source: trunk/libs/newlib/src/libgloss/sparc/sparc-stub.c @ 675

#include "sparclite.h"
/****************************************************************************

                THIS SOFTWARE IS NOT COPYRIGHTED

   HP offers the following for use in the public domain.  HP makes no
   warranty with regard to the software or it's performance and the
   user accepts the software "AS IS" with all faults.

   HP DISCLAIMS ANY WARRANTIES, EXPRESS OR IMPLIED, WITH REGARD
   TO THIS SOFTWARE INCLUDING BUT NOT LIMITED TO THE WARRANTIES
   OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

****************************************************************************/

/****************************************************************************
 *  Header: remcom.c,v 1.34 91/03/09 12:29:49 glenne Exp $
 *
 *  Module name: remcom.c $
 *  Revision: 1.34 $
 *  Date: 91/03/09 12:29:49 $
 *  Contributor:     Lake Stevens Instrument Division$
 *
 *  Description:     low level support for gdb debugger. $
 *
 *  Considerations:  only works on target hardware $
 *
 *  Written by:      Glenn Engel $
 *  ModuleState:     Experimental $
 *
 *  NOTES:           See Below $
 *
 *  Modified for SPARC by Stu Grossman, Cygnus Support.
 *
 *  This code has been extensively tested on the Fujitsu SPARClite demo board.
 *
 *  To enable debugger support, two things need to happen.  One, a
 *  call to set_debug_traps() is necessary in order to allow any breakpoints
 *  or error conditions to be properly intercepted and reported to gdb.
 *  Two, a breakpoint needs to be generated to begin communication.  This
 *  is most easily accomplished by a call to breakpoint().  Breakpoint()
 *  simulates a breakpoint by executing a trap #1.
 *
 *************
 *
 *    The following gdb commands are supported:
 *
 * command          function                               Return value
 *
 *    g             return the value of the CPU registers  hex data or ENN
 *    G             set the value of the CPU registers     OK or ENN
 *
 *    mAA..AA,LLLL  Read LLLL bytes at address AA..AA      hex data or ENN
 *    MAA..AA,LLLL: Write LLLL bytes at address AA.AA      OK or ENN
 *
 *    c             Resume at current address              SNN   ( signal NN)
 *    cAA..AA       Continue at address AA..AA             SNN
 *
 *    s             Step one instruction                   SNN
 *    sAA..AA       Step one instruction from AA..AA       SNN
 *
 *    k             kill
 *
 *    ?             What was the last sigval ?             SNN   (signal NN)
 *
 *    bBB..BB       Set baud rate to BB..BB                OK or BNN, then sets
 *                                                         baud rate
 *
 * All commands and responses are sent with a packet which includes a
 * checksum.  A packet consists of
 *
 * $<packet info>#<checksum>.
 *
 * where
 * <packet info> :: <characters representing the command or response>
 * <checksum>    :: < two hex digits computed as modulo 256 sum of <packetinfo>>
 *
 * When a packet is received, it is first acknowledged with either '+' or '-'.
 * '+' indicates a successful transfer.  '-' indicates a failed transfer.
 *
 * Example:
 *
 * Host:                  Reply:
 * $m0,10#2a               +$00010203040506070809101112131415#42
 *
 ****************************************************************************/

#include <string.h>
#include <signal.h>

/************************************************************************
 *
 * external low-level support routines
 */

extern putDebugChar();   /* write a single character      */
extern getDebugChar();   /* read and return a single char */

/************************************************************************/
/* BUFMAX defines the maximum number of characters in inbound/outbound buffers*/
/* at least NUMREGBYTES*2 are needed for register packets */
#define BUFMAX 2048

static int initialized = 0;     /* !0 means we've been initialized */

static void set_mem_fault_trap();

static const char hexchars[]="0123456789abcdef";

#define NUMREGS 72

/* Number of bytes of registers.  */
#define NUMREGBYTES (NUMREGS * 4)
enum regnames {G0, G1, G2, G3, G4, G5, G6, G7,
                 O0, O1, O2, O3, O4, O5, SP, O7,
                 L0, L1, L2, L3, L4, L5, L6, L7,
                 I0, I1, I2, I3, I4, I5, FP, I7,

