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   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/string.h>
 124 #include <linux/kernel.h>
 125 #include <linux/signal.h>
 126 #include <linux/sched.h>
 127 #include <linux/mm.h>
 128 #include <linux/console.h>
 129 #include <linux/init.h>
 130 #include <linux/smp.h>
 131 #include <linux/spinlock.h>
 132 #include <linux/slab.h>
 133 #include <linux/reboot.h>
 134
 135 #include <asm/asm.h>
 136 #include <asm/cacheflush.h>
 137 #include <asm/mipsregs.h>
 138 #include <asm/pgtable.h>
 139 #include <asm/system.h>
 140 #include <asm/gdb-stub.h>
 141 #include <asm/inst.h>
 142
 143 /*
 144  * external low-level support routines
 145  */
 146
 147 extern int putDebugChar(char c);    /* write a single character      */
 148 extern char getDebugChar(void);     /* read and return a single char */
 149 extern void trap_low(void);
 150
 151 /*
 152  * breakpoint and test functions
 153  */
 154 extern void breakpoint(void);
 155 extern void breakinst(void);
 156 extern void async_breakpoint(void);
 157 extern void async_breakinst(void);
 158 extern void adel(void);
 159
 160 /*
 161  * local prototypes
 162  */
 163
 164 static void getpacket(char *buffer);
 165 static void putpacket(char *buffer);
 166 static int computeSignal(int tt);
 167 static int hex(unsigned char ch);
 168 static int hexToInt(char **ptr, int *intValue);
 169 static int hexToLong(char **ptr, long *longValue);
 170 static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault);
 171 void handle_exception(struct gdb_regs *regs);
 172
 173 int kgdb_enabled;
 174
 175 /*
 176  * spin locks for smp case
 177  */
 178 static DEFINE_SPINLOCK(kgdb_lock);
 179 static raw_spinlock_t kgdb_cpulock[NR_CPUS] = {
 180         [0 ... NR_CPUS-1] = __RAW_SPIN_LOCK_UNLOCKED,
 181 };
 182
 183 /*
 184  * BUFMAX defines the maximum number of characters in inbound/outbound buffers
 185  * at least NUMREGBYTES*2 are needed for register packets
 186  */
 187 #define BUFMAX 2048
 188
 189 static char input_buffer[BUFMAX];
 190 static char output_buffer[BUFMAX];
 191 static int initialized; /* !0 means we've been initialized */
 192 static int kgdb_started;
 193 static const char hexchars[]="0123456789abcdef";
 194
 195 /* Used to prevent crashes in memory access.  Note that they'll crash anyway if
 196    we haven't set up fault handlers yet... */
 197 int kgdb_read_byte(unsigned char *address, unsigned char *dest);
 198 int kgdb_write_byte(unsigned char val, unsigned char *dest);
 199
 200 /*
 201  * Convert ch from a hex digit to an int
 202  */
 203 static int hex(unsigned char ch)
 204 {
 205         if (ch >= 'a' && ch <= 'f')
 206                 return ch-'a'+10;
 207         if (ch >= '0' && ch <= '9')
 208                 return ch-'0';
 209         if (ch >= 'A' && ch <= 'F')
 210                 return ch-'A'+10;
 211         return -1;
 212 }
 213
 214 /*
 215  * scan for the sequence $<data>#<checksum>
 216  */
 217 static void getpacket(char *buffer)
 218 {
 219         unsigned char checksum;
 220         unsigned char xmitcsum;
 221         int i;
 222         int count;
 223         unsigned char ch;
 224
 225         do {
 226                 /*
 227                  * wait around for the start character,
 228                  * ignore all other characters
 229                  */
 230                 while ((ch = (getDebugChar() & 0x7f)) != '$') ;
 231
 232                 checksum = 0;
 233                 xmitcsum = -1;
 234                 count = 0;
 235
 236                 /*
 237                  * now, read until a # or end of buffer is found
 238                  */
 239                 while (count < BUFMAX) {
 240                         ch = getDebugChar();
 241                         if (ch == '#')
 242                                 break;
 243                         checksum = checksum + ch;
 244                         buffer[count] = ch;
 245                         count = count + 1;
 246                 }
 247
 248                 if (count >= BUFMAX)
 249                         continue;
 250
 251                 buffer[count] = 0;
 252
 253                 if (ch == '#') {
 254                         xmitcsum = hex(getDebugChar() & 0x7f) << 4;
 255                         xmitcsum |= hex(getDebugChar() & 0x7f);
 256
 257                         if (checksum != xmitcsum)
 258                                 putDebugChar('-');      /* failed checksum */
 259                         else {
 260                                 putDebugChar('+'); /* successful transfer */
 261
 262                                 /*
 263                                  * if a sequence char is present,
 264                                  * reply the sequence ID
 265                                  */
 266                                 if (buffer[2] == ':') {
 267                                         putDebugChar(buffer[0]);
 268                                         putDebugChar(buffer[1]);
 269
 270                                         /*
 271                                          * remove sequence chars from buffer
 272                                          */
 273                                         count = strlen(buffer);
 274                                         for (i=3; i <= count; i++)
 275                                                 buffer[i-3] = buffer[i];
 276                                 }
 277                         }
 278                 }
 279         }
 280         while (checksum != xmitcsum);
 281 }
 282
 283 /*
 284  * send the packet in buffer.
