1 /* $NetBSD: t_sigstack.c,v 1.1 2024/02/19 04:30:39 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 1.1 2024/02/19 04:30:39 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 unsigned nentries; 43 44 static void 45 on_sigusr1(int signo, siginfo_t *si, void *ctx) 46 { 47 ucontext_t *uc = ctx; 48 void *sp = (void *)(uintptr_t)_UC_MACHINE_SP(uc); 49 void *fp = __builtin_frame_address(0); 50 51 /* 52 * Ensure that the signal handler was called in the alternate 53 * signal stack. 54 */ 55 ATF_REQUIRE_MSG(fp >= ss.ss_sp, 56 "sigaltstack failed to take effect --" 57 " signal handler's frame pointer %p doesn't lie in sigaltstack" 58 " [%p, %p), size 0x%zx", 59 fp, ss.ss_sp, (char *)ss.ss_sp + ss.ss_size, ss.ss_size); 60 ATF_REQUIRE_MSG(fp < (void *)((char *)ss.ss_sp + ss.ss_size), 61 "sigaltstack failed to take effect --" 62 " signal handler's frame pointer %p doesn't lie in sigaltstack" 63 " [%p, %p), size 0x%zx", 64 fp, ss.ss_sp, (char *)ss.ss_sp + ss.ss_size, ss.ss_size); 65 66 /* 67 * Ensure that if we enter the signal handler, we are entering 68 * it from the original stack, not from the alternate signal 69 * stack. 70 * 71 * On some architectures, this is broken. Those that appear to 72 * get this right are: 73 * 74 * alpha, m68k, or1k, powerpc, powerpc64, riscv, vax 75 */ 76 #if defined __arm__ || defined __hppa__ || defined __i386__ || \ 77 defined __ia64__ || defined __mips__ || defined __sh3__ || \ 78 defined __sparc__ || defined __sparc64__ || defined __x86_64__ 79 if (nentries > 0) 80 atf_tc_expect_fail("PR lib/57946"); 81 #endif 82 ATF_REQUIRE_MSG((sp < ss.ss_sp || 83 sp > (void *)((char *)ss.ss_sp + ss.ss_size)), 84 "longjmp failed to restore stack before allowing signal --" 85 " interrupted stack pointer %p lies in sigaltstack" 86 " [%p, %p), size 0x%zx", 87 sp, ss.ss_sp, (char *)ss.ss_sp + ss.ss_size, ss.ss_size); 88 89 /* 90 * First time through, we want to test whether longjmp restores 91 * the signal mask first, or restores the stack pointer first. 92 * The signal should be blocked at this point, so we re-raise 93 * the signal to queue it up for delivery as soon as it is 94 * unmasked -- which should wait until the stack pointer has 95 * been restored in longjmp. 96 */ 97 if (nentries++ == 0) 98 RL(raise(SIGUSR1)); 99 100 /* 101 * Jump back to the original context. 102 */ 103 longjmp(jmp, 1); 104 } 105 106 ATF_TC(setjmp); 107 ATF_TC_HEAD(setjmp, tc) 108 { 109 atf_tc_set_md_var(tc, "descr", 110 "Test longjmp restores stack first, then signal mask"); 111 } 112 ATF_TC_BODY(setjmp, tc) 113 { 114 struct sigaction sa; 115 116 /* 117 * Allocate a stack for the signal handler to run in, and 118 * configure the system to use it. 119 * 120 * XXX Should maybe use a guard page but this is simpler. 121 */ 122 ss.ss_size = SIGSTKSZ; 123 REQUIRE_LIBC(ss.ss_sp = malloc(ss.ss_size), NULL); 124 RL(sigaltstack(&ss, NULL)); 125 126 /* 127 * Set up a test signal handler for SIGUSR1. Allow all 128 * signals, except SIGUSR1 (which is masked by default) -- that 129 * way we don't inadvertently obscure weird crashes in the 130 * signal handler. 131 * 132 * Set SA_SIGINFO so the system will pass siginfo -- and, more 133 * to the point, ucontext, so the signal handler can determine 134 * the stack pointer of the logic it interrupted. 135 * 136 * Set SA_ONSTACK so the system will use the alternate signal 137 * stack to call the signal handler -- that way, it can tell 138 * whether the stack was restored before the second time 139 * around. 140 */ 141 memset(&sa, 0, sizeof(sa)); 142 sa.sa_sigaction = &on_sigusr1; 143 sigemptyset(&sa.sa_mask); 144 sa.sa_flags = SA_SIGINFO|SA_ONSTACK; 145 RL(sigaction(SIGUSR1, &sa, NULL)); 146 147 /* 148 * Set up a return point for the signal handler: when the 149 * signal handler does longjmp(jmp, 1), it comes flying out of 150 * here. 151 */ 152 if (setjmp(jmp) == 1) 153 return; 154 155 /* 156 * Raise the signal to enter the signal handler the first time. 157 */ 158 raise(SIGUSR1); 159 160 /* 161 * If we ever reach this point, something went seriously wrong. 162 */ 163 atf_tc_fail("unreachable"); 164 } 165 166 ATF_TP_ADD_TCS(tp) 167 { 168 169 ATF_TP_ADD_TC(tp, setjmp); 170 // ATF_TP_ADD_TC(tp, sigsetjmp); 171 172 return atf_no_error(); 173 } 174