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/string.h>
  34#include <linux/reboot.h>
  35#include <linux/uaccess.h>
  36#include <asm/cacheflush.h>
  37#include <linux/unaligned.h>
  38#include "debug_core.h"
  39
  40#define KGDB_MAX_THREAD_QUERY 17
  41
  42/* Our I/O buffers. */
  43static char			remcom_in_buffer[BUFMAX];
  44static char			remcom_out_buffer[BUFMAX];
  45static int			gdbstub_use_prev_in_buf;
  46static int			gdbstub_prev_in_buf_pos;
  47
  48/* Storage for the registers, in GDB format. */
  49static unsigned long		gdb_regs[(NUMREGBYTES +
  50					sizeof(unsigned long) - 1) /
  51					sizeof(unsigned long)];
  52
  53/*
  54 * GDB remote protocol parser:
  55 */
  56
  57#ifdef CONFIG_KGDB_KDB
  58static int gdbstub_read_wait(void)
  59{
  60	int ret = -1;
  61	int i;
  62
  63	if (unlikely(gdbstub_use_prev_in_buf)) {
  64		if (gdbstub_prev_in_buf_pos < gdbstub_use_prev_in_buf)
  65			return remcom_in_buffer[gdbstub_prev_in_buf_pos++];
  66		else
  67			gdbstub_use_prev_in_buf = 0;
  68	}
  69
  70	/* poll any additional I/O interfaces that are defined */
  71	while (ret < 0)
  72		for (i = 0; kdb_poll_funcs[i] != NULL; i++) {
  73			ret = kdb_poll_funcs[i]();
  74			if (ret > 0)
  75				break;
  76		}
  77	return ret;
  78}
  79#else
  80static int gdbstub_read_wait(void)
  81{
  82	int ret = dbg_io_ops->read_char();
  83	while (ret == NO_POLL_CHAR)
  84		ret = dbg_io_ops->read_char();
  85	return ret;
  86}
  87#endif
  88/* scan for the sequence $<data>#<checksum> */
  89static void get_packet(char *buffer)
  90{
  91	unsigned char checksum;
  92	unsigned char xmitcsum;
  93	int count;
  94	char ch;
  95
  96	do {
  97		/*
  98		 * Spin and wait around for the start character, ignore all
  99		 * other characters:
 100		 */
 101		while ((ch = (gdbstub_read_wait())) != '$')
 102			/* nothing */;
 103
 104		kgdb_connected = 1;
 105		checksum = 0;
 106		xmitcsum = -1;
 107
 108		count = 0;
 109
 110		/*
 111		 * now, read until a # or end of buffer is found:
 112		 */
 113		while (count < (BUFMAX - 1)) {
 114			ch = gdbstub_read_wait();
 115			if (ch == '#')
 116				break;
 117			checksum = checksum + ch;
 118			buffer[count] = ch;
 119			count = count + 1;
 120		}
 121
 122		if (ch == '#') {
 123			xmitcsum = hex_to_bin(gdbstub_read_wait()) << 4;
 124			xmitcsum += hex_to_bin(gdbstub_read_wait());
 125
 126			if (checksum != xmitcsum)
 127				/* failed checksum */
 128				dbg_io_ops->write_char('-');
 129			else
 130				/* successful transfer */
 131				dbg_io_ops->write_char('+');
 132			if (dbg_io_ops->flush)
 133				dbg_io_ops->flush();
 134		}
 135		buffer[count] = 0;
 136	} while (checksum != xmitcsum);
 137}
 138
 139/*
 140 * Send the packet in buffer.
 141 * Check for gdb connection if asked for.
 142 */
 143static void put_packet(char *buffer)
 144{
 145	unsigned char checksum;
 146	int count;
 147	char ch;
 148
 149	/*
 150	 * $<packet info>#<checksum>.
 151	 */
 152	while (1) {
 153		dbg_io_ops->write_char('$');
 154		checksum = 0;
 155		count = 0;
 156
 157		while ((ch = buffer[count])) {
 158			dbg_io_ops->write_char(ch);
 159			checksum += ch;
 160			count++;
 161		}
 162
 163		dbg_io_ops->write_char('#');
 164		dbg_io_ops->write_char(hex_asc_hi(checksum));
 165		dbg_io_ops->write_char(hex_asc_lo(checksum));
 166		if (dbg_io_ops->flush)
 167			dbg_io_ops->flush();
 168
 169		/* Now see what we get in reply. */
 170		ch = gdbstub_read_wait();
 171
 172		if (ch == 3)
 173			ch = gdbstub_read_wait();
 174
 175		/* If we get an ACK, we are done. */
 176		if (ch == '+')
 177			return;
 178
 179		/*
 180		 * If we get the start of another packet, this means
 181		 * that GDB is attempting to reconnect.  We will NAK
 182		 * the packet being sent, and stop trying to send this
 183		 * packet.
