arch/mips/kernel/gdb-stub.c

   1 /*
   2  *  arch/mips/kernel/gdb-stub.c
   3  *
   4  *  Originally written by Glenn Engel, Lake Stevens Instrument Division
   5  *
   6  *  Contributed by HP Systems
   7  *
   8  *  Modified for SPARC by Stu Grossman, Cygnus Support.
   9  *
  10  *  Modified for Linux/MIPS (and MIPS in general) by Andreas Busse
  11  *  Send complaints, suggestions etc. to <andy@waldorf-gmbh.de>
  12  *
  13  *  Copyright (C) 1995 Andreas Busse
  14  *
  15  *  Copyright (C) 2003 MontaVista Software Inc.
  16  *  Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
  17  */
  18
  19 /*
  20  *  To enable debugger support, two things need to happen.  One, a
  21  *  call to set_debug_traps() is necessary in order to allow any breakpoints
  22  *  or error conditions to be properly intercepted and reported to gdb.
  23  *  Two, a breakpoint needs to be generated to begin communication.  This
  24  *  is most easily accomplished by a call to breakpoint().  Breakpoint()
  25  *  simulates a breakpoint by executing a BREAK instruction.
  26  *
  27  *
  28  *    The following gdb commands are supported:
  29  *
  30  * command          function                               Return value
  31  *
  32  *    g             return the value of the CPU registers  hex data or ENN
  33  *    G             set the value of the CPU registers     OK or ENN
  34  *
  35  *    mAA..AA,LLLL  Read LLLL bytes at address AA..AA      hex data or ENN
  36  *    MAA..AA,LLLL: Write LLLL bytes at address AA.AA      OK or ENN
  37  *
  38  *    c             Resume at current address              SNN   ( signal NN)
  39  *    cAA..AA       Continue at address AA..AA             SNN
  40  *
  41  *    s             Step one instruction                   SNN
  42  *    sAA..AA       Step one instruction from AA..AA       SNN
  43  *
  44  *    k             kill
  45  *
  46  *    ?             What was the last sigval ?             SNN   (signal NN)
  47  *
  48  *    bBB..BB       Set baud rate to BB..BB                OK or BNN, then sets
  49  *                                                         baud rate
  50  *
  51  * All commands and responses are sent with a packet which includes a
  52  * checksum.  A packet consists of
  53  *
  54  * $<packet info>#<checksum>.
  55  *
  56  * where
  57  * <packet info> :: <characters representing the command or response>
  58  * <checksum>    :: < two hex digits computed as modulo 256 sum of <packetinfo>>
  59  *
  60  * When a packet is received, it is first acknowledged with either '+' or '-'.
  61  * '+' indicates a successful transfer.  '-' indicates a failed transfer.
  62  *
  63  * Example:
  64  *
  65  * Host:                  Reply:
  66  * $m0,10#2a               +$00010203040506070809101112131415#42
  67  *
  68  *
  69  *  ==============
  70  *  MORE EXAMPLES:
  71  *  ==============
  72  *
  73  *  For reference -- the following are the steps that one
  74  *  company took (RidgeRun Inc) to get remote gdb debugging
  75  *  going. In this scenario the host machine was a PC and the
  76  *  target platform was a Galileo EVB64120A MIPS evaluation
  77  *  board.
  78  *
  79  *  Step 1:
  80  *  First download gdb-5.0.tar.gz from the internet.
  81  *  and then build/install the package.
  82  *
  83  *  Example:
  84  *    $ tar zxf gdb-5.0.tar.gz
  85  *    $ cd gdb-5.0
  86  *    $ ./configure --target=mips-linux-elf
  87  *    $ make
  88  *    $ install
  89  *    $ which mips-linux-elf-gdb
  90  *    /usr/local/bin/mips-linux-elf-gdb
  91  *
  92  *  Step 2:
  93  *  Configure linux for remote debugging and build it.
  94  *
  95  *  Example:
  96  *    $ cd ~/linux
  97  *    $ make menuconfig <go to "Kernel Hacking" and turn on remote debugging>
  98  *    $ make
  99  *
 100  *  Step 3:
 101  *  Download the kernel to the remote target and start
 102  *  the kernel running. It will promptly halt and wait
 103  *  for the host gdb session to connect. It does this
 104  *  since the "Kernel Hacking" option has defined
 105  *  CONFIG_KGDB which in turn enables your calls
 106  *  to:
 107  *     set_debug_traps();
 108  *     breakpoint();
 109  *
 110  *  Step 4:
 111  *  Start the gdb session on the host.
