1 /* $NetBSD: t_sigstack.c,v 1.7 2024/02/19 19:43:27 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 1.7 2024/02/19 19:43:27 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, vax 85 */ 86 #if defined __arm__ || defined __hppa__ || defined __i386__ || \ 87 defined __ia64__ || defined __mips__ || defined __sh3__ || \ 88 defined __sparc__ || defined __sparc64__ || defined __x86_64__ 89 if (nentries > 0) 90 atf_tc_expect_fail("PR lib/57946"); 91 #endif 92 for (ssp = &ss[0]; ssp < &ss[__arraycount(ss)]; ssp++) { 93 ATF_REQUIRE_MSG((sp < ssp->ss_sp || 94 sp >= (void *)((char *)ssp->ss_sp + ssp->ss_size)), 95 "%s failed to restore stack" 96 " before allowing signal on entry %u --" 97 " interrupted stack pointer %p lies in sigaltstack %zd" 98 " [%p, %p), size 0x%zx", 99 bailname, 100 nentries, 101 sp, ssp - ss, 102 ssp->ss_sp, (char *)ssp->ss_sp + ssp->ss_size, 103 ssp->ss_size); 104 } 105 106 /* 107 * First time through, we want to test whether longjmp restores 108 * the signal mask first, or restores the stack pointer first. 109 * The signal should be blocked at this point, so we re-raise 110 * the signal to queue it up for delivery as soon as it is 111 * unmasked -- which should wait until the stack pointer has 112 * been restored in longjmp. 113 */ 114 if (nentries++ == 0) 115 RL(raise(SIGUSR1)); 116 117 /* 118 * Set up the next sigaltstack. We can't reuse the current one 119 * for the next signal handler re-entry until the system clears 120 * the SS_ONSTACK process state -- which normal return from 121 * signal handler does, but which longjmp does not. So to keep 122 * it simple (ha), we just use another sigaltstack. 123 */ 124 RL(sigaltstack(&ss[nentries], NULL)); 125 126 /* 127 * Jump back to the original context. 128 */ 129 (*bailfn)(); 130 } 131 132 static void 133 go(const char *name, void (*fn)(void) __dead) 134 { 135 struct sigaction sa; 136 unsigned i; 137 138 bailname = name; 139 bailfn = fn; 140 141 /* 142 * Allocate a stack for the signal handler to run in, and 143 * configure the system to use the first one. 144 * 145 * XXX Should maybe use a guard page but this is simpler. 146 */ 147 for (i = 0; i < __arraycount(ss); i++) { 148 ss[i].ss_size = SIGSTKSZ; 149 REQUIRE_LIBC(ss[i].ss_sp = malloc(ss[i].ss_size), NULL); 150 } 151 RL(sigaltstack(&ss[0], NULL)); 152 153 /* 154 * Set up a test signal handler for SIGUSR1. Allow all 155 * signals, except SIGUSR1 (which is masked by default) -- that 156 * way we don't inadvertently obscure weird crashes in the 157 * signal handler. 158 * 159 * Set SA_SIGINFO so the system will pass siginfo -- and, more 160 * to the point, ucontext, so the signal handler can determine 161 * the stack pointer of the logic it interrupted. 162 * 163 * Set SA_ONSTACK so the system will use the alternate signal 164 * stack to call the signal handler -- that way, it can tell 165 * whether the stack was restored before the second time 166 * around. 167 */ 168 memset(&sa, 0, sizeof(sa)); 169 sa.sa_sigaction = &on_sigusr1; 170 RL(sigemptyset(&sa.sa_mask)); 171 sa.sa_flags = SA_SIGINFO|SA_ONSTACK; 172 RL(sigaction(SIGUSR1, &sa, NULL)); 173 174 /* 175 * Raise the signal to enter the signal handler the first time. 176 */ 177 RL(raise(SIGUSR1)); 178 179 /* 180 * If we ever reach this point, something went seriously wrong. 181 */ 182 atf_tc_fail("unreachable"); 183 } 184 185 static void __dead 186 bail_longjmp(void) 187 { 188 189 longjmp(jmp, 1); 190 } 191 192 ATF_TC(setjmp); 193 ATF_TC_HEAD(setjmp, tc) 194 { 195 atf_tc_set_md_var(tc, "descr", 196 "Test longjmp restores stack first, then signal mask"); 197 } 198 ATF_TC_BODY(setjmp, tc) 199 { 200 201 /* 202 * Set up a return point for the signal handler: when the 203 * signal handler does longjmp(jmp, 1), it comes flying out of 204 * here. 205 */ 206 if (setjmp(jmp) == 1) 207 return; 208 209 /* 210 * Run the test with longjmp. 211 */ 212 go("longjmp", &bail_longjmp); 213 } 214 215 static void __dead 216 bail_siglongjmp(void) 217 { 218 219 siglongjmp(sigjmp, 1); 220 } 221 222 ATF_TC(sigsetjmp); 223 ATF_TC_HEAD(sigsetjmp, tc) 224 { 225 atf_tc_set_md_var(tc, "descr", 226 "Test siglongjmp restores stack first, then signal mask"); 227 } 228 ATF_TC_BODY(sigsetjmp, tc) 229 { 230 231 /* 232 * Set up a return point for the signal handler: when the 233 * signal handler does siglongjmp(sigjmp, 1), it comes flying 234 * out of here. 235 */ 236 if (sigsetjmp(sigjmp, /*savesigmask*/1) == 1) 237 return; 238 239 /* 240 * Run the test with siglongjmp. 241 */ 242 go("siglongjmp", &bail_siglongjmp); 243 } 244 245 ATF_TP_ADD_TCS(tp) 246 { 247 248 ATF_TP_ADD_TC(tp, setjmp); 249 ATF_TP_ADD_TC(tp, sigsetjmp); 250 251 return atf_no_error(); 252 } 253