 184		 */
 185		if (ch == '$') {
 186			dbg_io_ops->write_char('-');
 187			if (dbg_io_ops->flush)
 188				dbg_io_ops->flush();
 189			return;
 190		}
 191	}
 192}
 193
 194static char gdbmsgbuf[BUFMAX + 1];
 195
 196void gdbstub_msg_write(const char *s, int len)
 197{
 198	char *bufptr;
 199	int wcount;
 200	int i;
 201
 202	if (len == 0)
 203		len = strlen(s);
 204
 205	/* 'O'utput */
 206	gdbmsgbuf[0] = 'O';
 207
 208	/* Fill and send buffers... */
 209	while (len > 0) {
 210		bufptr = gdbmsgbuf + 1;
 211
 212		/* Calculate how many this time */
 213		if ((len << 1) > (BUFMAX - 2))
 214			wcount = (BUFMAX - 2) >> 1;
 215		else
 216			wcount = len;
 217
 218		/* Pack in hex chars */
 219		for (i = 0; i < wcount; i++)
 220			bufptr = hex_byte_pack(bufptr, s[i]);
 221		*bufptr = '\0';
 222
 223		/* Move up */
 224		s += wcount;
 225		len -= wcount;
 226
 227		/* Write packet */
 228		put_packet(gdbmsgbuf);
 229	}
 230}
 231
 232/*
 233 * Convert the memory pointed to by mem into hex, placing result in
 234 * buf.  Return a pointer to the last char put in buf (null). May
 235 * return an error.
 236 */
 237char *kgdb_mem2hex(char *mem, char *buf, int count)
 238{
 239	char *tmp;
 240	int err;
 241
 242	/*
 243	 * We use the upper half of buf as an intermediate buffer for the
 244	 * raw memory copy.  Hex conversion will work against this one.
 245	 */
 246	tmp = buf + count;
 247
 248	err = copy_from_kernel_nofault(tmp, mem, count);
 249	if (err)
 250		return NULL;
 251	while (count > 0) {
 252		buf = hex_byte_pack(buf, *tmp);
 253		tmp++;
 254		count--;
 255	}
 256	*buf = 0;
 257
 258	return buf;
 259}
 260
 261/*
 262 * Convert the hex array pointed to by buf into binary to be placed in
 263 * mem.  Return a pointer to the character AFTER the last byte
 264 * written.  May return an error.
 265 */
 266int kgdb_hex2mem(char *buf, char *mem, int count)
 267{
 268	char *tmp_raw;
 269	char *tmp_hex;
 270
 271	/*
 272	 * We use the upper half of buf as an intermediate buffer for the
 273	 * raw memory that is converted from hex.
 274	 */
 275	tmp_raw = buf + count * 2;
 276
 277	tmp_hex = tmp_raw - 1;
 278	while (tmp_hex >= buf) {
 279		tmp_raw--;
 280		*tmp_raw = hex_to_bin(*tmp_hex--);
 281		*tmp_raw |= hex_to_bin(*tmp_hex--) << 4;
 282	}
 283
 284	return copy_to_kernel_nofault(mem, tmp_raw, count);
 285}
 286
 287/*
 288 * While we find nice hex chars, build a long_val.
 289 * Return number of chars processed.
 290 */
 291int kgdb_hex2long(char **ptr, unsigned long *long_val)
 292{
 293	int hex_val;
 294	int num = 0;
 295	int negate = 0;
 296
 297	*long_val = 0;
 298
 299	if (**ptr == '-') {
 300		negate = 1;
 301		(*ptr)++;
 302	}
 303	while (**ptr) {
 304		hex_val = hex_to_bin(**ptr);
 305		if (hex_val < 0)
 306			break;
 307
 308		*long_val = (*long_val << 4) | hex_val;
 309		num++;
 310		(*ptr)++;
 311	}
 312
 313	if (negate)
 314		*long_val = -*long_val;
 315
 316	return num;
 317}
 318
 319/*
 320 * Copy the binary array pointed to by buf into mem.  Fix $, #, and
 321 * 0x7d escaped with 0x7d. Return -EFAULT on failure or 0 on success.
 322 * The input buf is overwritten with the result to write to mem.