 112  *
 113  *  Example:
 114  *    $ mips-linux-elf-gdb vmlinux
 115  *    (gdb) set remotebaud 115200
 116  *    (gdb) target remote /dev/ttyS1
 117  *    ...at this point you are connected to
 118  *       the remote target and can use gdb
 119  *       in the normal fasion. Setting
 120  *       breakpoints, single stepping,
 121  *       printing variables, etc.
 122  */
 123 #include <linux/config.h>
 124 #include <linux/string.h>
 125 #include <linux/kernel.h>
 126 #include <linux/signal.h>
 127 #include <linux/sched.h>
 128 #include <linux/mm.h>
 129 #include <linux/console.h>
 130 #include <linux/init.h>
 131 #include <linux/smp.h>
 132 #include <linux/spinlock.h>
 133 #include <linux/slab.h>
 134 #include <linux/reboot.h>
 135
 136 #include <asm/asm.h>
 137 #include <asm/cacheflush.h>
 138 #include <asm/mipsregs.h>
 139 #include <asm/pgtable.h>
 140 #include <asm/system.h>
 141 #include <asm/gdb-stub.h>
 142 #include <asm/inst.h>
 143
 144 /*
 145  * external low-level support routines
 146  */
 147
 148 extern int putDebugChar(char c);    /* write a single character      */
 149 extern char getDebugChar(void);     /* read and return a single char */
 150 extern void trap_low(void);
 151
 152 /*
 153  * breakpoint and test functions
 154  */
 155 extern void breakpoint(void);
 156 extern void breakinst(void);
 157 extern void async_breakpoint(void);
 158 extern void async_breakinst(void);
 159 extern void adel(void);
 160
 161 /*
 162  * local prototypes
 163  */
 164
 165 static void getpacket(char *buffer);
 166 static void putpacket(char *buffer);
 167 static int computeSignal(int tt);
 168 static int hex(unsigned char ch);
 169 static int hexToInt(char **ptr, int *intValue);
 170 static int hexToLong(char **ptr, long *longValue);
 171 static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault);
 172 void handle_exception(struct gdb_regs *regs);
 173
 174 int kgdb_enabled;
 175
 176 /*
 177  * spin locks for smp case
 178  */
 179 static DEFINE_SPINLOCK(kgdb_lock);
 180 static raw_spinlock_t kgdb_cpulock[NR_CPUS] = {
 181         [0 ... NR_CPUS-1] = __RAW_SPIN_LOCK_UNLOCKED,
 182 };
 183
 184 /*
 185  * BUFMAX defines the maximum number of characters in inbound/outbound buffers
 186  * at least NUMREGBYTES*2 are needed for register packets
 187  */
 188 #define BUFMAX 2048
 189
 190 static char input_buffer[BUFMAX];
 191 static char output_buffer[BUFMAX];
 192 static int initialized; /* !0 means we've been initialized */
 193 static int kgdb_started;
 194 static const char hexchars[]="0123456789abcdef";
 195
 196 /* Used to prevent crashes in memory access.  Note that they'll crash anyway if
 197    we haven't set up fault handlers yet... */
 198 int kgdb_read_byte(unsigned char *address, unsigned char *dest);
 199 int kgdb_write_byte(unsigned char val, unsigned char *dest);
 200
 201 /*
 202  * Convert ch from a hex digit to an int
 203  */
 204 static int hex(unsigned char ch)
 205 {
 206         if (ch >= 'a' && ch <= 'f')
 207                 return ch-'a'+10;
 208         if (ch >= '0' && ch <= '9')
 209                 return ch-'0';
 210         if (ch >= 'A' && ch <= 'F')
 211                 return ch-'A'+10;
 212         return -1;
 213 }
 214
 215 /*
 216  * scan for the sequence $<data>#<checksum>
 217  */
 218 static void getpacket(char *buffer)
 219 {
 220         unsigned char checksum;
 221         unsigned char xmitcsum;
 222         int i;
 223         int count;
 224         unsigned char ch;
 225
 226         do {
 227                 /*
 228                  * wait around for the start character,
 229                  * ignore all other characters
 230                  */
 231                 while ((ch = (getDebugChar() & 0x7f)) != '$') ;
 232
 233                 checksum = 0;
 234                 xmitcsum = -1;
 235                 count = 0;
 236
 237                 /*
 238                  * now, read until a # or end of buffer is found
 239                  */
 240                 while (count < BUFMAX) {
 241                         ch = getDebugChar();
 242                         if (ch == '#')
 243                                 break;
 244                         checksum = checksum + ch;
 245                         buffer[count] = ch;
 246                         count = count + 1;
 247                 }
 248
 249                 if (count >= BUFMAX)
 250                         continue;
 251
 252                 buffer[count] = 0;
 253
 254                 if (ch == '#') {
 255                         xmitcsum = hex(getDebugChar() & 0x7f) << 4;
 256                         xmitcsum |= hex(getDebugChar() & 0x7f);
 257
 258                         if (checksum != xmitcsum)
 259                                 putDebugChar('-');      /* failed checksum */
 260                         else {
 261                                 putDebugChar('+'); /* successful transfer */
 262
 263                                 /*
 264                                  * if a sequence char is present,
 265                                  * reply the sequence ID
 266                                  */
 267                                 if (buffer[2] == ':') {
 268                                         putDebugChar(buffer[0]);
 269                                         putDebugChar(buffer[1]);
 270
 271                                         /*
 272                                          * remove sequence chars from buffer
 273                                          */
 274                                         count = strlen(buffer);
 275                                         for (i=3; i <= count; i++)
 276                                                 buffer[i-3] = buffer[i];
 277                                 }
 278                         }
 279                 }
 280         }
 281         while (checksum != xmitcsum);
 282 }
 283
 284 /*
 285  * send the packet in buffer.
