[PATCH v4 4/7] selftests/proc: test PROCMAP_QUERY ioctl while vma is concurrently modified

[Suren Baghdasaryan <surenb@google.com>]

Extend /proc/pid/maps tearing test to verify PROCMAP_QUERY ioctl operation
correctness while the vma is being concurrently modified.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 tools/testing/selftests/proc/proc-pid-vm.c | 60 ++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/tools/testing/selftests/proc/proc-pid-vm.c b/tools/testing/selftests/proc/proc-pid-vm.c
index 1aef2db7e893..b582f40851fb 100644
--- a/tools/testing/selftests/proc/proc-pid-vm.c
+++ b/tools/testing/selftests/proc/proc-pid-vm.c
@@ -486,6 +486,21 @@ static void capture_mod_pattern(int maps_fd,
 	assert(strcmp(restored_first_line->text, first_line->text) == 0);
 }
 
+static void query_addr_at(int maps_fd, void *addr,
+			  unsigned long *vma_start, unsigned long *vma_end)
+{
+	struct procmap_query q;
+
+	memset(&q, 0, sizeof(q));
+	q.size = sizeof(q);
+	/* Find the VMA at the split address */
+	q.query_addr = (unsigned long long)addr;
+	q.query_flags = 0;
+	assert(!ioctl(maps_fd, PROCMAP_QUERY, &q));
+	*vma_start = q.vma_start;
+	*vma_end = q.vma_end;
+}
+
 static inline void split_vma(const struct vma_modifier_info *mod_info)
 {
 	assert(mmap(mod_info->addr, page_size, mod_info->prot | PROT_EXEC,
@@ -546,6 +561,8 @@ static void test_maps_tearing_from_split(int maps_fd,
 	do {
 		bool last_line_changed;
 		bool first_line_changed;
+		unsigned long vma_start;
+		unsigned long vma_end;
 
 		read_boundary_lines(maps_fd, page1, page2, &new_last_line, &new_first_line);
 
@@ -576,6 +593,19 @@ static void test_maps_tearing_from_split(int maps_fd,
 		first_line_changed = strcmp(new_first_line.text, first_line->text) != 0;
 		assert(last_line_changed == first_line_changed);
 
+		/* Check if PROCMAP_QUERY ioclt() finds the right VMA */
+		query_addr_at(maps_fd, mod_info->addr + page_size,
+			      &vma_start, &vma_end);
+		/*
+		 * The vma at the split address can be either the same as
+		 * original one (if read before the split) or the same as the
+		 * first line in the second page (if read after the split).
+		 */
+		assert((vma_start == last_line->start_addr &&
+			vma_end == last_line->end_addr) ||
+		       (vma_start == split_first_line.start_addr &&
+			vma_end == split_first_line.end_addr));
+
 		clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts);
 	} while (end_ts.tv_sec - start_ts.tv_sec < test_duration_sec);
 
@@ -637,6 +667,9 @@ static void test_maps_tearing_from_resize(int maps_fd,
 
 	clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts);
 	do {
+		unsigned long vma_start;
+		unsigned long vma_end;
+
 		read_boundary_lines(maps_fd, page1, page2, &new_last_line, &new_first_line);
 
 		/* Check if we read vmas after shrinking it */
@@ -656,6 +689,17 @@ static void test_maps_tearing_from_resize(int maps_fd,
 			assert(!strcmp(new_last_line.text, restored_last_line.text) &&
 			       !strcmp(new_first_line.text, restored_first_line.text));
 		}
+
+		/* Check if PROCMAP_QUERY ioclt() finds the right VMA */
+		query_addr_at(maps_fd, mod_info->addr, &vma_start, &vma_end);
+		/*
+		 * The vma should stay at the same address and have either the
+		 * original size of 3 pages or 1 page if read after shrinking.
+		 */
+		assert(vma_start == last_line->start_addr &&
+		       (vma_end - vma_start == page_size * 3 ||
+			vma_end - vma_start == page_size));
+
 		clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts);
 	} while (end_ts.tv_sec - start_ts.tv_sec < test_duration_sec);
 
@@ -726,6 +770,9 @@ static void test_maps_tearing_from_remap(int maps_fd,
 
 	clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts);
 	do {
+		unsigned long vma_start;
+		unsigned long vma_end;
+
 		read_boundary_lines(maps_fd, page1, page2, &new_last_line, &new_first_line);
 
 		/* Check if we read vmas after remapping it */
@@ -745,6 +792,19 @@ static void test_maps_tearing_from_remap(int maps_fd,
 			assert(!strcmp(new_last_line.text, restored_last_line.text) &&
 			       !strcmp(new_first_line.text, restored_first_line.text));
 		}
+
+		/* Check if PROCMAP_QUERY ioclt() finds the right VMA */
+		query_addr_at(maps_fd, mod_info->addr + page_size, &vma_start, &vma_end);
+		/*
+		 * The vma should either stay at the same address and have the
+		 * original size of 3 pages or we should find the remapped vma
+		 * at the remap destination address with size of 1 page.
+		 */
+		assert((vma_start == last_line->start_addr &&
+			vma_end - vma_start == page_size * 3) ||
+		       (vma_start == last_line->start_addr + page_size &&
+			vma_end - vma_start == page_size));
+
 		clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts);
 	} while (end_ts.tv_sec - start_ts.tv_sec < test_duration_sec);
 
-- 
2.49.0.1266.g31b7d2e469-goog