                 F0, F1, F2, F3, F4, F5, F6, F7,
                 F8, F9, F10, F11, F12, F13, F14, F15,
                 F16, F17, F18, F19, F20, F21, F22, F23,
                 F24, F25, F26, F27, F28, F29, F30, F31,
                 Y, PSR, WIM, TBR, PC, NPC, FPSR, CPSR };

/***************************  ASSEMBLY CODE MACROS *************************/
/*                                                                         */

extern void trap_low();

asm("
        .reserve trapstack, 1000 * 4, \"bss\", 8

        .data
        .align  4

in_trap_handler:
        .word   0

        .text
        .align 4

! This function is called when any SPARC trap (except window overflow or
! underflow) occurs.  It makes sure that the invalid register window is still
! available before jumping into C code.  It will also restore the world if you
! return from handle_exception.

        .globl _trap_low
_trap_low:
        mov     %psr, %l0
        mov     %wim, %l3

        srl     %l3, %l0, %l4           ! wim >> cwp
        cmp     %l4, 1
        bne     window_fine             ! Branch if not in the invalid window
        nop

! Handle window overflow

        mov     %g1, %l4                ! Save g1, we use it to hold the wim
        srl     %l3, 1, %g1             ! Rotate wim right
        tst     %g1
        bg      good_wim                ! Branch if new wim is non-zero
        nop

! At this point, we need to bring a 1 into the high order bit of the wim.
! Since we don't want to make any assumptions about the number of register
! windows, we figure it out dynamically so as to setup the wim correctly.

        not     %g1                     ! Fill g1 with ones
        mov     %g1, %wim               ! Fill the wim with ones
        nop
        nop
        nop
        mov     %wim, %g1               ! Read back the wim
        inc     %g1                     ! Now g1 has 1 just to left of wim
        srl     %g1, 1, %g1             ! Now put 1 at top of wim
        mov     %g0, %wim               ! Clear wim so that subsequent save
        nop                             !  won't trap
        nop
        nop

good_wim:
        save    %g0, %g0, %g0           ! Slip into next window
        mov     %g1, %wim               ! Install the new wim

        std     %l0, [%sp + 0 * 4]      ! save L & I registers
        std     %l2, [%sp + 2 * 4]
        std     %l4, [%sp + 4 * 4]
        std     %l6, [%sp + 6 * 4]

        std     %i0, [%sp + 8 * 4]
        std     %i2, [%sp + 10 * 4]
        std     %i4, [%sp + 12 * 4]
        std     %i6, [%sp + 14 * 4]

        restore                         ! Go back to trap window.
        mov     %l4, %g1                ! Restore %g1

window_fine:
        sethi   %hi(in_trap_handler), %l4
        ld      [%lo(in_trap_handler) + %l4], %l5
        tst     %l5
        bg      recursive_trap
        inc     %l5

        set     trapstack+1000*4, %sp   ! Switch to trap stack

recursive_trap:
        st      %l5, [%lo(in_trap_handler) + %l4]
        sub     %sp,(16+1+6+1+72)*4,%sp ! Make room for input & locals
                                        ! + hidden arg + arg spill
                                        ! + doubleword alignment
                                        ! + registers[72] local var

        std     %g0, [%sp + (24 + 0) * 4] ! registers[Gx]
        std     %g2, [%sp + (24 + 2) * 4]
        std     %g4, [%sp + (24 + 4) * 4]
        std     %g6, [%sp + (24 + 6) * 4]

        std     %i0, [%sp + (24 + 8) * 4] ! registers[Ox]
        std     %i2, [%sp + (24 + 10) * 4]
        std     %i4, [%sp + (24 + 12) * 4]
        std     %i6, [%sp + (24 + 14) * 4]
                                        ! F0->F31 not implemented
        mov     %y, %l4
        mov     %tbr, %l5
        st      %l4, [%sp + (24 + 64) * 4] ! Y
        st      %l0, [%sp + (24 + 65) * 4] ! PSR
        st      %l3, [%sp + (24 + 66) * 4] ! WIM
        st      %l5, [%sp + (24 + 67) * 4] ! TBR
        st      %l1, [%sp + (24 + 68) * 4] ! PC
        st      %l2, [%sp + (24 + 69) * 4] ! NPC