 286  */
 287 static void putpacket(char *buffer)
 288 {
 289         unsigned char checksum;
 290         int count;
 291         unsigned char ch;
 292
 293         /*
 294          * $<packet info>#<checksum>.
 295          */
 296
 297         do {
 298                 putDebugChar('$');
 299                 checksum = 0;
 300                 count = 0;
 301
 302                 while ((ch = buffer[count]) != 0) {
 303                         if (!(putDebugChar(ch)))
 304                                 return;
 305                         checksum += ch;
 306                         count += 1;
 307                 }
 308
 309                 putDebugChar('#');
 310                 putDebugChar(hexchars[checksum >> 4]);
 311                 putDebugChar(hexchars[checksum & 0xf]);
 312
 313         }
 314         while ((getDebugChar() & 0x7f) != '+');
 315 }
 316
 317
 318 /*
 319  * Convert the memory pointed to by mem into hex, placing result in buf.
 320  * Return a pointer to the last char put in buf (null), in case of mem fault,
 321  * return 0.
 322  * may_fault is non-zero if we are reading from arbitrary memory, but is currently
 323  * not used.
 324  */
 325 static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault)
 326 {
 327         unsigned char ch;
 328
 329         while (count-- > 0) {
 330                 if (kgdb_read_byte(mem++, &ch) != 0)
 331                         return 0;
 332                 *buf++ = hexchars[ch >> 4];
 333                 *buf++ = hexchars[ch & 0xf];
 334         }
 335
 336         *buf = 0;
 337
 338         return buf;
 339 }
 340
 341 /*
 342  * convert the hex array pointed to by buf into binary to be placed in mem
 343  * return a pointer to the character AFTER the last byte written
 344  * may_fault is non-zero if we are reading from arbitrary memory, but is currently
 345  * not used.
 346  */
 347 static char *hex2mem(char *buf, char *mem, int count, int binary, int may_fault)
 348 {
 349         int i;
 350         unsigned char ch;
 351
 352         for (i=0; i<count; i++)
 353         {
 354                 if (binary) {
 355                         ch = *buf++;
 356                         if (ch == 0x7d)
 357                                 ch = 0x20 ^ *buf++;
 358                 }
 359                 else {
 360                         ch = hex(*buf++) << 4;
 361                         ch |= hex(*buf++);
 362                 }
 363                 if (kgdb_write_byte(ch, mem++) != 0)
 364                         return 0;
 365         }
 366
 367         return mem;
 368 }
 369
 370 /*
 371  * This table contains the mapping between SPARC hardware trap types, and
 372  * signals, which are primarily what GDB understands.  It also indicates
 373  * which hardware traps we need to commandeer when initializing the stub.
 374  */
 375 static struct hard_trap_info {
 376         unsigned char tt;               /* Trap type code for MIPS R3xxx and R4xxx */
 377         unsigned char signo;            /* Signal that we map this trap into */
 378 } hard_trap_info[] = {
 379         { 6, SIGBUS },                  /* instruction bus error */
 380         { 7, SIGBUS },                  /* data bus error */
 381         { 9, SIGTRAP },                 /* break */
 382         { 10, SIGILL },                 /* reserved instruction */
 383 /*      { 11, SIGILL },         */      /* CPU unusable */
 384         { 12, SIGFPE },                 /* overflow */
 385         { 13, SIGTRAP },                /* trap */
 386         { 14, SIGSEGV },                /* virtual instruction cache coherency */
 387         { 15, SIGFPE },                 /* floating point exception */
 388         { 23, SIGSEGV },                /* watch */
 389         { 31, SIGSEGV },                /* virtual data cache coherency */
 390         { 0, 0}                         /* Must be last */
 391 };
 392
 393 /* Save the normal trap handlers for user-mode traps. */
 394 void *saved_vectors[32];
 395
 396 /*
 397  * Set up exception handlers for tracing and breakpoints
 398  */
 399 void set_debug_traps(void)
 400 {
 401         struct hard_trap_info *ht;
 402         unsigned long flags;
 403         unsigned char c;
 404
 405         local_irq_save(flags);
 406         for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
 407                 saved_vectors[ht->tt] = set_except_vector(ht->tt, trap_low);
 408
 409         putDebugChar('+'); /* 'hello world' */
 410         /*
 411          * In case GDB is started before us, ack any packets
 412          * (presumably "$?#xx") sitting there.
