tools/selftests: add guard region test for /proc/$pid/pagemap

Add a test to the guard region self tests to assert that the
/proc/$pid/pagemap information now made availabile to the user correctly
identifies and reports guard regions.

As a part of this change, update vm_util.h to add the new bit (note there
is no header file in the kernel where this is exposed, the user is
expected to provide their own mask) and utilise the helper functions there
for pagemap functionality.

[lorenzo.stoakes@oracle.com: fixup define name]
Link: https://lkml.kernel.org/r/32e83941-e6f5-42ee-9292-a44c16463cf1@lucifer.local
Link: https://lkml.kernel.org/r/164feb0a43ae72650e6b20c3910213f469566311.1740139449.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
index ea9b5815e8280d60b2dde50667f180f24ac3890b..280d1831bf730fdd8359ac13453c6f081099135d 100644 (file)
--- a/tools/testing/selftests/mm/guard-regions.c
+++ b/tools/testing/selftests/mm/guard-regions.c
@@ -19,6 +19,7 @@
 #include <sys/syscall.h>
 #include <sys/uio.h>
 #include <unistd.h>
+#include "vm_util.h"
 
 /*
  * Ignore the checkpatch warning, as per the C99 standard, section 7.14.1.1:
@@ -2032,4 +2033,50 @@ TEST_F(guard_regions, anon_zeropage)
        ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
 }
 
+/*
+ * Assert that /proc/$pid/pagemap correctly identifies guard region ranges.
+ */
+TEST_F(guard_regions, pagemap)
+{
+       const unsigned long page_size = self->page_size;
+       int proc_fd;
+       char *ptr;
+       int i;
+
+       proc_fd = open("/proc/self/pagemap", O_RDONLY);
+       ASSERT_NE(proc_fd, -1);
+
+       ptr = mmap_(self, variant, NULL, 10 * page_size,
+                   PROT_READ | PROT_WRITE, 0, 0);
+       ASSERT_NE(ptr, MAP_FAILED);
+
+       /* Read from pagemap, and assert no guard regions are detected. */
+       for (i = 0; i < 10; i++) {
+               char *ptr_p = &ptr[i * page_size];
+               unsigned long entry = pagemap_get_entry(proc_fd, ptr_p);
+               unsigned long masked = entry & PM_GUARD_REGION;
+
+               ASSERT_EQ(masked, 0);
+       }
+
+       /* Install a guard region in every other page. */
+       for (i = 0; i < 10; i += 2) {
+               char *ptr_p = &ptr[i * page_size];
+
+               ASSERT_EQ(madvise(ptr_p, page_size, MADV_GUARD_INSTALL), 0);
+       }
+
+       /* Re-read from pagemap, and assert guard regions are detected. */
+       for (i = 0; i < 10; i++) {
+               char *ptr_p = &ptr[i * page_size];
+               unsigned long entry = pagemap_get_entry(proc_fd, ptr_p);
+               unsigned long masked = entry & PM_GUARD_REGION;
+
+               ASSERT_EQ(masked, i % 2 == 0 ? PM_GUARD_REGION : 0);
+       }
+
+       ASSERT_EQ(close(proc_fd), 0);
+       ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
+}
+
 TEST_HARNESS_MAIN

diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
index b60ac68a9dc8893895f49946b258260f7a82218a..0e629586556b5aae580d8e4ce7491bc93adcc4d6 100644 (file)
--- a/tools/testing/selftests/mm/vm_util.h
+++ b/tools/testing/selftests/mm/vm_util.h
@@ -10,6 +10,7 @@
 #define PM_SOFT_DIRTY                 BIT_ULL(55)
 #define PM_MMAP_EXCLUSIVE             BIT_ULL(56)
 #define PM_UFFD_WP                    BIT_ULL(57)
+#define PM_GUARD_REGION               BIT_ULL(58)
 #define PM_FILE                       BIT_ULL(61)
 #define PM_SWAP                       BIT_ULL(62)
 #define PM_PRESENT                    BIT_ULL(63)