6068 libdisasm: previnstr arch op should have a sane default
Reviewed by: Robert Mustacchi <rm@joyent.com>

   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  * Copyright 2015 Nexenta Systems, Inc.  All rights reserved.
  27  */
  28 
  29 #include <libdisasm.h>
  30 
  31 #include "dis_tables.h"
  32 #include "libdisasm_impl.h"
  33 
  34 typedef struct dis_handle_i386 {
  35         int             dhx_mode;
  36         dis86_t         dhx_dis;
  37         uint64_t        dhx_end;
  38 } dis_handle_i386_t;
  39 
  40 /*
  41  * Returns true if we are near the end of a function.  This is a cheap hack at
  42  * detecting NULL padding between functions.  If we're within a few bytes of the
  43  * next function, or past the start, then return true.
  44  */
  45 static int
  46 check_func(void *data)
  47 {
  48         dis_handle_t *dhp = data;
  49         uint64_t start;
  50         size_t len;
  51 
  52         if (dhp->dh_lookup(dhp->dh_data, dhp->dh_addr, NULL, 0, &start, &len)
  53             != 0)
  54                 return (0);
  55 
  56         if (start < dhp->dh_addr)
  57                 return (dhp->dh_addr > start + len - 0x10);
  58 
  59         return (1);
  60 }
  61 
  62 static int
  63 get_byte(void *data)
  64 {
  65         uchar_t byte;
  66         dis_handle_t *dhp = data;
  67 
  68         if (dhp->dh_read(dhp->dh_data, dhp->dh_addr, &byte, sizeof (byte)) !=
  69             sizeof (byte))
  70                 return (-1);
  71 
  72         dhp->dh_addr++;
  73 
  74         return ((int)byte);
  75 }
  76 
  77 static int
  78 do_lookup(void *data, uint64_t addr, char *buf, size_t buflen)
  79 {
  80         dis_handle_t *dhp = data;
  81 
  82         return (dhp->dh_lookup(dhp->dh_data, addr, buf, buflen, NULL, NULL));
  83 }
  84 
  85 static void
  86 dis_i386_handle_detach(dis_handle_t *dhp)
  87 {
  88         dis_free(dhp->dh_arch_private, sizeof (dis_handle_i386_t));
  89         dhp->dh_arch_private = NULL;
  90 }
  91 
  92 static int
  93 dis_i386_handle_attach(dis_handle_t *dhp)
  94 {
  95         dis_handle_i386_t *dhx;
  96 
  97         /*
  98          * Validate architecture flags
  99          */
 100         if (dhp->dh_flags & ~(DIS_X86_SIZE16 | DIS_X86_SIZE32 | DIS_X86_SIZE64 |
 101             DIS_OCTAL | DIS_NOIMMSYM)) {
 102                 (void) dis_seterrno(E_DIS_INVALFLAG);
 103                 return (-1);
 104         }
 105 
 106         /*
 107          * Create and initialize the internal structure
 108          */
 109         if ((dhx = dis_zalloc(sizeof (dis_handle_i386_t))) == NULL) {
 110                 (void) dis_seterrno(E_DIS_NOMEM);
 111                 return (-1);
 112         }
 113         dhp->dh_arch_private = dhx;
 114 
 115         /*
 116          * Initialize x86-specific architecture structure
 117          */
 118         if (dhp->dh_flags & DIS_X86_SIZE16)
 119                 dhx->dhx_mode = SIZE16;
 120         else if (dhp->dh_flags & DIS_X86_SIZE64)
 121                 dhx->dhx_mode = SIZE64;
 122         else
 123                 dhx->dhx_mode = SIZE32;
 124 
 125         if (dhp->dh_flags & DIS_OCTAL)
 126                 dhx->dhx_dis.d86_flags = DIS_F_OCTAL;
 127 
 128         dhx->dhx_dis.d86_sprintf_func = dis_snprintf;
 129         dhx->dhx_dis.d86_get_byte = get_byte;
 130         dhx->dhx_dis.d86_sym_lookup = do_lookup;
 131         dhx->dhx_dis.d86_check_func = check_func;
 132 
 133         dhx->dhx_dis.d86_data = dhp;
 134 
 135         return (0);
 136 }
 137 
 138 static int
 139 dis_i386_disassemble(dis_handle_t *dhp, uint64_t addr, char *buf,
 140     size_t buflen)
 141 {
 142         dis_handle_i386_t *dhx = dhp->dh_arch_private;
 143         dhp->dh_addr = addr;
 144 
 145         /* DIS_NOIMMSYM might not be set until now, so update */
