1 /* $NetBSD: t_sigstack.c,v 1.12 2024/07/17 07:11:57 uwe Exp $ */ 2 3 /*- 4 * Copyright (c) 2024 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26 * POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __RCSID("$NetBSD: t_sigstack.c,v 1.12 2024/07/17 07:11:57 uwe Exp $"); 31 32 #include <setjmp.h> 33 #include <signal.h> 34 #include <stddef.h> 35 #include <stdlib.h> 36 #include <ucontext.h> 37 38 #include "h_macros.h" 39 40 struct sigaltstack ss[3]; 41 jmp_buf jmp; 42 sigjmp_buf sigjmp; 43 unsigned nentries; 44 const char *bailname; 45 void (*bailfn)(void) __dead; 46 47 static void 48 on_sigusr1(int signo, siginfo_t *si, void *ctx) 49 { 50 ucontext_t *uc = ctx; 51 void *sp = (void *)(uintptr_t)_UC_MACHINE_SP(uc); 52 void *fp = __builtin_frame_address(0); 53 struct sigaltstack *ssp; 54 55 /* 56 * Ensure we haven't re-entered the signal handler too many 57 * times. We should enter only twice. 58 */ 59 ATF_REQUIRE_MSG(nentries < 2, 60 "%u recursive signal handler entries is too many in this test", 61 nentries + 1); 62 63 /* 64 * Ensure that the signal handler was called in the alternate 65 * signal stack. 66 */ 67 ssp = &ss[nentries]; 68 ATF_REQUIRE_MSG((fp >= ssp->ss_sp && 69 fp < (void *)((char *)ssp->ss_sp + ssp->ss_size)), 70 "sigaltstack failed to take effect on entry %u --" 71 " signal handler's frame pointer %p doesn't lie in sigaltstack" 72 " [%p, %p), size 0x%zx", 73 nentries, 74 fp, ssp->ss_sp, (char *)ssp->ss_sp + ssp->ss_size, ssp->ss_size); 75 76 /* 77 * Ensure that if we enter the signal handler, we are entering 78 * it from the original stack, not from any of the alternate 79 * signal stacks. 80 * 81 * On some architectures, this is broken. Those that appear to 82 * get this right are: 83 * 84 * aarch64 85 * alpha 86 * arm 87 * i386 88 * m68k 89 * or1k 90 * powerpc 91 * powerpc64 92 * riscv 93 * vax 94 * x86_64 95 */ 96 #if defined __hppa__ || \ 97 defined __ia64__ || defined __mips__ || \ 98 defined __sparc__ || defined __sparc64__ 99 if (nentries > 0) 100 atf_tc_expect_fail("PR lib/57946"); 101 #endif 102 for (ssp = &ss[0]; ssp < &ss[__arraycount(ss)]; ssp++) { 103 ATF_REQUIRE_MSG((sp < ssp->ss_sp || 104 sp >= (void *)((char *)ssp->ss_sp + ssp->ss_size)), 105 "%s failed to restore stack" 106 " before allowing signal on entry %u --" 107 " interrupted stack pointer %p lies in sigaltstack %zd" 108 " [%p, %p), size 0x%zx", 109 bailname, 110 nentries, 111 sp, ssp - ss, 112 ssp->ss_sp, (char *)ssp->ss_sp + ssp->ss_size, 113 ssp->ss_size); 114 } 115 116 /* 117 * First time through, we want to test whether longjmp restores 118 * the signal mask first, or restores the stack pointer first. 119 * The signal should be blocked at this point, so we re-raise 120 * the signal to queue it up for delivery as soon as it is 121 * unmasked -- which should wait until the stack pointer has 122 * been restored in longjmp. 123 */ 124 if (nentries++ == 0) 125 RL(raise(SIGUSR1)); 126 127 /* 128 * Set up the next sigaltstack. We can't reuse the current one 129 * for the next signal handler re-entry until the system clears 130 * the SS_ONSTACK process state -- which normal return from 131 * signal handler does, but which longjmp does not. So to keep 132 * it simple (ha), we just use another sigaltstack. 