 285  */
 286 static void putpacket(char *buffer)
 287 {
 288         unsigned char checksum;
 289         int count;
 290         unsigned char ch;
 291
 292         /*
 293          * $<packet info>#<checksum>.
 294          */
 295
 296         do {
 297                 putDebugChar('$');
 298                 checksum = 0;
 299                 count = 0;
 300
 301                 while ((ch = buffer[count]) != 0) {
 302                         if (!(putDebugChar(ch)))
 303                                 return;
 304                         checksum += ch;
 305                         count += 1;
 306                 }
 307
 308                 putDebugChar('#');
 309                 putDebugChar(hexchars[checksum >> 4]);
 310                 putDebugChar(hexchars[checksum & 0xf]);
 311
 312         }
 313         while ((getDebugChar() & 0x7f) != '+');
 314 }
 315
 316
 317 /*
 318  * Convert the memory pointed to by mem into hex, placing result in buf.
 319  * Return a pointer to the last char put in buf (null), in case of mem fault,
 320  * return 0.
 321  * may_fault is non-zero if we are reading from arbitrary memory, but is currently
 322  * not used.
 323  */
 324 static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault)
 325 {
 326         unsigned char ch;
 327
 328         while (count-- > 0) {
 329                 if (kgdb_read_byte(mem++, &ch) != 0)
 330                         return 0;
 331                 *buf++ = hexchars[ch >> 4];
 332                 *buf++ = hexchars[ch & 0xf];
 333         }
 334
 335         *buf = 0;
 336
 337         return buf;
 338 }
 339
 340 /*
 341  * convert the hex array pointed to by buf into binary to be placed in mem
 342  * return a pointer to the character AFTER the last byte written
 343  * may_fault is non-zero if we are reading from arbitrary memory, but is currently
 344  * not used.
 345  */
 346 static char *hex2mem(char *buf, char *mem, int count, int binary, int may_fault)
 347 {
 348         int i;
 349         unsigned char ch;
 350
 351         for (i=0; i<count; i++)
 352         {
 353                 if (binary) {
 354                         ch = *buf++;
 355                         if (ch == 0x7d)
 356                                 ch = 0x20 ^ *buf++;
 357                 }
 358                 else {
 359                         ch = hex(*buf++) << 4;
 360                         ch |= hex(*buf++);
 361                 }
 362                 if (kgdb_write_byte(ch, mem++) != 0)
 363                         return 0;
 364         }
 365
 366         return mem;
 367 }
 368
 369 /*
 370  * This table contains the mapping between SPARC hardware trap types, and
 371  * signals, which are primarily what GDB understands.  It also indicates
 372  * which hardware traps we need to commandeer when initializing the stub.
