kernel/debug/gdbstub.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Kernel Debug Core
   4  *
   5  * Maintainer: Jason Wessel <jason.wessel@windriver.com>
   6  *
   7  * Copyright (C) 2000-2001 VERITAS Software Corporation.
   8  * Copyright (C) 2002-2004 Timesys Corporation
   9  * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
  10  * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz>
  11  * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
  12  * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
  13  * Copyright (C) 2005-2009 Wind River Systems, Inc.
  14  * Copyright (C) 2007 MontaVista Software, Inc.
  15  * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  16  *
  17  * Contributors at various stages not listed above:
  18  *  Jason Wessel ( jason.wessel@windriver.com )
  19  *  George Anzinger <george@mvista.com>
  20  *  Anurekh Saxena (anurekh.saxena@timesys.com)
  21  *  Lake Stevens Instrument Division (Glenn Engel)
  22  *  Jim Kingdon, Cygnus Support.
  23  *
  24  * Original KGDB stub: David Grothe <dave@gcom.com>,
  25  * Tigran Aivazian <tigran@sco.com>
  26  */
  27
  28 #include <linux/kernel.h>
  29 #include <linux/sched/signal.h>
  30 #include <linux/kgdb.h>
  31 #include <linux/kdb.h>
  32 #include <linux/serial_core.h>
  33 #include <linux/reboot.h>
  34 #include <linux/uaccess.h>
  35 #include <asm/cacheflush.h>
  36 #include <asm/unaligned.h>
  37 #include "debug_core.h"
  38
  39 #define KGDB_MAX_THREAD_QUERY 17
  40
  41 /* Our I/O buffers. */
  42 static char                     remcom_in_buffer[BUFMAX];
  43 static char                     remcom_out_buffer[BUFMAX];
  44 static int                      gdbstub_use_prev_in_buf;
  45 static int                      gdbstub_prev_in_buf_pos;
  46
  47 /* Storage for the registers, in GDB format. */
  48 static unsigned long            gdb_regs[(NUMREGBYTES +
  49                                         sizeof(unsigned long) - 1) /
  50                                         sizeof(unsigned long)];
  51
  52 /*
  53  * GDB remote protocol parser:
  54  */
  55
  56 #ifdef CONFIG_KGDB_KDB
  57 static int gdbstub_read_wait(void)
  58 {
  59         int ret = -1;
  60         int i;
  61
  62         if (unlikely(gdbstub_use_prev_in_buf)) {
  63                 if (gdbstub_prev_in_buf_pos < gdbstub_use_prev_in_buf)
  64                         return remcom_in_buffer[gdbstub_prev_in_buf_pos++];
  65                 else
  66                         gdbstub_use_prev_in_buf = 0;
  67         }
  68
  69         /* poll any additional I/O interfaces that are defined */
  70         while (ret < 0)
  71                 for (i = 0; kdb_poll_funcs[i] != NULL; i++) {
  72                         ret = kdb_poll_funcs[i]();
  73                         if (ret > 0)
  74                                 break;
  75                 }
  76         return ret;
  77 }
  78 #else
  79 static int gdbstub_read_wait(void)
  80 {
  81         int ret = dbg_io_ops->read_char();
  82         while (ret == NO_POLL_CHAR)
  83                 ret = dbg_io_ops->read_char();
  84         return ret;
  85 }
  86 #endif
  87 /* scan for the sequence $<data>#<checksum> */
  88 static void get_packet(char *buffer)
  89 {
  90         unsigned char checksum;
  91         unsigned char xmitcsum;
  92         int count;
  93         char ch;
  94
  95         do {
  96                 /*
  97                  * Spin and wait around for the start character, ignore all
  98                  * other characters:
  99                  */
 100                 while ((ch = (gdbstub_read_wait())) != '$')
 101                         /* nothing */;
 102
 103                 kgdb_connected = 1;
 104                 checksum = 0;
 105                 xmitcsum = -1;
 106
 107                 count = 0;
 108
 109                 /*
 110                  * now, read until a # or end of buffer is found:
 111                  */
 112                 while (count < (BUFMAX - 1)) {
 113                         ch = gdbstub_read_wait();
 114                         if (ch == '#')
 115                                 break;
 116                         checksum = checksum + ch;
 117                         buffer[count] = ch;
 118                         count = count + 1;
 119                 }
 120
 121                 if (ch == '#') {
 122                         xmitcsum = hex_to_bin(gdbstub_read_wait()) << 4;
 123                         xmitcsum += hex_to_bin(gdbstub_read_wait());
 124
 125                         if (checksum != xmitcsum)
 126                                 /* failed checksum */
 127                                 dbg_io_ops->write_char('-');
 128                         else
 129                                 /* successful transfer */
 130                                 dbg_io_ops->write_char('+');
 131                         if (dbg_io_ops->flush)
 132                                 dbg_io_ops->flush();
 133                 }
 134                 buffer[count] = 0;
 135         } while (checksum != xmitcsum);
 136 }
 137
 138 /*
 139  * Send the packet in buffer.
 140  * Check for gdb connection if asked for.