 413          */
 414         while((c = getDebugChar()) != '$');
 415         while((c = getDebugChar()) != '#');
 416         c = getDebugChar(); /* eat first csum byte */
 417         c = getDebugChar(); /* eat second csum byte */
 418         putDebugChar('+'); /* ack it */
 419
 420         initialized = 1;
 421         local_irq_restore(flags);
 422 }
 423
 424 void restore_debug_traps(void)
 425 {
 426         struct hard_trap_info *ht;
 427         unsigned long flags;
 428
 429         local_irq_save(flags);
 430         for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
 431                 set_except_vector(ht->tt, saved_vectors[ht->tt]);
 432         local_irq_restore(flags);
 433 }
 434
 435 /*
 436  * Convert the MIPS hardware trap type code to a Unix signal number.
 437  */
 438 static int computeSignal(int tt)
 439 {
 440         struct hard_trap_info *ht;
 441
 442         for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
 443                 if (ht->tt == tt)
 444                         return ht->signo;
 445
 446         return SIGHUP;          /* default for things we don't know about */
 447 }
 448
 449 /*
 450  * While we find nice hex chars, build an int.
 451  * Return number of chars processed.
 452  */
 453 static int hexToInt(char **ptr, int *intValue)
 454 {
 455         int numChars = 0;
 456         int hexValue;
 457
 458         *intValue = 0;
 459
 460         while (**ptr) {
 461                 hexValue = hex(**ptr);
 462                 if (hexValue < 0)
 463                         break;
 464
 465                 *intValue = (*intValue << 4) | hexValue;
 466                 numChars ++;
 467
 468                 (*ptr)++;
 469         }
 470
 471         return (numChars);
 472 }
 473
 474 static int hexToLong(char **ptr, long *longValue)
 475 {
 476         int numChars = 0;
 477         int hexValue;
 478
 479         *longValue = 0;
 480
 481         while (**ptr) {
 482                 hexValue = hex(**ptr);
 483                 if (hexValue < 0)
 484                         break;
 485
 486                 *longValue = (*longValue << 4) | hexValue;
 487                 numChars ++;
 488
 489                 (*ptr)++;
 490         }
 491
 492         return numChars;
 493 }
 494
 495
 496 #if 0
 497 /*
 498  * Print registers (on target console)
 499  * Used only to debug the stub...
 500  */
 501 void show_gdbregs(struct gdb_regs * regs)
 502 {
 503         /*
 504          * Saved main processor registers
 505          */
 506         printk("$0 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
 507                regs->reg0, regs->reg1, regs->reg2, regs->reg3,
 508                regs->reg4, regs->reg5, regs->reg6, regs->reg7);
 509         printk("$8 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
 510                regs->reg8, regs->reg9, regs->reg10, regs->reg11,
 511                regs->reg12, regs->reg13, regs->reg14, regs->reg15);
 512         printk("$16: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
 513                regs->reg16, regs->reg17, regs->reg18, regs->reg19,
 514                regs->reg20, regs->reg21, regs->reg22, regs->reg23);
 515         printk("$24: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
 516                regs->reg24, regs->reg25, regs->reg26, regs->reg27,
 517                regs->reg28, regs->reg29, regs->reg30, regs->reg31);
 518
 519         /*
 520          * Saved cp0 registers
 521          */
 522         printk("epc  : %08lx\nStatus: %08lx\nCause : %08lx\n",
 523                regs->cp0_epc, regs->cp0_status, regs->cp0_cause);
 524 }
 525 #endif /* dead code */
 526
 527 /*
 528  * We single-step by setting breakpoints. When an exception
 529  * is handled, we need to restore the instructions hoisted
 530  * when the breakpoints were set.
 531  *
 532  * This is where we save the original instructions.
 533  */
 534 static struct gdb_bp_save {
 535         unsigned long addr;
 536         unsigned int val;
 537 } step_bp[2];
 538
 539 #define BP 0x0000000d  /* break opcode */
 540
 541 /*
 542  * Set breakpoint instructions for single stepping.
