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