 141  */
 142 static void put_packet(char *buffer)
 143 {
 144         unsigned char checksum;
 145         int count;
 146         char ch;
 147
 148         /*
 149          * $<packet info>#<checksum>.
 150          */
 151         while (1) {
 152                 dbg_io_ops->write_char('$');
 153                 checksum = 0;
 154                 count = 0;
 155
 156                 while ((ch = buffer[count])) {
 157                         dbg_io_ops->write_char(ch);
 158                         checksum += ch;
 159                         count++;
 160                 }
 161
 162                 dbg_io_ops->write_char('#');
 163                 dbg_io_ops->write_char(hex_asc_hi(checksum));
 164                 dbg_io_ops->write_char(hex_asc_lo(checksum));
 165                 if (dbg_io_ops->flush)
 166                         dbg_io_ops->flush();
 167
 168                 /* Now see what we get in reply. */
 169                 ch = gdbstub_read_wait();
 170
 171                 if (ch == 3)
 172                         ch = gdbstub_read_wait();
 173
 174                 /* If we get an ACK, we are done. */
 175                 if (ch == '+')
 176                         return;
 177
 178                 /*
 179                  * If we get the start of another packet, this means
 180                  * that GDB is attempting to reconnect.  We will NAK
 181                  * the packet being sent, and stop trying to send this
 182                  * packet.
 183                  */
 184                 if (ch == '$') {
 185                         dbg_io_ops->write_char('-');
 186                         if (dbg_io_ops->flush)
 187                                 dbg_io_ops->flush();
 188                         return;
 189                 }
 190         }
 191 }
 192
 193 static char gdbmsgbuf[BUFMAX + 1];
 194
 195 void gdbstub_msg_write(const char *s, int len)
 196 {
 197         char *bufptr;
 198         int wcount;
 199         int i;
 200
 201         if (len == 0)
 202                 len = strlen(s);
 203
 204         /* 'O'utput */
 205         gdbmsgbuf[0] = 'O';
 206
 207         /* Fill and send buffers... */
 208         while (len > 0) {
 209                 bufptr = gdbmsgbuf + 1;
 210
 211                 /* Calculate how many this time */
 212                 if ((len << 1) > (BUFMAX - 2))
 213                         wcount = (BUFMAX - 2) >> 1;
 214                 else
 215                         wcount = len;
 216
 217                 /* Pack in hex chars */
 218                 for (i = 0; i < wcount; i++)
 219                         bufptr = hex_byte_pack(bufptr, s[i]);
 220                 *bufptr = '\0';
 221
 222                 /* Move up */
 223                 s += wcount;
 224                 len -= wcount;
 225
 226                 /* Write packet */
 227                 put_packet(gdbmsgbuf);
 228         }
 229 }
 230
 231 /*
 232  * Convert the memory pointed to by mem into hex, placing result in
 233  * buf.  Return a pointer to the last char put in buf (null). May
 234  * return an error.
 235  */
 236 char *kgdb_mem2hex(char *mem, char *buf, int count)
 237 {
 238         char *tmp;
 239         int err;
 240
 241         /*
 242          * We use the upper half of buf as an intermediate buffer for the
 243          * raw memory copy.  Hex conversion will work against this one.
 244          */
 245         tmp = buf + count;
 246
 247         err = copy_from_kernel_nofault(tmp, mem, count);
 248         if (err)
 249                 return NULL;
 250         while (count > 0) {
 251                 buf = hex_byte_pack(buf, *tmp);
 252                 tmp++;
 253                 count--;
 254         }
 255         *buf = 0;
 256
 257         return buf;
 258 }
 259
 260 /*
 261  * Convert the hex array pointed to by buf into binary to be placed in
 262  * mem.  Return a pointer to the character AFTER the last byte
 263  * written.  May return an error.
 264  */
 265 int kgdb_hex2mem(char *buf, char *mem, int count)
 266 {
 267         char *tmp_raw;
 268         char *tmp_hex;
 269
 270         /*
 271          * We use the upper half of buf as an intermediate buffer for the
 272          * raw memory that is converted from hex.
 273          */
 274         tmp_raw = buf + count * 2;
 275
 276         tmp_hex = tmp_raw - 1;
 277         while (tmp_hex >= buf) {
 278                 tmp_raw--;
 279                 *tmp_raw = hex_to_bin(*tmp_hex--);
 280                 *tmp_raw |= hex_to_bin(*tmp_hex--) << 4;
 281         }
 282
 283         return copy_to_kernel_nofault(mem, tmp_raw, count);
 284 }
 285
 286 /*
 287  * While we find nice hex chars, build a long_val.
 288  * Return number of chars processed.
 289  */
 290 int kgdb_hex2long(char **ptr, unsigned long *long_val)
 291 {
 292         int hex_val;
 293         int num = 0;
 294         int negate = 0;
 295
 296         *long_val = 0;
 297
 298         if (**ptr == '-') {
 299                 negate = 1;
 300                 (*ptr)++;
 301         }
 302         while (**ptr) {
 303                 hex_val = hex_to_bin(**ptr);
 304                 if (hex_val < 0)
 305                         break;
 306
 307                 *long_val = (*long_val << 4) | hex_val;
 308                 num++;
 309                 (*ptr)++;
 310         }
 311
 312         if (negate)
 313                 *long_val = -*long_val;
 314
 315         return num;
 316 }
 317
 318 /*
 319  * Copy the binary array pointed to by buf into mem.  Fix $, #, and
 320  * 0x7d escaped with 0x7d. Return -EFAULT on failure or 0 on success.
