1 /* $NetBSD: t_sigstack.c,v 1.3 2024/02/19 12:29:48 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 1.3 2024/02/19 12:29:48 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; 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 54 /* 55 * Ensure that the signal handler was called in the alternate 56 * signal stack. 57 */ 58 ATF_REQUIRE_MSG(fp >= ss.ss_sp, 59 "sigaltstack failed to take effect --" 60 " signal handler's frame pointer %p doesn't lie in sigaltstack" 61 " [%p, %p), size 0x%zx", 62 fp, ss.ss_sp, (char *)ss.ss_sp + ss.ss_size, ss.ss_size); 63 ATF_REQUIRE_MSG(fp < (void *)((char *)ss.ss_sp + ss.ss_size), 64 "sigaltstack failed to take effect --" 65 " signal handler's frame pointer %p doesn't lie in sigaltstack" 66 " [%p, %p), size 0x%zx", 67 fp, ss.ss_sp, (char *)ss.ss_sp + ss.ss_size, ss.ss_size); 68 69 /* 70 * Ensure that if we enter the signal handler, we are entering 71 * it from the original stack, not from the alternate signal 72 * stack. 73 * 74 * On some architectures, this is broken. Those that appear to 75 * get this right are: 76 * 77 * alpha, m68k, or1k, powerpc, powerpc64, riscv, vax 78 */ 79 #if defined __arm__ || defined __hppa__ || defined __i386__ || \ 80 defined __ia64__ || defined __mips__ || defined __sh3__ || \ 81 defined __sparc__ || defined __sparc64__ || defined __x86_64__ 82 if (nentries > 0) 83 atf_tc_expect_fail("PR lib/57946"); 84 #endif 85 ATF_REQUIRE_MSG((sp < ss.ss_sp || 86 sp > (void *)((char *)ss.ss_sp + ss.ss_size)), 87 "%s failed to restore stack before allowing signal --" 88 " interrupted stack pointer %p lies in sigaltstack" 89 " [%p, %p), size 0x%zx", 90 bailname, sp, ss.ss_sp, (char *)ss.ss_sp + ss.ss_size, ss.ss_size); 91 92 /* 93 * First time through, we want to test whether longjmp restores 94 * the signal mask first, or restores the stack pointer first. 95 * The signal should be blocked at this point, so we re-raise 96 * the signal to queue it up for delivery as soon as it is 97 * unmasked -- which should wait until the stack pointer has 98 * been restored in longjmp. 99 */ 100 if (nentries++ == 0) 101 RL(raise(SIGUSR1)); 102 103 /* 104 * Jump back to the original context. 105 */ 106 (*bailfn)(); 107 } 108 109 static void 110 go(const char *name, void (*fn)(void) __dead) 111 { 112 struct sigaction sa; 113 114 bailname = name; 115 bailfn = fn; 116 117 /* 118 * Allocate a stack for the signal handler to run in, and 119 * configure the system to use it. 120 * 121 * XXX Should maybe use a guard page but this is simpler. 122 */ 123 ss.ss_size = SIGSTKSZ; 124 REQUIRE_LIBC(ss.ss_sp = malloc(ss.ss_size), NULL); 125 RL(sigaltstack(&ss, NULL)); 126 127 /* 128 * Set up a test signal handler for SIGUSR1. Allow all 129 * signals, except SIGUSR1 (which is masked by default) -- that 130 * way we don't inadvertently obscure weird crashes in the 131 * signal handler. 132 * 133 * Set SA_SIGINFO so the system will pass siginfo -- and, more 134 * to the point, ucontext, so the signal handler can determine 135 * the stack pointer of the logic it interrupted. 136 * 137 * Set SA_ONSTACK so the system will use the alternate signal 138 * stack to call the signal handler -- that way, it can tell 139 * whether the stack was restored before the second time 140 * around. 141 */ 142 memset(&sa, 0, sizeof(sa)); 143 sa.sa_sigaction = &on_sigusr1; 144 RL(sigemptyset(&sa.sa_mask)); 145 sa.sa_flags = SA_SIGINFO|SA_ONSTACK; 146 RL(sigaction(SIGUSR1, &sa, NULL)); 147 148 /* 149 * Raise the signal to enter the signal handler the first time. 150 */ 151 RL(raise(SIGUSR1)); 152 153 /* 154 * If we ever reach this point, something went seriously wrong. 155 */ 156 atf_tc_fail("unreachable"); 157 } 158 159 static void __dead 160 bail_longjmp(void) 161 { 162 163 longjmp(jmp, 1); 164 } 165 166 ATF_TC(setjmp); 167 ATF_TC_HEAD(setjmp, tc) 168 { 169 atf_tc_set_md_var(tc, "descr", 170 "Test longjmp restores stack first, then signal mask"); 171 } 172 ATF_TC_BODY(setjmp, tc) 173 { 174 175 /* 176 * Set up a return point for the signal handler: when the 177 * signal handler does longjmp(jmp, 1), it comes flying out of 178 * here. 179 */ 180 if (setjmp(jmp) == 1) 181 return; 182 183 /* 184 * Run the test with longjmp. 185 */ 186 go("longjmp", &bail_longjmp); 187 } 188 189 static void __dead 190 bail_siglongjmp(void) 191 { 192 193 siglongjmp(sigjmp, 1); 194 } 195 196 ATF_TC(sigsetjmp); 197 ATF_TC_HEAD(sigsetjmp, tc) 198 { 199 atf_tc_set_md_var(tc, "descr", 200 "Test siglongjmp restores stack first, then signal mask"); 201 } 202 ATF_TC_BODY(sigsetjmp, tc) 203 { 204 205 /* 206 * Set up a return point for the signal handler: when the 207 * signal handler does siglongjmp(sigjmp, 1), it comes flying 208 * out of here. 209 */ 210 if (sigsetjmp(sigjmp, /*savesigmask*/1) == 1) 211 return; 212 213 /* 214 * Run the test with siglongjmp. 215 */ 216 go("siglongjmp", &bail_siglongjmp); 217 } 218 219 ATF_TP_ADD_TCS(tp) 220 { 221 222 ATF_TP_ADD_TC(tp, setjmp); 223 ATF_TP_ADD_TC(tp, sigsetjmp); 224 225 return atf_no_error(); 226 } 227