                                        ! CPSR and FPSR not impl

        or      %l0, 0xf20, %l4
        mov     %l4, %psr               ! Turn on traps, disable interrupts

        call    _handle_exception
        add     %sp, 24 * 4, %o0        ! Pass address of registers

! Reload all of the registers that aren't on the stack

        ld      [%sp + (24 + 1) * 4], %g1 ! registers[Gx]
        ldd     [%sp + (24 + 2) * 4], %g2
        ldd     [%sp + (24 + 4) * 4], %g4
        ldd     [%sp + (24 + 6) * 4], %g6

        ldd     [%sp + (24 + 8) * 4], %i0 ! registers[Ox]
        ldd     [%sp + (24 + 10) * 4], %i2
        ldd     [%sp + (24 + 12) * 4], %i4
        ldd     [%sp + (24 + 14) * 4], %i6

        ldd     [%sp + (24 + 64) * 4], %l0 ! Y & PSR
        ldd     [%sp + (24 + 68) * 4], %l2 ! PC & NPC

        restore                         ! Ensure that previous window is valid
        save    %g0, %g0, %g0           !  by causing a window_underflow trap

        mov     %l0, %y
        mov     %l1, %psr               ! Make sure that traps are disabled
                                        ! for rett

        sethi   %hi(in_trap_handler), %l4
        ld      [%lo(in_trap_handler) + %l4], %l5
        dec     %l5
        st      %l5, [%lo(in_trap_handler) + %l4]

        jmpl    %l2, %g0                ! Restore old PC
        rett    %l3                     ! Restore old nPC
");

/* Convert ch from a hex digit to an int */

static int
hex(ch)
     unsigned char ch;
{
  if (ch >= 'a' && ch <= 'f')
    return ch-'a'+10;
  if (ch >= '0' && ch <= '9')
    return ch-'0';
  if (ch >= 'A' && ch <= 'F')
    return ch-'A'+10;
  return -1;
}

/* scan for the sequence $<data>#<checksum>     */

static void
getpacket(buffer)
     char *buffer;
{
  unsigned char checksum;
  unsigned char xmitcsum;
  int i;
  int count;
  unsigned char ch;

  do
    {
      /* wait around for the start character, ignore all other characters */
      while ((ch = (getDebugChar() & 0x7f)) != '$') ;

      checksum = 0;
      xmitcsum = -1;

      count = 0;

      /* now, read until a # or end of buffer is found */
      while (count < BUFMAX)
        {
          ch = getDebugChar() & 0x7f;
          if (ch == '#')
            break;
          checksum = checksum + ch;
          buffer[count] = ch;
          count = count + 1;
        }

      if (count >= BUFMAX)
        continue;

      buffer[count] = 0;

      if (ch == '#')
        {
          xmitcsum = hex(getDebugChar() & 0x7f) << 4;
          xmitcsum |= hex(getDebugChar() & 0x7f);
#if 0
          /* Humans shouldn't have to figure out checksums to type to it. */
          putDebugChar ('+');
          return;
#endif
          if (checksum != xmitcsum)
            putDebugChar('-');  /* failed checksum */
          else
            {
              putDebugChar('+'); /* successful transfer */
              /* if a sequence char is present, reply the sequence ID */
              if (buffer[2] == ':')
                {
                  putDebugChar(buffer[0]);
                  putDebugChar(buffer[1]);
                  /* remove sequence chars from buffer */
                  count = strlen(buffer);
                  for (i=3; i <= count; i++)
                    buffer[i-3] = buffer[i];
                }
            }
        }
    }
  while (checksum != xmitcsum);
}

/* send the packet in buffer.  */

static void
putpacket(buffer)
     unsigned char *buffer;
{
  unsigned char checksum;
  int count;
  unsigned char ch;

  /*  $<packet info>#<checksum>. */
  do
    {
      putDebugChar('$');
      checksum = 0;
      count = 0;

      while (ch = buffer[count])
        {
          if (! putDebugChar(ch))
            return;
          checksum += ch;
          count += 1;
        }

      putDebugChar('#');
      putDebugChar(hexchars[checksum >> 4]);
      putDebugChar(hexchars[checksum & 0xf]);

