78 lines · c
1// SPDX-License-Identifier: GPL-2.02#include <stdio.h>3#include <sys/mman.h>4#include <unistd.h>5 6#include "utils.h"7 8/* This must match the huge page & THP size */9#define SIZE (16 * 1024 * 1024)10 11static int test_body(void)12{13 void *addr;14 char *p;15 16 addr = (void *)0xa0000000;17 18 p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,19 MAP_HUGETLB | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);20 if (p != MAP_FAILED) {21 /*22 * Typically the mmap will fail because no huge pages are23 * allocated on the system. But if there are huge pages24 * allocated the mmap will succeed. That's fine too, we just25 * munmap here before continuing. munmap() length of26 * MAP_HUGETLB memory must be hugepage aligned.27 */28 if (munmap(addr, SIZE)) {29 perror("munmap");30 return 1;31 }32 }33 34 p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,35 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);36 if (p == MAP_FAILED) {37 printf("Mapping failed @ %p\n", addr);38 perror("mmap");39 return 1;40 }41 42 /*43 * Either a user or kernel access is sufficient to trigger the bug.44 * A kernel access is easier to spot & debug, as it will trigger the45 * softlockup or RCU stall detectors, and when the system is kicked46 * into xmon we get a backtrace in the kernel.47 *48 * A good option is:49 * getcwd(p, SIZE);50 *51 * For the purposes of this testcase it's preferable to spin in52 * userspace, so the harness can kill us if we get stuck. That way we53 * see a test failure rather than a dead system.54 */55 *p = 0xf;56 57 munmap(addr, SIZE);58 59 return 0;60}61 62static int test_main(void)63{64 int i;65 66 /* 10,000 because it's a "bunch", and completes reasonably quickly */67 for (i = 0; i < 10000; i++)68 if (test_body())69 return 1;70 71 return 0;72}73 74int main(void)75{76 return test_harness(test_main, "hugetlb_vs_thp");77}78