1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 #pragma ident "%Z%%M% %I% %E% SMI" 28 29 /* 30 * Debugger co-routine context support: In order to implement the context- 31 * switching necessary for MDB pipes, we need the ability to establish a 32 * co-routine context that has a separate stack. We use this stack to execute 33 * the MDB parser, and then switch back and forth between this code and the 34 * dcmd which is producing output to be consumed. We implement a context by 35 * mapping a few pages of anonymous memory, and then using setcontext(2) to 36 * switch to this stack and begin execution of a new function. 37 */ 38 39 #include <mdb/mdb_context_impl.h> 40 #include <mdb/mdb_modapi.h> 41 #include <mdb/mdb_debug.h> 42 #include <mdb/mdb_err.h> 43 44 #include <sys/types.h> 45 #include <sys/mman.h> 46 47 #include <ucontext.h> 48 #include <unistd.h> 49 #include <setjmp.h> 50 #include <fcntl.h> 51 #include <errno.h> 52 53 static void 54 context_init(mdb_context_t *volatile c) 55 { 56 c->ctx_status = c->ctx_func(); 57 ASSERT(c->ctx_resumes > 0); 58 longjmp(c->ctx_pcb, 1); 59 } 60 61 mdb_context_t * 62 mdb_context_create(int (*func)(void)) 63 { 64 mdb_context_t *c = mdb_zalloc(sizeof (mdb_context_t), UM_NOSLEEP); 65 size_t pagesize = sysconf(_SC_PAGESIZE); 66 int prot = sysconf(_SC_STACK_PROT); 67 static int zfd = -1; 68 69 if (c == NULL) 70 return (NULL); 71 72 if (prot == -1) 73 prot = PROT_READ | PROT_WRITE | PROT_EXEC; 74 75 c->ctx_func = func; 76 c->ctx_stacksize = pagesize * 4; 77 c->ctx_stack = mmap(NULL, c->ctx_stacksize, prot, 78 MAP_PRIVATE | MAP_ANON, -1, 0); 79 80 /* 81 * If the mmap failed with EBADFD, this kernel doesn't have MAP_ANON 82 * support; fall back to opening /dev/zero, caching the fd, and using 83 * that to mmap chunks of anonymous memory. 84 */ 85 if (c->ctx_stack == MAP_FAILED && errno == EBADF) { 86 if (zfd == -1 && (zfd = open("/dev/zero", O_RDWR)) >= 0) 87 (void) fcntl(zfd, F_SETFD, FD_CLOEXEC); 88 89 if (zfd >= 0) { 90 c->ctx_stack = mmap(NULL, c->ctx_stacksize, prot, 91 MAP_PRIVATE, zfd, 0); 92 } 93 } 94 95 c->ctx_uc.uc_flags = UC_ALL; 96 if (c->ctx_stack == MAP_FAILED || getcontext(&c->ctx_uc) != 0) { 97 mdb_free(c, sizeof (mdb_context_t)); 98 return (NULL); 99 } 100 101 c->ctx_uc.uc_stack.ss_sp = c->ctx_stack; 102 c->ctx_uc.uc_stack.ss_size = c->ctx_stacksize; 103 c->ctx_uc.uc_stack.ss_flags = 0; 104 c->ctx_uc.uc_link = NULL; 105 makecontext(&c->ctx_uc, context_init, 1, c); 106 107 return (c); 108 } 109 110 void 111 mdb_context_destroy(mdb_context_t *c) 112 { 113 if (munmap(c->ctx_stack, c->ctx_stacksize) == -1) 114 fail("failed to unmap stack %p", c->ctx_stack); 115 116 mdb_free(c, sizeof (mdb_context_t)); 117 } 118 119 void 120 mdb_context_switch(mdb_context_t *c) 121 { 122 if (setjmp(c->ctx_pcb) == 0 && setcontext(&c->ctx_uc) == -1) 123 fail("failed to change context to %p", (void *)c); 124 else 125 fail("unexpectedly returned from context %p", (void *)c); 126 } 127 128 jmp_buf * 129 mdb_context_getpcb(mdb_context_t *c) 130 { 131 c->ctx_resumes++; 132 return (&c->ctx_pcb); 133 } 134