new file mode 100644
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * A test case of using hugepage memory in a user application using the
+ * mmap system call with MAP_HUGETLB flag. Before running this program
+ * make sure the administrator has allocated enough default sized huge
+ * pages to cover the 2 MB allocation.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+
+#define MAP_LENGTH (2UL * 1024 * 1024)
+
+#ifndef MAP_HUGETLB
+#define MAP_HUGETLB 0x40000 /* arch specific */
+#endif
+
+#define PAGE_SIZE 4096
+
+#define PAGE_COMPOUND_HEAD (1UL << 15)
+#define PAGE_COMPOUND_TAIL (1UL << 16)
+#define PAGE_HUGE (1UL << 17)
+
+#define HEAD_PAGE_FLAGS (PAGE_COMPOUND_HEAD | PAGE_HUGE)
+#define TAIL_PAGE_FLAGS (PAGE_COMPOUND_TAIL | PAGE_HUGE)
+
+#define PM_PFRAME_BITS 55
+#define PM_PFRAME_MASK ~((1UL << PM_PFRAME_BITS) - 1)
+
+/*
+ * For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
+ * That means the addresses starting with 0x800000... will need to be
+ * specified. Specifying a fixed address is not required on ppc64, i386
+ * or x86_64.
+ */
+#ifdef __ia64__
+#define MAP_ADDR (void *)(0x8000000000000000UL)
+#define MAP_FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
+#else
+#define MAP_ADDR NULL
+#define MAP_FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
+#endif
+
+static void write_bytes(char *addr, size_t length)
+{
+ unsigned long i;
+
+ for (i = 0; i < length; i++)
+ *(addr + i) = (char)i;
+}
+
+static unsigned long virt_to_pfn(void *addr)
+{
+ int fd;
+ unsigned long pagemap;
+
+ fd = open("/proc/self/pagemap", O_RDONLY);
+ if (fd < 0)
+ return -1UL;
+
+ lseek(fd, (unsigned long)addr / PAGE_SIZE * sizeof(pagemap), SEEK_SET);
+ read(fd, &pagemap, sizeof(pagemap));
+ close(fd);
+
+ return pagemap & ~PM_PFRAME_MASK;
+}
+
+static int check_page_flags(unsigned long pfn)
+{
+ int fd, i;
+ unsigned long pageflags;
+
+ fd = open("/proc/kpageflags", O_RDONLY);
+ if (fd < 0)
+ return -1;
+
+ lseek(fd, pfn * sizeof(pageflags), SEEK_SET);
+
+ read(fd, &pageflags, sizeof(pageflags));
+ if ((pageflags & HEAD_PAGE_FLAGS) != HEAD_PAGE_FLAGS) {
+ close(fd);
+ printf("Head page flags (%lx) is invalid\n", pageflags);
+ return -1;
+ }
+
+ /*
+ * pages other than the first page must be tail and shouldn't be head;
+ * 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++) {
+ read(fd, &pageflags, sizeof(pageflags));
+ if ((pageflags & TAIL_PAGE_FLAGS) != TAIL_PAGE_FLAGS ||
+ (pageflags & HEAD_PAGE_FLAGS) == HEAD_PAGE_FLAGS) {
+ close(fd);
+ printf("Tail page flags (%lx) is invalid\n", pageflags);
+ return -1;
+ }
+ }
+
+ close(fd);
+
+ return 0;
+}
+
+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);
+ if (addr == MAP_FAILED) {
+ perror("mmap");
+ exit(1);
+ }
+
+ /* Trigger allocation of HugeTLB page. */
+ write_bytes(addr, MAP_LENGTH);
+
+ pfn = virt_to_pfn(addr);
+ if (pfn == -1UL) {
+ munmap(addr, MAP_LENGTH);
+ 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);
+ perror("check_page_flags");
+ exit(1);
+ }
+
+ /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
+ if (munmap(addr, MAP_LENGTH)) {
+ perror("munmap");
+ exit(1);
+ }
+
+ return 0;
+}