 321  * The input buf is overwritten with the result to write to mem.
 322  */
 323 static int kgdb_ebin2mem(char *buf, char *mem, int count)
 324 {
 325         int size = 0;
 326         char *c = buf;
 327
 328         while (count-- > 0) {
 329                 c[size] = *buf++;
 330                 if (c[size] == 0x7d)
 331                         c[size] = *buf++ ^ 0x20;
 332                 size++;
 333         }
 334
 335         return copy_to_kernel_nofault(mem, c, size);
 336 }
 337
 338 #if DBG_MAX_REG_NUM > 0
 339 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 340 {
 341         int i;
 342         int idx = 0;
 343         char *ptr = (char *)gdb_regs;
 344
 345         for (i = 0; i < DBG_MAX_REG_NUM; i++) {
 346                 dbg_get_reg(i, ptr + idx, regs);
 347                 idx += dbg_reg_def[i].size;
 348         }
 349 }
 350
 351 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 352 {
 353         int i;
 354         int idx = 0;
 355         char *ptr = (char *)gdb_regs;
 356
 357         for (i = 0; i < DBG_MAX_REG_NUM; i++) {
 358                 dbg_set_reg(i, ptr + idx, regs);
 359                 idx += dbg_reg_def[i].size;
 360         }
 361 }
 362 #endif /* DBG_MAX_REG_NUM > 0 */
 363
 364 /* Write memory due to an 'M' or 'X' packet. */
 365 static int write_mem_msg(int binary)
 366 {
 367         char *ptr = &remcom_in_buffer[1];
 368         unsigned long addr;
 369         unsigned long length;
 370         int err;
 371
 372         if (kgdb_hex2long(&ptr, &addr) > 0 && *(ptr++) == ',' &&
 373             kgdb_hex2long(&ptr, &length) > 0 && *(ptr++) == ':') {
 374                 if (binary)
 375                         err = kgdb_ebin2mem(ptr, (char *)addr, length);
 376                 else
 377                         err = kgdb_hex2mem(ptr, (char *)addr, length);
 378                 if (err)
 379                         return err;
 380                 if (CACHE_FLUSH_IS_SAFE)
 381                         flush_icache_range(addr, addr + length);
 382                 return 0;
 383         }
 384
 385         return -EINVAL;
 386 }
 387
 388 static void error_packet(char *pkt, int error)
 389 {
 390         error = -error;
 391         pkt[0] = 'E';
 392         pkt[1] = hex_asc[(error / 10)];
 393         pkt[2] = hex_asc[(error % 10)];
 394         pkt[3] = '\0';
 395 }
 396
 397 /*
 398  * Thread ID accessors. We represent a flat TID space to GDB, where
 399  * the per CPU idle threads (which under Linux all have PID 0) are
 400  * remapped to negative TIDs.
 401  */
 402
 403 #define BUF_THREAD_ID_SIZE      8
 404
 405 static char *pack_threadid(char *pkt, unsigned char *id)
 406 {
 407         unsigned char *limit;
 408         int lzero = 1;
 409
 410         limit = id + (BUF_THREAD_ID_SIZE / 2);
 411         while (id < limit) {
 412                 if (!lzero || *id != 0) {
 413                         pkt = hex_byte_pack(pkt, *id);
 414                         lzero = 0;
 415                 }
 416                 id++;
 417         }
 418
 419         if (lzero)
 420                 pkt = hex_byte_pack(pkt, 0);
 421
 422         return pkt;
 423 }
 424
 425 static void int_to_threadref(unsigned char *id, int value)
 426 {
 427         put_unaligned_be32(value, id);
 428 }
 429
 430 static struct task_struct *getthread(struct pt_regs *regs, int tid)
 431 {
 432         /*
 433          * Non-positive TIDs are remapped to the cpu shadow information
 434          */
 435         if (tid == 0 || tid == -1)
 436                 tid = -atomic_read(&kgdb_active) - 2;
 437         if (tid < -1 && tid > -NR_CPUS - 2) {
 438                 if (kgdb_info[-tid - 2].task)
 439                         return kgdb_info[-tid - 2].task;
 440                 else
 441                         return idle_task(-tid - 2);
 442         }
 443         if (tid <= 0) {
 444                 printk(KERN_ERR "KGDB: Internal thread select error\n");
 445                 dump_stack();
 446                 return NULL;
 447         }
 448
 449         /*
 450          * find_task_by_pid_ns() does not take the tasklist lock anymore
 451          * but is nicely RCU locked - hence is a pretty resilient
 452          * thing to use:
 453          */
 454         return find_task_by_pid_ns(tid, &init_pid_ns);
 455 }
 456
 457
 458 /*
 459  * Remap normal tasks to their real PID,
 460  * CPU shadow threads are mapped to -CPU - 2
 461  */
 462 static inline int shadow_pid(int realpid)
 463 {
 464         if (realpid)
 465                 return realpid;
 466
 467         return -raw_smp_processor_id() - 2;
 468 }
 469
 470 /*
 471  * All the functions that start with gdb_cmd are the various
 472  * operations to implement the handlers for the gdbserial protocol
 473  * where KGDB is communicating with an external debugger
 474  */
 475
 476 /* Handle the '?' status packets */
 477 static void gdb_cmd_status(struct kgdb_state *ks)
 478 {
 479         /*
 480          * We know that this packet is only sent
 481          * during initial connect.  So to be safe,
 482          * we clear out our breakpoints now in case
 483          * GDB is reconnecting.
