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.txt
	TAP version 13
	1..1
	# Starting 1 tests from 1 test cases.
	#  RUN           pfnmap.madvise_disallowed ...
	#      SKIP      Invalid file: 'randfile.txt'. Not pfnmap'ed

Link: https://lkml.kernel.org/r/20250805013629.47629-1-sudarsanm@google.com
Signed-off-by: Sudarsan Mahendran <sudarsanm@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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)
 {
@@ -51,7 +53,7 @@ static int test_read_access(char *addr, size_t size, size_t pagesize)
 	return ret;
 }
 
-static int find_ram_target(off_t *phys_addr,
+static int find_ram_target(off_t *offset,
 		unsigned long long pagesize)
 {
 	unsigned long long start, end;
@@ -91,7 +93,7 @@ static int find_ram_target(off_t *phys_addr,
 		/* We need two pages. */
 		if (end > start + 2 * pagesize) {
 			fclose(file);
-			*phys_addr = start;
+			*offset = start;
 			return 0;
 		}
 	}
@@ -100,7 +102,7 @@ static int find_ram_target(off_t *phys_addr,
 
 FIXTURE(pfnmap)
 {
-	off_t phys_addr;
+	off_t offset;
 	size_t pagesize;
 	int dev_mem_fd;
 	char *addr1;
@@ -113,23 +115,31 @@ 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->offset, self->pagesize))
+			SKIP(return,
+				   "Cannot find ram target in '/proc/iomem'\n");
+	} else {
+		self->offset = 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);
+			   self->dev_mem_fd, self->offset);
 	if (self->addr1 == MAP_FAILED)
-		SKIP(return, "Cannot mmap '/dev/mem'\n");
+		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, 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;
@@ -182,7 +192,7 @@ TEST_F(pfnmap, munmap_split)
 	 */
 	self->size2 = self->pagesize;
 	self->addr2 = mmap(NULL, self->pagesize, PROT_READ, MAP_SHARED,
-			   self->dev_mem_fd, self->phys_addr);
+			   self->dev_mem_fd, self->offset);
 	ASSERT_NE(self->addr2, MAP_FAILED);
 }
 
@@ -246,4 +256,14 @@ 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);
+}

tools/testing/selftests/mm/vm_util.c

@@ -402,7 +402,7 @@ unsigned long get_free_hugepages(void)
 	return fhp;
 }
 
-bool check_vmflag_io(void *addr)
+static bool check_vmflag(void *addr, const char *flag)
 {
 	char buffer[MAX_LINE_LENGTH];
 	const char *flags;
@@ -419,13 +419,23 @@ bool check_vmflag_io(void *addr)
 		if (!flaglen)
 			return false;
 
-		if (flaglen == strlen("io") && !memcmp(flags, "io", flaglen))
+		if (flaglen == strlen(flag) && !memcmp(flags, flag, flaglen))
 			return true;
 
 		flags += flaglen;
 	}
 }
 
+bool check_vmflag_io(void *addr)
+{
+	return check_vmflag(addr, "io");
+}
+
+bool check_vmflag_pfnmap(void *addr)
+{
+	return check_vmflag(addr, "pf");
+}
+
 /*
  * Open an fd at /proc/$pid/maps and configure procmap_out ready for
  * PROCMAP_QUERY query. Returns 0 on success, or an error code otherwise.

tools/testing/selftests/mm/vm_util.h

@@ -93,6 +93,7 @@ int uffd_register_with_ioctls(int uffd, void *addr, uint64_t len,
 			      bool miss, bool wp, bool minor, uint64_t *ioctls);
 unsigned long get_free_hugepages(void);
 bool check_vmflag_io(void *addr);
+bool check_vmflag_pfnmap(void *addr);
 int open_procmap(pid_t pid, struct procmap_fd *procmap_out);
 int query_procmap(struct procmap_fd *procmap);
 bool find_vma_procmap(struct procmap_fd *procmap, void *address);