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alpha-arch.c

/*
 * This software is part of the SBCL system. See the README file for
 * more information.
 *
 * This software is derived from the CMU CL system, which was
 * written at Carnegie Mellon University and released into the
 * public domain. The software is in the public domain and is
 * provided with absolutely no warranty. See the COPYING and CREDITS
 * files for more information.
 */

/* Note that although superficially it appears that we use
 * os_context_t like we ought to, we actually just assume its a
 * ucontext in places.  Naughty */

#include <stdio.h>
#include <string.h>

#include "sbcl.h"
#include "runtime.h"
#include "globals.h"
#include "validate.h"
#include "os.h"
#include "arch.h"
#include "lispregs.h"
#include "signal.h"
#include "alloc.h"
#include "interrupt.h"
#include "interr.h"
#include "breakpoint.h"
#include "monitor.h"

extern char call_into_lisp_LRA[], call_into_lisp_end[];

extern size_t os_vm_page_size;
#define BREAKPOINT_INST 0x80


void
arch_init(void)
{
    /* This must be called _after_ os_init(), so that we know what the
     * page size is. */

    if (mmap((os_vm_address_t) call_into_lisp_LRA_page,os_vm_page_size,
           OS_VM_PROT_ALL,MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,-1,0)
      == (os_vm_address_t) -1)
      perror("mmap");
    
    /* call_into_lisp_LRA is a collection of trampolines written in asm -
     * see alpha-assem.S.  We copy it to call_into_lisp_LRA_page where
     * VOPs and things can find it. (I don't know why they can't find it 
     * where it was to start with.) */
    bcopy(call_into_lisp_LRA,(void *)call_into_lisp_LRA_page,os_vm_page_size);

    os_flush_icache((os_vm_address_t)call_into_lisp_LRA_page,
                os_vm_page_size);
    return;
}

os_vm_address_t 
arch_get_bad_addr (int sig, siginfo_t *code, os_context_t *context)
{
    unsigned int badinst;

    /* Instructions are 32 bit quantities. */
    unsigned int *pc ;
    /*  fprintf(stderr,"arch_get_bad_addr %d %p %p\n",
      sig, code, context); */
    pc= (unsigned int *)(*os_context_pc_addr(context));

    if (((unsigned long)pc) & 3) {
      return NULL;            /* In what case would pc be unaligned?? */
    }

    if ( (pc < READ_ONLY_SPACE_START ||
        pc >= READ_ONLY_SPACE_START+READ_ONLY_SPACE_SIZE) && 
       (pc < current_dynamic_space ||
        pc >= current_dynamic_space + DYNAMIC_SPACE_SIZE))
      return NULL;

    return context->uc_mcontext.sc_traparg_a0;
}

void
arch_skip_instruction(os_context_t *context)
{
    /* This may be complete rubbish, as (at least for traps) pc points
     * _after_ the instruction that caused us to be here anyway.
     */
    ((char*)*os_context_pc_addr(context)) +=4; }

unsigned char *
arch_internal_error_arguments(os_context_t *context)
{
    return (unsigned char *)(*os_context_pc_addr(context)+4);
}

boolean
arch_pseudo_atomic_atomic(os_context_t *context)
{
    return ((*os_context_register_addr(context,reg_ALLOC)) & 1);
}

void arch_set_pseudo_atomic_interrupted(os_context_t *context)
{
    /* On coming out of an atomic section, we subtract 1 from
     * reg_Alloc, then try to store something at that address.  So,
     * to signal that it was interrupted and a signal should be handled, 
     * we set bit 63 of reg_ALLOC here so that the end-of-atomic code
     * will raise SIGSEGV (no ram mapped there).  We catch the signal
     * (see the appropriate *-os.c) and call interrupt_handle_pending() 
     * for the saved signal instead */

    *os_context_register_addr(context,reg_ALLOC) |=  (1L<<63);
}

unsigned long arch_install_breakpoint(void *pc)
{
    unsigned int *ptr = (unsigned int *)pc;
    unsigned long result = (unsigned long) *ptr;
    *ptr = BREAKPOINT_INST;
    
    os_flush_icache((os_vm_address_t)ptr, sizeof(unsigned long));
    
    return result;
}

void arch_remove_breakpoint(void *pc, unsigned long orig_inst)
{
    /* was (unsigned int) but gcc complains.  Changed to mirror
     * install_breakpoint() above */
    unsigned long *ptr=(unsigned long *)pc;
    *ptr = orig_inst;
    os_flush_icache((os_vm_address_t)pc, sizeof(unsigned long));
}

static unsigned int *skipped_break_addr, displaced_after_inst,
     after_breakpoint;