 484          */
 485         dbg_remove_all_break();
 486
 487         remcom_out_buffer[0] = 'S';
 488         hex_byte_pack(&remcom_out_buffer[1], ks->signo);
 489 }
 490
 491 static void gdb_get_regs_helper(struct kgdb_state *ks)
 492 {
 493         struct task_struct *thread;
 494         void *local_debuggerinfo;
 495         int i;
 496
 497         thread = kgdb_usethread;
 498         if (!thread) {
 499                 thread = kgdb_info[ks->cpu].task;
 500                 local_debuggerinfo = kgdb_info[ks->cpu].debuggerinfo;
 501         } else {
 502                 local_debuggerinfo = NULL;
 503                 for_each_online_cpu(i) {
 504                         /*
 505                          * Try to find the task on some other
 506                          * or possibly this node if we do not
 507                          * find the matching task then we try
 508                          * to approximate the results.
 509                          */
 510                         if (thread == kgdb_info[i].task)
 511                                 local_debuggerinfo = kgdb_info[i].debuggerinfo;
 512                 }
 513         }
 514
 515         /*
 516          * All threads that don't have debuggerinfo should be
 517          * in schedule() sleeping, since all other CPUs
 518          * are in kgdb_wait, and thus have debuggerinfo.
 519          */
 520         if (local_debuggerinfo) {
 521                 pt_regs_to_gdb_regs(gdb_regs, local_debuggerinfo);
 522         } else {
 523                 /*
 524                  * Pull stuff saved during switch_to; nothing
 525                  * else is accessible (or even particularly
 526                  * relevant).
 527                  *
 528                  * This should be enough for a stack trace.
 529                  */
 530                 sleeping_thread_to_gdb_regs(gdb_regs, thread);
 531         }
 532 }
 533
 534 /* Handle the 'g' get registers request */
 535 static void gdb_cmd_getregs(struct kgdb_state *ks)
 536 {
 537         gdb_get_regs_helper(ks);
 538         kgdb_mem2hex((char *)gdb_regs, remcom_out_buffer, NUMREGBYTES);
 539 }
 540
 541 /* Handle the 'G' set registers request */
 542 static void gdb_cmd_setregs(struct kgdb_state *ks)
 543 {
 544         kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs, NUMREGBYTES);
 545
 546         if (kgdb_usethread && kgdb_usethread != current) {
 547                 error_packet(remcom_out_buffer, -EINVAL);
 548         } else {
 549                 gdb_regs_to_pt_regs(gdb_regs, ks->linux_regs);
 550                 strcpy(remcom_out_buffer, "OK");
 551         }
 552 }
 553
 554 /* Handle the 'm' memory read bytes */
 555 static void gdb_cmd_memread(struct kgdb_state *ks)
 556 {
 557         char *ptr = &remcom_in_buffer[1];
 558         unsigned long length;
 559         unsigned long addr;
 560         char *err;
 561
 562         if (kgdb_hex2long(&ptr, &addr) > 0 && *ptr++ == ',' &&
 563                                         kgdb_hex2long(&ptr, &length) > 0) {
 564                 err = kgdb_mem2hex((char *)addr, remcom_out_buffer, length);
 565                 if (!err)
 566                         error_packet(remcom_out_buffer, -EINVAL);
 567         } else {
 568                 error_packet(remcom_out_buffer, -EINVAL);
 569         }
 570 }
 571
 572 /* Handle the 'M' memory write bytes */
 573 static void gdb_cmd_memwrite(struct kgdb_state *ks)
 574 {
 575         int err = write_mem_msg(0);
 576
 577         if (err)
 578                 error_packet(remcom_out_buffer, err);
 579         else
 580                 strcpy(remcom_out_buffer, "OK");
 581 }
 582
 583 #if DBG_MAX_REG_NUM > 0
 584 static char *gdb_hex_reg_helper(int regnum, char *out)
 585 {
 586         int i;
 587         int offset = 0;
 588
 589         for (i = 0; i < regnum; i++)
 590                 offset += dbg_reg_def[i].size;
 591         return kgdb_mem2hex((char *)gdb_regs + offset, out,
 592                             dbg_reg_def[i].size);
 593 }
 594
 595 /* Handle the 'p' individual register get */
 596 static void gdb_cmd_reg_get(struct kgdb_state *ks)
 597 {
 598         unsigned long regnum;
 599         char *ptr = &remcom_in_buffer[1];
 600
 601         kgdb_hex2long(&ptr, &regnum);
 602         if (regnum >= DBG_MAX_REG_NUM) {
 603                 error_packet(remcom_out_buffer, -EINVAL);
 604                 return;
 605         }
 606         gdb_get_regs_helper(ks);
 607         gdb_hex_reg_helper(regnum, remcom_out_buffer);
 608 }
 609
 610 /* Handle the 'P' individual register set */
 611 static void gdb_cmd_reg_set(struct kgdb_state *ks)
 612 {
 613         unsigned long regnum;
 614         char *ptr = &remcom_in_buffer[1];
 615         int i = 0;
 616
 617         kgdb_hex2long(&ptr, &regnum);
 618         if (*ptr++ != '=' ||
 619             !(!kgdb_usethread || kgdb_usethread == current) ||
