// SPDX-License-Identifier: GPL-2.0
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/*
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* Example of using hugepage memory in a user application using the mmap
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* system call with MAP_HUGETLB flag. Before running this program make
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* sure the administrator has allocated enough default sized huge pages
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* to cover the 256 MB allocation.
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*
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* For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
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* That means the addresses starting with 0x800000... will need to be
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* specified. Specifying a fixed address is not required on ppc64, i386
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* or x86_64.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/mman.h>
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#include <fcntl.h>
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#define LENGTH (256UL*1024*1024)
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#define PROTECTION (PROT_READ | PROT_WRITE)
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#ifndef MAP_HUGETLB
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#define MAP_HUGETLB 0x40000 /* arch specific */
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#endif
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#ifndef MAP_HUGE_SHIFT
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#define MAP_HUGE_SHIFT 26
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#endif
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#ifndef MAP_HUGE_MASK
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#define MAP_HUGE_MASK 0x3f
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#endif
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/* Only ia64 requires this */
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#ifdef __ia64__
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#define ADDR (void *)(0x8000000000000000UL)
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#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
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#else
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#define ADDR (void *)(0x0UL)
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#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
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#endif
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static void check_bytes(char *addr)
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{
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printf("First hex is %x\n", *((unsigned int *)addr));
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}
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static void write_bytes(char *addr, size_t length)
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{
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unsigned long i;
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for (i = 0; i < length; i++)
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*(addr + i) = (char)i;
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}
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static int read_bytes(char *addr, size_t length)
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{
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unsigned long i;
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check_bytes(addr);
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for (i = 0; i < length; i++)
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if (*(addr + i) != (char)i) {
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printf("Mismatch at %lu\n", i);
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return 1;
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}
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return 0;
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}
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int main(int argc, char **argv)
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{
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void *addr;
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int ret;
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size_t length = LENGTH;
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int flags = FLAGS;
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int shift = 0;
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if (argc > 1)
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length = atol(argv[1]) << 20;
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if (argc > 2) {
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shift = atoi(argv[2]);
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if (shift)
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flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
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}
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if (shift)
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printf("%u kB hugepages\n", 1 << (shift - 10));
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else
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printf("Default size hugepages\n");
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printf("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
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addr = mmap(ADDR, length, PROTECTION, flags, -1, 0);
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if (addr == MAP_FAILED) {
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perror("mmap");
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exit(1);
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}
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printf("Returned address is %p\n", addr);
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check_bytes(addr);
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write_bytes(addr, length);
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ret = read_bytes(addr, length);
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/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
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if (munmap(addr, length)) {
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perror("munmap");
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exit(1);
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}
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return ret;
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}
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