    }
  while ((getDebugChar() & 0x7f) != '+');
}

static char remcomInBuffer[BUFMAX];
static char remcomOutBuffer[BUFMAX];

/* Indicate to caller of mem2hex or hex2mem that there has been an
   error.  */
static volatile int mem_err = 0;

/* Convert the memory pointed to by mem into hex, placing result in buf.
 * Return a pointer to the last char put in buf (null), in case of mem fault,
 * return 0.
 * If MAY_FAULT is non-zero, then we will handle memory faults by returning
 * a 0, else treat a fault like any other fault in the stub.
 */

static unsigned char *
mem2hex(mem, buf, count, may_fault)
     unsigned char *mem;
     unsigned char *buf;
     int count;
     int may_fault;
{
  unsigned char ch;

  set_mem_fault_trap(may_fault);

  while (count-- > 0)
    {
      ch = *mem++;
      if (mem_err)
        return 0;
      *buf++ = hexchars[ch >> 4];
      *buf++ = hexchars[ch & 0xf];
    }

  *buf = 0;

  set_mem_fault_trap(0);

  return buf;
}

/* convert the hex array pointed to by buf into binary to be placed in mem
 * return a pointer to the character AFTER the last byte written */

static char *
hex2mem(buf, mem, count, may_fault)
     unsigned char *buf;
     unsigned char *mem;
     int count;
     int may_fault;
{
  int i;
  unsigned char ch;

  set_mem_fault_trap(may_fault);

  for (i=0; i<count; i++)
    {
      ch = hex(*buf++) << 4;
      ch |= hex(*buf++);
      *mem++ = ch;
      if (mem_err)
        return 0;
    }

  set_mem_fault_trap(0);

  return mem;
}

/* This table contains the mapping between SPARC hardware trap types, and
   signals, which are primarily what GDB understands.  It also indicates
   which hardware traps we need to commandeer when initializing the stub. */

static struct hard_trap_info
{
  unsigned char tt;             /* Trap type code for SPARClite */
  unsigned char signo;          /* Signal that we map this trap into */
} hard_trap_info[] = {
  {1, SIGSEGV},                 /* instruction access error */
  {2, SIGILL},                  /* privileged instruction */
  {3, SIGILL},                  /* illegal instruction */
  {4, SIGEMT},                  /* fp disabled */
  {36, SIGEMT},                 /* cp disabled */
  {7, SIGBUS},                  /* mem address not aligned */
  {9, SIGSEGV},                 /* data access exception */
  {10, SIGEMT},                 /* tag overflow */
  {128+1, SIGTRAP},             /* ta 1 - normal breakpoint instruction */
  {0, 0}                        /* Must be last */
};

/* Set up exception handlers for tracing and breakpoints */

void
set_debug_traps()
{
  struct hard_trap_info *ht;

  for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
    exceptionHandler(ht->tt, trap_low);

  /* In case GDB is started before us, ack any packets (presumably
     "$?#xx") sitting there.  */

  putDebugChar ('+');

  initialized = 1;
}

asm ("
! Trap handler for memory errors.  This just sets mem_err to be non-zero.  It
! assumes that %l1 is non-zero.  This should be safe, as it is doubtful that
! 0 would ever contain code that could mem fault.  This routine will skip
! past the faulting instruction after setting mem_err.

        .text
        .align 4

_fltr_set_mem_err:
        sethi %hi(_mem_err), %l0
        st %l1, [%l0 + %lo(_mem_err)]
        jmpl %l2, %g0
        rett %l2+4
");

static void
set_mem_fault_trap(enable)
     int enable;
{
  extern void fltr_set_mem_err();
  mem_err = 0;

  if (enable)
    exceptionHandler(9, fltr_set_mem_err);
  else
    exceptionHandler(9, trap_low);
}

/* Convert the SPARC hardware trap type code to a unix signal number. */

static int
computeSignal(tt)
     int tt;
{
  struct hard_trap_info *ht;

  for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
    if (ht->tt == tt)
      return ht->signo;

  return SIGHUP;                /* default for things we don't know about */
}

/*
 * While we find nice hex chars, build an int.
 * Return number of chars processed.
 */

static unsigned int
hexToInt(char **ptr, int *intValue)
{
  int numChars = 0;
  int hexValue;

