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1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright 2018, Breno Leitao, Gustavo Romero, IBM Corp.4 *5 * This test raises a SIGUSR1 signal, and toggle the MSR[TS]6 * fields at the signal handler. With MSR[TS] being set, the kernel will7 * force a recheckpoint, which may cause a segfault when returning to8 * user space. Since the test needs to re-run, the segfault needs to be9 * caught and handled.10 *11 * In order to continue the test even after a segfault, the context is12 * saved prior to the signal being raised, and it is restored when there is13 * a segmentation fault. This happens for COUNT_MAX times.14 *15 * This test never fails (as returning EXIT_FAILURE). It either succeeds,16 * or crash the kernel (on a buggy kernel).17 */18 19#define _GNU_SOURCE20#include <stdio.h>21#include <stdlib.h>22#include <signal.h>23#include <string.h>24#include <ucontext.h>25#include <unistd.h>26#include <sys/mman.h>27 28#include "tm.h"29#include "utils.h"30#include "reg.h"31 32#define COUNT_MAX 5000 /* Number of interactions */33 34/*35 * This test only runs on 64 bits system. Unsetting MSR_TS_S to avoid36 * compilation issue on 32 bits system. There is no side effect, since the37 * whole test will be skipped if it is not running on 64 bits system.38 */39#ifndef __powerpc64__40#undef MSR_TS_S41#define MSR_TS_S 042#endif43 44/* Setting contexts because the test will crash and we want to recover */45ucontext_t init_context;46 47/* count is changed in the signal handler, so it must be volatile */48static volatile int count;49 50void usr_signal_handler(int signo, siginfo_t *si, void *uc)51{52 ucontext_t *ucp = uc;53 int ret;54 55 /*56 * Allocating memory in a signal handler, and never freeing it on57 * purpose, forcing the heap increase, so, the memory leak is what58 * we want here.59 */60 ucp->uc_link = mmap(NULL, sizeof(ucontext_t),61 PROT_READ | PROT_WRITE,62 MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);63 if (ucp->uc_link == (void *)-1) {64 perror("Mmap failed");65 exit(-1);66 }67 68 /* Forcing the page to be allocated in a page fault */69 ret = madvise(ucp->uc_link, sizeof(ucontext_t), MADV_DONTNEED);70 if (ret) {71 perror("madvise failed");72 exit(-1);73 }74 75 memcpy(&ucp->uc_link->uc_mcontext, &ucp->uc_mcontext,76 sizeof(ucp->uc_mcontext));77 78 /* Forcing to enable MSR[TM] */79 UCONTEXT_MSR(ucp) |= MSR_TS_S;80 81 /*82 * A fork inside a signal handler seems to be more efficient than a83 * fork() prior to the signal being raised.84 */85 if (fork() == 0) {86 /*87 * Both child and parent will return, but, child returns88 * with count set so it will exit in the next segfault.89 * Parent will continue to loop.90 */91 count = COUNT_MAX;92 }93 94 /*95 * If the change above does not hit the bug, it will cause a96 * segmentation fault, since the ck structures are NULL.97 */98}99 100void seg_signal_handler(int signo, siginfo_t *si, void *uc)101{102 count++;103 104 /* Reexecute the test */105 setcontext(&init_context);106}107 108void tm_trap_test(void)109{110 struct sigaction usr_sa, seg_sa;111 stack_t ss;112 113 usr_sa.sa_flags = SA_SIGINFO | SA_ONSTACK;114 usr_sa.sa_sigaction = usr_signal_handler;115 116 seg_sa.sa_flags = SA_SIGINFO;117 seg_sa.sa_sigaction = seg_signal_handler;118 119 /*120 * Set initial context. Will get back here from121 * seg_signal_handler()122 */123 getcontext(&init_context);124 125 while (count < COUNT_MAX) {126 /* Allocated an alternative signal stack area */127 ss.ss_sp = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,128 MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);129 ss.ss_size = SIGSTKSZ;130 ss.ss_flags = 0;131 132 if (ss.ss_sp == (void *)-1) {133 perror("mmap error\n");134 exit(-1);135 }136 137 /* Force the allocation through a page fault */138 if (madvise(ss.ss_sp, SIGSTKSZ, MADV_DONTNEED)) {139 perror("madvise\n");140 exit(-1);141 }142 143 /*144 * Setting an alternative stack to generate a page fault when145 * the signal is raised.146 */147 if (sigaltstack(&ss, NULL)) {148 perror("sigaltstack\n");149 exit(-1);150 }151 152 /* The signal handler will enable MSR_TS */153 sigaction(SIGUSR1, &usr_sa, NULL);154 /* If it does not crash, it might segfault, avoid it to retest */155 sigaction(SIGSEGV, &seg_sa, NULL);156 157 raise(SIGUSR1);158 count++;159 }160}161 162int tm_signal_context_force_tm(void)163{164 SKIP_IF(!have_htm());165 /*166 * Skipping if not running on 64 bits system, since I think it is167 * not possible to set mcontext's [MSR] with TS, due to it being 32168 * bits.169 */170 SKIP_IF(!is_ppc64le());171 172 tm_trap_test();173 174 return EXIT_SUCCESS;175}176 177int main(int argc, char **argv)178{179 test_harness(tm_signal_context_force_tm, "tm_signal_context_force_tm");180}181