 373  */
 374 static struct hard_trap_info {
 375         unsigned char tt;               /* Trap type code for MIPS R3xxx and R4xxx */
 376         unsigned char signo;            /* Signal that we map this trap into */
 377 } hard_trap_info[] = {
 378         { 6, SIGBUS },                  /* instruction bus error */
 379         { 7, SIGBUS },                  /* data bus error */
 380         { 9, SIGTRAP },                 /* break */
 381         { 10, SIGILL },                 /* reserved instruction */
 382 /*      { 11, SIGILL },         */      /* CPU unusable */
 383         { 12, SIGFPE },                 /* overflow */
 384         { 13, SIGTRAP },                /* trap */
 385         { 14, SIGSEGV },                /* virtual instruction cache coherency */
 386         { 15, SIGFPE },                 /* floating point exception */
 387         { 23, SIGSEGV },                /* watch */
 388         { 31, SIGSEGV },                /* virtual data cache coherency */
 389         { 0, 0}                         /* Must be last */
 390 };
 391
 392 /* Save the normal trap handlers for user-mode traps. */
 393 void *saved_vectors[32];
 394
 395 /*
 396  * Set up exception handlers for tracing and breakpoints
 397  */
 398 void set_debug_traps(void)
 399 {
 400         struct hard_trap_info *ht;
 401         unsigned long flags;
 402         unsigned char c;
 403
 404         local_irq_save(flags);
 405         for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
 406                 saved_vectors[ht->tt] = set_except_vector(ht->tt, trap_low);
 407
 408         putDebugChar('+'); /* 'hello world' */
 409         /*
 410          * In case GDB is started before us, ack any packets
 411          * (presumably "$?#xx") sitting there.
 412          */
 413         while((c = getDebugChar()) != '$');
 414         while((c = getDebugChar()) != '#');
 415         c = getDebugChar(); /* eat first csum byte */
 416         c = getDebugChar(); /* eat second csum byte */
 417         putDebugChar('+'); /* ack it */
 418
 419         initialized = 1;
 420         local_irq_restore(flags);
 421 }
 422
 423 void restore_debug_traps(void)
 424 {
 425         struct hard_trap_info *ht;
 426         unsigned long flags;
 427
 428         local_irq_save(flags);
 429         for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
 430                 set_except_vector(ht->tt, saved_vectors[ht->tt]);
 431         local_irq_restore(flags);
 432 }
 433
 434 /*
 435  * Convert the MIPS hardware trap type code to a Unix signal number.
 436  */
 437 static int computeSignal(int tt)
 438 {
 439         struct hard_trap_info *ht;
 440
 441         for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
 442                 if (ht->tt == tt)
 443                         return ht->signo;
 444
 445         return SIGHUP;          /* default for things we don't know about */
 446 }
 447
 448 /*
 449  * While we find nice hex chars, build an int.
 450  * Return number of chars processed.
 451  */
 452 static int hexToInt(char **ptr, int *intValue)
 453 {
 454         int numChars = 0;
 455         int hexValue;
 456
 457         *intValue = 0;
 458
 459         while (**ptr) {
 460                 hexValue = hex(**ptr);
 461                 if (hexValue < 0)
 462                         break;
 463
 464                 *intValue = (*intValue << 4) | hexValue;
 465                 numChars ++;
 466
 467                 (*ptr)++;
 468         }
 469
 470         return (numChars);
 471 }
 472
 473 static int hexToLong(char **ptr, long *longValue)
 474 {
 475         int numChars = 0;
 476         int hexValue;
 477
 478         *longValue = 0;
 479
 480         while (**ptr) {
 481                 hexValue = hex(**ptr);
 482                 if (hexValue < 0)
 483                         break;
 484
 485                 *longValue = (*longValue << 4) | hexValue;
 486                 numChars ++;
 487
 488                 (*ptr)++;
 489         }
 490
 491         return numChars;
 492 }
 493
 494
 495 #if 0
 496 /*
 497  * Print registers (on target console)
 498  * Used only to debug the stub...
