gdb/bsd-kvm.c

   1 /* BSD Kernel Data Access Library (libkvm) interface.
   2
   3    Copyright (C) 2004-2023 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 "filenames.h"
  25 #include "frame.h"
  26 #include "regcache.h"
  27 #include "target.h"
  28 #include "process-stratum-target.h"
  29 #include "value.h"
  30 #include "gdbcore.h"
  31 #include "inferior.h"
  32 #include "gdbthread.h"
  33 #include "gdbsupport/pathstuff.h"
  34 #include "gdbsupport/gdb_tilde_expand.h"
  35
  36 #include <fcntl.h>
  37 #include <kvm.h>
  38 #ifdef HAVE_NLIST_H
  39 #include <nlist.h>
  40 #endif
  41 #include <paths.h>
  42 #include "readline/readline.h"
  43 #include <sys/param.h>
  44 #include <sys/proc.h>
  45 #ifdef HAVE_SYS_USER_H
  46 #include <sys/user.h>
  47 #endif
  48
  49 #include "bsd-kvm.h"
  50
  51 /* Kernel memory device file.  */
  52 static std::string bsd_kvm_corefile;
  53
  54 /* Kernel memory interface descriptor.  */
  55 static kvm_t *core_kd;
  56
  57 /* Address of process control block.  */
  58 static struct pcb *bsd_kvm_paddr;
  59
  60 /* Pointer to architecture-specific function that reconstructs the
  61    register state from PCB and supplies it to REGCACHE.  */
  62 static int (*bsd_kvm_supply_pcb)(struct regcache *regcache, struct pcb *pcb);
  63
  64 /* This is the ptid we use while we're connected to kvm.  The kvm
  65    target currently doesn't export any view of the running processes,
  66    so this represents the kernel task.  */
  67 static ptid_t bsd_kvm_ptid;
  68
  69 /* The libkvm target.  */
  70
  71 static const target_info bsd_kvm_target_info = {
  72   "kvm",
  73   N_("Kernel memory interface"),
  74   N_("Use a kernel virtual memory image as a target.\n\
  75 Optionally specify the filename of a core dump.")
  76 };
  77
  78 class bsd_kvm_target final : public process_stratum_target
  79 {
  80 public:
  81   bsd_kvm_target () = default;
  82
  83   const target_info &info () const override
  84   { return bsd_kvm_target_info; }
  85
  86   void close () override;
  87
  88   void fetch_registers (struct regcache *, int) override;
  89   enum target_xfer_status xfer_partial (enum target_object object,
  90                                         const char *annex,
  91                                         gdb_byte *readbuf,
  92                                         const gdb_byte *writebuf,
  93                                         ULONGEST offset, ULONGEST len,
  94                                         ULONGEST *xfered_len) override;
  95
  96   void files_info () override;
  97   bool thread_alive (ptid_t ptid) override;
  98   std::string pid_to_str (ptid_t) override;
  99
 100   bool has_memory () override { return true; }
 101   bool has_stack () override { return true; }
 102   bool has_registers () override { return true; }
 103 };
 104
 105 /* Target ops for libkvm interface.  */
 106 static bsd_kvm_target bsd_kvm_ops;
 107
 108 static void
 109 bsd_kvm_target_open (const char *arg, int from_tty)
 110 {
 111   char errbuf[_POSIX2_LINE_MAX];
 112   const char *execfile = NULL;
 113   kvm_t *temp_kd;
 114   std::string filename;
 115
 116   target_preopen (from_tty);
 117
 118   if (arg)
 119     {
 120       filename = gdb_tilde_expand (arg);
 121       if (!IS_ABSOLUTE_PATH (filename))
 122         filename = gdb_abspath (filename.c_str ());
 123     }
 124
 125   execfile = get_exec_file (0);
 126   temp_kd = kvm_openfiles (execfile, filename.c_str (), NULL,
 127                            write_files ? O_RDWR : O_RDONLY, errbuf);
 128   if (temp_kd == NULL)
 129     error (("%s"), errbuf);
 130
 131   bsd_kvm_corefile = filename;
 132   current_inferior ()->unpush_target (&bsd_kvm_ops);
 133   core_kd = temp_kd;
 134   current_inferior ()->push_target (&bsd_kvm_ops);
 135
 136   thread_info *thr = add_thread_silent (&bsd_kvm_ops, bsd_kvm_ptid);
 137   switch_to_thread (thr);
 138
 139   target_fetch_registers (get_current_regcache (), -1);
 140
 141   reinit_frame_cache ();
 142   print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
 143 }
 144
 145 void
 146 bsd_kvm_target::close ()