 543  */
 544 static void single_step(struct gdb_regs *regs)
 545 {
 546         union mips_instruction insn;
 547         unsigned long targ;
 548         int is_branch, is_cond, i;
 549
 550         targ = regs->cp0_epc;
 551         insn.word = *(unsigned int *)targ;
 552         is_branch = is_cond = 0;
 553
 554         switch (insn.i_format.opcode) {
 555         /*
 556          * jr and jalr are in r_format format.
 557          */
 558         case spec_op:
 559                 switch (insn.r_format.func) {
 560                 case jalr_op:
 561                 case jr_op:
 562                         targ = *(&regs->reg0 + insn.r_format.rs);
 563                         is_branch = 1;
 564                         break;
 565                 }
 566                 break;
 567
 568         /*
 569          * This group contains:
 570          * bltz_op, bgez_op, bltzl_op, bgezl_op,
 571          * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
 572          */
 573         case bcond_op:
 574                 is_branch = is_cond = 1;
 575                 targ += 4 + (insn.i_format.simmediate << 2);
 576                 break;
 577
 578         /*
 579          * These are unconditional and in j_format.
 580          */
 581         case jal_op:
 582         case j_op:
 583                 is_branch = 1;
 584                 targ += 4;
 585                 targ >>= 28;
 586                 targ <<= 28;
 587                 targ |= (insn.j_format.target << 2);
 588                 break;
 589
 590         /*
 591          * These are conditional.
 592          */
 593         case beq_op:
 594         case beql_op:
 595         case bne_op:
 596         case bnel_op:
 597         case blez_op:
 598         case blezl_op:
 599         case bgtz_op:
 600         case bgtzl_op:
 601         case cop0_op:
 602         case cop1_op:
 603         case cop2_op:
 604         case cop1x_op:
 605                 is_branch = is_cond = 1;
 606                 targ += 4 + (insn.i_format.simmediate << 2);
 607                 break;
 608         }
 609
 610         if (is_branch) {
 611                 i = 0;
 612                 if (is_cond && targ != (regs->cp0_epc + 8)) {
 613                         step_bp[i].addr = regs->cp0_epc + 8;
 614                         step_bp[i++].val = *(unsigned *)(regs->cp0_epc + 8);
 615                         *(unsigned *)(regs->cp0_epc + 8) = BP;
 616                 }
 617                 step_bp[i].addr = targ;
 618                 step_bp[i].val  = *(unsigned *)targ;
 619                 *(unsigned *)targ = BP;
 620         } else {
 621                 step_bp[0].addr = regs->cp0_epc + 4;
 622                 step_bp[0].val  = *(unsigned *)(regs->cp0_epc + 4);
 623                 *(unsigned *)(regs->cp0_epc + 4) = BP;
 624         }
 625 }
 626
 627 /*
 628  *  If asynchronously interrupted by gdb, then we need to set a breakpoint
 629  *  at the interrupted instruction so that we wind up stopped with a
 630  *  reasonable stack frame.
 631  */
 632 static struct gdb_bp_save async_bp;
 633
 634 /*
 635  * Swap the interrupted EPC with our asynchronous breakpoint routine.
 636  * This is safer than stuffing the breakpoint in-place, since no cache
 637  * flushes (or resulting smp_call_functions) are required.  The
 638  * assumption is that only one CPU will be handling asynchronous bp's,
 639  * and only one can be active at a time.
 640  */
 641 extern spinlock_t smp_call_lock;
 642
 643 void set_async_breakpoint(unsigned long *epc)
 644 {
 645         /* skip breaking into userland */
 646         if ((*epc & 0x80000000) == 0)
 647                 return;
 648
 649 #ifdef CONFIG_SMP
 650         /* avoid deadlock if someone is make IPC */
 651         if (spin_is_locked(&smp_call_lock))
 652                 return;
 653 #endif
 654
 655         async_bp.addr = *epc;
 656         *epc = (unsigned long)async_breakpoint;
 657 }
 658
 659 static void kgdb_wait(void *arg)
 660 {
 661         unsigned flags;
 662         int cpu = smp_processor_id();
 663
 664         local_irq_save(flags);
 665
 666         __raw_spin_lock(&kgdb_cpulock[cpu]);
 667         __raw_spin_unlock(&kgdb_cpulock[cpu]);
 668
 669         local_irq_restore(flags);
 670 }
 671
 672
 673 /*
 674  * This function does all command processing for interfacing to gdb.  It
 675  * returns 1 if you should skip the instruction at the trap address, 0
 676  * otherwise.
