1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2018 The FreeBSD Foundation 5 * All rights reserved. 6 * 7 * This software was developed by Konstantin Belousov <kib@FreeBSD.org> 8 * under sponsorship from the FreeBSD Foundation. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * $Id: popss.c,v 1.28 2018/05/09 21:35:29 kostik Exp kostik $ 32 * 33 * cc -m32 -Wall -Wextra -O2 -g -o popss popss.c 34 * Use as "popss <instruction>", where instruction is one of 35 * bound, into, int1, int3, int80, syscall, sysenter. 36 */ 37 38 #include <sys/param.h> 39 #include <sys/ptrace.h> 40 #include <sys/wait.h> 41 #include <err.h> 42 #include <signal.h> 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include <string.h> 46 #include <unistd.h> 47 #include <machine/reg.h> 48 49 static u_long *stk; 50 51 #define ITERATIONS 4 52 53 static void 54 setup(pid_t child) 55 { 56 struct reg r; 57 struct dbreg dbr; 58 int error, i, status; 59 60 error = waitpid(child, &status, WTRAPPED | WEXITED); 61 if (error == -1) 62 err(1, "waitpid 1"); 63 error = ptrace(PT_GETREGS, child, (caddr_t)&r, 0); 64 if (error == -1) 65 err(1, "ptrace PT_GETREGS"); 66 printf("child %d stopped eip %#x esp %#x\n", child, r.r_eip, r.r_esp); 67 68 error = ptrace(PT_GETDBREGS, child, (caddr_t)&dbr, 0); 69 if (error != 0) 70 err(1, "ptrace PT_GETDBREGS"); 71 dbr.dr[7] &= ~DBREG_DR7_MASK(0); 72 dbr.dr[7] |= DBREG_DR7_SET(0, DBREG_DR7_LEN_4, DBREG_DR7_RDWR, 73 DBREG_DR7_LOCAL_ENABLE | DBREG_DR7_GLOBAL_ENABLE); 74 dbr.dr[0] = (uintptr_t)stk; 75 error = ptrace(PT_SETDBREGS, child, (caddr_t)&dbr, 0); 76 if (error != 0) 77 err(1, "ptrace PT_SETDBREGS"); 78 error = ptrace(PT_CONTINUE, child, (caddr_t)1, 0); 79 if (error != 0) 80 err(1, "ptrace PT_CONTINUE fire"); 81 82 for (i = 0; i < ITERATIONS; i++) { 83 error = waitpid(child, &status, WTRAPPED | WEXITED); 84 if (error == -1) 85 err(1, "waitpid 2"); 86 if (WIFEXITED(status)) 87 break; 88 error = ptrace(PT_GETREGS, child, (caddr_t)&r, 0); 89 if (error == -1) 90 err(1, "ptrace PT_GETREGS"); 91 error = ptrace(PT_GETDBREGS, child, (caddr_t)&dbr, 0); 92 if (error != 0) 93 err(1, "ptrace PT_GETDBREGS"); 94 printf("child %d stopped eip %#x esp %#x dr0 %#x " 95 "dr6 %#x dr7 %#x\n", child, r.r_eip, r.r_esp, 96 dbr.dr[0], dbr.dr[6], dbr.dr[7]); 97 error = ptrace(PT_CONTINUE, child, (caddr_t)1, 0); 98 if (error == -1) 99 err(1, "ptrace PT_CONTINUE tail"); 100 } 101 if (i == ITERATIONS) { 102 kill(child, SIGKILL); 103 ptrace(PT_DETACH, child, NULL, 0); 104 } 105 } 106 107 static u_long tmpstk[1024 * 128]; 108 109 static u_int 110 read_ss(void) 111 { 112 u_int res; 113 114 __asm volatile("movl\t%%ss,%0" : "=r" (res)); 115 return (res); 116 } 117 118 #define PROLOGUE "int3;movl\t%0,%%esp;popl\t%%ss;" 119 120 static void 121 act(const char *cmd) 122 { 123 int error; 124 static const int boundx[2] = {0, 1}; 125 126 printf("child pid %d, stk at %p\n", getpid(), stk); 127 *stk = read_ss(); 128 129 error = ptrace(PT_TRACE_ME, 0, NULL, 0); 130 if (error != 0) 131 err(1, "ptrace PT_TRACE_ME"); 132 133 if (strcmp(cmd, "bound") == 0) { 134 /* XXX BOUND args order clang ias bug */ 135 __asm volatile("int3;movl\t$11,%%eax;" 136 "movl\t%0,%%esp;popl\t%%ss;bound\t%1,%%eax" 137 : : "r" (stk), "m" (boundx) : "memory"); 138 } else if (strcmp(cmd, "int1") == 0) { 139 __asm volatile(PROLOGUE ".byte 0xf1" 140 : : "r" (stk) : "memory"); 141 } else if (strcmp(cmd, "int3") == 0) { 142 __asm volatile(PROLOGUE "int3" 143 : : "r" (stk) : "memory"); 144 } else if (strcmp(cmd, "into") == 0) { 145 __asm volatile("int3;movl\t$0x80000000,%%eax;" 146 "addl\t%%eax,%%eax;movl\t%0,%%esp;popl\t%%ss;into" 147 : : "r" (stk) : "memory"); 148 } else if (strcmp(cmd, "int80") == 0) { 149 __asm volatile(PROLOGUE "int\t$0x80" 150 : : "r" (stk) : "memory"); 151 } else if (strcmp(cmd, "syscall") == 0) { 152 __asm volatile(PROLOGUE "syscall" 153 : : "r" (stk) : "memory"); 154 } else if (strcmp(cmd, "sysenter") == 0) { 155 __asm volatile(PROLOGUE "sysenter" 156 : : "r" (stk) : "memory"); 157 } else { 158 fprintf(stderr, "unknown instruction\n"); 159 exit(1); 160 } 161 printf("ho\n"); 162 } 163 164 int 165 main(int argc, char *argv[]) 166 { 167 int child; 168 169 if (argc != 2) { 170 printf( 171 "Usage: popss [bound|int1|int3|into|int80|syscall|sysenter]\n"); 172 exit(1); 173 } 174 stk = &tmpstk[nitems(tmpstk) - 1]; 175 child = fork(); 176 if (child == -1) 177 err(1, "fork"); 178 if (child == 0) 179 act(argv[1]); 180 else 181 setup(child); 182 } 183