  *intValue = 0;

  while (**ptr)
    {
      hexValue = hex(**ptr);
      if (hexValue < 0)
        break;

      *intValue = (*intValue << 4) | hexValue;
      numChars ++;

      (*ptr)++;
    }

  return (numChars);
}

/*
 * This function does all command procesing for interfacing to gdb.  It
 * returns 1 if you should skip the instruction at the trap address, 0
 * otherwise.
 */

extern void breakinst();

static void
handle_exception (registers)
     unsigned long *registers;
{
  int tt;                       /* Trap type */
  int sigval;
  unsigned int addr;
  int length;
  char *ptr;
  unsigned long *sp;

/* First, we must force all of the windows to be spilled out */

  asm(" save %sp, -64, %sp
        save %sp, -64, %sp
        save %sp, -64, %sp
        save %sp, -64, %sp
        save %sp, -64, %sp
        save %sp, -64, %sp
        save %sp, -64, %sp
        save %sp, -64, %sp
        restore
        restore
        restore
        restore
        restore
        restore
        restore
        restore
");

  if (registers[PC] == (unsigned long)breakinst)
    {
      registers[PC] = registers[NPC];
      registers[NPC] += 4;
    }

  sp = (unsigned long *)registers[SP];

  tt = (registers[TBR] >> 4) & 0xff;

  /* reply to host that an exception has occurred */
  sigval = computeSignal(tt);
  ptr = remcomOutBuffer;

  *ptr++ = 'T';
  *ptr++ = hexchars[sigval >> 4];
  *ptr++ = hexchars[sigval & 0xf];

  *ptr++ = hexchars[PC >> 4];
  *ptr++ = hexchars[PC & 0xf];
  *ptr++ = ':';
  ptr = mem2hex((char *)&registers[PC], ptr, 4, 0);
  *ptr++ = ';';

  *ptr++ = hexchars[FP >> 4];
  *ptr++ = hexchars[FP & 0xf];
  *ptr++ = ':';
  ptr = mem2hex(sp + 8 + 6, ptr, 4, 0); /* FP */
  *ptr++ = ';';

  *ptr++ = hexchars[SP >> 4];
  *ptr++ = hexchars[SP & 0xf];
  *ptr++ = ':';
  ptr = mem2hex((char *)&sp, ptr, 4, 0);
  *ptr++ = ';';

  *ptr++ = hexchars[NPC >> 4];
  *ptr++ = hexchars[NPC & 0xf];
  *ptr++ = ':';
  ptr = mem2hex((char *)&registers[NPC], ptr, 4, 0);
  *ptr++ = ';';

  *ptr++ = hexchars[O7 >> 4];
  *ptr++ = hexchars[O7 & 0xf];
  *ptr++ = ':';
  ptr = mem2hex((char *)&registers[O7], ptr, 4, 0);
  *ptr++ = ';';

  *ptr++ = 0;

  putpacket(remcomOutBuffer);

  while (1)
    {
      remcomOutBuffer[0] = 0;

      getpacket(remcomInBuffer);
      switch (remcomInBuffer[0])
        {
        case '?':
          remcomOutBuffer[0] = 'S';
          remcomOutBuffer[1] = hexchars[sigval >> 4];
          remcomOutBuffer[2] = hexchars[sigval & 0xf];
          remcomOutBuffer[3] = 0;
          break;

        case 'd':
                                /* toggle debug flag */
          break;

        case 'g':               /* return the value of the CPU registers */
          {
            ptr = remcomOutBuffer;
            ptr = mem2hex((char *)registers, ptr, 16 * 4, 0); /* G & O regs */
            ptr = mem2hex(sp + 0, ptr, 16 * 4, 0); /* L & I regs */
            memset(ptr, '0', 32 * 8); /* Floating point */
            mem2hex((char *)&registers[Y],
                    ptr + 32 * 4 * 2,
                    8 * 4,
                    0);         /* Y, PSR, WIM, TBR, PC, NPC, FPSR, CPSR */
          }
          break;

        case 'G':          /* set the value of the CPU registers - return OK */
          {
            unsigned long *newsp, psr;

            psr = registers[PSR];

            ptr = &remcomInBuffer[1];
            hex2mem(ptr, (char *)registers, 16 * 4, 0); /* G & O regs */
            hex2mem(ptr + 16 * 4 * 2, sp + 0, 16 * 4, 0); /* L & I regs */
            hex2mem(ptr + 64 * 4 * 2, (char *)&registers[Y],
                    8 * 4, 0);  /* Y, PSR, WIM, TBR, PC, NPC, FPSR, CPSR */

