[PATCH v2 8/8] selftests/mm: report SKIP in pfnmap if a check fails

Kevin Brodsky
2026-01-07T16:49:07Z

pfnmap currently checks the target file in FIXTURE_SETUP(pfnmap),
meaning once for every test, and skips the test if any check fails.

The target file is the same for every test so this is a little
overkill. More importantly, this approach means that the whole suite
will report PASS even if all the tests are skipped because kernel
configuration (e.g. CONFIG_STRICT_DEVMEM=y) prevented /dev/mem from
being mapped, for instance.

Let's ensure that KSFT_SKIP is returned as exit code if any check
fails by performing the checks in pfnmap_init(), run once. That
function also takes care of finding the offset of the pages to be
mapped and saves it in a global. The file is still mapped/unmapped
for every test, as some of them modify the mapping.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
---
tools/testing/selftests/mm/pfnmap.c | 81 ++++++++++++++++++++---------
1 file changed, 55 insertions(+), 26 deletions(-)

diff --git a/tools/testing/selftests/mm/pfnmap.c b/tools/testing/selftests/mm/pfnmap.c
index 35b0e3ed54cd..e41d5464130b 100644
--- a/tools/testing/selftests/mm/pfnmap.c
+++ b/tools/testing/selftests/mm/pfnmap.c
@@ -25,8 +25,11 @@
#include "kselftest_harness.h"
#include "vm_util.h"

+#define DEV_MEM_NPAGES 2
+
static sigjmp_buf sigjmp_buf_env;
static char *file = "/dev/mem";
+static off_t file_offset;

static void signal_handler(int sig)
{
@@ -88,7 +91,7 @@ static int find_ram_target(off_t *offset,
break;

/* We need two pages. */
- if (end > start + 2 * pagesize) {
+ if (end > start + DEV_MEM_NPAGES * pagesize) {
fclose(file);
*offset = start;
return 0;
@@ -97,9 +100,49 @@ static int find_ram_target(off_t *offset,
return -ENOENT;
}

+static void pfnmap_init(void)
+{
+ size_t pagesize = getpagesize();
+ size_t size = DEV_MEM_NPAGES * pagesize;
+ int fd;
+ void *addr;
+
+ if (strncmp(file, "/dev/mem", strlen("/dev/mem")) == 0) {
+ int err = find_ram_target(&file_offset, pagesize);
+
+ if (err)
+ ksft_exit_skip("Cannot find ram target in '/proc/iomem': %s\n",
+ strerror(-err));
+ } else {
+ file_offset = 0;
+ }
+
+ /*
+ * Make sure we can open and map the file, and perform some basic
+ * checks; skip the whole suite if anything goes wrong.
+ * A fresh mapping is then created for every test case by
+ * FIXTURE_SETUP(pfnmap).
+ */
+ fd = open(file, O_RDONLY);
+ if (fd < 0)
+ ksft_exit_skip("Cannot open '%s': %s\n", file, strerror(errno));
+
+ addr = mmap(NULL, size, PROT_READ, MAP_SHARED, fd, file_offset);
+ if (addr == MAP_FAILED)
+ ksft_exit_skip("Cannot mmap '%s': %s\n", file, strerror(errno));
+
+ if (!check_vmflag_pfnmap(addr))
+ ksft_exit_skip("Invalid file: '%s'. Not pfnmap'ed\n", file);
+
+ if (test_read_access(addr, size))
+ ksft_exit_skip("Cannot read-access mmap'ed '%s'\n", file);
+
+ munmap(addr, size);
+ close(fd);
+}
+
FIXTURE(pfnmap)
{
- off_t offset;
size_t pagesize;
int dev_mem_fd;
char *addr1;
@@ -112,31 +155,13 @@ FIXTURE_SETUP(pfnmap)
{
self->pagesize = getpagesize();

- if (strncmp(file, "/dev/mem", strlen("/dev/mem")) == 0) {
- /* We'll require two physical pages throughout our tests ... */
- if (find_ram_target(&self->offset, self->pagesize))
- SKIP(return,
- "Cannot find ram target in '/proc/iomem'\n");
- } else {
- self->offset = 0;
- }
-
self->dev_mem_fd = open(file, O_RDONLY);
- if (self->dev_mem_fd < 0)
- SKIP(return, "Cannot open '%s'\n", file);
+ ASSERT_GE(self->dev_mem_fd, 0);

- self->size1 = self->pagesize * 2;
+ self->size1 = DEV_MEM_NPAGES * self->pagesize;
self->addr1 = mmap(NULL, self->size1, PROT_READ, MAP_SHARED,
- self->dev_mem_fd, self->offset);
- if (self->addr1 == MAP_FAILED)
- SKIP(return, "Cannot mmap '%s'\n", file);
-
- if (!check_vmflag_pfnmap(self->addr1))
- SKIP(return, "Invalid file: '%s'. Not pfnmap'ed\n", file);
-
- /* ... and want to be able to read from them. */
- if (test_read_access(self->addr1, self->size1))
- SKIP(return, "Cannot read-access mmap'ed '%s'\n", file);
+ self->dev_mem_fd, file_offset);
+ ASSERT_NE(self->addr1, MAP_FAILED);

self->size2 = 0;
self->addr2 = MAP_FAILED;
@@ -189,7 +214,7 @@ TEST_F(pfnmap, munmap_split)
*/
self->size2 = self->pagesize;
self->addr2 = mmap(NULL, self->pagesize, PROT_READ, MAP_SHARED,
- self->dev_mem_fd, self->offset);
+ self->dev_mem_fd, file_offset);
ASSERT_NE(self->addr2, MAP_FAILED);
}

@@ -258,8 +283,12 @@ int main(int argc, char **argv)
if (strcmp(argv[i], "--") == 0) {
if (i + 1 < argc && strlen(argv[i + 1]) > 0)
file = argv[i + 1];
- return test_harness_run(i, argv);
+ argc = i;
+ break;
}
}
+
+ pfnmap_init();
+
return test_harness_run(argc, argv);
}
--
2.51.2