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 (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  * Copyright 2012 Joshua M. Clulow <josh@sysmgr.org>
  26  */
  27 
  28 #include <libdisasm.h>
  29 #include <stdlib.h>
  30 #include <stdio.h>
  31 
  32 #include "dis_tables.h"
  33 #include "libdisasm_impl.h"
  34 
  35 typedef struct dis_handle_i386 {
  36         int             dhx_mode;
  37         dis86_t         dhx_dis;
  38         uint64_t        dhx_end;
  39 } dis_handle_i386_t;
  40 
  41 /*
  42  * Returns true if we are near the end of a function.  This is a cheap hack at
  43  * detecting NULL padding between functions.  If we're within a few bytes of the
  44  * next function, or past the start, then return true.
  45  */
  46 static int
  47 check_func(void *data)
  48 {
  49         dis_handle_t *dhp = data;
  50         uint64_t start;
  51         size_t len;
  52 
  53         if (dhp->dh_lookup(dhp->dh_data, dhp->dh_addr, NULL, 0, &start, &len)
  54             != 0)
  55                 return (0);
  56 
  57         if (start < dhp->dh_addr)
  58                 return (dhp->dh_addr > start + len - 0x10);
  59 
  60         return (1);
  61 }
  62 
  63 static int
  64 get_byte(void *data)
  65 {
  66         uchar_t byte;
  67         dis_handle_t *dhp = data;
  68 
  69         if (dhp->dh_read(dhp->dh_data, dhp->dh_addr, &byte, sizeof (byte)) !=
  70             sizeof (byte))
  71                 return (-1);
  72 
  73         dhp->dh_addr++;
  74 
  75         return ((int)byte);
  76 }
  77 
  78 static int
  79 do_lookup(void *data, uint64_t addr, char *buf, size_t buflen)
  80 {
  81         dis_handle_t *dhp = data;
  82 
  83         return (dhp->dh_lookup(dhp->dh_data, addr, buf, buflen, NULL, NULL));
  84 }
  85 
  86 static void
  87 dis_i386_handle_detach(dis_handle_t *dhp)
  88 {
  89         dis_free(dhp->dh_arch_private, sizeof (dis_handle_i386_t));
  90         dhp->dh_arch_private = NULL;
  91 }
  92 
  93 static int
  94 dis_i386_handle_attach(dis_handle_t *dhp)
  95 {
  96         dis_handle_i386_t *dhx;
  97 
  98         /*
  99          * Validate architecture flags
 100          */
 101         if (dhp->dh_flags & ~(DIS_X86_SIZE16 | DIS_X86_SIZE32 | DIS_X86_SIZE64 |
 102             DIS_OCTAL | DIS_NOIMMSYM)) {
 103                 (void) dis_seterrno(E_DIS_INVALFLAG);
 104                 return (-1);
 105         }
 106 
 107         /*
 108          * Create and initialize the internal structure
 109          */
 110         if ((dhx = dis_zalloc(sizeof (dis_handle_i386_t))) == NULL) {
 111                 (void) dis_seterrno(E_DIS_NOMEM);
 112                 return (-1);
 113         }
 114         dhp->dh_arch_private = dhx;
 115 
 116         /*
 117          * Initialize x86-specific architecture structure
 118          */
 119         if (dhp->dh_flags & DIS_X86_SIZE16)
 120                 dhx->dhx_mode = SIZE16;
 121         else if (dhp->dh_flags & DIS_X86_SIZE64)
 122                 dhx->dhx_mode = SIZE64;
 123         else
 124                 dhx->dhx_mode = SIZE32;
 125 
 126         if (dhp->dh_flags & DIS_OCTAL)
 127                 dhx->dhx_dis.d86_flags = DIS_F_OCTAL;
 128 
 129         dhx->dhx_dis.d86_sprintf_func = snprintf;
 130         dhx->dhx_dis.d86_get_byte = get_byte;
 131         dhx->dhx_dis.d86_sym_lookup = do_lookup;
 132         dhx->dhx_dis.d86_check_func = check_func;
 133 
 134         dhx->dhx_dis.d86_data = dhp;
 135 
 136         return (0);
 137 }
 138 
 139 static int
 140 dis_i386_disassemble(dis_handle_t *dhp, uint64_t addr, char *buf,