 677  */
 678 void handle_exception (struct gdb_regs *regs)
 679 {
 680         int trap;                       /* Trap type */
 681         int sigval;
 682         long addr;
 683         int length;
 684         char *ptr;
 685         unsigned long *stack;
 686         int i;
 687         int bflag = 0;
 688
 689         kgdb_started = 1;
 690
 691         /*
 692          * acquire the big kgdb spinlock
 693          */
 694         if (!spin_trylock(&kgdb_lock)) {
 695                 /*
 696                  * some other CPU has the lock, we should go back to
 697                  * receive the gdb_wait IPC
 698                  */
 699                 return;
 700         }
 701
 702         /*
 703          * If we're in async_breakpoint(), restore the real EPC from
 704          * the breakpoint.
 705          */
 706         if (regs->cp0_epc == (unsigned long)async_breakinst) {
 707                 regs->cp0_epc = async_bp.addr;
 708                 async_bp.addr = 0;
 709         }
 710
 711         /*
 712          * acquire the CPU spinlocks
 713          */
 714         for (i = num_online_cpus()-1; i >= 0; i--)
 715                 if (__raw_spin_trylock(&kgdb_cpulock[i]) == 0)
 716                         panic("kgdb: couldn't get cpulock %d\n", i);
 717
 718         /*
 719          * force other cpus to enter kgdb
 720          */
 721         smp_call_function(kgdb_wait, NULL, 0, 0);
 722
 723         /*
 724          * If we're in breakpoint() increment the PC
 725          */
 726         trap = (regs->cp0_cause & 0x7c) >> 2;
 727         if (trap == 9 && regs->cp0_epc == (unsigned long)breakinst)
 728                 regs->cp0_epc += 4;
 729
 730         /*
 731          * If we were single_stepping, restore the opcodes hoisted
 732          * for the breakpoint[s].
 733          */
 734         if (step_bp[0].addr) {
 735                 *(unsigned *)step_bp[0].addr = step_bp[0].val;
 736                 step_bp[0].addr = 0;
 737
 738                 if (step_bp[1].addr) {
 739                         *(unsigned *)step_bp[1].addr = step_bp[1].val;
 740                         step_bp[1].addr = 0;
 741                 }
 742         }
 743
 744         stack = (long *)regs->reg29;                    /* stack ptr */
 745         sigval = computeSignal(trap);
 746
 747         /*
 748          * reply to host that an exception has occurred
 749          */
 750         ptr = output_buffer;
 751
 752         /*
 753          * Send trap type (converted to signal)
 754          */
 755         *ptr++ = 'T';
 756         *ptr++ = hexchars[sigval >> 4];
 757         *ptr++ = hexchars[sigval & 0xf];
 758
 759         /*
 760          * Send Error PC
 761          */
 762         *ptr++ = hexchars[REG_EPC >> 4];
 763         *ptr++ = hexchars[REG_EPC & 0xf];
 764         *ptr++ = ':';
 765         ptr = mem2hex((char *)&regs->cp0_epc, ptr, sizeof(long), 0);
 766         *ptr++ = ';';
 767
 768         /*
 769          * Send frame pointer
 770          */
 771         *ptr++ = hexchars[REG_FP >> 4];
 772         *ptr++ = hexchars[REG_FP & 0xf];
 773         *ptr++ = ':';
 774         ptr = mem2hex((char *)&regs->reg30, ptr, sizeof(long), 0);
 775         *ptr++ = ';';
 776
 777         /*
 778          * Send stack pointer
 779          */
 780         *ptr++ = hexchars[REG_SP >> 4];
 781         *ptr++ = hexchars[REG_SP & 0xf];
 782         *ptr++ = ':';
 783         ptr = mem2hex((char *)&regs->reg29, ptr, sizeof(long), 0);
 784         *ptr++ = ';';
 785
 786         *ptr++ = 0;
 787         putpacket(output_buffer);       /* send it off... */
 788
 789         /*
 790          * Wait for input from remote GDB
 791          */
 792         while (1) {
 793                 output_buffer[0] = 0;
 794                 getpacket(input_buffer);
 795
 796                 switch (input_buffer[0])
 797                 {
 798                 case '?':
 799                         output_buffer[0] = 'S';
 800                         output_buffer[1] = hexchars[sigval >> 4];
 801                         output_buffer[2] = hexchars[sigval & 0xf];
 802                         output_buffer[3] = 0;
 803                         break;
 804
 805                 /*
 806                  * Detach debugger; let CPU run
 807                  */
 808                 case 'D':
 809                         putpacket(output_buffer);
 810                         goto finish_kgdb;
 811                         break;
 812
 813                 case 'd':
 814                         /* toggle debug flag */
 815                         break;
 816
 817                 /*
 818                  * Return the value of the CPU registers
 819                  */
 820                 case 'g':
 821                         ptr = output_buffer;
