1 // SPDX-License-Identifier: GPL-2.0
2 /*
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 will
7 * force a recheckpoint, which may cause a segfault when returning to
8 * user space. Since the test needs to re-run, the segfault needs to be
9 * caught and handled.
10 *
11 * In order to continue the test even after a segfault, the context is
12 * saved prior to the signal being raised, and it is restored when there is
13 * 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_SOURCE
20 #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 avoid
36 * compilation issue on 32 bits system. There is no side effect, since the
37 * whole test will be skipped if it is not running on 64 bits system.
38 */
39 #ifndef __powerpc64__
40 #undef MSR_TS_S
41 #define MSR_TS_S 0
42 #endif
43
44 /* Setting contexts because the test will crash and we want to recover */
45 ucontext_t init_context;
46
47 /* count is changed in the signal handler, so it must be volatile */
48 static volatile int count;
49
usr_signal_handler(int signo,siginfo_t * si,void * uc)50 void 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 on
57 * purpose, forcing the heap increase, so, the memory leak is what
58 * 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 a
83 * fork() prior to the signal being raised.
84 */
85 if (fork() == 0) {
86 /*
87 * Both child and parent will return, but, child returns
88 * 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 a
96 * segmentation fault, since the ck structures are NULL.
97 */
98 }
99
seg_signal_handler(int signo,siginfo_t * si,void * uc)100 void seg_signal_handler(int signo, siginfo_t *si, void *uc)
101 {
102 count++;
103
104 /* Reexecute the test */
105 setcontext(&init_context);
106 }
107
tm_trap_test(void)108 void 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 from
121 * 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 when
145 * 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
tm_signal_context_force_tm(void)162 int 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 is
167 * not possible to set mcontext's [MSR] with TS, due to it being 32
168 * bits.
169 */
170 SKIP_IF(!is_ppc64le());
171
172 tm_trap_test();
173
174 return EXIT_SUCCESS;
175 }
176
main(int argc,char ** argv)177 int main(int argc, char **argv)
178 {
179 test_harness(tm_signal_context_force_tm, "tm_signal_context_force_tm");
180 }
181