 141     size_t buflen)
 142 {
 143         dis_handle_i386_t *dhx = dhp->dh_arch_private;
 144         dhp->dh_addr = addr;
 145 
 146         /* DIS_NOIMMSYM might not be set until now, so update */
 147         if (dhp->dh_flags & DIS_NOIMMSYM)
 148                 dhx->dhx_dis.d86_flags |= DIS_F_NOIMMSYM;
 149         else
 150                 dhx->dhx_dis.d86_flags &= ~DIS_F_NOIMMSYM;
 151 
 152         if (dtrace_disx86(&dhx->dhx_dis, dhx->dhx_mode) != 0)
 153                 return (-1);
 154 
 155         if (buf != NULL)
 156                 dtrace_disx86_str(&dhx->dhx_dis, dhx->dhx_mode, addr, buf,
 157                     buflen);
 158 
 159         return (0);
 160 }
 161 
 162 /* ARGSUSED */
 163 static int
 164 dis_i386_max_instrlen(dis_handle_t *dhp)
 165 {
 166         return (15);
 167 }
 168 
 169 /* ARGSUSED */
 170 static int
 171 dis_i386_min_instrlen(dis_handle_t *dhp)
 172 {
 173         return (1);
 174 }
 175 
 176 #define MIN(a, b)       ((a) < (b) ? (a) : (b))
 177 
 178 /*
 179  * Return the previous instruction.  On x86, we have no choice except to
 180  * disassemble everything from the start of the symbol, and stop when we have
 181  * reached our instruction address.  If we're not in the middle of a known
 182  * symbol, then we return the same address to indicate failure.
 183  */
 184 static uint64_t
 185 dis_i386_previnstr(dis_handle_t *dhp, uint64_t pc, int n)
 186 {
 187         uint64_t *hist, addr, start;
 188         int cur, nseen;
 189         uint64_t res = pc;
 190 
 191         if (n <= 0)
 192                 return (pc);
 193 
 194         if (dhp->dh_lookup(dhp->dh_data, pc, NULL, 0, &start, NULL) != 0 ||
 195             start == pc)
 196                 return (res);
 197 
 198         hist = dis_zalloc(sizeof (uint64_t) * n);
 199 
 200         for (cur = 0, nseen = 0, addr = start; addr < pc; addr = dhp->dh_addr) {
 201                 hist[cur] = addr;
 202                 cur = (cur + 1) % n;
 203                 nseen++;
 204 
 205                 /* if we cannot make forward progress, give up */
 206                 if (dis_disassemble(dhp, addr, NULL, 0) != 0)
 207                         goto done;
 208         }
 209 
 210         if (addr != pc) {
 211                 /*
 212                  * We scanned past %pc, but didn't find an instruction that
 213                  * started at %pc.  This means that either the caller specified
 214                  * an invalid address, or we ran into something other than code
 215                  * during our scan.  Virtually any combination of bytes can be
 216                  * construed as a valid Intel instruction, so any non-code bytes
 217                  * we encounter will have thrown off the scan.
 218                  */
 219                 goto done;
 220         }
 221 
 222         res = hist[(cur + n - MIN(n, nseen)) % n];
 223 
 224 done:
 225         dis_free(hist, sizeof (uint64_t) * n);
 226         return (res);
 227 }
 228 
 229 static int
 230 dis_i386_supports_flags(int flags)
 231 {
 232         int archflags = flags & DIS_ARCH_MASK;
 233 
 234         if (archflags == DIS_X86_SIZE16 || archflags == DIS_X86_SIZE32 ||
 235             archflags == DIS_X86_SIZE64)
 236                 return (1);
 237 
 238         return (0);
 239 }
 240 
 241 dis_arch_t dis_arch_i386 = {
 242         dis_i386_supports_flags,
 243         dis_i386_handle_attach,
 244         dis_i386_handle_detach,
 245         dis_i386_disassemble,
 246         dis_i386_previnstr,
 247         dis_i386_min_instrlen,
 248         dis_i386_max_instrlen
 249 };