/* This returns a PC value.  Lisp code is all in the 32-bit-addressable
 * space, so we should be ok with an unsigned int. */
unsigned int
emulate_branch(os_context_t *context,unsigned long orig_inst)
{
    int op = orig_inst >> 26;
    int reg_a = (orig_inst >> 21) & 0x1f;
    int reg_b = (orig_inst >> 16) & 0x1f;
    int disp =
      (orig_inst&(1<<20)) ?
      orig_inst | (-1 << 21) :
      orig_inst&0x1fffff;
    int next_pc = *os_context_pc_addr(context);
    int branch = 0; /* was NULL;           */

    switch(op) {
    case 0x1a: /* jmp, jsr, jsr_coroutine, ret */
      *os_context_register_addr(context,reg_a) =
          *os_context_pc_addr(context);
      *os_context_pc_addr(context) =
          *os_context_register_addr(context,reg_b)& ~3;
      break;
    case 0x30: /* br */
      *os_context_register_addr(context,reg_a)=*os_context_pc_addr(context);
      branch = 1;
      break;
    case 0x31: /* fbeq */
      if (*(os_context_float_register_addr(context,reg_a))==0) branch = 1;
      break;
    case 0x32: /* fblt */
      if (*os_context_float_register_addr(context,reg_a)<0) branch = 1;
      break;
    case 0x33: /* fble */
      if (*os_context_float_register_addr(context,reg_a)<=0) branch = 1;
      break;
    case 0x34: /* bsr */
      *os_context_register_addr(context,reg_a)=*os_context_pc_addr(context);
      branch = 1;
      break;
    case 0x35: /* fbne */
      if (*os_context_register_addr(context,reg_a)!=0) branch = 1;
      break;
    case 0x36: /* fbge */
      if (*os_context_float_register_addr(context,reg_a)>=0) branch = 1;
      break;
    case 0x37: /* fbgt */
      if (*os_context_float_register_addr(context,reg_a)>0) branch = 1;
      break;
    case 0x38: /* blbc */
      if ((*os_context_register_addr(context,reg_a)&1) == 0) branch = 1;
      break;
    case 0x39: /* beq */
      if (*os_context_register_addr(context,reg_a)==0) branch = 1;
      break;
    case 0x3a: /* blt */
      if (*os_context_register_addr(context,reg_a)<0) branch = 1;
      break;
    case 0x3b: /* ble */
      if (*os_context_register_addr(context,reg_a)<=0) branch = 1;
      break;
    case 0x3c: /* blbs */
      if ((*os_context_register_addr(context,reg_a)&1)!=0) branch = 1;
      break;
    case 0x3d: /* bne */
      if (*os_context_register_addr(context,reg_a)!=0) branch = 1;
      break;
    case 0x3e: /* bge */
      if (*os_context_register_addr(context,reg_a)>=0) branch = 1;
      break;
    case 0x3f: /* bgt */
      if (*os_context_register_addr(context,reg_a)>0) branch = 1;
      break;
    }
    if (branch)
      next_pc += disp*4;
    return next_pc;
}

static sigset_t orig_sigmask;

/* Perform the instruction that we overwrote with a breakpoint.  As we
 * don't have a single-step facility, this means we have to:
 * - put the instruction back
 * - put a second breakpoint at the following instruction, 
 *   set after_breakpoint and continue execution.
 *
 * When the second breakpoint is hit (very shortly thereafter, we hope)
 * sigtrap_handler gets called again, but follows the AfterBreakpoint 
 * arm, which 
 * - puts a bpt back in the first breakpoint place (running across a 
 *   breakpoint shouldn't cause it to be uninstalled)
 * - replaces the second bpt with the instruction it was meant to be
 * - carries on 
 *
 * Clear?
 */

void arch_do_displaced_inst(os_context_t *context,unsigned int orig_inst)
{
    /* Apparent off-by-one errors ahoy.  If you consult the Alpha ARM,
     * it will tell you that after a BPT, the saved PC is the address
     * of the instruction _after_ the instruction that caused the trap.
     *
     * However, we decremented PC by 4 before calling the Lisp-level
     * handler that calls this routine (see alpha-arch.c line 322 and
     * friends) so when we get to this point PC is actually pointing
     * at the BPT instruction itself.  This is good, because this is
     * where we want to restart execution when we do that */

    unsigned int *pc=(unsigned int *)(*os_context_pc_addr(context));
    unsigned int *next_pc;
    int op = orig_inst >> 26;;

    orig_sigmask = *os_context_sigmask_addr(context);
    sigaddset_blockable(os_context_sigmask_addr(context));

    /* Put the original instruction back. */
    *pc = orig_inst;
    os_flush_icache((os_vm_address_t)pc, sizeof(unsigned long));
    skipped_break_addr = pc;

