gdb/bsd-kvm.c

   1 /* BSD Kernel Data Access Library (libkvm) interface.
   2
   3    Copyright (C) 2004-2021 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #define _KMEMUSER
  21 #include "defs.h"
  22 #include "cli/cli-cmds.h"
  23 #include "command.h"
  24 #include "frame.h"
  25 #include "regcache.h"
  26 #include "target.h"
  27 #include "process-stratum-target.h"
  28 #include "value.h"
  29 #include "gdbcore.h"
  30 #include "inferior.h"          /* for get_exec_file */
  31 #include "gdbthread.h"
  32 #include "gdbsupport/pathstuff.h"
  33
  34 #include <fcntl.h>
  35 #include <kvm.h>
  36 #ifdef HAVE_NLIST_H
  37 #include <nlist.h>
  38 #endif
  39 #include <paths.h>
  40 #include "readline/readline.h"
  41 #include <sys/param.h>
  42 #include <sys/proc.h>
  43 #ifdef HAVE_SYS_USER_H
  44 #include <sys/user.h>
  45 #endif
  46
  47 #include "bsd-kvm.h"
  48
  49 /* Kernel memory device file.  */
  50 static const char *bsd_kvm_corefile;
  51
  52 /* Kernel memory interface descriptor.  */
  53 static kvm_t *core_kd;
  54
  55 /* Address of process control block.  */
  56 static struct pcb *bsd_kvm_paddr;
  57
  58 /* Pointer to architecture-specific function that reconstructs the
  59    register state from PCB and supplies it to REGCACHE.  */
  60 static int (*bsd_kvm_supply_pcb)(struct regcache *regcache, struct pcb *pcb);
  61
  62 /* This is the ptid we use while we're connected to kvm.  The kvm
  63    target currently doesn't export any view of the running processes,
  64    so this represents the kernel task.  */
  65 static ptid_t bsd_kvm_ptid;
  66
  67 /* The libkvm target.  */
  68
  69 static const target_info bsd_kvm_target_info = {
  70   "kvm",
  71   N_("Kernel memory interface"),
  72   N_("Use a kernel virtual memory image as a target.\n\
  73 Optionally specify the filename of a core dump.")
  74 };
  75
  76 class bsd_kvm_target final : public process_stratum_target
  77 {
  78 public:
  79   bsd_kvm_target () = default;
  80
  81   const target_info &info () const override
  82   { return bsd_kvm_target_info; }
  83
  84   void close () override;
  85
  86   void fetch_registers (struct regcache *, int) override;
  87   enum target_xfer_status xfer_partial (enum target_object object,
  88                                         const char *annex,
  89                                         gdb_byte *readbuf,
  90                                         const gdb_byte *writebuf,
  91                                         ULONGEST offset, ULONGEST len,
  92                                         ULONGEST *xfered_len) override;
  93
  94   void files_info () override;
  95   bool thread_alive (ptid_t ptid) override;
  96   std::string pid_to_str (ptid_t) override;
  97
  98   bool has_memory () override { return true; }
  99   bool has_stack () override { return true; }
 100   bool has_registers () override { return true; }
 101 };
 102
 103 /* Target ops for libkvm interface.  */
 104 static bsd_kvm_target bsd_kvm_ops;
 105
 106 static void
 107 bsd_kvm_target_open (const char *arg, int from_tty)
 108 {
 109   char errbuf[_POSIX2_LINE_MAX];
 110   const char *execfile = NULL;
 111   kvm_t *temp_kd;
 112   char *filename = NULL;
 113
 114   target_preopen (from_tty);
 115
 116   if (arg)
 117     {
 118       filename = tilde_expand (arg);
 119       if (filename[0] != '/')
 120         {
 121           gdb::unique_xmalloc_ptr<char> temp (gdb_abspath (filename));
 122
 123           xfree (filename);
 124           filename = temp.release ();
 125         }
 126     }
 127
 128   execfile = get_exec_file (0);
 129   temp_kd = kvm_openfiles (execfile, filename, NULL,
 130                            write_files ? O_RDWR : O_RDONLY, errbuf);
 131   if (temp_kd == NULL)
 132     error (("%s"), errbuf);
 133
 134   bsd_kvm_corefile = filename;
 135   current_inferior ()->unpush_target (&bsd_kvm_ops);
 136   core_kd = temp_kd;
 137   current_inferior ()->push_target (&bsd_kvm_ops);
 138
 139   thread_info *thr = add_thread_silent (&bsd_kvm_ops, bsd_kvm_ptid);
 140   switch_to_thread (thr);
 141
 142   target_fetch_registers (get_current_regcache (), -1);
 143
 144   reinit_frame_cache ();