 499  */
 500 void show_gdbregs(struct gdb_regs * regs)
 501 {
 502         /*
 503          * Saved main processor registers
 504          */
 505         printk("$0 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
 506                regs->reg0, regs->reg1, regs->reg2, regs->reg3,
 507                regs->reg4, regs->reg5, regs->reg6, regs->reg7);
 508         printk("$8 : %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
 509                regs->reg8, regs->reg9, regs->reg10, regs->reg11,
 510                regs->reg12, regs->reg13, regs->reg14, regs->reg15);
 511         printk("$16: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
 512                regs->reg16, regs->reg17, regs->reg18, regs->reg19,
 513                regs->reg20, regs->reg21, regs->reg22, regs->reg23);
 514         printk("$24: %08lx %08lx %08lx %08lx %08lx %08lx %08lx %08lx\n",
 515                regs->reg24, regs->reg25, regs->reg26, regs->reg27,
 516                regs->reg28, regs->reg29, regs->reg30, regs->reg31);
 517
 518         /*
 519          * Saved cp0 registers
 520          */
 521         printk("epc  : %08lx\nStatus: %08lx\nCause : %08lx\n",
 522                regs->cp0_epc, regs->cp0_status, regs->cp0_cause);
 523 }
 524 #endif /* dead code */
 525
 526 /*
 527  * We single-step by setting breakpoints. When an exception
 528  * is handled, we need to restore the instructions hoisted
 529  * when the breakpoints were set.
 530  *
 531  * This is where we save the original instructions.
 532  */
 533 static struct gdb_bp_save {
 534         unsigned long addr;
 535         unsigned int val;
 536 } step_bp[2];
 537
 538 #define BP 0x0000000d  /* break opcode */
 539
 540 /*
 541  * Set breakpoint instructions for single stepping.
 542  */
 543 static void single_step(struct gdb_regs *regs)
 544 {
 545         union mips_instruction insn;
 546         unsigned long targ;
 547         int is_branch, is_cond, i;
 548
 549         targ = regs->cp0_epc;
 550         insn.word = *(unsigned int *)targ;
 551         is_branch = is_cond = 0;
 552
 553         switch (insn.i_format.opcode) {
 554         /*
 555          * jr and jalr are in r_format format.
 556          */
 557         case spec_op:
 558                 switch (insn.r_format.func) {
 559                 case jalr_op:
 560                 case jr_op:
 561                         targ = *(&regs->reg0 + insn.r_format.rs);
 562                         is_branch = 1;
 563                         break;
 564                 }
 565                 break;
 566
 567         /*
 568          * This group contains:
 569          * bltz_op, bgez_op, bltzl_op, bgezl_op,
 570          * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
 571          */
 572         case bcond_op:
 573                 is_branch = is_cond = 1;
 574                 targ += 4 + (insn.i_format.simmediate << 2);
 575                 break;
 576
 577         /*
 578          * These are unconditional and in j_format.
 579          */
 580         case jal_op:
 581         case j_op:
 582                 is_branch = 1;
 583                 targ += 4;
 584                 targ >>= 28;
 585                 targ <<= 28;
 586                 targ |= (insn.j_format.target << 2);
 587                 break;
 588
 589         /*
 590          * These are conditional.
 591          */
 592         case beq_op:
 593         case beql_op:
 594         case bne_op:
 595         case bnel_op:
 596         case blez_op:
 597         case blezl_op:
 598         case bgtz_op:
 599         case bgtzl_op:
 600         case cop0_op:
 601         case cop1_op:
 602         case cop2_op:
 603         case cop1x_op:
 604                 is_branch = is_cond = 1;
 605                 targ += 4 + (insn.i_format.simmediate << 2);
 606                 break;
 607         }
 608
 609         if (is_branch) {
 610                 i = 0;
 611                 if (is_cond && targ != (regs->cp0_epc + 8)) {
 612                         step_bp[i].addr = regs->cp0_epc + 8;
 613                         step_bp[i++].val = *(unsigned *)(regs->cp0_epc + 8);
 614                         *(unsigned *)(regs->cp0_epc + 8) = BP;
 615                 }
 616                 step_bp[i].addr = targ;
 617                 step_bp[i].val  = *(unsigned *)targ;
 618                 *(unsigned *)targ = BP;
 619         } else {
 620                 step_bp[0].addr = regs->cp0_epc + 4;
 621                 step_bp[0].val  = *(unsigned *)(regs->cp0_epc + 4);
 622                 *(unsigned *)(regs->cp0_epc + 4) = BP;
 623         }
 624 }
 625
 626 /*
 627  *  If asynchronously interrupted by gdb, then we need to set a breakpoint
 628  *  at the interrupted instruction so that we wind up stopped with a
 629  *  reasonable stack frame.
 630  */
 631 static struct gdb_bp_save async_bp;
 632
 633 /*
 634  * Swap the interrupted EPC with our asynchronous breakpoint routine.