 323 */
 324static int kgdb_ebin2mem(char *buf, char *mem, int count)
 325{
 326	int size = 0;
 327	char *c = buf;
 328
 329	while (count-- > 0) {
 330		c[size] = *buf++;
 331		if (c[size] == 0x7d)
 332			c[size] = *buf++ ^ 0x20;
 333		size++;
 334	}
 335
 336	return copy_to_kernel_nofault(mem, c, size);
 337}
 338
 339#if DBG_MAX_REG_NUM > 0
 340void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 341{
 342	int i;
 343	int idx = 0;
 344	char *ptr = (char *)gdb_regs;
 345
 346	for (i = 0; i < DBG_MAX_REG_NUM; i++) {
 347		dbg_get_reg(i, ptr + idx, regs);
 348		idx += dbg_reg_def[i].size;
 349	}
 350}
 351
 352void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 353{
 354	int i;
 355	int idx = 0;
 356	char *ptr = (char *)gdb_regs;
 357
 358	for (i = 0; i < DBG_MAX_REG_NUM; i++) {
 359		dbg_set_reg(i, ptr + idx, regs);
 360		idx += dbg_reg_def[i].size;
 361	}
 362}
 363#endif /* DBG_MAX_REG_NUM > 0 */
 364
 365/* Write memory due to an 'M' or 'X' packet. */
 366static int write_mem_msg(int binary)
 367{
 368	char *ptr = &remcom_in_buffer[1];
 369	unsigned long addr;
 370	unsigned long length;
 371	int err;
 372
 373	if (kgdb_hex2long(&ptr, &addr) > 0 && *(ptr++) == ',' &&
 374	    kgdb_hex2long(&ptr, &length) > 0 && *(ptr++) == ':') {
 375		if (binary)
 376			err = kgdb_ebin2mem(ptr, (char *)addr, length);
 377		else
 378			err = kgdb_hex2mem(ptr, (char *)addr, length);
 379		if (err)
 380			return err;
 381		if (CACHE_FLUSH_IS_SAFE)
 382			flush_icache_range(addr, addr + length);
 383		return 0;
 384	}
 385
 386	return -EINVAL;
 387}
 388
 389static void error_packet(char *pkt, int error)
 390{
 391	error = -error;
 392	pkt[0] = 'E';
 393	pkt[1] = hex_asc[(error / 10)];
 394	pkt[2] = hex_asc[(error % 10)];
 395	pkt[3] = '\0';
 396}
 397
 398/*
 399 * Thread ID accessors. We represent a flat TID space to GDB, where
 400 * the per CPU idle threads (which under Linux all have PID 0) are
 401 * remapped to negative TIDs.
 402 */
 403
 404#define BUF_THREAD_ID_SIZE	8
 405
 406static char *pack_threadid(char *pkt, unsigned char *id)
 407{
 408	unsigned char *limit;
 409	int lzero = 1;
 410
 411	limit = id + (BUF_THREAD_ID_SIZE / 2);
 412	while (id < limit) {
 413		if (!lzero || *id != 0) {
 414			pkt = hex_byte_pack(pkt, *id);
 415			lzero = 0;
 416		}
 417		id++;
 418	}
 419
 420	if (lzero)
 421		pkt = hex_byte_pack(pkt, 0);
 422
 423	return pkt;
 424}
 425
 426static void int_to_threadref(unsigned char *id, int value)
 427{
 428	put_unaligned_be32(value, id);
 429}
 430
 431static struct task_struct *getthread(struct pt_regs *regs, int tid)
 432{
 433	/*
 434	 * Non-positive TIDs are remapped to the cpu shadow information
 435	 */
 436	if (tid == 0 || tid == -1)
 437		tid = -atomic_read(&kgdb_active) - 2;
 438	if (tid < -1 && tid > -NR_CPUS - 2) {
 439		if (kgdb_info[-tid - 2].task)
 440			return kgdb_info[-tid - 2].task;
 441		else
 442			return idle_task(-tid - 2);
 443	}
 444	if (tid <= 0) {
 445		printk(KERN_ERR "KGDB: Internal thread select error\n");
 446		dump_stack();
 447		return NULL;
 448	}
 449
 450	/*
 451	 * find_task_by_pid_ns() does not take the tasklist lock anymore
 452	 * but is nicely RCU locked - hence is a pretty resilient
 453	 * thing to use:
 454	 */
 455	return find_task_by_pid_ns(tid, &init_pid_ns);
 456}
 457
 458
 459/*
 460 * Remap normal tasks to their real PID,
 461 * CPU shadow threads are mapped to -CPU - 2
 462 */
 463static inline int shadow_pid(int realpid)
 464{
 465	if (realpid)
 466		return realpid;
 467
 468	return -raw_smp_processor_id() - 2;
 469}
 470
 471/*
 472 * All the functions that start with gdb_cmd are the various
 473 * operations to implement the handlers for the gdbserial protocol
 474 * where KGDB is communicating with an external debugger
 475 */
 476
 477/* Handle the '?' status packets */
 478static void gdb_cmd_status(struct kgdb_state *ks)
 479{
 480	/*
 481	 * We know that this packet is only sent
 482	 * during initial connect.  So to be safe,
 483	 * we clear out our breakpoints now in case
 484	 * GDB is reconnecting.
