gdbstub/system.c

   1 /*
   2  * gdb server stub - softmmu specific bits
   3  *
   4  * Debug integration depends on support from the individual
   5  * accelerators so most of this involves calling the ops helpers.
   6  *
   7  * Copyright (c) 2003-2005 Fabrice Bellard
   8  * Copyright (c) 2022 Linaro Ltd
   9  *
  10  * SPDX-License-Identifier: LGPL-2.0+
  11  */
  12
  13 #include "qemu/osdep.h"
  14 #include "qapi/error.h"
  15 #include "qemu/error-report.h"
  16 #include "qemu/cutils.h"
  17 #include "exec/gdbstub.h"
  18 #include "gdbstub/syscalls.h"
  19 #include "exec/hwaddr.h"
  20 #include "exec/tb-flush.h"
  21 #include "sysemu/cpus.h"
  22 #include "sysemu/runstate.h"
  23 #include "sysemu/replay.h"
  24 #include "hw/core/cpu.h"
  25 #include "hw/cpu/cluster.h"
  26 #include "hw/boards.h"
  27 #include "chardev/char.h"
  28 #include "chardev/char-fe.h"
  29 #include "monitor/monitor.h"
  30 #include "trace.h"
  31 #include "internals.h"
  32
  33 /* System emulation specific state */
  34 typedef struct {
  35     CharBackend chr;
  36     Chardev *mon_chr;
  37 } GDBSystemState;
  38
  39 GDBSystemState gdbserver_system_state;
  40
  41 static void reset_gdbserver_state(void)
  42 {
  43     g_free(gdbserver_state.processes);
  44     gdbserver_state.processes = NULL;
  45     gdbserver_state.process_num = 0;
  46     gdbserver_state.allow_stop_reply = false;
  47 }
  48
  49 /*
  50  * Return the GDB index for a given vCPU state.
  51  *
  52  * In system mode GDB numbers CPUs from 1 as 0 is reserved as an "any
  53  * cpu" index.
  54  */
  55 int gdb_get_cpu_index(CPUState *cpu)
  56 {
  57     return cpu->cpu_index + 1;
  58 }
  59
  60 /*
  61  * We check the status of the last message in the chardev receive code
  62  */
  63 bool gdb_got_immediate_ack(void)
  64 {
  65     return true;
  66 }
  67
  68 /*
  69  * GDB Connection management. For system emulation we do all of this
  70  * via our existing Chardev infrastructure which allows us to support
  71  * network and unix sockets.
  72  */
  73
  74 void gdb_put_buffer(const uint8_t *buf, int len)
  75 {
  76     /*
  77      * XXX this blocks entire thread. Rewrite to use
  78      * qemu_chr_fe_write and background I/O callbacks
  79      */
  80     qemu_chr_fe_write_all(&gdbserver_system_state.chr, buf, len);
  81 }
  82
  83 static void gdb_chr_event(void *opaque, QEMUChrEvent event)
  84 {
  85     int i;
  86     GDBState *s = (GDBState *) opaque;
  87
  88     switch (event) {
  89     case CHR_EVENT_OPENED:
  90         /* Start with first process attached, others detached */
  91         for (i = 0; i < s->process_num; i++) {
  92             s->processes[i].attached = !i;
  93         }
  94
  95         s->c_cpu = gdb_first_attached_cpu();
  96         s->g_cpu = s->c_cpu;
  97
  98         vm_stop(RUN_STATE_PAUSED);
  99         replay_gdb_attached();
 100         break;
 101     default:
 102         break;
 103     }
 104 }
 105
 106 /*
 107  * In system-mode we stop the VM and wait to send the syscall packet
 108  * until notification that the CPU has stopped. This must be done
 109  * because if the packet is sent now the reply from the syscall
 110  * request could be received while the CPU is still in the running
 111  * state, which can cause packets to be dropped and state transition
 112  * 'T' packets to be sent while the syscall is still being processed.
