selftests: mm: hugepage-vmemmap fails on 64K page size systems

The kernel sefltest mm/hugepage-vmemmap fails on architectures which has
different page size other than 4K.  In hugepage-vmemmap page size used is
4k so the pfn calculation will go wrong on systems which has different
page size .The length of MAP_HUGETLB memory must be hugepage aligned but
in hugepage-vmemmap map length is 2M so this will not get aligned if the
system has differnet hugepage size.

Added  psize() to get the page size and default_huge_page_size() to
get the default hugepage size at run time, hugepage-vmemmap test pass
on powerpc with 64K page size and x86 with 4K page size.

Result on powerpc without patch (page size 64K)
*# ./hugepage-vmemmap
Returned address is 0x7effff000000 whose pfn is 0
Head page flags (100000000) is invalid
check_page_flags: Invalid argument
*#

Result on powerpc with patch (page size 64K)
*# ./hugepage-vmemmap
Returned address is 0x7effff000000 whose pfn is 600
*#

Result on x86 with patch (page size 4K)
*# ./hugepage-vmemmap
Returned address is 0x7fc7c2c00000 whose pfn is 1dac00
*#

Link: https://lkml.kernel.org/r/3b3a3ae37ba21218481c482a872bbf7526031600.1704865754.git.donettom@linux.vnet.ibm.com
Fixes: b147c89 ("selftests: vm: add a hugetlb test case")
Signed-off-by: Donet Tom <donettom@linux.vnet.ibm.com>
Reported-by: Geetika Moolchandani <geetika@linux.ibm.com>
Tested-by: Geetika Moolchandani <geetika@linux.ibm.com>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: DonetTom1

tools/testing/selftests/mm/hugepage-vmemmap.c

@@ -10,10 +10,7 @@
 #include <unistd.h>
 #include <sys/mman.h>
 #include <fcntl.h>
-
-#define MAP_LENGTH		(2UL * 1024 * 1024)
-
-#define PAGE_SIZE		4096
+#include "vm_util.h"
 
 #define PAGE_COMPOUND_HEAD	(1UL << 15)
 #define PAGE_COMPOUND_TAIL	(1UL << 16)
@@ -39,6 +36,9 @@
 #define MAP_FLAGS		(MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
 #endif
 
+static size_t pagesize;
+static size_t maplength;
+
 static void write_bytes(char *addr, size_t length)
 {
 	unsigned long i;
@@ -56,7 +56,7 @@ static unsigned long virt_to_pfn(void *addr)
 	if (fd < 0)
 		return -1UL;
 
-	lseek(fd, (unsigned long)addr / PAGE_SIZE * sizeof(pagemap), SEEK_SET);
+	lseek(fd, (unsigned long)addr / pagesize * sizeof(pagemap), SEEK_SET);
 	read(fd, &pagemap, sizeof(pagemap));
 	close(fd);
 
@@ -86,7 +86,7 @@ static int check_page_flags(unsigned long pfn)
 	 * this also verifies kernel has correctly set the fake page_head to tail
 	 * while hugetlb_free_vmemmap is enabled.
 	 */
-	for (i = 1; i < MAP_LENGTH / PAGE_SIZE; i++) {
+	for (i = 1; i < maplength / pagesize; i++) {
 		read(fd, &pageflags, sizeof(pageflags));
 		if ((pageflags & TAIL_PAGE_FLAGS) != TAIL_PAGE_FLAGS ||
 		    (pageflags & HEAD_PAGE_FLAGS) == HEAD_PAGE_FLAGS) {
@@ -106,32 +106,39 @@ int main(int argc, char **argv)
 	void *addr;
 	unsigned long pfn;
 
-	addr = mmap(MAP_ADDR, MAP_LENGTH, PROT_READ | PROT_WRITE, MAP_FLAGS, -1, 0);
+	pagesize  = psize();
+	maplength = default_huge_page_size();
+	if (!maplength) {
+		printf("Unable to determine huge page size\n");
+		exit(1);
+	}
+
+	addr = mmap(MAP_ADDR, maplength, PROT_READ | PROT_WRITE, MAP_FLAGS, -1, 0);
 	if (addr == MAP_FAILED) {
 		perror("mmap");
 		exit(1);
 	}
 
 	/* Trigger allocation of HugeTLB page. */
-	write_bytes(addr, MAP_LENGTH);
+	write_bytes(addr, maplength);
 
 	pfn = virt_to_pfn(addr);
 	if (pfn == -1UL) {
-		munmap(addr, MAP_LENGTH);
+		munmap(addr, maplength);
 		perror("virt_to_pfn");
 		exit(1);
 	}
 
 	printf("Returned address is %p whose pfn is %lx\n", addr, pfn);
 
 	if (check_page_flags(pfn) < 0) {
-		munmap(addr, MAP_LENGTH);
+		munmap(addr, maplength);
 		perror("check_page_flags");
 		exit(1);
 	}
 
 	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
-	if (munmap(addr, MAP_LENGTH)) {
+	if (munmap(addr, maplength)) {
 		perror("munmap");
 		exit(1);
 	}