 485	 */
 486	dbg_remove_all_break();
 487
 488	remcom_out_buffer[0] = 'S';
 489	hex_byte_pack(&remcom_out_buffer[1], ks->signo);
 490}
 491
 492static void gdb_get_regs_helper(struct kgdb_state *ks)
 493{
 494	struct task_struct *thread;
 495	void *local_debuggerinfo;
 496	int i;
 497
 498	thread = kgdb_usethread;
 499	if (!thread) {
 500		thread = kgdb_info[ks->cpu].task;
 501		local_debuggerinfo = kgdb_info[ks->cpu].debuggerinfo;
 502	} else {
 503		local_debuggerinfo = NULL;
 504		for_each_online_cpu(i) {
 505			/*
 506			 * Try to find the task on some other
 507			 * or possibly this node if we do not
 508			 * find the matching task then we try
 509			 * to approximate the results.
 510			 */
 511			if (thread == kgdb_info[i].task)
 512				local_debuggerinfo = kgdb_info[i].debuggerinfo;
 513		}
 514	}
 515
 516	/*
 517	 * All threads that don't have debuggerinfo should be
 518	 * in schedule() sleeping, since all other CPUs
 519	 * are in kgdb_wait, and thus have debuggerinfo.
 520	 */
 521	if (local_debuggerinfo) {
 522		pt_regs_to_gdb_regs(gdb_regs, local_debuggerinfo);
 523	} else {
 524		/*
 525		 * Pull stuff saved during switch_to; nothing
 526		 * else is accessible (or even particularly
 527		 * relevant).
 528		 *
 529		 * This should be enough for a stack trace.
 530		 */
 531		sleeping_thread_to_gdb_regs(gdb_regs, thread);
 532	}
 533}
 534
 535/* Handle the 'g' get registers request */
 536static void gdb_cmd_getregs(struct kgdb_state *ks)
 537{
 538	gdb_get_regs_helper(ks);
 539	kgdb_mem2hex((char *)gdb_regs, remcom_out_buffer, NUMREGBYTES);
 540}
 541
 542/* Handle the 'G' set registers request */
 543static void gdb_cmd_setregs(struct kgdb_state *ks)
 544{
 545	kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs, NUMREGBYTES);
 546
 547	if (kgdb_usethread && kgdb_usethread != current) {
 548		error_packet(remcom_out_buffer, -EINVAL);
 549	} else {
 550		gdb_regs_to_pt_regs(gdb_regs, ks->linux_regs);
 551		strscpy(remcom_out_buffer, "OK");
 552	}
 553}
 554
 555/* Handle the 'm' memory read bytes */
 556static void gdb_cmd_memread(struct kgdb_state *ks)
 557{
 558	char *ptr = &remcom_in_buffer[1];
 559	unsigned long length;
 560	unsigned long addr;
 561	char *err;
 562
 563	if (kgdb_hex2long(&ptr, &addr) > 0 && *ptr++ == ',' &&
 564					kgdb_hex2long(&ptr, &length) > 0) {
 565		err = kgdb_mem2hex((char *)addr, remcom_out_buffer, length);
 566		if (!err)
 567			error_packet(remcom_out_buffer, -EINVAL);
 568	} else {
 569		error_packet(remcom_out_buffer, -EINVAL);
 570	}
 571}
 572
 573/* Handle the 'M' memory write bytes */
 574static void gdb_cmd_memwrite(struct kgdb_state *ks)
 575{
 576	int err = write_mem_msg(0);
 577
 578	if (err)
 579		error_packet(remcom_out_buffer, err);
 580	else
 581		strscpy(remcom_out_buffer, "OK");
 582}
 583
 584#if DBG_MAX_REG_NUM > 0
 585static char *gdb_hex_reg_helper(int regnum, char *out)
 586{
 587	int i;
 588	int offset = 0;
 589
 590	for (i = 0; i < regnum; i++)
 591		offset += dbg_reg_def[i].size;
 592	return kgdb_mem2hex((char *)gdb_regs + offset, out,
 593			    dbg_reg_def[i].size);
 594}
 595
 596/* Handle the 'p' individual register get */
 597static void gdb_cmd_reg_get(struct kgdb_state *ks)
 598{
 599	unsigned long regnum;
 600	char *ptr = &remcom_in_buffer[1];
 601
 602	kgdb_hex2long(&ptr, &regnum);
 603	if (regnum >= DBG_MAX_REG_NUM) {
 604		error_packet(remcom_out_buffer, -EINVAL);
 605		return;
 606	}
 607	gdb_get_regs_helper(ks);
 608	gdb_hex_reg_helper(regnum, remcom_out_buffer);