 635  * This is safer than stuffing the breakpoint in-place, since no cache
 636  * flushes (or resulting smp_call_functions) are required.  The
 637  * assumption is that only one CPU will be handling asynchronous bp's,
 638  * and only one can be active at a time.
 639  */
 640 extern spinlock_t smp_call_lock;
 641
 642 void set_async_breakpoint(unsigned long *epc)
 643 {
 644         /* skip breaking into userland */
 645         if ((*epc & 0x80000000) == 0)
 646                 return;
 647
 648 #ifdef CONFIG_SMP
 649         /* avoid deadlock if someone is make IPC */
 650         if (spin_is_locked(&smp_call_lock))
 651                 return;
 652 #endif
 653
 654         async_bp.addr = *epc;
 655         *epc = (unsigned long)async_breakpoint;
 656 }
 657
 658 #ifdef CONFIG_SMP
 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 #endif
 672
 673 /*
 674  * GDB stub needs to call kgdb_wait on all processor with interrupts
 675  * disabled, so it uses it's own special variant.
 676  */
 677 static int kgdb_smp_call_kgdb_wait(void)
 678 {
 679 #ifdef CONFIG_SMP
 680         cpumask_t mask = cpu_online_map;
 681         struct call_data_struct data;
 682         int cpu = smp_processor_id();
 683         int cpus;
 684
 685         /*
 686          * Can die spectacularly if this CPU isn't yet marked online
 687          */
 688         BUG_ON(!cpu_online(cpu));
 689
 690         cpu_clear(cpu, mask);
 691         cpus = cpus_weight(mask);
 692         if (!cpus)
 693                 return 0;
 694
 695         if (spin_is_locked(&smp_call_lock)) {
 696                 /*
 697                  * Some other processor is trying to make us do something
 698                  * but we're not going to respond... give up
 699                  */
 700                 return -1;
 701                 }
 702
 703         /*
 704          * We will continue here, accepting the fact that
 705          * the kernel may deadlock if another CPU attempts
 706          * to call smp_call_function now...
 707          */
 708
 709         data.func = kgdb_wait;
 710         data.info = NULL;
 711         atomic_set(&data.started, 0);
 712         data.wait = 0;
 713
 714         spin_lock(&smp_call_lock);
 715         call_data = &data;
 716         mb();
 717
 718         core_send_ipi_mask(mask, SMP_CALL_FUNCTION);
 719
 720         /* Wait for response */
 721         /* FIXME: lock-up detection, backtrace on lock-up */
 722         while (atomic_read(&data.started) != cpus)
 723                 barrier();
 724
 725         call_data = NULL;
 726         spin_unlock(&smp_call_lock);
 727 #endif
 728
 729         return 0;
 730 }
 731
 732 /*
 733  * This function does all command processing for interfacing to gdb.  It
 734  * returns 1 if you should skip the instruction at the trap address, 0
 735  * otherwise.
 736  */
 737 void handle_exception(struct gdb_regs *regs)
 738 {
 739         int trap;                       /* Trap type */
 740         int sigval;
 741         long addr;
 742         int length;
 743         char *ptr;
 744         unsigned long *stack;
 745         int i;
 746         int bflag = 0;
 747
 748         kgdb_started = 1;
 749
 750         /*
 751          * acquire the big kgdb spinlock
 752          */
 753         if (!spin_trylock(&kgdb_lock)) {
 754                 /*
 755                  * some other CPU has the lock, we should go back to
 756                  * receive the gdb_wait IPC
 757                  */
 758                 return;
 759         }
 760
 761         /*
 762          * If we're in async_breakpoint(), restore the real EPC from
 763          * the breakpoint.
 764          */
 765         if (regs->cp0_epc == (unsigned long)async_breakinst) {
 766                 regs->cp0_epc = async_bp.addr;
 767                 async_bp.addr = 0;
 768         }
 769
 770         /*
 771          * acquire the CPU spinlocks
 772          */
 773         for_each_online_cpu(i)
 774                 if (__raw_spin_trylock(&kgdb_cpulock[i]) == 0)
 775                         panic("kgdb: couldn't get cpulock %d\n", i);
 776
 777         /*
 778          * force other cpus to enter kgdb
 779          */
 780         kgdb_smp_call_kgdb_wait();
 781
 782         /*
 783          * If we're in breakpoint() increment the PC
 784          */
 785         trap = (regs->cp0_cause & 0x7c) >> 2;
 786         if (trap == 9 && regs->cp0_epc == (unsigned long)breakinst)
 787                 regs->cp0_epc += 4;
 788
 789         /*
 790          * If we were single_stepping, restore the opcodes hoisted
 791          * for the breakpoint[s].
