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 | |
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 | |
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 | |
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 | |
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 | |
177 | int main(int argc, char **argv) |
178 | { |
179 | test_harness(tm_signal_context_force_tm, "tm_signal_context_force_tm" ); |
180 | } |
181 | |