133 */ 134 RL(sigaltstack(&ss[nentries], NULL)); 135 136 /* 137 * Jump back to the original context. 138 */ 139 (*bailfn)(); 140 } 141 142 static void 143 go(const char *name, void (*fn)(void) __dead) 144 { 145 struct sigaction sa; 146 unsigned i; 147 148 bailname = name; 149 bailfn = fn; 150 151 /* 152 * Allocate a stack for the signal handler to run in, and 153 * configure the system to use the first one. 154 * 155 * XXX Should maybe use a guard page but this is simpler. 156 */ 157 for (i = 0; i < __arraycount(ss); i++) { 158 ss[i].ss_size = SIGSTKSZ; 159 REQUIRE_LIBC(ss[i].ss_sp = malloc(ss[i].ss_size), NULL); 160 } 161 RL(sigaltstack(&ss[0], NULL)); 162 163 /* 164 * Set up a test signal handler for SIGUSR1. Allow all 165 * signals, except SIGUSR1 (which is masked by default) -- that 166 * way we don't inadvertently obscure weird crashes in the 167 * signal handler. 168 * 169 * Set SA_SIGINFO so the system will pass siginfo -- and, more 170 * to the point, ucontext, so the signal handler can determine 171 * the stack pointer of the logic it interrupted. 172 * 173 * Set SA_ONSTACK so the system will use the alternate signal 174 * stack to call the signal handler -- that way, it can tell 175 * whether the stack was restored before the second time 176 * around. 177 */ 178 memset(&sa, 0, sizeof(sa)); 179 sa.sa_sigaction = &on_sigusr1; 180 RL(sigemptyset(&sa.sa_mask)); 181 sa.sa_flags = SA_SIGINFO|SA_ONSTACK; 182 RL(sigaction(SIGUSR1, &sa, NULL)); 183 184 /* 185 * Raise the signal to enter the signal handler the first time. 186 */ 187 RL(raise(SIGUSR1)); 188 189 /* 190 * If we ever reach this point, something went seriously wrong. 191 */ 192 atf_tc_fail("unreachable"); 193 } 194 195 static void __dead 196 bail_longjmp(void) 197 { 198 199 longjmp(jmp, 1); 200 } 201 202 ATF_TC(setjmp); 203 ATF_TC_HEAD(setjmp, tc) 204 { 205 atf_tc_set_md_var(tc, "descr", 206 "Test longjmp restores stack first, then signal mask"); 207 } 208 ATF_TC_BODY(setjmp, tc) 209 { 210 211 /* 212 * Set up a return point for the signal handler: when the 213 * signal handler does longjmp(jmp, 1), it comes flying out of 214 * here. 215 */ 216 if (setjmp(jmp) == 1) 217 return; 218 219 /* 220 * Run the test with longjmp. 221 */ 222 go("longjmp", &bail_longjmp); 223 } 224 225 static void __dead 226 bail_siglongjmp(void) 227 { 228 229 siglongjmp(sigjmp, 1); 230 } 231 232 ATF_TC(sigsetjmp); 233 ATF_TC_HEAD(sigsetjmp, tc) 234 { 235 atf_tc_set_md_var(tc, "descr", 236 "Test siglongjmp restores stack first, then signal mask"); 237 } 238 ATF_TC_BODY(sigsetjmp, tc) 239 { 240 241 /* 242 * Set up a return point for the signal handler: when the 243 * signal handler does siglongjmp(sigjmp, 1), it comes flying 244 * out of here. 245 */ 246 if (sigsetjmp(sigjmp, /*savesigmask*/1) == 1) 247 return; 248 249 /* 250 * Run the test with siglongjmp. 251 */ 252 go("siglongjmp", &bail_siglongjmp); 253 } 254 255 ATF_TP_ADD_TCS(tp) 256 { 257 258 ATF_TP_ADD_TC(tp, setjmp); 259 ATF_TP_ADD_TC(tp, sigsetjmp); 260 261 return atf_no_error(); 262 } 263