 620             !dbg_get_reg(regnum, gdb_regs, ks->linux_regs)) {
 621                 error_packet(remcom_out_buffer, -EINVAL);
 622                 return;
 623         }
 624         memset(gdb_regs, 0, sizeof(gdb_regs));
 625         while (i < sizeof(gdb_regs) * 2)
 626                 if (hex_to_bin(ptr[i]) >= 0)
 627                         i++;
 628                 else
 629                         break;
 630         i = i / 2;
 631         kgdb_hex2mem(ptr, (char *)gdb_regs, i);
 632         dbg_set_reg(regnum, gdb_regs, ks->linux_regs);
 633         strcpy(remcom_out_buffer, "OK");
 634 }
 635 #endif /* DBG_MAX_REG_NUM > 0 */
 636
 637 /* Handle the 'X' memory binary write bytes */
 638 static void gdb_cmd_binwrite(struct kgdb_state *ks)
 639 {
 640         int err = write_mem_msg(1);
 641
 642         if (err)
 643                 error_packet(remcom_out_buffer, err);
 644         else
 645                 strcpy(remcom_out_buffer, "OK");
 646 }
 647
 648 /* Handle the 'D' or 'k', detach or kill packets */
 649 static void gdb_cmd_detachkill(struct kgdb_state *ks)
 650 {
 651         int error;
 652
 653         /* The detach case */
 654         if (remcom_in_buffer[0] == 'D') {
 655                 error = dbg_remove_all_break();
 656                 if (error < 0) {
 657                         error_packet(remcom_out_buffer, error);
 658                 } else {
 659                         strcpy(remcom_out_buffer, "OK");
 660                         kgdb_connected = 0;
 661                 }
 662                 put_packet(remcom_out_buffer);
 663         } else {
 664                 /*
 665                  * Assume the kill case, with no exit code checking,
 666                  * trying to force detach the debugger:
 667                  */
 668                 dbg_remove_all_break();
 669                 kgdb_connected = 0;
 670         }
 671 }
 672
 673 /* Handle the 'R' reboot packets */
 674 static int gdb_cmd_reboot(struct kgdb_state *ks)
 675 {
 676         /* For now, only honor R0 */
 677         if (strcmp(remcom_in_buffer, "R0") == 0) {
 678                 printk(KERN_CRIT "Executing emergency reboot\n");
 679                 strcpy(remcom_out_buffer, "OK");
 680                 put_packet(remcom_out_buffer);
 681
 682                 /*
 683                  * Execution should not return from
 684                  * machine_emergency_restart()
 685                  */
 686                 machine_emergency_restart();
 687                 kgdb_connected = 0;
 688
 689                 return 1;
 690         }
 691         return 0;
 692 }
 693
 694 /* Handle the 'q' query packets */
 695 static void gdb_cmd_query(struct kgdb_state *ks)
 696 {
 697         struct task_struct *g;
 698         struct task_struct *p;
 699         unsigned char thref[BUF_THREAD_ID_SIZE];
 700         char *ptr;
 701         int i;
 702         int cpu;
 703         int finished = 0;
 704
 705         switch (remcom_in_buffer[1]) {
 706         case 's':
 707         case 'f':
 708                 if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10))
 709                         break;
 710
 711                 i = 0;
 712                 remcom_out_buffer[0] = 'm';
 713                 ptr = remcom_out_buffer + 1;
 714                 if (remcom_in_buffer[1] == 'f') {
 715                         /* Each cpu is a shadow thread */
 716                         for_each_online_cpu(cpu) {
 717                                 ks->thr_query = 0;
 718                                 int_to_threadref(thref, -cpu - 2);
 719                                 ptr = pack_threadid(ptr, thref);
 720                                 *(ptr++) = ',';
 721                                 i++;
 722                         }
 723                 }
 724
 725                 for_each_process_thread(g, p) {
 726                         if (i >= ks->thr_query && !finished) {
 727                                 int_to_threadref(thref, p->pid);
 728                                 ptr = pack_threadid(ptr, thref);
 729                                 *(ptr++) = ',';
 730                                 ks->thr_query++;
 731                                 if (ks->thr_query % KGDB_MAX_THREAD_QUERY == 0)
 732                                         finished = 1;
 733                         }
 734                         i++;
 735                 }
 736
 737                 *(--ptr) = '\0';
 738                 break;
 739
 740         case 'C':
 741                 /* Current thread id */
 742                 strcpy(remcom_out_buffer, "QC");
 743                 ks->threadid = shadow_pid(current->pid);
 744                 int_to_threadref(thref, ks->threadid);
 745                 pack_threadid(remcom_out_buffer + 2, thref);
 746                 break;
 747         case 'T':