 822                         ptr = mem2hex((char *)&regs->reg0, ptr, 32*sizeof(long), 0); /* r0...r31 */
 823                         ptr = mem2hex((char *)&regs->cp0_status, ptr, 6*sizeof(long), 0); /* cp0 */
 824                         ptr = mem2hex((char *)&regs->fpr0, ptr, 32*sizeof(long), 0); /* f0...31 */
 825                         ptr = mem2hex((char *)&regs->cp1_fsr, ptr, 2*sizeof(long), 0); /* cp1 */
 826                         ptr = mem2hex((char *)&regs->frame_ptr, ptr, 2*sizeof(long), 0); /* frp */
 827                         ptr = mem2hex((char *)&regs->cp0_index, ptr, 16*sizeof(long), 0); /* cp0 */
 828                         break;
 829
 830                 /*
 831                  * set the value of the CPU registers - return OK
 832                  */
 833                 case 'G':
 834                 {
 835                         ptr = &input_buffer[1];
 836                         hex2mem(ptr, (char *)&regs->reg0, 32*sizeof(long), 0, 0);
 837                         ptr += 32*(2*sizeof(long));
 838                         hex2mem(ptr, (char *)&regs->cp0_status, 6*sizeof(long), 0, 0);
 839                         ptr += 6*(2*sizeof(long));
 840                         hex2mem(ptr, (char *)&regs->fpr0, 32*sizeof(long), 0, 0);
 841                         ptr += 32*(2*sizeof(long));
 842                         hex2mem(ptr, (char *)&regs->cp1_fsr, 2*sizeof(long), 0, 0);
 843                         ptr += 2*(2*sizeof(long));
 844                         hex2mem(ptr, (char *)&regs->frame_ptr, 2*sizeof(long), 0, 0);
 845                         ptr += 2*(2*sizeof(long));
 846                         hex2mem(ptr, (char *)&regs->cp0_index, 16*sizeof(long), 0, 0);
 847                         strcpy(output_buffer,"OK");
 848                  }
 849                 break;
 850
 851                 /*
 852                  * mAA..AA,LLLL  Read LLLL bytes at address AA..AA
 853                  */
 854                 case 'm':
 855                         ptr = &input_buffer[1];
 856
 857                         if (hexToLong(&ptr, &addr)
 858                                 && *ptr++ == ','
 859                                 && hexToInt(&ptr, &length)) {
 860                                 if (mem2hex((char *)addr, output_buffer, length, 1))
 861                                         break;
 862                                 strcpy (output_buffer, "E03");
 863                         } else
 864                                 strcpy(output_buffer,"E01");
 865                         break;
 866
 867                 /*
 868                  * XAA..AA,LLLL: Write LLLL escaped binary bytes at address AA.AA
 869                  */
 870                 case 'X':
 871                         bflag = 1;
 872                         /* fall through */
 873
 874                 /*
 875                  * MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK
 876                  */
 877                 case 'M':
 878                         ptr = &input_buffer[1];
 879
 880                         if (hexToLong(&ptr, &addr)
 881                                 && *ptr++ == ','
 882                                 && hexToInt(&ptr, &length)
 883                                 && *ptr++ == ':') {
 884                                 if (hex2mem(ptr, (char *)addr, length, bflag, 1))
 885                                         strcpy(output_buffer, "OK");
 886                                 else
 887                                         strcpy(output_buffer, "E03");
 888                         }
 889                         else
 890                                 strcpy(output_buffer, "E02");
 891                         break;
 892
 893                 /*
 894                  * cAA..AA    Continue at address AA..AA(optional)
 895                  */
 896                 case 'c':
 897                         /* try to read optional parameter, pc unchanged if no parm */
 898
 899                         ptr = &input_buffer[1];
 900                         if (hexToLong(&ptr, &addr))
 901                                 regs->cp0_epc = addr;
 902
 903                         goto exit_kgdb_exception;
 904                         break;
 905
 906                 /*
 907                  * kill the program; let us try to restart the machine
 908                  * Reset the whole machine.
 909                  */
 910                 case 'k':
 911                 case 'r':
 912                         machine_restart("kgdb restarts machine");
 913                         break;
 914
 915                 /*
 916                  * Step to next instruction
 917                  */
 918                 case 's':
 919                         /*
 920                          * There is no single step insn in the MIPS ISA, so we
 921                          * use breakpoints and continue, instead.
