1 /* 2 * Copyright (c) 2007 Matthew T. Emmerton <matt@gsicomp.on.ca> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Neither the name of the author nor the names of its contributors 11 * may be used to endorse or promote products derived from this software 12 * without specific prior written permission. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 #include "namespace.h" 28 #include <sys/param.h> 29 #include <sys/signal.h> 30 #include <sys/ucontext.h> 31 32 #include <errno.h> 33 #include <stdarg.h> 34 #include <stdlib.h> 35 #include <unistd.h> 36 #include <signal.h> 37 #include "un-namespace.h" 38 39 /* Prototypes */ 40 __weak_reference(_swapcontext, swapcontext); 41 __weak_reference(_setcontext, setcontext); 42 43 int get_mcontext(mcontext_t *); 44 int set_mcontext(const mcontext_t *); 45 46 /* 47 * We need to block most signals during a context switch so we do not 48 * dispatch a signal vector during a context switch. 49 */ 50 static sigset_t sigset_block_all; 51 52 static void __sigset_block_all_setup(void) __attribute__ ((constructor)); 53 54 static void 55 __sigset_block_all_setup(void) 56 { 57 sigfillset(&sigset_block_all); 58 sigdelset(&sigset_block_all, SIGSEGV); 59 sigdelset(&sigset_block_all, SIGBUS); 60 sigdelset(&sigset_block_all, SIGILL); 61 } 62 63 /* 64 * Save the calling context in (oucp) then switch to (ucp). 65 * 66 * Block all signals while switching contexts. get_mcontext() returns zero 67 * when retrieving a context. 68 * 69 * When some other thread calls set_mcontext() to resume our thread, 70 * the resume point causes get_mcontext() to return non-zero to us. 71 * Signals will be blocked and we must restore the signal mask before 72 * returning. 73 */ 74 int 75 _swapcontext(ucontext_t *oucp, const ucontext_t *ucp) 76 { 77 int ret; 78 79 ret = _sigprocmask(SIG_BLOCK, &sigset_block_all, &oucp->uc_sigmask); 80 if (ret == 0) { 81 if (get_mcontext(&oucp->uc_mcontext) == 0) { 82 ret = set_mcontext(&ucp->uc_mcontext); 83 } else { 84 ret = _sigprocmask(SIG_SETMASK, &oucp->uc_sigmask, NULL); 85 } 86 } 87 return(ret); 88 } 89 90 /* 91 * Switch to the target context. The current signal mask is saved in ucp 92 * and all signals are blocked. The call to set_mcontext() causes the 93 * specified context to be switched to (usually resuming as a return from 94 * the get_mcontext() procedure). The current context is thrown away. 95 * 96 * The target context being resumed is responsible for restoring the 97 * signal mask appropriate for the target context. 98 */ 99 int 100 _setcontext(ucontext_t *ucp) 101 { 102 int ret; 103 104 ret = _sigprocmask(SIG_BLOCK, &sigset_block_all, &ucp->uc_sigmask); 105 if (ret == 0) 106 ret = set_mcontext(&ucp->uc_mcontext); 107 return(ret); 108 } 109 110