 748                 if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16))
 749                         break;
 750
 751                 ks->threadid = 0;
 752                 ptr = remcom_in_buffer + 17;
 753                 kgdb_hex2long(&ptr, &ks->threadid);
 754                 if (!getthread(ks->linux_regs, ks->threadid)) {
 755                         error_packet(remcom_out_buffer, -EINVAL);
 756                         break;
 757                 }
 758                 if ((int)ks->threadid > 0) {
 759                         kgdb_mem2hex(getthread(ks->linux_regs,
 760                                         ks->threadid)->comm,
 761                                         remcom_out_buffer, 16);
 762                 } else {
 763                         static char tmpstr[23 + BUF_THREAD_ID_SIZE];
 764
 765                         sprintf(tmpstr, "shadowCPU%d",
 766                                         (int)(-ks->threadid - 2));
 767                         kgdb_mem2hex(tmpstr, remcom_out_buffer, strlen(tmpstr));
 768                 }
 769                 break;
 770 #ifdef CONFIG_KGDB_KDB
 771         case 'R':
 772                 if (strncmp(remcom_in_buffer, "qRcmd,", 6) == 0) {
 773                         int len = strlen(remcom_in_buffer + 6);
 774
 775                         if ((len % 2) != 0) {
 776                                 strcpy(remcom_out_buffer, "E01");
 777                                 break;
 778                         }
 779                         kgdb_hex2mem(remcom_in_buffer + 6,
 780                                      remcom_out_buffer, len);
 781                         len = len / 2;
 782                         remcom_out_buffer[len++] = 0;
 783
 784                         kdb_common_init_state(ks);
 785                         kdb_parse(remcom_out_buffer);
 786                         kdb_common_deinit_state();
 787
 788                         strcpy(remcom_out_buffer, "OK");
 789                 }
 790                 break;
 791 #endif
 792 #ifdef CONFIG_HAVE_ARCH_KGDB_QXFER_PKT
 793         case 'S':
 794                 if (!strncmp(remcom_in_buffer, "qSupported:", 11))
 795                         strcpy(remcom_out_buffer, kgdb_arch_gdb_stub_feature);
 796                 break;
 797         case 'X':
 798                 if (!strncmp(remcom_in_buffer, "qXfer:", 6))
 799                         kgdb_arch_handle_qxfer_pkt(remcom_in_buffer,
 800                                                    remcom_out_buffer);
 801                 break;
 802 #endif
 803         default:
 804                 break;
 805         }
 806 }
 807
 808 /* Handle the 'H' task query packets */
 809 static void gdb_cmd_task(struct kgdb_state *ks)
 810 {
 811         struct task_struct *thread;
 812         char *ptr;
 813
 814         switch (remcom_in_buffer[1]) {
 815         case 'g':
 816                 ptr = &remcom_in_buffer[2];
 817                 kgdb_hex2long(&ptr, &ks->threadid);
 818                 thread = getthread(ks->linux_regs, ks->threadid);
 819                 if (!thread && ks->threadid > 0) {
 820                         error_packet(remcom_out_buffer, -EINVAL);
 821                         break;
 822                 }
 823                 kgdb_usethread = thread;
 824                 ks->kgdb_usethreadid = ks->threadid;
 825                 strcpy(remcom_out_buffer, "OK");
 826                 break;
 827         case 'c':
 828                 ptr = &remcom_in_buffer[2];
 829                 kgdb_hex2long(&ptr, &ks->threadid);
 830                 if (!ks->threadid) {
 831                         kgdb_contthread = NULL;
 832                 } else {
 833                         thread = getthread(ks->linux_regs, ks->threadid);
 834                         if (!thread && ks->threadid > 0) {
 835                                 error_packet(remcom_out_buffer, -EINVAL);
 836                                 break;
 837                         }
 838                         kgdb_contthread = thread;
 839                 }
 840                 strcpy(remcom_out_buffer, "OK");
 841                 break;
 842         }
 843 }
 844
 845 /* Handle the 'T' thread query packets */
 846 static void gdb_cmd_thread(struct kgdb_state *ks)
 847 {
 848         char *ptr = &remcom_in_buffer[1];
 849         struct task_struct *thread;
 850
 851         kgdb_hex2long(&ptr, &ks->threadid);
 852         thread = getthread(ks->linux_regs, ks->threadid);
 853         if (thread)
 854                 strcpy(remcom_out_buffer, "OK");
 855         else
 856                 error_packet(remcom_out_buffer, -EINVAL);
 857 }
 858
 859 /* Handle the 'z' or 'Z' breakpoint remove or set packets */
 860 static void gdb_cmd_break(struct kgdb_state *ks)
 861 {
 862         /*
 863          * Since GDB-5.3, it's been drafted that '0' is a software
 864          * breakpoint, '1' is a hardware breakpoint, so let's do that.
