1 /* $NetBSD: t_sigstack.c,v 1.8 2024/04/04 00:46:30 riastradh 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 1.8 2024/04/04 00:46:30 riastradh 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, alpha, m68k, or1k, powerpc, powerpc64, riscv, 85 * vax, x86_64 86 */ 87 #if defined __arm__ || defined __hppa__ || defined __i386__ || \ 88 defined __ia64__ || defined __mips__ || defined __sh3__ || \ 89 defined __sparc__ || defined __sparc64__ 90 if (nentries > 0) 91 atf_tc_expect_fail("PR lib/57946"); 92 #endif 93 for (ssp = &ss[0]; ssp < &ss[__arraycount(ss)]; ssp++) { 94 ATF_REQUIRE_MSG((sp < ssp->ss_sp || 95 sp >= (void *)((char *)ssp->ss_sp + ssp->ss_size)), 96 "%s failed to restore stack" 97 " before allowing signal on entry %u --" 98 " interrupted stack pointer %p lies in sigaltstack %zd" 99 " [%p, %p), size 0x%zx", 100 bailname, 101 nentries, 102 sp, ssp - ss, 103 ssp->ss_sp, (char *)ssp->ss_sp + ssp->ss_size, 104 ssp->ss_size); 105 } 106 107 /* 108 * First time through, we want to test whether longjmp restores 109 * the signal mask first, or restores the stack pointer first. 110 * The signal should be blocked at this point, so we re-raise 111 * the signal to queue it up for delivery as soon as it is 112 * unmasked -- which should wait until the stack pointer has 113 * been restored in longjmp. 114 */ 115 if (nentries++ == 0) 116 RL(raise(SIGUSR1)); 117 118 /* 119 * Set up the next sigaltstack. We can't reuse the current one 120 * for the next signal handler re-entry until the system clears 121 * the SS_ONSTACK process state -- which normal return from 122 * signal handler does, but which longjmp does not. So to keep 123 * it simple (ha), we just use another sigaltstack. 124 */ 125 RL(sigaltstack(&ss[nentries], NULL)); 126 127 /* 128 * Jump back to the original context. 129 */ 130 (*bailfn)(); 131 } 132 133 static void 134 go(const char *name, void (*fn)(void) __dead) 135 { 136 struct sigaction sa; 137 unsigned i; 138 139 bailname = name; 140 bailfn = fn; 141 142 /* 143 * Allocate a stack for the signal handler to run in, and 144 * configure the system to use the first one. 145 * 146 * XXX Should maybe use a guard page but this is simpler. 147 */ 148 for (i = 0; i < __arraycount(ss); i++) { 149 ss[i].ss_size = SIGSTKSZ; 150 REQUIRE_LIBC(ss[i].ss_sp = malloc(ss[i].ss_size), NULL); 151 } 152 RL(sigaltstack(&ss[0], NULL)); 153 154 /* 155 * Set up a test signal handler for SIGUSR1. Allow all 156 * signals, except SIGUSR1 (which is masked by default) -- that 157 * way we don't inadvertently obscure weird crashes in the 158 * signal handler. 159 * 160 * Set SA_SIGINFO so the system will pass siginfo -- and, more 161 * to the point, ucontext, so the signal handler can determine 162 * the stack pointer of the logic it interrupted. 163 * 164 * Set SA_ONSTACK so the system will use the alternate signal 165 * stack to call the signal handler -- that way, it can tell 166 * whether the stack was restored before the second time 167 * around. 168 */ 169 memset(&sa, 0, sizeof(sa)); 170 sa.sa_sigaction = &on_sigusr1; 171 RL(sigemptyset(&sa.sa_mask)); 172 sa.sa_flags = SA_SIGINFO|SA_ONSTACK; 173 RL(sigaction(SIGUSR1, &sa, NULL)); 174 175 /* 176 * Raise the signal to enter the signal handler the first time. 177 */ 178 RL(raise(SIGUSR1)); 179 180 /* 181 * If we ever reach this point, something went seriously wrong. 182 */ 183 atf_tc_fail("unreachable"); 184 } 185 186 static void __dead 187 bail_longjmp(void) 188 { 189 190 longjmp(jmp, 1); 191 } 192 193 ATF_TC(setjmp); 194 ATF_TC_HEAD(setjmp, tc) 195 { 196 atf_tc_set_md_var(tc, "descr", 197 "Test longjmp restores stack first, then signal mask"); 198 } 199 ATF_TC_BODY(setjmp, tc) 200 { 201 202 /* 203 * Set up a return point for the signal handler: when the 204 * signal handler does longjmp(jmp, 1), it comes flying out of 205 * here. 206 */ 207 if (setjmp(jmp) == 1) 208 return; 209 210 /* 211 * Run the test with longjmp. 212 */ 213 go("longjmp", &bail_longjmp); 214 } 215 216 static void __dead 217 bail_siglongjmp(void) 218 { 219 220 siglongjmp(sigjmp, 1); 221 } 222 223 ATF_TC(sigsetjmp); 224 ATF_TC_HEAD(sigsetjmp, tc) 225 { 226 atf_tc_set_md_var(tc, "descr", 227 "Test siglongjmp restores stack first, then signal mask"); 228 } 229 ATF_TC_BODY(sigsetjmp, tc) 230 { 231 232 /* 233 * Set up a return point for the signal handler: when the 234 * signal handler does siglongjmp(sigjmp, 1), it comes flying 235 * out of here. 236 */ 237 if (sigsetjmp(sigjmp, /*savesigmask*/1) == 1) 238 return; 239 240 /* 241 * Run the test with siglongjmp. 242 */ 243 go("siglongjmp", &bail_siglongjmp); 244 } 245 246 ATF_TP_ADD_TCS(tp) 247 { 248 249 ATF_TP_ADD_TC(tp, setjmp); 250 ATF_TP_ADD_TC(tp, sigsetjmp); 251 252 return atf_no_error(); 253 } 254