 609}
 610
 611/* Handle the 'P' individual register set */
 612static void gdb_cmd_reg_set(struct kgdb_state *ks)
 613{
 614	unsigned long regnum;
 615	char *ptr = &remcom_in_buffer[1];
 616	int i = 0;
 617
 618	kgdb_hex2long(&ptr, &regnum);
 619	if (*ptr++ != '=' ||
 620	    !(!kgdb_usethread || kgdb_usethread == current) ||
 621	    !dbg_get_reg(regnum, gdb_regs, ks->linux_regs)) {
 622		error_packet(remcom_out_buffer, -EINVAL);
 623		return;
 624	}
 625	memset(gdb_regs, 0, sizeof(gdb_regs));
 626	while (i < sizeof(gdb_regs) * 2)
 627		if (hex_to_bin(ptr[i]) >= 0)
 628			i++;
 629		else
 630			break;
 631	i = i / 2;
 632	kgdb_hex2mem(ptr, (char *)gdb_regs, i);
 633	dbg_set_reg(regnum, gdb_regs, ks->linux_regs);
 634	strscpy(remcom_out_buffer, "OK");
 635}
 636#endif /* DBG_MAX_REG_NUM > 0 */
 637
 638/* Handle the 'X' memory binary write bytes */
 639static void gdb_cmd_binwrite(struct kgdb_state *ks)
 640{
 641	int err = write_mem_msg(1);
 642
 643	if (err)
 644		error_packet(remcom_out_buffer, err);
 645	else
 646		strscpy(remcom_out_buffer, "OK");
 647}
 648
 649/* Handle the 'D' or 'k', detach or kill packets */
 650static void gdb_cmd_detachkill(struct kgdb_state *ks)
 651{
 652	int error;
 653
 654	/* The detach case */
 655	if (remcom_in_buffer[0] == 'D') {
 656		error = dbg_remove_all_break();
 657		if (error < 0) {
 658			error_packet(remcom_out_buffer, error);
 659		} else {
 660			strscpy(remcom_out_buffer, "OK");
 661			kgdb_connected = 0;
 662		}
 663		put_packet(remcom_out_buffer);
 664	} else {
 665		/*
 666		 * Assume the kill case, with no exit code checking,
 667		 * trying to force detach the debugger:
 668		 */
 669		dbg_remove_all_break();
 670		kgdb_connected = 0;
 671	}
 672}
 673
 674/* Handle the 'R' reboot packets */
 675static int gdb_cmd_reboot(struct kgdb_state *ks)
 676{
 677	/* For now, only honor R0 */
 678	if (strcmp(remcom_in_buffer, "R0") == 0) {
 679		printk(KERN_CRIT "Executing emergency reboot\n");
 680		strscpy(remcom_out_buffer, "OK");
 681		put_packet(remcom_out_buffer);
 682
 683		/*
 684		 * Execution should not return from
 685		 * machine_emergency_restart()
 686		 */
 687		machine_emergency_restart();
 688		kgdb_connected = 0;
 689
 690		return 1;
 691	}
 692	return 0;
 693}
 694
 695/* Handle the 'q' query packets */
 696static void gdb_cmd_query(struct kgdb_state *ks)
 697{
 698	struct task_struct *g;
 699	struct task_struct *p;
 700	unsigned char thref[BUF_THREAD_ID_SIZE];
 701	char *ptr;
 702	int i;
 703	int cpu;
 704	int finished = 0;
 705
 706	switch (remcom_in_buffer[1]) {
 707	case 's':
 708	case 'f':
 709		if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10))
 710			break;
 711
 712		i = 0;
 713		remcom_out_buffer[0] = 'm';
 714		ptr = remcom_out_buffer + 1;
 715		if (remcom_in_buffer[1] == 'f') {
 716			/* Each cpu is a shadow thread */
 717			for_each_online_cpu(cpu) {
 718				ks->thr_query = 0;
 719				int_to_threadref(thref, -cpu - 2);
 720				ptr = pack_threadid(ptr, thref);
 721				*(ptr++) = ',';
 722				i++;
 723			}
 724		}
 725
 726		for_each_process_thread(g, p) {
 727			if (i >= ks->thr_query && !finished) {
 728				int_to_threadref(thref, p->pid);
 729				ptr = pack_threadid(ptr, thref);
 730				*(ptr++) = ',';
 731				ks->thr_query++;
 732				if (ks->thr_query % KGDB_MAX_THREAD_QUERY == 0)
 733					finished = 1;
 734			}
 735			i++;
 736		}
 737
 738		*(--ptr) = '\0';
 739		break;
 740
 741	case 'C':
 742		/* Current thread id */
 743		strscpy(remcom_out_buffer, "QC");