 792          */
 793         if (step_bp[0].addr) {
 794                 *(unsigned *)step_bp[0].addr = step_bp[0].val;
 795                 step_bp[0].addr = 0;
 796
 797                 if (step_bp[1].addr) {
 798                         *(unsigned *)step_bp[1].addr = step_bp[1].val;
 799                         step_bp[1].addr = 0;
 800                 }
 801         }
 802
 803         stack = (long *)regs->reg29;                    /* stack ptr */
 804         sigval = computeSignal(trap);
 805
 806         /*
 807          * reply to host that an exception has occurred
 808          */
 809         ptr = output_buffer;
 810
 811         /*
 812          * Send trap type (converted to signal)
 813          */
 814         *ptr++ = 'T';
 815         *ptr++ = hexchars[sigval >> 4];
 816         *ptr++ = hexchars[sigval & 0xf];
 817
 818         /*
 819          * Send Error PC
 820          */
 821         *ptr++ = hexchars[REG_EPC >> 4];
 822         *ptr++ = hexchars[REG_EPC & 0xf];
 823         *ptr++ = ':';
 824         ptr = mem2hex((char *)&regs->cp0_epc, ptr, sizeof(long), 0);
 825         *ptr++ = ';';
 826
 827         /*
 828          * Send frame pointer
 829          */
 830         *ptr++ = hexchars[REG_FP >> 4];
 831         *ptr++ = hexchars[REG_FP & 0xf];
 832         *ptr++ = ':';
 833         ptr = mem2hex((char *)&regs->reg30, ptr, sizeof(long), 0);
 834         *ptr++ = ';';
 835
 836         /*
 837          * Send stack pointer
 838          */
 839         *ptr++ = hexchars[REG_SP >> 4];
 840         *ptr++ = hexchars[REG_SP & 0xf];
 841         *ptr++ = ':';
 842         ptr = mem2hex((char *)&regs->reg29, ptr, sizeof(long), 0);
 843         *ptr++ = ';';
 844
 845         *ptr++ = 0;
 846         putpacket(output_buffer);       /* send it off... */
 847
 848         /*
 849          * Wait for input from remote GDB
 850          */
 851         while (1) {
 852                 output_buffer[0] = 0;
 853                 getpacket(input_buffer);
 854
 855                 switch (input_buffer[0])
 856                 {
 857                 case '?':
 858                         output_buffer[0] = 'S';
 859                         output_buffer[1] = hexchars[sigval >> 4];
 860                         output_buffer[2] = hexchars[sigval & 0xf];
 861                         output_buffer[3] = 0;
 862                         break;
 863
 864                 /*
 865                  * Detach debugger; let CPU run
 866                  */
 867                 case 'D':
 868                         putpacket(output_buffer);
 869                         goto finish_kgdb;
 870                         break;
 871
 872                 case 'd':
 873                         /* toggle debug flag */
 874                         break;
 875
 876                 /*
 877                  * Return the value of the CPU registers
 878                  */
 879                 case 'g':
 880                         ptr = output_buffer;
 881                         ptr = mem2hex((char *)&regs->reg0, ptr, 32*sizeof(long), 0); /* r0...r31 */
 882                         ptr = mem2hex((char *)&regs->cp0_status, ptr, 6*sizeof(long), 0); /* cp0 */
 883                         ptr = mem2hex((char *)&regs->fpr0, ptr, 32*sizeof(long), 0); /* f0...31 */
 884                         ptr = mem2hex((char *)&regs->cp1_fsr, ptr, 2*sizeof(long), 0); /* cp1 */
 885                         ptr = mem2hex((char *)&regs->frame_ptr, ptr, 2*sizeof(long), 0); /* frp */
 886                         ptr = mem2hex((char *)&regs->cp0_index, ptr, 16*sizeof(long), 0); /* cp0 */
 887                         break;
 888
 889                 /*
 890                  * set the value of the CPU registers - return OK
 891                  */
 892                 case 'G':
 893                 {
 894                         ptr = &input_buffer[1];
 895                         hex2mem(ptr, (char *)&regs->reg0, 32*sizeof(long), 0, 0);
