[PATCH] selftests/mm: pass filename as input param to VM_PFNMAP tests

[Sudarsan Mahendran]

Enable these tests to be run on other pfnmap'ed memory like
NVIDIA's EGM.

Add '--' as a separator to pass in file path. This allows
passing of cmd line arguments to kselftest_harness.
Use '/dev/mem' as default filename.

Existing test passes:
        pfnmap
        TAP version 13
        1..6
        # Starting 6 tests from 1 test cases.
        # PASSED: 6 / 6 tests passed.
        # Totals: pass:6 fail:0 xfail:0 xpass:0 skip:0 error:0

Pass params to kselftest_harness:
        pfnmap -r pfnmap:mremap_fixed
        TAP version 13
        1..1
        # Starting 1 tests from 1 test cases.
        #  RUN           pfnmap.mremap_fixed ...
        #            OK  pfnmap.mremap_fixed
        ok 1 pfnmap.mremap_fixed
        # PASSED: 1 / 1 tests passed.
        # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0

Pass random file name as input:
        pfnmap -- /dev/blah
        TAP version 13
        1..6
        # Starting 6 tests from 1 test cases.
        #  RUN           pfnmap.madvise_disallowed ...
        #      SKIP      Cannot open '/dev/blah'

Signed-off-by: Sudarsan Mahendran <sudars...@google.com>
---
 tools/testing/selftests/mm/pfnmap.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/mm/pfnmap.c 
b/tools/testing/selftests/mm/pfnmap.c
index 866ac023baf5..2d4e8b165f91 100644
--- a/tools/testing/selftests/mm/pfnmap.c
+++ b/tools/testing/selftests/mm/pfnmap.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * Basic VM_PFNMAP tests relying on mmap() of '/dev/mem'
+ * Basic VM_PFNMAP tests relying on mmap() of input file provided.
+ * Use '/dev/mem' as default.
  *
  * Copyright 2025, Red Hat, Inc.
  *
@@ -25,6 +26,7 @@
 #include "vm_util.h"
 
 static sigjmp_buf sigjmp_buf_env;
+static char *file = "/dev/mem";
 
 static void signal_handler(int sig)
 {
@@ -117,19 +119,19 @@ FIXTURE_SETUP(pfnmap)
        if (find_ram_target(&self->phys_addr, self->pagesize))
                SKIP(return, "Cannot find ram target in '/proc/iomem'\n");
 
-       self->dev_mem_fd = open("/dev/mem", O_RDONLY);
+       self->dev_mem_fd = open(file, O_RDONLY);
        if (self->dev_mem_fd < 0)
-               SKIP(return, "Cannot open '/dev/mem'\n");
+               SKIP(return, "Cannot open '%s'\n", file);
 
        self->size1 = self->pagesize * 2;
        self->addr1 = mmap(NULL, self->size1, PROT_READ, MAP_SHARED,
                           self->dev_mem_fd, self->phys_addr);
        if (self->addr1 == MAP_FAILED)
-               SKIP(return, "Cannot mmap '/dev/mem'\n");
+               SKIP(return, "Cannot mmap '%s'\n", file);
 
        /* ... and want to be able to read from them. */
        if (test_read_access(self->addr1, self->size1, self->pagesize))
-               SKIP(return, "Cannot read-access mmap'ed '/dev/mem'\n");
+               SKIP(return, "Cannot read-access mmap'ed '%s'\n", file);
 
        self->size2 = 0;
        self->addr2 = MAP_FAILED;
@@ -246,4 +248,14 @@ TEST_F(pfnmap, fork)
        ASSERT_EQ(ret, 0);
 }
 
-TEST_HARNESS_MAIN
+int main(int argc, char **argv)
+{
+       for (int i = 1; i < argc; i++) {
+               if (strcmp(argv[i], "--") == 0) {
+                       if (i + 1 < argc && strlen(argv[i + 1]) > 0)
+                               file = argv[i + 1];
+                       return test_harness_run(i, argv);
+               }
+       }
+       return test_harness_run(argc, argv);
+}
-- 
2.50.1.565.gc32cd1483b-goog