 865          */
 866         char *bpt_type = &remcom_in_buffer[1];
 867         char *ptr = &remcom_in_buffer[2];
 868         unsigned long addr;
 869         unsigned long length;
 870         int error = 0;
 871
 872         if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
 873                 /* Unsupported */
 874                 if (*bpt_type > '4')
 875                         return;
 876         } else {
 877                 if (*bpt_type != '0' && *bpt_type != '1')
 878                         /* Unsupported. */
 879                         return;
 880         }
 881
 882         /*
 883          * Test if this is a hardware breakpoint, and
 884          * if we support it:
 885          */
 886         if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
 887                 /* Unsupported. */
 888                 return;
 889
 890         if (*(ptr++) != ',') {
 891                 error_packet(remcom_out_buffer, -EINVAL);
 892                 return;
 893         }
 894         if (!kgdb_hex2long(&ptr, &addr)) {
 895                 error_packet(remcom_out_buffer, -EINVAL);
 896                 return;
 897         }
 898         if (*(ptr++) != ',' ||
 899                 !kgdb_hex2long(&ptr, &length)) {
 900                 error_packet(remcom_out_buffer, -EINVAL);
 901                 return;
 902         }
 903
 904         if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
 905                 error = dbg_set_sw_break(addr);
 906         else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
 907                 error = dbg_remove_sw_break(addr);
 908         else if (remcom_in_buffer[0] == 'Z')
 909                 error = arch_kgdb_ops.set_hw_breakpoint(addr,
 910                         (int)length, *bpt_type - '0');
 911         else if (remcom_in_buffer[0] == 'z')
 912                 error = arch_kgdb_ops.remove_hw_breakpoint(addr,
 913                         (int) length, *bpt_type - '0');
 914
 915         if (error == 0)
 916                 strcpy(remcom_out_buffer, "OK");
 917         else
 918                 error_packet(remcom_out_buffer, error);
 919 }
 920
 921 /* Handle the 'C' signal / exception passing packets */
 922 static int gdb_cmd_exception_pass(struct kgdb_state *ks)
 923 {
 924         /* C09 == pass exception
 925          * C15 == detach kgdb, pass exception
 926          */
 927         if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {
 928
 929                 ks->pass_exception = 1;
 930                 remcom_in_buffer[0] = 'c';
 931
 932         } else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {
 933
 934                 ks->pass_exception = 1;
 935                 remcom_in_buffer[0] = 'D';
 936                 dbg_remove_all_break();
 937                 kgdb_connected = 0;
 938                 return 1;
 939
 940         } else {
 941                 gdbstub_msg_write("KGDB only knows signal 9 (pass)"
 942                         " and 15 (pass and disconnect)\n"
 943                         "Executing a continue without signal passing\n", 0);
 944                 remcom_in_buffer[0] = 'c';
 945         }
 946
 947         /* Indicate fall through */
 948         return -1;
 949 }
 950
 951 /*
 952  * This function performs all gdbserial command processing
 953  */
 954 int gdb_serial_stub(struct kgdb_state *ks)
 955 {
 956         int error = 0;
 957         int tmp;
 958
 959         /* Initialize comm buffer and globals. */
 960         memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
 961         kgdb_usethread = kgdb_info[ks->cpu].task;
 962         ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
 963         ks->pass_exception = 0;
 964
 965         if (kgdb_connected) {
 966                 unsigned char thref[BUF_THREAD_ID_SIZE];
 967                 char *ptr;
 968
 969                 /* Reply to host that an exception has occurred */
 970                 ptr = remcom_out_buffer;
 971                 *ptr++ = 'T';
 972                 ptr = hex_byte_pack(ptr, ks->signo);
 973                 ptr += strlen(strcpy(ptr, "thread:"));
 974                 int_to_threadref(thref, shadow_pid(current->pid));
 975                 ptr = pack_threadid(ptr, thref);
 976                 *ptr++ = ';';
 977                 put_packet(remcom_out_buffer);
 978         }
 979
 980         while (1) {
 981                 error = 0;
 982
 983                 /* Clear the out buffer. */
 984                 memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
 985
 986                 get_packet(remcom_in_buffer);
 987
 988                 switch (remcom_in_buffer[0]) {
 989                 case '?': /* gdbserial status */
 990                         gdb_cmd_status(ks);
 991                         break;
 992                 case 'g': /* return the value of the CPU registers */
 993                         gdb_cmd_getregs(ks);
 994                         break;
 995                 case 'G': /* set the value of the CPU registers - return OK */
 996                         gdb_cmd_setregs(ks);
 997                         break;
 998                 case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
 999                         gdb_cmd_memread(ks);
1000                         break;
1001                 case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1002                         gdb_cmd_memwrite(ks);
1003                         break;
1004 #if DBG_MAX_REG_NUM > 0
1005                 case 'p': /* pXX Return gdb register XX (in hex) */
1006                         gdb_cmd_reg_get(ks);
1007                         break;
1008                 case 'P': /* PXX=aaaa Set gdb register XX to aaaa (in hex) */
1009                         gdb_cmd_reg_set(ks);
1010                         break;
1011 #endif /* DBG_MAX_REG_NUM > 0 */
1012                 case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1013                         gdb_cmd_binwrite(ks);
1014                         break;
1015                         /* kill or detach. KGDB should treat this like a
1016                          * continue.