 896                         ptr += 32*(2*sizeof(long));
 897                         hex2mem(ptr, (char *)&regs->cp0_status, 6*sizeof(long), 0, 0);
 898                         ptr += 6*(2*sizeof(long));
 899                         hex2mem(ptr, (char *)&regs->fpr0, 32*sizeof(long), 0, 0);
 900                         ptr += 32*(2*sizeof(long));
 901                         hex2mem(ptr, (char *)&regs->cp1_fsr, 2*sizeof(long), 0, 0);
 902                         ptr += 2*(2*sizeof(long));
 903                         hex2mem(ptr, (char *)&regs->frame_ptr, 2*sizeof(long), 0, 0);
 904                         ptr += 2*(2*sizeof(long));
 905                         hex2mem(ptr, (char *)&regs->cp0_index, 16*sizeof(long), 0, 0);
 906                         strcpy(output_buffer, "OK");
 907                  }
 908                 break;
 909
 910                 /*
 911                  * mAA..AA,LLLL  Read LLLL bytes at address AA..AA
 912                  */
 913                 case 'm':
 914                         ptr = &input_buffer[1];
 915
 916                         if (hexToLong(&ptr, &addr)
 917                                 && *ptr++ == ','
 918                                 && hexToInt(&ptr, &length)) {
 919                                 if (mem2hex((char *)addr, output_buffer, length, 1))
 920                                         break;
 921                                 strcpy(output_buffer, "E03");
 922                         } else
 923                                 strcpy(output_buffer, "E01");
 924                         break;
 925
 926                 /*
 927                  * XAA..AA,LLLL: Write LLLL escaped binary bytes at address AA.AA
 928                  */
 929                 case 'X':
 930                         bflag = 1;
 931                         /* fall through */
 932
 933                 /*
 934                  * MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK
 935                  */
 936                 case 'M':
 937                         ptr = &input_buffer[1];
 938
 939                         if (hexToLong(&ptr, &addr)
 940                                 && *ptr++ == ','
 941                                 && hexToInt(&ptr, &length)
 942                                 && *ptr++ == ':') {
 943                                 if (hex2mem(ptr, (char *)addr, length, bflag, 1))
 944                                         strcpy(output_buffer, "OK");
 945                                 else
 946                                         strcpy(output_buffer, "E03");
 947                         }
 948                         else
 949                                 strcpy(output_buffer, "E02");
 950                         break;
 951
 952                 /*
 953                  * cAA..AA    Continue at address AA..AA(optional)
 954                  */
 955                 case 'c':
 956                         /* try to read optional parameter, pc unchanged if no parm */
 957
 958                         ptr = &input_buffer[1];
 959                         if (hexToLong(&ptr, &addr))
 960                                 regs->cp0_epc = addr;
 961
 962                         goto exit_kgdb_exception;
 963                         break;
 964
 965                 /*
 966                  * kill the program; let us try to restart the machine
 967                  * Reset the whole machine.
 968                  */
 969                 case 'k':
 970                 case 'r':
 971                         machine_restart("kgdb restarts machine");
 972                         break;
 973
 974                 /*
 975                  * Step to next instruction
 976                  */
 977                 case 's':
 978                         /*
 979                          * There is no single step insn in the MIPS ISA, so we
 980                          * use breakpoints and continue, instead.