 146         if (dhp->dh_flags & DIS_NOIMMSYM)
 147                 dhx->dhx_dis.d86_flags |= DIS_F_NOIMMSYM;
 148         else
 149                 dhx->dhx_dis.d86_flags &= ~DIS_F_NOIMMSYM;
 150 
 151         if (dtrace_disx86(&dhx->dhx_dis, dhx->dhx_mode) != 0)
 152                 return (-1);
 153 
 154         if (buf != NULL)
 155                 dtrace_disx86_str(&dhx->dhx_dis, dhx->dhx_mode, addr, buf,
 156                     buflen);
 157 
 158         return (0);
 159 }
 160 
 161 /* ARGSUSED */
 162 static int
 163 dis_i386_max_instrlen(dis_handle_t *dhp)
 164 {
 165         return (15);
 166 }
 167 
 168 /* ARGSUSED */
 169 static int
 170 dis_i386_min_instrlen(dis_handle_t *dhp)
 171 {
 172         return (1);
 173 }
 174 
 175 /*
 176  * Return the previous instruction.  On x86, we have no choice except to
 177  * disassemble everything from the start of the symbol, and stop when we have
 178  * reached our instruction address.  If we're not in the middle of a known
 179  * symbol, then we return the same address to indicate failure.
 180  */
 181 static uint64_t
 182 dis_i386_previnstr(dis_handle_t *dhp, uint64_t pc, int n)
 183 {
 184         uint64_t *hist, addr, start;
 185         int cur, nseen;
 186         uint64_t res = pc;
 187 
 188         if (n <= 0)
 189                 return (pc);
 190 
 191         if (dhp->dh_lookup(dhp->dh_data, pc, NULL, 0, &start, NULL) != 0 ||
 192             start == pc)
 193                 return (res);
 194 
 195         hist = dis_zalloc(sizeof (uint64_t) * n);
 196 
 197         for (cur = 0, nseen = 0, addr = start; addr < pc; addr = dhp->dh_addr) {
 198                 hist[cur] = addr;
 199                 cur = (cur + 1) % n;
 200                 nseen++;
 201 
 202                 /* if we cannot make forward progress, give up */
 203                 if (dis_disassemble(dhp, addr, NULL, 0) != 0)
 204                         goto done;
 205         }
 206 
 207         if (addr != pc) {
 208                 /*
 209                  * We scanned past %pc, but didn't find an instruction that
 210                  * started at %pc.  This means that either the caller specified
 211                  * an invalid address, or we ran into something other than code
 212                  * during our scan.  Virtually any combination of bytes can be
 213                  * construed as a valid Intel instruction, so any non-code bytes
 214                  * we encounter will have thrown off the scan.
 215                  */
 216                 goto done;
 217         }
 218 
 219         res = hist[(cur + n - MIN(n, nseen)) % n];
 220 
 221 done:
 222         dis_free(hist, sizeof (uint64_t) * n);
 223         return (res);
 224 }
 225 
 226 static int
 227 dis_i386_supports_flags(int flags)
 228 {
 229         int archflags = flags & DIS_ARCH_MASK;
 230 
 231         if (archflags == DIS_X86_SIZE16 || archflags == DIS_X86_SIZE32 ||
 232             archflags == DIS_X86_SIZE64)
 233                 return (1);
 234 
 235         return (0);
 236 }
 237 
 238 static int
 239 dis_i386_instrlen(dis_handle_t *dhp, uint64_t pc)
 240 {
 241         if (dis_disassemble(dhp, pc, NULL, 0) != 0)
 242                 return (-1);
 243 
 244         return (dhp->dh_addr - pc);
 245 }
 246 
 247 dis_arch_t dis_arch_i386 = {
 248         .da_supports_flags      = dis_i386_supports_flags,
 249         .da_handle_attach       = dis_i386_handle_attach,
 250         .da_handle_detach       = dis_i386_handle_detach,
 251         .da_disassemble         = dis_i386_disassemble,
 252         .da_previnstr           = dis_i386_previnstr,
 253         .da_min_instrlen        = dis_i386_min_instrlen,
 254         .da_max_instrlen        = dis_i386_max_instrlen,
 255         .da_instrlen            = dis_i386_instrlen,
 256 };
--- EOF ---