 113  */
 114 void gdb_syscall_handling(const char *syscall_packet)
 115 {
 116     vm_stop(RUN_STATE_DEBUG);
 117     qemu_cpu_kick(gdbserver_state.c_cpu);
 118 }
 119
 120 static void gdb_vm_state_change(void *opaque, bool running, RunState state)
 121 {
 122     CPUState *cpu = gdbserver_state.c_cpu;
 123     g_autoptr(GString) buf = g_string_new(NULL);
 124     g_autoptr(GString) tid = g_string_new(NULL);
 125     const char *type;
 126     int ret;
 127
 128     if (running || gdbserver_state.state == RS_INACTIVE) {
 129         return;
 130     }
 131
 132     /* Is there a GDB syscall waiting to be sent?  */
 133     if (gdb_handled_syscall()) {
 134         return;
 135     }
 136
 137     if (cpu == NULL) {
 138         /* No process attached */
 139         return;
 140     }
 141
 142     if (!gdbserver_state.allow_stop_reply) {
 143         return;
 144     }
 145
 146     gdb_append_thread_id(cpu, tid);
 147
 148     switch (state) {
 149     case RUN_STATE_DEBUG:
 150         if (cpu->watchpoint_hit) {
 151             switch (cpu->watchpoint_hit->flags & BP_MEM_ACCESS) {
 152             case BP_MEM_READ:
 153                 type = "r";
 154                 break;
 155             case BP_MEM_ACCESS:
 156                 type = "a";
 157                 break;
 158             default:
 159                 type = "";
 160                 break;
 161             }
 162             trace_gdbstub_hit_watchpoint(type,
 163                                          gdb_get_cpu_index(cpu),
 164                                          cpu->watchpoint_hit->vaddr);
 165             g_string_printf(buf, "T%02xthread:%s;%swatch:%" VADDR_PRIx ";",
 166                             GDB_SIGNAL_TRAP, tid->str, type,
 167                             cpu->watchpoint_hit->vaddr);
 168             cpu->watchpoint_hit = NULL;
 169             goto send_packet;
 170         } else {
 171             trace_gdbstub_hit_break();
 172         }
 173         tb_flush(cpu);
 174         ret = GDB_SIGNAL_TRAP;
 175         break;
 176     case RUN_STATE_PAUSED:
 177         trace_gdbstub_hit_paused();
 178         ret = GDB_SIGNAL_INT;
 179         break;
 180     case RUN_STATE_SHUTDOWN:
 181         trace_gdbstub_hit_shutdown();
 182         ret = GDB_SIGNAL_QUIT;
 183         break;
 184     case RUN_STATE_IO_ERROR:
 185         trace_gdbstub_hit_io_error();
 186         ret = GDB_SIGNAL_IO;
 187         break;
 188     case RUN_STATE_WATCHDOG:
 189         trace_gdbstub_hit_watchdog();
 190         ret = GDB_SIGNAL_ALRM;
 191         break;
 192     case RUN_STATE_INTERNAL_ERROR:
 193         trace_gdbstub_hit_internal_error();
 194         ret = GDB_SIGNAL_ABRT;
 195         break;
 196     case RUN_STATE_SAVE_VM:
 197     case RUN_STATE_RESTORE_VM:
 198         return;
 199     case RUN_STATE_FINISH_MIGRATE:
 200         ret = GDB_SIGNAL_XCPU;
 201         break;
 202     default:
 203         trace_gdbstub_hit_unknown(state);
 204         ret = GDB_SIGNAL_UNKNOWN;
 205         break;
 206     }
 207     gdb_set_stop_cpu(cpu);
 208     g_string_printf(buf, "T%02xthread:%s;", ret, tid->str);
 209
 210 send_packet:
 211     gdb_put_packet(buf->str);
 212     gdbserver_state.allow_stop_reply = false;
 213
 214     /* disable single step if it was enabled */
 215     cpu_single_step(cpu, 0);
 216 }
 217
 218 #ifndef _WIN32
 219 static void gdb_sigterm_handler(int signal)
 220 {
 221     if (runstate_is_running()) {
 222         vm_stop(RUN_STATE_PAUSED);
 223     }
 224 }
 225 #endif
 226
 227 static int gdb_monitor_write(Chardev *chr, const uint8_t *buf, int len)
 228 {
 229     g_autoptr(GString) hex_buf = g_string_new("O");
 230     gdb_memtohex(hex_buf, buf, len);
 231     gdb_put_packet(hex_buf->str);
 232     return len;
 233 }
 234
 235 static void gdb_monitor_open(Chardev *chr, ChardevBackend *backend,
 236                              bool *be_opened, Error **errp)
 237 {
 238     *be_opened = false;
 239 }
 240
 241 static void char_gdb_class_init(ObjectClass *oc, void *data)
 242 {
 243     ChardevClass *cc = CHARDEV_CLASS(oc);
 244
 245     cc->internal = true;
 246     cc->open = gdb_monitor_open;
 247     cc->chr_write = gdb_monitor_write;
 248 }
 249
 250 #define TYPE_CHARDEV_GDB "chardev-gdb"
 251
 252 static const TypeInfo char_gdb_type_info = {
 253     .name = TYPE_CHARDEV_GDB,
 254     .parent = TYPE_CHARDEV,
 255     .class_init = char_gdb_class_init,
 256 };
 257
 258 static int gdb_chr_can_receive(void *opaque)
 259 {
 260   /*
 261    * We can handle an arbitrarily large amount of data.