 145   print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
 146 }
 147
 148 void
 149 bsd_kvm_target::close ()
 150 {
 151   if (core_kd)
 152     {
 153       if (kvm_close (core_kd) == -1)
 154         warning (("%s"), kvm_geterr(core_kd));
 155       core_kd = NULL;
 156     }
 157
 158   switch_to_no_thread ();
 159   exit_inferior_silent (current_inferior ());
 160 }
 161
 162 static LONGEST
 163 bsd_kvm_xfer_memory (CORE_ADDR addr, ULONGEST len,
 164                      gdb_byte *readbuf, const gdb_byte *writebuf)
 165 {
 166   ssize_t nbytes = len;
 167
 168   if (readbuf)
 169     nbytes = kvm_read (core_kd, addr, readbuf, nbytes);
 170   if (writebuf && nbytes > 0)
 171     nbytes = kvm_write (core_kd, addr, writebuf, nbytes);
 172   return nbytes;
 173 }
 174
 175 enum target_xfer_status
 176 bsd_kvm_target::xfer_partial (enum target_object object,
 177                               const char *annex, gdb_byte *readbuf,
 178                               const gdb_byte *writebuf,
 179                               ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
 180 {
 181   switch (object)
 182     {
 183     case TARGET_OBJECT_MEMORY:
 184       {
 185         LONGEST ret = bsd_kvm_xfer_memory (offset, len, readbuf, writebuf);
 186
 187         if (ret < 0)
 188           return TARGET_XFER_E_IO;
 189         else if (ret == 0)
 190           return TARGET_XFER_EOF;
 191         else
 192           {
 193             *xfered_len = (ULONGEST) ret;
 194             return TARGET_XFER_OK;
 195           }
 196       }
 197
 198     default:
 199       return TARGET_XFER_E_IO;
 200     }
 201 }
 202
 203 void
 204 bsd_kvm_target::files_info ()
 205 {
 206   if (bsd_kvm_corefile && strcmp (bsd_kvm_corefile, _PATH_MEM) != 0)
 207     printf_filtered (_("\tUsing the kernel crash dump %s.\n"),
 208                      bsd_kvm_corefile);
 209   else
 210     printf_filtered (_("\tUsing the currently running kernel.\n"));
 211 }
 212
 213 /* Fetch process control block at address PADDR.  */
 214
 215 static int
 216 bsd_kvm_fetch_pcb (struct regcache *regcache, struct pcb *paddr)
 217 {
 218   struct pcb pcb;
 219
 220   if (kvm_read (core_kd, (unsigned long) paddr, &pcb, sizeof pcb) == -1)
 221     error (("%s"), kvm_geterr (core_kd));
 222
 223   gdb_assert (bsd_kvm_supply_pcb);
 224   return bsd_kvm_supply_pcb (regcache, &pcb);
 225 }
 226
 227 void
 228 bsd_kvm_target::fetch_registers (struct regcache *regcache, int regnum)
 229 {
 230   struct nlist nl[2];
 231
 232   if (bsd_kvm_paddr)
 233     {
 234       bsd_kvm_fetch_pcb (regcache, bsd_kvm_paddr);
 235       return;
 236     }
 237
 238   /* On dumping core, BSD kernels store the faulting context (PCB)
 239      in the variable "dumppcb".  */
 240   memset (nl, 0, sizeof nl);
 241   nl[0].n_name = (char *) "_dumppcb";
 242
 243   if (kvm_nlist (core_kd, nl) == -1)
 244     error (("%s"), kvm_geterr (core_kd));
 245
 246   if (nl[0].n_value != 0)
 247     {
 248       /* Found dumppcb.  If it contains a valid context, return
 249          immediately.  */
 250       if (bsd_kvm_fetch_pcb (regcache, (struct pcb *) nl[0].n_value))
 251         return;
 252     }
 253
 254   /* Traditional BSD kernels have a process proc0 that should always
 255      be present.  The address of proc0's PCB is stored in the variable
 256      "proc0paddr".  */
 257
 258   memset (nl, 0, sizeof nl);
 259   nl[0].n_name = (char *) "_proc0paddr";
 260
 261   if (kvm_nlist (core_kd, nl) == -1)
 262     error (("%s"), kvm_geterr (core_kd));
 263
 264   if (nl[0].n_value != 0)
 265     {
 266       struct pcb *paddr;
 267
 268       /* Found proc0paddr.  */
 269       if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
 270         error (("%s"), kvm_geterr (core_kd));
 271
 272       bsd_kvm_fetch_pcb (regcache, paddr);
 273       return;
 274     }
 275
 276 #ifdef HAVE_STRUCT_THREAD_TD_PCB
 277   /* In FreeBSD kernels for 5.0-RELEASE and later, the PCB no longer
 278      lives in `struct proc' but in `struct thread'.  The `struct
 279      thread' for the initial thread for proc0 can be found in the
 280      variable "thread0".  */
 281
 282   memset (nl, 0, sizeof nl);
