selftests/proc: test PROCMAP_QUERY ioctl while vma is concurrently modified

Patch series " execute PROCMAP_QUERY ioctl under per-vma lock", v4.

With /proc/pid/maps now being read under per-vma lock protection we can
reuse parts of that code to execute PROCMAP_QUERY ioctl also without
taking mmap_lock.  The change is designed to reduce mmap_lock contention
and prevent PROCMAP_QUERY ioctl calls from blocking address space updates.

This patchset was split out of the original patchset [1] that introduced
per-vma lock usage for /proc/pid/maps reading.  It contains PROCMAP_QUERY
tests, code refactoring patch to simplify the main change and the actual
transition to per-vma lock.


This patch (of 3):

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

Link: https://lkml.kernel.org/r/20250808152850.2580887-1-surenb@google.com
Link: https://lkml.kernel.org/r/20250808152850.2580887-2-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Tested-by: SeongJae Park <sj@kernel.org>
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Cc: T.J. Mercier <tjmercier@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Ye Bin <yebin10@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/tools/testing/selftests/proc/proc-maps-race.c b/tools/testing/selftests/proc/proc-maps-race.c
index 94bba4553130..a546475db550 100644
--- a/tools/testing/selftests/proc/proc-maps-race.c
+++ b/tools/testing/selftests/proc/proc-maps-race.c
@@ -32,6 +32,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <linux/fs.h>
+#include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -317,6 +319,25 @@ static bool capture_mod_pattern(FIXTURE_DATA(proc_maps_race) *self,
 	       strcmp(restored_first_line->text, self->first_line.text) == 0;
 }
 
+static bool 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;
+	if (ioctl(maps_fd, PROCMAP_QUERY, &q))
+		return false;
+
+	*vma_start = q.vma_start;
+	*vma_end = q.vma_end;
+
+	return true;
+}
+
 static inline bool split_vma(FIXTURE_DATA(proc_maps_race) *self)
 {
 	return mmap(self->mod_info->addr, self->page_size, self->mod_info->prot | PROT_EXEC,
@@ -559,6 +580,8 @@ TEST_F(proc_maps_race, test_maps_tearing_from_split)
 	do {
 		bool last_line_changed;
 		bool first_line_changed;
+		unsigned long vma_start;
+		unsigned long vma_end;
 
 		ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line));
 
@@ -595,6 +618,19 @@ TEST_F(proc_maps_race, test_maps_tearing_from_split)
 		first_line_changed = strcmp(new_first_line.text, self->first_line.text) != 0;
 		ASSERT_EQ(last_line_changed, first_line_changed);
 
+		/* Check if PROCMAP_QUERY ioclt() finds the right VMA */
+		ASSERT_TRUE(query_addr_at(self->maps_fd, mod_info->addr + self->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_TRUE((vma_start == self->last_line.start_addr &&
+			     vma_end == self->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);
 		end_test_iteration(&end_ts, self->verbose);
 	} while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec);
@@ -636,6 +672,9 @@ TEST_F(proc_maps_race, test_maps_tearing_from_resize)
 	clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts);
 	start_test_loop(&start_ts, self->verbose);
 	do {
+		unsigned long vma_start;
+		unsigned long vma_end;
+
 		ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line));
 
 		/* Check if we read vmas after shrinking it */
@@ -662,6 +701,16 @@ TEST_F(proc_maps_race, test_maps_tearing_from_resize)
 					"Expand result invalid", self));
 		}
 
+		/* Check if PROCMAP_QUERY ioclt() finds the right VMA */
+		ASSERT_TRUE(query_addr_at(self->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_TRUE(vma_start == self->last_line.start_addr &&
+			    (vma_end - vma_start == self->page_size * 3 ||
+			     vma_end - vma_start == self->page_size));
+
 		clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts);
 		end_test_iteration(&end_ts, self->verbose);
 	} while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec);
@@ -703,6 +752,9 @@ TEST_F(proc_maps_race, test_maps_tearing_from_remap)
 	clock_gettime(CLOCK_MONOTONIC_COARSE, &start_ts);
 	start_test_loop(&start_ts, self->verbose);
 	do {
+		unsigned long vma_start;
+		unsigned long vma_end;
+
 		ASSERT_TRUE(read_boundary_lines(self, &new_last_line, &new_first_line));
 
 		/* Check if we read vmas after remapping it */
@@ -729,6 +781,19 @@ TEST_F(proc_maps_race, test_maps_tearing_from_remap)
 					"Remap restore result invalid", self));
 		}
 
+		/* Check if PROCMAP_QUERY ioclt() finds the right VMA */
+		ASSERT_TRUE(query_addr_at(self->maps_fd, mod_info->addr + self->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_TRUE((vma_start == self->last_line.start_addr &&
+			     vma_end - vma_start == self->page_size * 3) ||
+			    (vma_start == self->last_line.start_addr + self->page_size &&
+			     vma_end - vma_start == self->page_size));
+
 		clock_gettime(CLOCK_MONOTONIC_COARSE, &end_ts);
 		end_test_iteration(&end_ts, self->verbose);
 	} while (end_ts.tv_sec - start_ts.tv_sec < self->duration_sec);