 262    * Pick the maximum packet size, which is as good as anything.
 263    */
 264   return MAX_PACKET_LENGTH;
 265 }
 266
 267 static void gdb_chr_receive(void *opaque, const uint8_t *buf, int size)
 268 {
 269     int i;
 270
 271     for (i = 0; i < size; i++) {
 272         gdb_read_byte(buf[i]);
 273     }
 274 }
 275
 276 static int find_cpu_clusters(Object *child, void *opaque)
 277 {
 278     if (object_dynamic_cast(child, TYPE_CPU_CLUSTER)) {
 279         GDBState *s = (GDBState *) opaque;
 280         CPUClusterState *cluster = CPU_CLUSTER(child);
 281         GDBProcess *process;
 282
 283         s->processes = g_renew(GDBProcess, s->processes, ++s->process_num);
 284
 285         process = &s->processes[s->process_num - 1];
 286
 287         /*
 288          * GDB process IDs -1 and 0 are reserved. To avoid subtle errors at
 289          * runtime, we enforce here that the machine does not use a cluster ID
 290          * that would lead to PID 0.
 291          */
 292         assert(cluster->cluster_id != UINT32_MAX);
 293         process->pid = cluster->cluster_id + 1;
 294         process->attached = false;
 295         process->target_xml = NULL;
 296
 297         return 0;
 298     }
 299
 300     return object_child_foreach(child, find_cpu_clusters, opaque);
 301 }
 302
 303 static int pid_order(const void *a, const void *b)
 304 {
 305     GDBProcess *pa = (GDBProcess *) a;
 306     GDBProcess *pb = (GDBProcess *) b;
 307
 308     if (pa->pid < pb->pid) {
 309         return -1;
 310     } else if (pa->pid > pb->pid) {
 311         return 1;
 312     } else {
 313         return 0;
 314     }
 315 }
 316
 317 static void create_processes(GDBState *s)
 318 {
 319     object_child_foreach(object_get_root(), find_cpu_clusters, s);
 320
 321     if (gdbserver_state.processes) {
 322         /* Sort by PID */
 323         qsort(gdbserver_state.processes,
 324               gdbserver_state.process_num,
 325               sizeof(gdbserver_state.processes[0]),
 326               pid_order);
 327     }
 328
 329     gdb_create_default_process(s);
 330 }
 331
 332 int gdbserver_start(const char *device)
 333 {
 334     Chardev *chr = NULL;
 335     Chardev *mon_chr;
 336     g_autoptr(GString) cs = g_string_new(device);
 337
 338     if (!first_cpu) {
 339         error_report("gdbstub: meaningless to attach gdb to a "
 340                      "machine without any CPU.");
 341         return -1;
 342     }
 343
 344     if (!gdb_supports_guest_debug()) {
 345         error_report("gdbstub: current accelerator doesn't "
 346                      "support guest debugging");
 347         return -1;
 348     }
 349
 350     if (cs->len == 0) {
 351         return -1;
 352     }
 353
 354     trace_gdbstub_op_start(cs->str);
 355
 356     if (g_strcmp0(cs->str, "none") != 0) {
 357         if (g_str_has_prefix(cs->str, "tcp:")) {
 358             /* enforce required TCP attributes */
 359             g_string_append_printf(cs, ",wait=off,nodelay=on,server=on");
 360         }
 361 #ifndef _WIN32
 362         else if (strcmp(device, "stdio") == 0) {
 363             struct sigaction act;
 364
 365             memset(&act, 0, sizeof(act));
 366             act.sa_handler = gdb_sigterm_handler;
 367             sigaction(SIGINT, &act, NULL);
 368         }
 369 #endif
 370         /*
 371          * FIXME: it's a bit weird to allow using a mux chardev here
 372          * and implicitly setup a monitor. We may want to break this.