 147 {
 148   if (core_kd)
 149     {
 150       if (kvm_close (core_kd) == -1)
 151         warning (("%s"), kvm_geterr(core_kd));
 152       core_kd = NULL;
 153     }
 154
 155   bsd_kvm_corefile.clear ();
 156   switch_to_no_thread ();
 157   exit_inferior (current_inferior ());
 158 }
 159
 160 static LONGEST
 161 bsd_kvm_xfer_memory (CORE_ADDR addr, ULONGEST len,
 162                      gdb_byte *readbuf, const gdb_byte *writebuf)
 163 {
 164   ssize_t nbytes = len;
 165
 166   if (readbuf)
 167     nbytes = kvm_read (core_kd, addr, readbuf, nbytes);
 168   if (writebuf && nbytes > 0)
 169     nbytes = kvm_write (core_kd, addr, writebuf, nbytes);
 170   return nbytes;
 171 }
 172
 173 enum target_xfer_status
 174 bsd_kvm_target::xfer_partial (enum target_object object,
 175                               const char *annex, gdb_byte *readbuf,
 176                               const gdb_byte *writebuf,
 177                               ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
 178 {
 179   switch (object)
 180     {
 181     case TARGET_OBJECT_MEMORY:
 182       {
 183         LONGEST ret = bsd_kvm_xfer_memory (offset, len, readbuf, writebuf);
 184
 185         if (ret < 0)
 186           return TARGET_XFER_E_IO;
 187         else if (ret == 0)
 188           return TARGET_XFER_EOF;
 189         else
 190           {
 191             *xfered_len = (ULONGEST) ret;
 192             return TARGET_XFER_OK;
 193           }
 194       }
 195
 196     default:
 197       return TARGET_XFER_E_IO;
 198     }
 199 }
 200
 201 void
 202 bsd_kvm_target::files_info ()
 203 {
 204   if (bsd_kvm_corefile != _PATH_MEM)
 205     gdb_printf (_("\tUsing the kernel crash dump %s.\n"),
 206                 bsd_kvm_corefile.c_str ());
 207   else
 208     gdb_printf (_("\tUsing the currently running kernel.\n"));
 209 }
 210
 211 /* Fetch process control block at address PADDR.  */
 212
 213 static int
 214 bsd_kvm_fetch_pcb (struct regcache *regcache, struct pcb *paddr)
 215 {
 216   struct pcb pcb;
 217
 218   if (kvm_read (core_kd, (unsigned long) paddr, &pcb, sizeof pcb) == -1)
 219     error (("%s"), kvm_geterr (core_kd));
 220
 221   gdb_assert (bsd_kvm_supply_pcb);
 222   return bsd_kvm_supply_pcb (regcache, &pcb);
 223 }
 224
 225 void
 226 bsd_kvm_target::fetch_registers (struct regcache *regcache, int regnum)
 227 {
 228   struct nlist nl[2];
 229
 230   if (bsd_kvm_paddr)
 231     {
 232       bsd_kvm_fetch_pcb (regcache, bsd_kvm_paddr);
 233       return;
 234     }
 235
 236   /* On dumping core, BSD kernels store the faulting context (PCB)
 237      in the variable "dumppcb".  */
 238   memset (nl, 0, sizeof nl);
 239   nl[0].n_name = (char *) "_dumppcb";
 240
 241   if (kvm_nlist (core_kd, nl) == -1)
 242     error (("%s"), kvm_geterr (core_kd));
 243
 244   if (nl[0].n_value != 0)
 245     {
 246       /* Found dumppcb.  If it contains a valid context, return
 247          immediately.  */
 248       if (bsd_kvm_fetch_pcb (regcache, (struct pcb *) nl[0].n_value))
 249         return;
 250     }
 251
 252   /* Traditional BSD kernels have a process proc0 that should always
 253      be present.  The address of proc0's PCB is stored in the variable
 254      "proc0paddr".  */
 255
 256   memset (nl, 0, sizeof nl);
 257   nl[0].n_name = (char *) "_proc0paddr";
 258
 259   if (kvm_nlist (core_kd, nl) == -1)
 260     error (("%s"), kvm_geterr (core_kd));
 261
 262   if (nl[0].n_value != 0)
 263     {
 264       struct pcb *paddr;
 265
 266       /* Found proc0paddr.  */
 267       if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
 268         error (("%s"), kvm_geterr (core_kd));
 269
 270       bsd_kvm_fetch_pcb (regcache, paddr);
 271       return;
 272     }
 273
 274 #ifdef HAVE_STRUCT_THREAD_TD_PCB
 275   /* In FreeBSD kernels for 5.0-RELEASE and later, the PCB no longer
 276      lives in `struct proc' but in `struct thread'.  The `struct
 277      thread' for the initial thread for proc0 can be found in the
 278      variable "thread0".  */
 279
 280   memset (nl, 0, sizeof nl);
 281   nl[0].n_name = (char *) "_thread0";
 282