 744		ks->threadid = shadow_pid(current->pid);
 745		int_to_threadref(thref, ks->threadid);
 746		pack_threadid(remcom_out_buffer + 2, thref);
 747		break;
 748	case 'T':
 749		if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16))
 750			break;
 751
 752		ks->threadid = 0;
 753		ptr = remcom_in_buffer + 17;
 754		kgdb_hex2long(&ptr, &ks->threadid);
 755		if (!getthread(ks->linux_regs, ks->threadid)) {
 756			error_packet(remcom_out_buffer, -EINVAL);
 757			break;
 758		}
 759		if ((int)ks->threadid > 0) {
 760			kgdb_mem2hex(getthread(ks->linux_regs,
 761					ks->threadid)->comm,
 762					remcom_out_buffer, 16);
 763		} else {
 764			static char tmpstr[23 + BUF_THREAD_ID_SIZE];
 765
 766			sprintf(tmpstr, "shadowCPU%d",
 767					(int)(-ks->threadid - 2));
 768			kgdb_mem2hex(tmpstr, remcom_out_buffer, strlen(tmpstr));
 769		}
 770		break;
 771#ifdef CONFIG_KGDB_KDB
 772	case 'R':
 773		if (strncmp(remcom_in_buffer, "qRcmd,", 6) == 0) {
 774			int len = strlen(remcom_in_buffer + 6);
 775
 776			if ((len % 2) != 0) {
 777				strscpy(remcom_out_buffer, "E01");
 778				break;
 779			}
 780			kgdb_hex2mem(remcom_in_buffer + 6,
 781				     remcom_out_buffer, len);
 782			len = len / 2;
 783			remcom_out_buffer[len++] = 0;
 784
 785			kdb_common_init_state(ks);
 786			kdb_parse(remcom_out_buffer);
 787			kdb_common_deinit_state();
 788
 789			strscpy(remcom_out_buffer, "OK");
 790		}
 791		break;
 792#endif
 793#ifdef CONFIG_HAVE_ARCH_KGDB_QXFER_PKT
 794	case 'S':
 795		if (!strncmp(remcom_in_buffer, "qSupported:", 11))
 796			strscpy(remcom_out_buffer, kgdb_arch_gdb_stub_feature);
 797		break;
 798	case 'X':
 799		if (!strncmp(remcom_in_buffer, "qXfer:", 6))
 800			kgdb_arch_handle_qxfer_pkt(remcom_in_buffer,
 801						   remcom_out_buffer);
 802		break;
 803#endif
 804	default:
 805		break;
 806	}
 807}
 808
 809/* Handle the 'H' task query packets */
 810static void gdb_cmd_task(struct kgdb_state *ks)
 811{
 812	struct task_struct *thread;
 813	char *ptr;
 814
 815	switch (remcom_in_buffer[1]) {
 816	case 'g':
 817		ptr = &remcom_in_buffer[2];
 818		kgdb_hex2long(&ptr, &ks->threadid);
 819		thread = getthread(ks->linux_regs, ks->threadid);
 820		if (!thread && ks->threadid > 0) {
 821			error_packet(remcom_out_buffer, -EINVAL);
 822			break;
 823		}
 824		kgdb_usethread = thread;
 825		ks->kgdb_usethreadid = ks->threadid;
 826		strscpy(remcom_out_buffer, "OK");
 827		break;
 828	case 'c':
 829		ptr = &remcom_in_buffer[2];
 830		kgdb_hex2long(&ptr, &ks->threadid);
 831		if (!ks->threadid) {
 832			kgdb_contthread = NULL;
 833		} else {
 834			thread = getthread(ks->linux_regs, ks->threadid);
 835			if (!thread && ks->threadid > 0) {
 836				error_packet(remcom_out_buffer, -EINVAL);
 837				break;
 838			}
 839			kgdb_contthread = thread;
 840		}
 841		strscpy(remcom_out_buffer, "OK");
 842		break;
 843	}
 844}
 845
 846/* Handle the 'T' thread query packets */
 847static void gdb_cmd_thread(struct kgdb_state *ks)
 848{
 849	char *ptr = &remcom_in_buffer[1];
 850	struct task_struct *thread;
 851
 852	kgdb_hex2long(&ptr, &ks->threadid);
 853	thread = getthread(ks->linux_regs, ks->threadid);
 854	if (thread)
 855		strscpy(remcom_out_buffer, "OK");
 856	else
 857		error_packet(remcom_out_buffer, -EINVAL);
 858}
 859
 860/* Handle the 'z' or 'Z' breakpoint remove or set packets */
 861static void gdb_cmd_break(struct kgdb_state *ks)
 862{
 863	/*
 864	 * Since GDB-5.3, it's been drafted that '0' is a software
 865	 * breakpoint, '1' is a hardware breakpoint, so let's do that.