            /* See if the stack pointer has moved.  If so, then copy the saved
               locals and ins to the new location.  This keeps the window
               overflow and underflow routines happy.  */

            newsp = (unsigned long *)registers[SP];
            if (sp != newsp)
              sp = memcpy(newsp, sp, 16 * 4);

            /* Don't allow CWP to be modified. */

            if (psr != registers[PSR])
              registers[PSR] = (psr & 0x1f) | (registers[PSR] & ~0x1f);

            strcpy(remcomOutBuffer,"OK");
          }
          break;

        case 'm':         /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
          /* Try to read %x,%x.  */

          ptr = &remcomInBuffer[1];

          if (hexToInt(&ptr, &addr)
              && *ptr++ == ','
              && hexToInt(&ptr, &length))
            {
              if (mem2hex((char *)addr, remcomOutBuffer, length, 1))
                break;

              strcpy (remcomOutBuffer, "E03");
            }
          else
            strcpy(remcomOutBuffer,"E01");
          break;

        case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
          /* Try to read '%x,%x:'.  */

          ptr = &remcomInBuffer[1];

          if (hexToInt(&ptr, &addr)
              && *ptr++ == ','
              && hexToInt(&ptr, &length)
              && *ptr++ == ':')
            {
              if (hex2mem(ptr, (char *)addr, length, 1))
                strcpy(remcomOutBuffer, "OK");
              else
                strcpy(remcomOutBuffer, "E03");
            }
          else
            strcpy(remcomOutBuffer, "E02");
          break;

        case 'c':    /* cAA..AA    Continue at address AA..AA(optional) */
          /* try to read optional parameter, pc unchanged if no parm */

          ptr = &remcomInBuffer[1];
          if (hexToInt(&ptr, &addr))
            {
              registers[PC] = addr;
              registers[NPC] = addr + 4;
            }

/* Need to flush the instruction cache here, as we may have deposited a
   breakpoint, and the icache probably has no way of knowing that a data ref to
   some location may have changed something that is in the instruction cache.
 */

          flush_i_cache();
          return;

          /* kill the program */
        case 'k' :              /* do nothing */
          break;
#if 0
        case 't':               /* Test feature */
          asm (" std %f30,[%sp]");
          break;
#endif
        case 'r':               /* Reset */
          asm ("call 0
                nop ");
          break;

#if 0
Disabled until we can unscrew this properly

        case 'b':         /* bBB...  Set baud rate to BB... */
          {
            int baudrate;
            extern void set_timer_3();

            ptr = &remcomInBuffer[1];
            if (!hexToInt(&ptr, &baudrate))
              {
                strcpy(remcomOutBuffer,"B01");
                break;
              }

            /* Convert baud rate to uart clock divider */
            switch (baudrate)
              {
              case 38400:
                baudrate = 16;
                break;
              case 19200:
                baudrate = 33;
                break;
              case 9600:
                baudrate = 65;
                break;
              default:
                strcpy(remcomOutBuffer,"B02");
                goto x1;
              }

            putpacket("OK");    /* Ack before changing speed */
            set_timer_3(baudrate); /* Set it */
          }
x1:       break;
#endif
        }                       /* switch */

      /* reply to the request */
      putpacket(remcomOutBuffer);
    }
}

/* This function will generate a breakpoint exception.  It is used at the
   beginning of a program to sync up with a debugger and can be used
   otherwise as a quick means to stop program execution and "break" into
   the debugger. */

void
breakpoint()
{
  if (!initialized)
    return;

  asm(" .globl _breakinst

        _breakinst: ta 1
      ");
}