 283   if (kvm_nlist (core_kd, nl) == -1)
 284     error (("%s"), kvm_geterr (core_kd));
 285
 286   if (nl[0].n_value != 0)
 287     {
 288       struct pcb *paddr;
 289
 290       /* Found thread0.  */
 291       nl[0].n_value += offsetof (struct thread, td_pcb);
 292       if (kvm_read (core_kd, nl[0].n_value, &paddr, sizeof paddr) == -1)
 293         error (("%s"), kvm_geterr (core_kd));
 294
 295       bsd_kvm_fetch_pcb (regcache, paddr);
 296       return;
 297     }
 298 #endif
 299
 300   /* i18n: PCB == "Process Control Block".  */
 301   error (_("Cannot find a valid PCB"));
 302 }
 303 \f
 304
 305 /* Kernel memory interface commands.  */
 306 struct cmd_list_element *bsd_kvm_cmdlist;
 307
 308 static void
 309 bsd_kvm_cmd (const char *arg, int fromtty)
 310 {
 311   /* ??? Should this become an alias for "target kvm"?  */
 312 }
 313
 314 #ifndef HAVE_STRUCT_THREAD_TD_PCB
 315
 316 static void
 317 bsd_kvm_proc_cmd (const char *arg, int fromtty)
 318 {
 319   CORE_ADDR addr;
 320
 321   if (arg == NULL)
 322     error_no_arg (_("proc address"));
 323
 324   if (core_kd == NULL)
 325     error (_("No kernel memory image."));
 326
 327   addr = parse_and_eval_address (arg);
 328 #ifdef HAVE_STRUCT_LWP
 329   addr += offsetof (struct lwp, l_addr);
 330 #else
 331   addr += offsetof (struct proc, p_addr);
 332 #endif
 333
 334   if (kvm_read (core_kd, addr, &bsd_kvm_paddr, sizeof bsd_kvm_paddr) == -1)
 335     error (("%s"), kvm_geterr (core_kd));
 336
 337   target_fetch_registers (get_current_regcache (), -1);
 338
 339   reinit_frame_cache ();
 340   print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
 341 }
 342
 343 #endif
 344
 345 static void
 346 bsd_kvm_pcb_cmd (const char *arg, int fromtty)
 347 {
 348   if (arg == NULL)
 349     /* i18n: PCB == "Process Control Block".  */
 350     error_no_arg (_("pcb address"));
 351
 352   if (core_kd == NULL)
 353     error (_("No kernel memory image."));
 354
 355   bsd_kvm_paddr = (struct pcb *)(u_long) parse_and_eval_address (arg);
 356
 357   target_fetch_registers (get_current_regcache (), -1);
 358
 359   reinit_frame_cache ();
 360   print_stack_frame (get_selected_frame (NULL), 0, SRC_AND_LOC, 1);
 361 }
 362
 363 bool
 364 bsd_kvm_target::thread_alive (ptid_t ptid)
 365 {
 366   return true;
 367 }
 368
 369 std::string
 370 bsd_kvm_target::pid_to_str (ptid_t ptid)
 371 {
 372   return "<kvm>";
 373 }
 374
 375 /* Add the libkvm interface to the list of all possible targets and
 376    register CUPPLY_PCB as the architecture-specific process control
 377    block interpreter.  */
 378
 379 void
 380 bsd_kvm_add_target (int (*supply_pcb)(struct regcache *, struct pcb *))
 381 {
 382   gdb_assert (bsd_kvm_supply_pcb == NULL);
 383   bsd_kvm_supply_pcb = supply_pcb;
 384
 385   add_target (bsd_kvm_target_info, bsd_kvm_target_open);
 386
 387   add_prefix_cmd ("kvm", class_obscure, bsd_kvm_cmd, _("\
 388 Generic command for manipulating the kernel memory interface."),
 389                   &bsd_kvm_cmdlist, 0, &cmdlist);
 390
 391 #ifndef HAVE_STRUCT_THREAD_TD_PCB
 392   add_cmd ("proc", class_obscure, bsd_kvm_proc_cmd,
 393            _("Set current context from proc address"), &bsd_kvm_cmdlist);
 394 #endif
 395   add_cmd ("pcb", class_obscure, bsd_kvm_pcb_cmd,
 396            /* i18n: PCB == "Process Control Block".  */
 397            _("Set current context from pcb address"), &bsd_kvm_cmdlist);
 398
 399   /* Some notes on the ptid usage on this target.
 400
 401      The pid field represents the kvm inferior instance.  Currently,
 402      we don't support multiple kvm inferiors, but we start at 1
 403      anyway.  The lwp field is set to != 0, in case the core wants to
 404      refer to the whole kvm inferior with ptid(1,0,0).
 405
 406      If kvm is made to export running processes as gdb threads,
 407      the following form can be used:
 408      ptid (1, 1, 0) -> kvm inferior 1, in kernel
 409      ptid (1, 1, 1) -> kvm inferior 1, process 1
 410      ptid (1, 1, 2) -> kvm inferior 1, process 2
 411      ptid (1, 1, n) -> kvm inferior 1, process n  */
 412
 413   bsd_kvm_ptid = ptid_t (1, 1, 0);
 414 }