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 int _swapcontext(ucontext_t *, const ucontext_t *); 40 int _setcontext(const ucontext_t *); 41 42 /* 43 * We need to block most signals during a context switch so we do not 44 * dispatch a signal vector during a context switch. 45 */ 46 #if 0 47 static sigset_t sigset_block_all; 48 49 static void __sigset_block_all_setup(void) __attribute__ ((constructor)); 50 51 static void 52 __sigset_block_all_setup(void) 53 { 54 sigfillset(&sigset_block_all); 55 sigdelset(&sigset_block_all, SIGSEGV); 56 sigdelset(&sigset_block_all, SIGBUS); 57 sigdelset(&sigset_block_all, SIGILL); 58 } 59 #endif 60 61 /* 62 * Save the calling context in (oucp) then switch to (ucp). 63 */ 64 int 65 _swapcontext(ucontext_t *oucp, const ucontext_t *ucp) 66 { 67 int ret; 68 69 if (getcontext(oucp) == 0) { 70 if (ucp->uc_mcontext.mc_len == 0) 71 ret = -1; 72 else 73 ret = sigreturn(__DECONST(ucontext_t *, ucp)); 74 } else { 75 ret = 0; 76 } 77 return(ret); 78 } 79 80 /* 81 * Switch to the target context, use sigreturn() to properly restore 82 * everything, including rflags and to avoid scribbling over the 83 * target stack's red-zone. 84 * 85 * Note that setcontext() can be called with a ucontext from a signal, 86 * so the signal state must be restored and there is really no way to 87 * avoid making a system call :-( 88 */ 89 int 90 _setcontext(const ucontext_t *ucp) 91 { 92 int ret; 93 94 /* 95 * Return failure if the context is invalid 96 */ 97 if (ucp->uc_mcontext.mc_len == 0) 98 return -1; 99 100 /* 101 * XXX: shouldn't sigreturn() take const? or does it modify ucp? 102 */ 103 ret = sigreturn(__DECONST(ucontext_t *, ucp)); 104 105 return(ret); 106 } 107 108 __weak_reference(_swapcontext, swapcontext); 109 __weak_reference(_setcontext, setcontext); 110