 373          */
 374         chr = qemu_chr_new_noreplay("gdb", cs->str, true, NULL);
 375         if (!chr) {
 376             return -1;
 377         }
 378     }
 379
 380     if (!gdbserver_state.init) {
 381         gdb_init_gdbserver_state();
 382
 383         qemu_add_vm_change_state_handler(gdb_vm_state_change, NULL);
 384
 385         /* Initialize a monitor terminal for gdb */
 386         mon_chr = qemu_chardev_new(NULL, TYPE_CHARDEV_GDB,
 387                                    NULL, NULL, &error_abort);
 388         monitor_init_hmp(mon_chr, false, &error_abort);
 389     } else {
 390         qemu_chr_fe_deinit(&gdbserver_system_state.chr, true);
 391         mon_chr = gdbserver_system_state.mon_chr;
 392         reset_gdbserver_state();
 393     }
 394
 395     create_processes(&gdbserver_state);
 396
 397     if (chr) {
 398         qemu_chr_fe_init(&gdbserver_system_state.chr, chr, &error_abort);
 399         qemu_chr_fe_set_handlers(&gdbserver_system_state.chr,
 400                                  gdb_chr_can_receive,
 401                                  gdb_chr_receive, gdb_chr_event,
 402                                  NULL, &gdbserver_state, NULL, true);
 403     }
 404     gdbserver_state.state = chr ? RS_IDLE : RS_INACTIVE;
 405     gdbserver_system_state.mon_chr = mon_chr;
 406     gdb_syscall_reset();
 407
 408     return 0;
 409 }
 410
 411 static void register_types(void)
 412 {
 413     type_register_static(&char_gdb_type_info);
 414 }
 415
 416 type_init(register_types);
 417
 418 /* Tell the remote gdb that the process has exited.  */
 419 void gdb_exit(int code)
 420 {
 421     char buf[4];
 422
 423     if (!gdbserver_state.init) {
 424         return;
 425     }
 426
 427     trace_gdbstub_op_exiting((uint8_t)code);
 428
 429     if (gdbserver_state.allow_stop_reply) {
 430         snprintf(buf, sizeof(buf), "W%02x", (uint8_t)code);
 431         gdb_put_packet(buf);
 432         gdbserver_state.allow_stop_reply = false;
 433     }
 434
 435     qemu_chr_fe_deinit(&gdbserver_system_state.chr, true);
 436 }
 437
 438 void gdb_qemu_exit(int code)
 439 {
 440     qemu_system_shutdown_request_with_code(SHUTDOWN_CAUSE_GUEST_SHUTDOWN,
 441                                            code);
 442 }
 443
 444 /*
 445  * Memory access
 446  */
 447 static int phy_memory_mode;
 448
 449 int gdb_target_memory_rw_debug(CPUState *cpu, hwaddr addr,
 450                                uint8_t *buf, int len, bool is_write)
 451 {
 452     CPUClass *cc;
 453
 454     if (phy_memory_mode) {
 455         if (is_write) {
 456             cpu_physical_memory_write(addr, buf, len);
 457         } else {
 458             cpu_physical_memory_read(addr, buf, len);
 459         }
 460         return 0;
 461     }
 462
 463     cc = CPU_GET_CLASS(cpu);
 464     if (cc->memory_rw_debug) {
 465         return cc->memory_rw_debug(cpu, addr, buf, len, is_write);
 466     }
 467
 468     return cpu_memory_rw_debug(cpu, addr, buf, len, is_write);
 469 }
 470
 471 /*
 472  * cpu helpers
 473  */
 474
 475 unsigned int gdb_get_max_cpus(void)
 476 {
 477     MachineState *ms = MACHINE(qdev_get_machine());
 478     return ms->smp.max_cpus;
 479 }
 480
 481 bool gdb_can_reverse(void)
 482 {
 483     return replay_mode == REPLAY_MODE_PLAY;
 484 }
 485
 486 /*
 487  * Softmmu specific command helpers
 488  */
 489
 490 void gdb_handle_query_qemu_phy_mem_mode(GArray *params,
 491                                         void *user_ctx)
 492 {
 493     g_string_printf(gdbserver_state.str_buf, "%d", phy_memory_mode);
 494     gdb_put_strbuf();
 495 }
 496
 497 void gdb_handle_set_qemu_phy_mem_mode(GArray *params, void *user_ctx)
 498 {
 499     if (!params->len) {
 500         gdb_put_packet("E22");
 501         return;
 502     }
 503
 504     if (!get_param(params, 0)->val_ul) {
 505         phy_memory_mode = 0;
 506     } else {
 507         phy_memory_mode = 1;
 508     }
 509     gdb_put_packet("OK");
 510 }
 511
 512 void gdb_handle_query_rcmd(GArray *params, void *user_ctx)
 513 {
 514     const guint8 zero = 0;
 515     int len;
 516
 517     if (!params->len) {
 518         gdb_put_packet("E22");
 519         return;
 520     }
 521
 522     len = strlen(get_param(params, 0)->data);
 523     if (len % 2) {
 524         gdb_put_packet("E01");
 525         return;
 526     }
 527
 528     g_assert(gdbserver_state.mem_buf->len == 0);
 529     len = len / 2;
 530     gdb_hextomem(gdbserver_state.mem_buf, get_param(params, 0)->data, len);
 531     g_byte_array_append(gdbserver_state.mem_buf, &zero, 1);
 532     qemu_chr_be_write(gdbserver_system_state.mon_chr,
 533                       gdbserver_state.mem_buf->data,
 534                       gdbserver_state.mem_buf->len);
 535     gdb_put_packet("OK");
 536 }
 537
 538 /*
 539  * Execution state helpers
 540  */
 541
 542 void gdb_handle_query_attached(GArray *params, void *user_ctx)
 543 {
 544     gdb_put_packet("1");
 545 }
 546
 547 void gdb_continue(void)
 548 {
 549     if (!runstate_needs_reset()) {
 550         trace_gdbstub_op_continue();
 551         vm_start();
 552     }
 553 }
 554
 555 /*
 556  * Resume execution, per CPU actions.