 981                          */
 982                         single_step(regs);
 983                         goto exit_kgdb_exception;
 984                         /* NOTREACHED */
 985                         break;
 986
 987                 /*
 988                  * Set baud rate (bBB)
 989                  * FIXME: Needs to be written
 990                  */
 991                 case 'b':
 992                 {
 993 #if 0
 994                         int baudrate;
 995                         extern void set_timer_3();
 996
 997                         ptr = &input_buffer[1];
 998                         if (!hexToInt(&ptr, &baudrate))
 999                         {
1000                                 strcpy(output_buffer, "B01");
1001                                 break;
1002                         }
1003
1004                         /* Convert baud rate to uart clock divider */
1005
1006                         switch (baudrate)
1007                         {
1008                                 case 38400:
1009                                         baudrate = 16;
1010                                         break;
1011                                 case 19200:
1012                                         baudrate = 33;
1013                                         break;
1014                                 case 9600:
1015                                         baudrate = 65;
1016                                         break;
1017                                 default:
1018                                         baudrate = 0;
1019                                         strcpy(output_buffer, "B02");
1020                                         goto x1;
1021                         }
1022
1023                         if (baudrate) {
1024                                 putpacket("OK");        /* Ack before changing speed */
1025                                 set_timer_3(baudrate); /* Set it */
1026                         }
1027 #endif
1028                 }
1029                 break;
1030
1031                 }                       /* switch */
1032
1033                 /*
1034                  * reply to the request
1035                  */
1036
1037                 putpacket(output_buffer);
1038
1039         } /* while */
1040
1041         return;
1042
1043 finish_kgdb:
1044         restore_debug_traps();
1045
1046 exit_kgdb_exception:
1047         /* release locks so other CPUs can go */
1048         for_each_online_cpu(i)
1049                 __raw_spin_unlock(&kgdb_cpulock[i]);
1050         spin_unlock(&kgdb_lock);
1051
1052         __flush_cache_all();
1053         return;
1054 }
1055
1056 /*
1057  * This function will generate a breakpoint exception.  It is used at the
1058  * beginning of a program to sync up with a debugger and can be used
1059  * otherwise as a quick means to stop program execution and "break" into
1060  * the debugger.
1061  */
1062 void breakpoint(void)
1063 {
1064         if (!initialized)
1065                 return;
1066
1067         __asm__ __volatile__(
1068                         ".globl breakinst\n\t"
1069                         ".set\tnoreorder\n\t"
1070                         "nop\n"
1071                         "breakinst:\tbreak\n\t"
1072                         "nop\n\t"
1073                         ".set\treorder"
1074                         );
1075 }
1076
1077 /* Nothing but the break; don't pollute any registers */
1078 void async_breakpoint(void)
1079 {
1080         __asm__ __volatile__(
1081                         ".globl async_breakinst\n\t"
1082                         ".set\tnoreorder\n\t"
1083                         "nop\n"
1084                         "async_breakinst:\tbreak\n\t"
1085                         "nop\n\t"
1086                         ".set\treorder"
1087                         );
1088 }
1089
1090 void adel(void)
1091 {
1092         __asm__ __volatile__(
1093                         ".globl\tadel\n\t"
1094                         "lui\t$8,0x8000\n\t"
1095                         "lw\t$9,1($8)\n\t"
1096                         );
1097 }
1098
1099 /*
1100  * malloc is needed by gdb client in "call func()", even a private one
1101  * will make gdb happy
1102  */
1103 static void __used *malloc(size_t size)
1104 {
1105         return kmalloc(size, GFP_ATOMIC);
1106 }
1107
1108 static void __used free(void *where)
1109 {
1110         kfree(where);
1111 }
1112
1113 #ifdef CONFIG_GDB_CONSOLE
1114
1115 void gdb_putsn(const char *str, int l)
1116 {
1117         char outbuf[18];
1118
1119         if (!kgdb_started)
1120                 return;
1121
1122         outbuf[0]='O';
1123
1124         while(l) {
1125                 int i = (l>8)?8:l;
1126                 mem2hex((char *)str, &outbuf[1], i, 0);
1127                 outbuf[(i*2)+1]=0;
1128                 putpacket(outbuf);
1129                 str += i;
1130                 l -= i;
1131         }
1132 }
1133
1134 static void gdb_console_write(struct console *con, const char *s, unsigned n)
1135 {
1136         gdb_putsn(s, n);
1137 }
1138
1139 static struct console gdb_console = {
1140         .name   = "gdb",
1141         .write  = gdb_console_write,
1142         .flags  = CON_PRINTBUFFER,
1143         .index  = -1
1144 };
1145
1146 static int __init register_gdb_console(void)
1147 {
1148         register_console(&gdb_console);
1149
1150         return 0;
1151 }
1152
1153 console_initcall(register_gdb_console);
1154
1155 #endif