 922                          */
 923                         single_step(regs);
 924                         goto exit_kgdb_exception;
 925                         /* NOTREACHED */
 926                         break;
 927
 928                 /*
 929                  * Set baud rate (bBB)
 930                  * FIXME: Needs to be written
 931                  */
 932                 case 'b':
 933                 {
 934 #if 0
 935                         int baudrate;
 936                         extern void set_timer_3();
 937
 938                         ptr = &input_buffer[1];
 939                         if (!hexToInt(&ptr, &baudrate))
 940                         {
 941                                 strcpy(output_buffer,"B01");
 942                                 break;
 943                         }
 944
 945                         /* Convert baud rate to uart clock divider */
 946
 947                         switch (baudrate)
 948                         {
 949                                 case 38400:
 950                                         baudrate = 16;
 951                                         break;
 952                                 case 19200:
 953                                         baudrate = 33;
 954                                         break;
 955                                 case 9600:
 956                                         baudrate = 65;
 957                                         break;
 958                                 default:
 959                                         baudrate = 0;
 960                                         strcpy(output_buffer,"B02");
 961                                         goto x1;
 962                         }
 963
 964                         if (baudrate) {
 965                                 putpacket("OK");        /* Ack before changing speed */
 966                                 set_timer_3(baudrate); /* Set it */
 967                         }
 968 #endif
 969                 }
 970                 break;
 971
 972                 }                       /* switch */
 973
 974                 /*
 975                  * reply to the request
 976                  */
 977
 978                 putpacket(output_buffer);
 979
 980         } /* while */
 981
 982         return;
 983
 984 finish_kgdb:
 985         restore_debug_traps();
 986
 987 exit_kgdb_exception:
 988         /* release locks so other CPUs can go */
 989         for (i = num_online_cpus()-1; i >= 0; i--)
 990                 __raw_spin_unlock(&kgdb_cpulock[i]);
 991         spin_unlock(&kgdb_lock);
 992
 993         __flush_cache_all();
 994         return;
 995 }
 996
 997 /*
 998  * This function will generate a breakpoint exception.  It is used at the
 999  * beginning of a program to sync up with a debugger and can be used
1000  * otherwise as a quick means to stop program execution and "break" into
1001  * the debugger.
1002  */
1003 void breakpoint(void)
1004 {
1005         if (!initialized)
1006                 return;
1007
1008         __asm__ __volatile__(
1009                         ".globl breakinst\n\t"
1010                         ".set\tnoreorder\n\t"
1011                         "nop\n"
1012                         "breakinst:\tbreak\n\t"
1013                         "nop\n\t"
1014                         ".set\treorder"
1015                         );
1016 }
1017
1018 /* Nothing but the break; don't pollute any registers */
1019 void async_breakpoint(void)
1020 {
1021         __asm__ __volatile__(
1022                         ".globl async_breakinst\n\t"
1023                         ".set\tnoreorder\n\t"
1024                         "nop\n"
1025                         "async_breakinst:\tbreak\n\t"
1026                         "nop\n\t"
1027                         ".set\treorder"
1028                         );
1029 }
1030
1031 void adel(void)
1032 {
1033         __asm__ __volatile__(
1034                         ".globl\tadel\n\t"
1035                         "lui\t$8,0x8000\n\t"
1036                         "lw\t$9,1($8)\n\t"
1037                         );
1038 }
1039
1040 /*
1041  * malloc is needed by gdb client in "call func()", even a private one
1042  * will make gdb happy
1043  */
1044 static void * __attribute_used__ malloc(size_t size)
1045 {
1046         return kmalloc(size, GFP_ATOMIC);
1047 }
1048
1049 static void __attribute_used__ free (void *where)
1050 {
1051         kfree(where);
1052 }
1053
1054 #ifdef CONFIG_GDB_CONSOLE
1055
1056 void gdb_putsn(const char *str, int l)
1057 {
1058         char outbuf[18];
1059
1060         if (!kgdb_started)
1061                 return;
1062
1063         outbuf[0]='O';
1064
1065         while(l) {
1066                 int i = (l>8)?8:l;
1067                 mem2hex((char *)str, &outbuf[1], i, 0);
1068                 outbuf[(i*2)+1]=0;
1069                 putpacket(outbuf);
1070                 str += i;
1071                 l -= i;
1072         }
1073 }
1074
1075 static void gdb_console_write(struct console *con, const char *s, unsigned n)
1076 {
1077         gdb_putsn(s, n);
1078 }
1079
1080 static struct console gdb_console = {
1081         .name   = "gdb",
1082         .write  = gdb_console_write,
1083         .flags  = CON_PRINTBUFFER,
1084         .index  = -1
1085 };
1086
1087 static int __init register_gdb_console(void)
1088 {
1089         register_console(&gdb_console);
1090
1091         return 0;
1092 }
1093
1094 console_initcall(register_gdb_console);
1095
1096 #endif