1017                          */
1018                 case 'D': /* Debugger detach */
1019                 case 'k': /* Debugger detach via kill */
1020                         gdb_cmd_detachkill(ks);
1021                         goto default_handle;
1022                 case 'R': /* Reboot */
1023                         if (gdb_cmd_reboot(ks))
1024                                 goto default_handle;
1025                         break;
1026                 case 'q': /* query command */
1027                         gdb_cmd_query(ks);
1028                         break;
1029                 case 'H': /* task related */
1030                         gdb_cmd_task(ks);
1031                         break;
1032                 case 'T': /* Query thread status */
1033                         gdb_cmd_thread(ks);
1034                         break;
1035                 case 'z': /* Break point remove */
1036                 case 'Z': /* Break point set */
1037                         gdb_cmd_break(ks);
1038                         break;
1039 #ifdef CONFIG_KGDB_KDB
1040                 case '3': /* Escape into back into kdb */
1041                         if (remcom_in_buffer[1] == '\0') {
1042                                 gdb_cmd_detachkill(ks);
1043                                 return DBG_PASS_EVENT;
1044                         }
1045                         fallthrough;
1046 #endif
1047                 case 'C': /* Exception passing */
1048                         tmp = gdb_cmd_exception_pass(ks);
1049                         if (tmp > 0)
1050                                 goto default_handle;
1051                         if (tmp == 0)
1052                                 break;
1053                         fallthrough;    /* on tmp < 0 */
1054                 case 'c': /* Continue packet */
1055                 case 's': /* Single step packet */
1056                         if (kgdb_contthread && kgdb_contthread != current) {
1057                                 /* Can't switch threads in kgdb */
1058                                 error_packet(remcom_out_buffer, -EINVAL);
1059                                 break;
1060                         }
1061                         fallthrough;    /* to default processing */
1062                 default:
1063 default_handle:
1064                         error = kgdb_arch_handle_exception(ks->ex_vector,
1065                                                 ks->signo,
1066                                                 ks->err_code,
1067                                                 remcom_in_buffer,
1068                                                 remcom_out_buffer,
1069                                                 ks->linux_regs);
1070                         /*
1071                          * Leave cmd processing on error, detach,
1072                          * kill, continue, or single step.
1073                          */
1074                         if (error >= 0 || remcom_in_buffer[0] == 'D' ||
1075                             remcom_in_buffer[0] == 'k') {
1076                                 error = 0;
1077                                 goto kgdb_exit;
1078                         }
1079
1080                 }
1081
1082                 /* reply to the request */
1083                 put_packet(remcom_out_buffer);
1084         }
1085
1086 kgdb_exit:
1087         if (ks->pass_exception)
1088                 error = 1;
1089         return error;
1090 }
1091
1092 int gdbstub_state(struct kgdb_state *ks, char *cmd)
1093 {
1094         int error;
1095
1096         switch (cmd[0]) {
1097         case 'e':
1098                 error = kgdb_arch_handle_exception(ks->ex_vector,
1099                                                    ks->signo,
1100                                                    ks->err_code,
1101                                                    remcom_in_buffer,
1102                                                    remcom_out_buffer,
1103                                                    ks->linux_regs);
1104                 return error;
1105         case 's':
1106         case 'c':
1107                 strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
1108                 return 0;
1109         case '$':
1110                 strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
1111                 gdbstub_use_prev_in_buf = strlen(remcom_in_buffer);
1112                 gdbstub_prev_in_buf_pos = 0;
1113                 return 0;
1114         }
1115         dbg_io_ops->write_char('+');
1116         put_packet(remcom_out_buffer);
1117         return 0;
1118 }
1119
1120 /**
1121  * gdbstub_exit - Send an exit message to GDB
1122  * @status: The exit code to report.
1123  */
1124 void gdbstub_exit(int status)
1125 {
1126         unsigned char checksum, ch, buffer[3];
1127         int loop;
1128
1129         if (!kgdb_connected)
1130                 return;
1131         kgdb_connected = 0;
1132
1133         if (!dbg_io_ops || dbg_kdb_mode)
1134                 return;
1135
1136         buffer[0] = 'W';
1137         buffer[1] = hex_asc_hi(status);
1138         buffer[2] = hex_asc_lo(status);
1139
1140         dbg_io_ops->write_char('$');
1141         checksum = 0;
1142
1143         for (loop = 0; loop < 3; loop++) {
1144                 ch = buffer[loop];
1145                 checksum += ch;
1146                 dbg_io_ops->write_char(ch);
1147         }
1148
1149         dbg_io_ops->write_char('#');
1150         dbg_io_ops->write_char(hex_asc_hi(checksum));
1151         dbg_io_ops->write_char(hex_asc_lo(checksum));
1152
1153         /* make sure the output is flushed, lest the bootloader clobber it */
1154         if (dbg_io_ops->flush)
1155                 dbg_io_ops->flush();
1156 }