 866	 */
 867	char *bpt_type = &remcom_in_buffer[1];
 868	char *ptr = &remcom_in_buffer[2];
 869	unsigned long addr;
 870	unsigned long length;
 871	int error = 0;
 872
 873	if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
 874		/* Unsupported */
 875		if (*bpt_type > '4')
 876			return;
 877	} else {
 878		if (*bpt_type != '0' && *bpt_type != '1')
 879			/* Unsupported. */
 880			return;
 881	}
 882
 883	/*
 884	 * Test if this is a hardware breakpoint, and
 885	 * if we support it:
 886	 */
 887	if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
 888		/* Unsupported. */
 889		return;
 890
 891	if (*(ptr++) != ',') {
 892		error_packet(remcom_out_buffer, -EINVAL);
 893		return;
 894	}
 895	if (!kgdb_hex2long(&ptr, &addr)) {
 896		error_packet(remcom_out_buffer, -EINVAL);
 897		return;
 898	}
 899	if (*(ptr++) != ',' ||
 900		!kgdb_hex2long(&ptr, &length)) {
 901		error_packet(remcom_out_buffer, -EINVAL);
 902		return;
 903	}
 904
 905	if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
 906		error = dbg_set_sw_break(addr);
 907	else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
 908		error = dbg_remove_sw_break(addr);
 909	else if (remcom_in_buffer[0] == 'Z')
 910		error = arch_kgdb_ops.set_hw_breakpoint(addr,
 911			(int)length, *bpt_type - '0');
 912	else if (remcom_in_buffer[0] == 'z')
 913		error = arch_kgdb_ops.remove_hw_breakpoint(addr,
 914			(int) length, *bpt_type - '0');
 915
 916	if (error == 0)
 917		strscpy(remcom_out_buffer, "OK");
 918	else
 919		error_packet(remcom_out_buffer, error);
 920}
 921
 922/* Handle the 'C' signal / exception passing packets */
 923static int gdb_cmd_exception_pass(struct kgdb_state *ks)
 924{
 925	/* C09 == pass exception
 926	 * C15 == detach kgdb, pass exception
 927	 */
 928	if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {
 929
 930		ks->pass_exception = 1;
 931		remcom_in_buffer[0] = 'c';
 932
 933	} else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {
 934
 935		ks->pass_exception = 1;
 936		remcom_in_buffer[0] = 'D';
 937		dbg_remove_all_break();
 938		kgdb_connected = 0;
 939		return 1;
 940
 941	} else {
 942		gdbstub_msg_write("KGDB only knows signal 9 (pass)"
 943			" and 15 (pass and disconnect)\n"
 944			"Executing a continue without signal passing\n", 0);
 945		remcom_in_buffer[0] = 'c';
 946	}
 947
 948	/* Indicate fall through */
 949	return -1;
 950}
 951
 952/*
 953 * This function performs all gdbserial command processing
 954 */
 955int gdb_serial_stub(struct kgdb_state *ks)
 956{
 957	int error = 0;
 958	int tmp;
 959
 960	/* Initialize comm buffer and globals. */
 961	memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
 962	kgdb_usethread = kgdb_info[ks->cpu].task;
 963	ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
 964	ks->pass_exception = 0;
 965
 966	if (kgdb_connected) {
 967		unsigned char thref[BUF_THREAD_ID_SIZE];
 968		char *ptr;
 969
 970		/* Reply to host that an exception has occurred */
 971		ptr = remcom_out_buffer;
 972		*ptr++ = 'T';
 973		ptr = hex_byte_pack(ptr, ks->signo);
 974		ptr += strlen(strcpy(ptr, "thread:"));
 975		int_to_threadref(thref, shadow_pid(current->pid));
 976		ptr = pack_threadid(ptr, thref);
 977		*ptr++ = ';';
 978		put_packet(remcom_out_buffer);
 979	}
 980
 981	while (1) {
 982		error = 0;
 983
 984		/* Clear the out buffer. */
 985		memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
 986
 987		get_packet(remcom_in_buffer);
 988
 989		switch (remcom_in_buffer[0]) {
 990		case '?': /* gdbserial status */
 991			gdb_cmd_status(ks);
 992			break;
 993		case 'g': /* return the value of the CPU registers */
 994			gdb_cmd_getregs(ks);
 995			break;
 996		case 'G': /* set the value of the CPU registers - return OK */
 997			gdb_cmd_setregs(ks);
 998			break;
 999		case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
1000			gdb_cmd_memread(ks);
1001			break;
1002		case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1003			gdb_cmd_memwrite(ks);
1004			break;
1005#if DBG_MAX_REG_NUM > 0
1006		case 'p': /* pXX Return gdb register XX (in hex) */
1007			gdb_cmd_reg_get(ks);
1008			break;
1009		case 'P': /* PXX=aaaa Set gdb register XX to aaaa (in hex) */
1010			gdb_cmd_reg_set(ks);
1011			break;
1012#endif /* DBG_MAX_REG_NUM > 0 */
1013		case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1014			gdb_cmd_binwrite(ks);
1015			break;
1016			/* kill or detach. KGDB should treat this like a
1017			 * continue.