    /* Figure out where we will end up after running the displaced 
     * instruction */
    if (op == 0x1a || (op&0xf) == 0x30) /* a branch */
      /* The cast to long is just to shut gcc up. */
      next_pc = (unsigned int *)((long)emulate_branch(context,orig_inst));
    else
      next_pc = pc+1;
    
    /* Set the after breakpoint. */
    displaced_after_inst = *next_pc;
    *next_pc = BREAKPOINT_INST;
    after_breakpoint=1;
    os_flush_icache((os_vm_address_t)next_pc, sizeof(unsigned long));
}

static void
sigtrap_handler(int signal, siginfo_t *siginfo, os_context_t *context)
{
    unsigned int code;
    sigset_t *mask;
#ifdef LISP_FEATURE_LINUX
    os_restore_fp_control(context);
#endif

    /* Don't disallow recursive breakpoint traps.  Otherwise, we can't */
    /* use debugger breakpoints anywhere in here. */
    mask=(os_context_sigmask_addr(context));
    sigsetmask(mask); 

    /* this is different from how CMUCL does it.  CMUCL used "call_pal
     * PAL_gentrap", which doesn't do anything on Linux (unless NL0
     * contains certain specific values).  We use "bugchk" instead.
     * It's (for our purposes) just the same as bpt but has a
     * different opcode so we can test whether we're dealing with a
     * breakpoint or a "system service" */

    if ((*(unsigned int*)(*os_context_pc_addr(context)-4))==BREAKPOINT_INST) {
      if (after_breakpoint) {
          /* see comments above arch_do_displaced_inst.  This is where
           * we reinsert the breakpoint that we removed earlier */

          *os_context_pc_addr(context) -=4;
          *skipped_break_addr = BREAKPOINT_INST;
          os_flush_icache((os_vm_address_t)skipped_break_addr,
                      sizeof(unsigned long));
          skipped_break_addr = NULL;
          *(unsigned int *)*os_context_pc_addr(context) =
            displaced_after_inst;
          os_flush_icache((os_vm_address_t)*os_context_pc_addr(context), sizeof(unsigned long));
          *os_context_sigmask_addr(context)= orig_sigmask;
          after_breakpoint=0; /* false */
          return;
      } else 
          code = trap_Breakpoint;
    } else
      /* a "system service" */
    code=*((u32 *)(*os_context_pc_addr(context)));
    
    switch (code) {
      case trap_PendingInterrupt:
      arch_skip_instruction(context);
      interrupt_handle_pending(context);
      break;

      case trap_Halt:
      fake_foreign_function_call(context);
      lose("%%primitive halt called; the party is over.\n");

      case trap_Error:
      case trap_Cerror:
      interrupt_internal_error(signal, siginfo, context, code==trap_Cerror);
      break;

    case trap_Breakpoint:      /* call lisp-level handler */
        *os_context_pc_addr(context) -=4;
      handle_breakpoint(signal, siginfo, context);
      break;

      case trap_FunEndBreakpoint:
        *os_context_pc_addr(context) -=4;
      *os_context_pc_addr(context) =
          (int)handle_fun_end_breakpoint(signal, siginfo, context);
      break;

      default:
      fprintf(stderr, "unidentified breakpoint/trap %d\n",code);
      interrupt_handle_now(signal, siginfo, context);
      break;
    }
}

unsigned long
arch_get_fp_control()
{
    return ieee_get_fp_control();
}

void
arch_set_fp_control(unsigned long fp)
{
    ieee_set_fp_control(fp);
}


void arch_install_interrupt_handlers()
{
    undoably_install_low_level_interrupt_handler(SIGTRAP, sigtrap_handler);
}

extern lispobj call_into_lisp(lispobj fun, lispobj *args, int nargs);

lispobj funcall0(lispobj function)
{
    lispobj *args = current_control_stack_pointer;

    return call_into_lisp(function, args, 0);
}

lispobj funcall1(lispobj function, lispobj arg0)
{
    lispobj *args = current_control_stack_pointer;

    current_control_stack_pointer += 1;
    args[0] = arg0;

    return call_into_lisp(function, args, 1);
}

lispobj funcall2(lispobj function, lispobj arg0, lispobj arg1)
{
    lispobj *args = current_control_stack_pointer;

    current_control_stack_pointer += 2;
    args[0] = arg0;
    args[1] = arg1;

    return call_into_lisp(function, args, 2);
}

lispobj funcall3(lispobj function, lispobj arg0, lispobj arg1, lispobj arg2)
{
    lispobj *args = current_control_stack_pointer;

    current_control_stack_pointer += 3;
    args[0] = arg0;
    args[1] = arg1;
    args[2] = arg2;

    return call_into_lisp(function, args, 3);
}


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