 283   nl[0].n_name = (char *) "_thread0";
 284
 285   if (kvm_nlist (core_kd, nl) == -1)
 286     error (("%s"), kvm_geterr (core_kd));
 287
 288   if (nl[0].n_value != 0)
 289     {
 290       struct pcb *paddr;
 291
 292       /* Found thread0.  */
 293       nl[0].n_value += offsetof (struct thread, td_pcb);
 294       if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
 295         error (("%s"), kvm_geterr (core_kd));
 296
 297       bsd_kvm_fetch_pcb (regcache, paddr);
 298       return;
 299     }
 300 #endif
 301
 302   /* i18n: PCB == "Process Control Block".  */
 303   error (_("Cannot find a valid PCB"));
 304 }
 305 \f
 306
 307 /* Kernel memory interface commands.  */
 308 struct cmd_list_element *bsd_kvm_cmdlist;
 309
 310 static void
 311 bsd_kvm_cmd (const char *arg, int fromtty)
 312 {
 313   /* ??? Should this become an alias for "target kvm"?  */
 314 }
 315
 316 #ifndef HAVE_STRUCT_THREAD_TD_PCB
 317
 318 static void
 319 bsd_kvm_proc_cmd (const char *arg, int fromtty)
 320 {
 321   CORE_ADDR addr;
 322
 323   if (arg == NULL)
 324     error_no_arg (_("proc address"));
 325
 326   if (core_kd == NULL)
 327     error (_("No kernel memory image."));
 328
 329   addr = parse_and_eval_address (arg);
 330 #ifdef HAVE_STRUCT_LWP
 331   addr += offsetof (struct lwp, l_addr);
 332 #else
 333   addr += offsetof (struct proc, p_addr);
 334 #endif
 335
 336   if (kvm_read (core_kd, addr, &bsd_kvm_paddr, sizeof bsd_kvm_paddr) == -1)
 337     error (("%s"), kvm_geterr (core_kd));
 338
 339   target_fetch_registers (get_current_regcache (), -1);
 340
 341   reinit_frame_cache ();
 342   print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
 343 }
 344
 345 #endif
 346
 347 static void
 348 bsd_kvm_pcb_cmd (const char *arg, int fromtty)
 349 {
 350   if (arg == NULL)
 351     /* i18n: PCB == "Process Control Block".  */
 352     error_no_arg (_("pcb address"));
 353
 354   if (core_kd == NULL)
 355     error (_("No kernel memory image."));
 356
 357   bsd_kvm_paddr = (struct pcb *)(u_long) parse_and_eval_address (arg);
 358
 359   target_fetch_registers (get_current_regcache (), -1);
 360
 361   reinit_frame_cache ();
 362   print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
 363 }
 364
 365 bool
 366 bsd_kvm_target::thread_alive (ptid_t ptid)
 367 {
 368   return true;
 369 }
 370
 371 std::string
 372 bsd_kvm_target::pid_to_str (ptid_t ptid)
 373 {
 374   return "<kvm>";
 375 }
 376
 377 /* Add the libkvm interface to the list of all possible targets and
 378    register CUPPLY_PCB as the architecture-specific process control
 379    block interpreter.  */
 380
 381 void
 382 bsd_kvm_add_target (int (*supply_pcb)(struct regcache *, struct pcb *))
 383 {
 384   gdb_assert (bsd_kvm_supply_pcb == NULL);
 385   bsd_kvm_supply_pcb = supply_pcb;
 386
 387   add_target (bsd_kvm_target_info, bsd_kvm_target_open);
 388
 389   add_prefix_cmd ("kvm", class_obscure, bsd_kvm_cmd, _("\
 390 Generic command for manipulating the kernel memory interface."),
 391                   &bsd_kvm_cmdlist, 0, &cmdlist);
 392
 393 #ifndef HAVE_STRUCT_THREAD_TD_PCB
 394   add_cmd ("proc", class_obscure, bsd_kvm_proc_cmd,
 395            _("Set current context from proc address"), &bsd_kvm_cmdlist);
 396 #endif
 397   add_cmd ("pcb", class_obscure, bsd_kvm_pcb_cmd,
 398            /* i18n: PCB == "Process Control Block".  */
 399            _("Set current context from pcb address"), &bsd_kvm_cmdlist);
 400
 401   /* Some notes on the ptid usage on this target.
 402
 403      The pid field represents the kvm inferior instance.  Currently,
 404      we don't support multiple kvm inferiors, but we start at 1
 405      anyway.  The lwp field is set to != 0, in case the core wants to
 406      refer to the whole kvm inferior with ptid(1,0,0).
 407
 408      If kvm is made to export running processes as gdb threads,
 409      the following form can be used:
 410      ptid (1, 1, 0) -> kvm inferior 1, in kernel
 411      ptid (1, 1, 1) -> kvm inferior 1, process 1
 412      ptid (1, 1, 2) -> kvm inferior 1, process 2
 413      ptid (1, 1, n) -> kvm inferior 1, process n  */
 414
 415   bsd_kvm_ptid = ptid_t (1, 1, 0);
 416 }