, const char **errmsg)
 {
 	unsigned long nr, cpu;
 	int ret;
@@ -296,13 +297,19 @@ int uffd_test_ctx_init(uint64_t features)
 	uffd_test_ctx_clear();
 
 	ret = uffd_test_ops->allocate_area((void **)&area_src, true);
-	if (ret)
-		return ret;
-	ret = uffd_test_ops->allocate_area((void **)&area_dst, false);
-	if (ret)
+	ret |= uffd_test_ops->allocate_area((void **)&area_dst, false);
+	if (ret) {
+		if (errmsg)
+			*errmsg = "memory allocation failed";
 		return ret;
+	}
 
-	userfaultfd_open(&features);
+	ret = userfaultfd_open(&features);
+	if (ret) {
+		if (errmsg)
+			*errmsg = "possible lack of priviledge";
+		return ret;
+	}
 
 	count_verify = malloc(nr_pages * sizeof(unsigned long long));
 	if (!count_verify)
diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h
index 16d32ddf8412..07d00e9809dc 100644
--- a/tools/testing/selftests/mm/uffd-common.h
+++ b/tools/testing/selftests/mm/uffd-common.h
@@ -101,8 +101,8 @@ extern uffd_test_ops_t hugetlb_uffd_test_ops;
 extern uffd_test_ops_t *uffd_test_ops;
 
 void uffd_stats_report(struct uffd_stats *stats, int n_cpus);
-int uffd_test_ctx_init(uint64_t features);
-void userfaultfd_open(uint64_t *features);
+int uffd_test_ctx_init(uint64_t features, const char **errmsg);
+int userfaultfd_open(uint64_t *features);
 int uffd_read_msg(int ufd, struct uffd_msg *msg);
 void wp_range(int ufd, __u64 start, __u64 len, bool wp);
 void uffd_handle_page_fault(struct uffd_msg *msg, struct uffd_stats *stats);
diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index a6f3609c1ad1..8f41bef2fbda 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -272,7 +272,8 @@ static int userfaultfd_stress(void)
 	struct uffd_stats uffd_stats[nr_cpus];
 	uint64_t mem_size = nr_pages * page_size;
 
-	uffd_test_ctx_init(UFFD_FEATURE_WP_UNPOPULATED);
+	if (uffd_test_ctx_init(UFFD_FEATURE_WP_UNPOPULATED, NULL))
+		err("context init failed");
 
 	if (posix_memalign(&area, page_size, page_size))
 		err("out of memory");
@@ -436,7 +437,8 @@ static void parse_test_type_arg(const char *raw_type)
 	 * feature.
 	 */
 
-	userfaultfd_open(&features);
+	if (userfaultfd_open(&features))
+		err("Userfaultfd open failed");
 
 	test_uffdio_wp = test_uffdio_wp &&
 		(features & UFFD_FEATURE_PAGEFAULT_FLAG_WP);
diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
index 82fd3aaa06c2..9e7f7c7f2982 100644
--- a/tools/testing/selftests/mm/uffd-unit-tests.c
+++ b/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -175,7 +175,8 @@ static int test_uffd_api(bool use_dev)
  * This function initializes the global variables.  TODO: remove global
  * vars and then remove this.
  */
-static int uffd_setup_environment(uffd_test_case_t *test, mem_type_t *mem_type)
+static int uffd_setup_environment(uffd_test_case_t *test, mem_type_t *mem_type,
+				  const char **errmsg)
 {
 	map_shared = mem_type->shared;
 	uffd_test_ops = mem_type->mem_ops;
@@ -189,7 +190,7 @@ static int uffd_setup_environment(uffd_test_case_t *test, mem_type_t *mem_type)
 	/* TODO: remove this global var.. it's so ugly */
 	nr_cpus = 1;
 
-	return uffd_test_ctx_init(test->uffd_feature_required);
+	return uffd_test_ctx_init(test->uffd_feature_required, errmsg);
 }
 
 static bool uffd_feature_supported(uffd_test_case_t *test)
@@ -838,6 +839,7 @@ int main(int argc, char *argv[])
 	uffd_test_case_t *test;
 	mem_type_t *mem_type;
 	char test_name[128];
+	const char *errmsg;
 	int has_uffd;
 	int i, j;
 
@@ -863,8 +865,8 @@ int main(int argc, char *argv[])
 				uffd_test_skip("feature missing");
 				continue;
 			}
-			if (uffd_setup_environment(test, mem_type)) {
-				uffd_test_skip("memory allocation failed");
+			if (uffd_setup_environment(test, mem_type, &errmsg)) {
+				uffd_test_skip(errmsg);
 				continue;
 			}
 			test->uffd_fn();
-- 
2.39.1