1018			 */
1019		case 'D': /* Debugger detach */
1020		case 'k': /* Debugger detach via kill */
1021			gdb_cmd_detachkill(ks);
1022			goto default_handle;
1023		case 'R': /* Reboot */
1024			if (gdb_cmd_reboot(ks))
1025				goto default_handle;
1026			break;
1027		case 'q': /* query command */
1028			gdb_cmd_query(ks);
1029			break;
1030		case 'H': /* task related */
1031			gdb_cmd_task(ks);
1032			break;
1033		case 'T': /* Query thread status */
1034			gdb_cmd_thread(ks);
1035			break;
1036		case 'z': /* Break point remove */
1037		case 'Z': /* Break point set */
1038			gdb_cmd_break(ks);
1039			break;
1040#ifdef CONFIG_KGDB_KDB
1041		case '3': /* Escape into back into kdb */
1042			if (remcom_in_buffer[1] == '\0') {
1043				gdb_cmd_detachkill(ks);
1044				return DBG_PASS_EVENT;
1045			}
1046			fallthrough;
1047#endif
1048		case 'C': /* Exception passing */
1049			tmp = gdb_cmd_exception_pass(ks);
1050			if (tmp > 0)
1051				goto default_handle;
1052			if (tmp == 0)
1053				break;
1054			fallthrough;	/* on tmp < 0 */
1055		case 'c': /* Continue packet */
1056		case 's': /* Single step packet */
1057			if (kgdb_contthread && kgdb_contthread != current) {
1058				/* Can't switch threads in kgdb */
1059				error_packet(remcom_out_buffer, -EINVAL);
1060				break;
1061			}
1062			fallthrough;	/* to default processing */
1063		default:
1064default_handle:
1065			error = kgdb_arch_handle_exception(ks->ex_vector,
1066						ks->signo,
1067						ks->err_code,
1068						remcom_in_buffer,
1069						remcom_out_buffer,
1070						ks->linux_regs);
1071			/*
1072			 * Leave cmd processing on error, detach,
1073			 * kill, continue, or single step.
1074			 */
1075			if (error >= 0 || remcom_in_buffer[0] == 'D' ||
1076			    remcom_in_buffer[0] == 'k') {
1077				error = 0;
1078				goto kgdb_exit;
1079			}
1080
1081		}
1082
1083		/* reply to the request */
1084		put_packet(remcom_out_buffer);
1085	}
1086
1087kgdb_exit:
1088	if (ks->pass_exception)
1089		error = 1;
1090	return error;
1091}
1092
1093int gdbstub_state(struct kgdb_state *ks, char *cmd)
1094{
1095	int error;
1096
1097	switch (cmd[0]) {
1098	case 'e':
1099		error = kgdb_arch_handle_exception(ks->ex_vector,
1100						   ks->signo,
1101						   ks->err_code,
1102						   remcom_in_buffer,
1103						   remcom_out_buffer,
1104						   ks->linux_regs);
1105		return error;
1106	case 's':
1107	case 'c':
1108		strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
1109		return 0;
1110	case '$':
1111		strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
1112		gdbstub_use_prev_in_buf = strlen(remcom_in_buffer);
1113		gdbstub_prev_in_buf_pos = 0;
1114		return 0;
1115	}
1116	dbg_io_ops->write_char('+');
1117	put_packet(remcom_out_buffer);
1118	return 0;
1119}
1120
1121/**
1122 * gdbstub_exit - Send an exit message to GDB
1123 * @status: The exit code to report.
1124 */
1125void gdbstub_exit(int status)
1126{
1127	unsigned char checksum, ch, buffer[3];
1128	int loop;
1129
1130	if (!kgdb_connected)
1131		return;
1132	kgdb_connected = 0;
1133
1134	if (!dbg_io_ops || dbg_kdb_mode)
1135		return;
1136
1137	buffer[0] = 'W';
1138	buffer[1] = hex_asc_hi(status);
1139	buffer[2] = hex_asc_lo(status);
1140
1141	dbg_io_ops->write_char('$');
1142	checksum = 0;
1143
1144	for (loop = 0; loop < 3; loop++) {
1145		ch = buffer[loop];
1146		checksum += ch;
1147		dbg_io_ops->write_char(ch);
1148	}
1149
1150	dbg_io_ops->write_char('#');
1151	dbg_io_ops->write_char(hex_asc_hi(checksum));
1152	dbg_io_ops->write_char(hex_asc_lo(checksum));
1153
1154	/* make sure the output is flushed, lest the bootloader clobber it */
1155	if (dbg_io_ops->flush)
1156		dbg_io_ops->flush();
1157}