linux-kernel - [PATCH v2] selftests/mm: pass filename as input param to VM

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Message-ID: <20250801234559.1178521-1-sudarsanm@google.com>
Date: Fri,  1 Aug 2025 16:45:59 -0700
From: Sudarsan Mahendran <sudarsanm@...gle.com>
To: linux-kselftest@...r.kernel.org, David Hildenbrand <david@...hat.com>
Cc: Shuah Khan <shuah@...nel.org>, Axel Rasmussen <axelrasmussen@...gle.com>, linux-mm@...ck.org, 
	Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, 
	trivial@...nel.org, Sudarsan Mahendran <sudarsanm@...gle.com>
Subject: [PATCH v2] selftests/mm: pass filename as input param to VM_PFNMAP tests

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 non-existent 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'

Pass non pfnmap'ed file as input:
	pfnmap -r pfnmap.madvise_disallowed -- randfile
	TAP version 13
	1..1
	# Starting 1 tests from 1 test cases.
	#  RUN           pfnmap.madvise_disallowed ...
	#      SKIP      Invalid file: 'randfile'. Not pfnmap'ed

Signed-off-by: Sudarsan Mahendran <sudarsanm@...gle.com>
---

v1 -> v2:
* Add verify_pfnmap func to sanity check the input param
* mmap with zero offset if filename != '/dev/mem'

---
 tools/testing/selftests/mm/pfnmap.c | 62 ++++++++++++++++++++++++-----
 1 file changed, 53 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/mm/pfnmap.c b/tools/testing/selftests/mm/pfnmap.c
index 866ac023baf5..e078b961c333 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)
 {
@@ -98,6 +100,30 @@ static int find_ram_target(off_t *phys_addr,
 	return -ENOENT;
 }
 
+static int verify_pfnmap(void)
+{
+	FILE *smaps_fp;
+	char line[512];
+	int found_mmap_entry = 0;
+
+	smaps_fp = fopen("/proc/self/smaps", "r");
+	if (!smaps_fp)
+		return -errno;
+	while (fgets(line, sizeof(line), smaps_fp) != NULL) {
+		if (strstr(line, file) && strstr(line, " r--s "))
+			found_mmap_entry = 1;
+
+		if (found_mmap_entry &&
+		    strncmp(line, "VmFlags:", strlen("VmFlags:")) == 0) {
+			if (strstr(line, " pf "))
+				return 0;
+			found_mmap_entry = 0;
+		}
+	}
+	fclose(smaps_fp);
+	return -ENOENT;
+}
+
 FIXTURE(pfnmap)
 {
 	off_t phys_addr;
@@ -113,23 +139,31 @@ FIXTURE_SETUP(pfnmap)
 {
 	self->pagesize = getpagesize();
 
-	/* We'll require two physical pages throughout our tests ... */
-	if (find_ram_target(&self->phys_addr, self->pagesize))
-		SKIP(return, "Cannot find ram target in '/proc/iomem'\n");
+	if (strncmp(file, "/dev/mem", strlen("/dev/mem")) == 0) {
+		/* We'll require two physical pages throughout our tests ... */
+		if (find_ram_target(&self->phys_addr, self->pagesize))
+			SKIP(return,
+				   "Cannot find ram target in '/proc/iomem'\n");
+	} else {
+		self->phys_addr = 0;
+	}
 
-	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);
+
+	if (verify_pfnmap())
+		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, 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 +280,14 @@ 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