 557  */
 558 int gdb_continue_partial(char *newstates)
 559 {
 560     CPUState *cpu;
 561     int res = 0;
 562     int flag = 0;
 563
 564     if (!runstate_needs_reset()) {
 565         bool step_requested = false;
 566         CPU_FOREACH(cpu) {
 567             if (newstates[cpu->cpu_index] == 's') {
 568                 step_requested = true;
 569                 break;
 570             }
 571         }
 572
 573         if (vm_prepare_start(step_requested)) {
 574             return 0;
 575         }
 576
 577         CPU_FOREACH(cpu) {
 578             switch (newstates[cpu->cpu_index]) {
 579             case 0:
 580             case 1:
 581                 break; /* nothing to do here */
 582             case 's':
 583                 trace_gdbstub_op_stepping(cpu->cpu_index);
 584                 cpu_single_step(cpu, gdbserver_state.sstep_flags);
 585                 cpu_resume(cpu);
 586                 flag = 1;
 587                 break;
 588             case 'c':
 589                 trace_gdbstub_op_continue_cpu(cpu->cpu_index);
 590                 cpu_resume(cpu);
 591                 flag = 1;
 592                 break;
 593             default:
 594                 res = -1;
 595                 break;
 596             }
 597         }
 598     }
 599     if (flag) {
 600         qemu_clock_enable(QEMU_CLOCK_VIRTUAL, true);
 601     }
 602     return res;
 603 }
 604
 605 /*
 606  * Signal Handling - in system mode we only need SIGINT and SIGTRAP; other
 607  * signals are not yet supported.
 608  */
 609
 610 enum {
 611     TARGET_SIGINT = 2,
 612     TARGET_SIGTRAP = 5
 613 };
 614
 615 int gdb_signal_to_target(int sig)
 616 {
 617     switch (sig) {
 618     case 2:
 619         return TARGET_SIGINT;
 620     case 5:
 621         return TARGET_SIGTRAP;
 622     default:
 623         return -1;
 624     }
 625 }
 626
 627 /*
 628  * Break/Watch point helpers
 629  */
 630
 631 bool gdb_supports_guest_debug(void)
 632 {
 633     const AccelOpsClass *ops = cpus_get_accel();
 634     if (ops->supports_guest_debug) {
 635         return ops->supports_guest_debug();
 636     }
 637     return false;
 638 }
 639
 640 int gdb_breakpoint_insert(CPUState *cs, int type, vaddr addr, vaddr len)
 641 {
 642     const AccelOpsClass *ops = cpus_get_accel();
 643     if (ops->insert_breakpoint) {
 644         return ops->insert_breakpoint(cs, type, addr, len);
 645     }
 646     return -ENOSYS;
 647 }
 648
 649 int gdb_breakpoint_remove(CPUState *cs, int type, vaddr addr, vaddr len)
 650 {
 651     const AccelOpsClass *ops = cpus_get_accel();
 652     if (ops->remove_breakpoint) {
 653         return ops->remove_breakpoint(cs, type, addr, len);
 654     }
 655     return -ENOSYS;
 656 }
 657
 658 void gdb_breakpoint_remove_all(CPUState *cs)
 659 {
 660     const AccelOpsClass *ops = cpus_get_accel();
 661     if (ops->remove_all_breakpoints) {
 662         ops->remove_all_breakpoints(cs);
 663     }
 664 }