[apple/xnu.git] / osfmk / ppc / model_dep.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/*
 * @APPLE_FREE_COPYRIGHT@
 */
/*
 *  (c) Copyright 1988 HEWLETT-PACKARD COMPANY
 *
 *  To anyone who acknowledges that this file is provided "AS IS"
 *  without any express or implied warranty:
 *      permission to use, copy, modify, and distribute this file
 *  for any purpose is hereby granted without fee, provided that
 *  the above copyright notice and this notice appears in all
 *  copies, and that the name of Hewlett-Packard Company not be
 *  used in advertising or publicity pertaining to distribution
 *  of the software without specific, written prior permission.
 *  Hewlett-Packard Company makes no representations about the
 *  suitability of this software for any purpose.
 */
/*
 * Copyright (c) 1990,1991,1992,1994 The University of Utah and
 * the Computer Systems Laboratory (CSL).  All rights reserved.
 *
 * THE UNIVERSITY OF UTAH AND CSL PROVIDE THIS SOFTWARE IN ITS "AS IS"
 * CONDITION, AND DISCLAIM ANY LIABILITY OF ANY KIND FOR ANY DAMAGES
 * WHATSOEVER RESULTING FROM ITS USE.
 *
 * CSL requests users of this software to return to csl-dist@cs.utah.edu any
 * improvements that they make and grant CSL redistribution rights.
 *
 *      Utah $Hdr: model_dep.c 1.34 94/12/14$
 */

#include <debug.h>
#include <mach_kdb.h>
#include <mach_kdp.h>
#include <db_machine_commands.h>
#include <cpus.h>

#include <kern/thread.h>
#include <machine/pmap.h>
#include <machine/mach_param.h>
#include <device/device_types.h>

#include <mach/vm_param.h>
#include <mach/clock_types.h>
#include <mach/machine.h>
#include <mach/kmod.h>
#include <ppc/boot.h>

#include <kern/misc_protos.h>
#include <kern/startup.h>
#include <ppc/misc_protos.h>
#include <ppc/proc_reg.h>
#include <ppc/thread.h>
#include <ppc/asm.h>
#include <ppc/mem.h>
#include <ppc/Firmware.h>
#include <ppc/low_trace.h>
#include <ppc/mappings.h>
#include <ppc/FirmwareCalls.h>
#include <ppc/setjmp.h>
#include <ppc/exception.h>

#include <kern/clock.h>
#include <kern/debug.h>
#include <machine/trap.h>
#include <kern/spl.h>
#include <pexpert/pexpert.h>
#include <ppc/mp.h>

#include <IOKit/IOPlatformExpert.h>

#include <mach/vm_prot.h>
#include <vm/pmap.h>
#include <mach/time_value.h>
#include <machine/machparam.h>  /* for btop */

#if     MACH_KDB
#include <ddb/db_aout.h>
#include <ddb/db_output.h>
#include <ddb/db_command.h>
#include <machine/db_machdep.h>

extern struct db_command ppc_db_commands[];
#endif  /* MACH_KDB */

char kernel_args_buf[256] = "/mach_kernel";
char boot_args_buf[256] = "/mach_servers/bootstrap";
char env_buf[256];

#define TRAP_DEBUGGER   __asm__ volatile("tw 4,r3,r3");
#define TRAP_DEBUGGER_INST      0x7c831808
#define TRAP_DIRECT     __asm__ volatile("tw 4,r4,r4");
#define TRAP_DIRECT_INST        0x7c842008
#define TRAP_INST_SIZE  4
#define BREAK_TO_KDP0 0x7fe00008
#define BREAK_TO_KDP1 0x7c800008
#define BREAK_TO_KDB0 0x7c810808

/*
 * Code used to synchronize debuggers among all cpus, one active at a time, switch
 * from on to another using kdb_on! #cpu or cpu #cpu
 */

decl_simple_lock_data(, debugger_lock)  /* debugger lock */
decl_simple_lock_data(, pbtlock)                /* backtrace print lock */

int                     debugger_cpu = -1;                      /* current cpu running debugger */
int                     debugger_debug = 0;                     /* Debug debugger */
int                     debugger_is_slave[NCPUS];       /* Show that we were entered via sigp */
int                     debugger_active[NCPUS];         /* Debugger active on CPU */
int                     debugger_pending[NCPUS];        /* Debugger entry pending on CPU (this is a HACK) */
int                     debugger_holdoff[NCPUS];        /* Holdoff debugger entry on this CPU (this is a HACK) */
int             db_run_mode;                            /* Debugger run mode */
unsigned int debugger_sync = 0;                 /* Cross processor debugger entry sync */
extern          unsigned int NMIss;                     /* NMI debounce switch */

extern volatile int panicwait;
volatile unsigned int pbtcnt = 0;
volatile unsigned int pbtcpu = -1;

unsigned int lastTrace;                                 /* Value of low-level exception trace controls */

volatile unsigned int   cpus_holding_bkpts;     /* counter for number of cpus holding
                                                                                           breakpoints (ie: cpus that did not
                                                                                           insert back breakpoints) */
void unlock_debugger(void);
void lock_debugger(void);
void dump_backtrace(unsigned int stackptr, unsigned int fence);
void dump_savearea(savearea *sv, unsigned int fence);

#if !MACH_KDB
boolean_t       db_breakpoints_inserted = TRUE;
jmp_buf_t *db_recover = 0;
#endif

#if     MACH_KDB
#include <ddb/db_run.h>
int     kdb_flag=0;
extern boolean_t db_breakpoints_inserted;
extern jmp_buf_t *db_recover;
#define KDB_READY       0x1
#endif

#if     MACH_KDP
extern int      kdp_flag;
#define KDP_READY       0x1
#endif

boolean_t db_im_stepping = 0xFFFFFFFF;  /* Remember if we were stepping */


char *failNames[] = {   

        "Debugging trap",                       /* failDebug */
        "Corrupt stack",                        /* failStack */
        "Corrupt mapping tables",       /* failMapping */
        "Corrupt context",                      /* failContext */
        "Unknown failure code"                  /* Unknown failure code - must always be last */
};

char *invxcption = "Unknown code";

extern const char version[];
extern char *trap_type[];
extern vm_offset_t mem_actual;

#if !MACH_KDB
void kdb_trap(int type, struct ppc_saved_state *regs);
void kdb_trap(int type, struct ppc_saved_state *regs) {
        return;
}
#endif

#if !MACH_KDP
void kdp_trap(int type, struct ppc_saved_state *regs);
void kdp_trap(int type, struct ppc_saved_state *regs) {
        return;
}
#endif

void
machine_startup(boot_args *args)
{
        int     boot_arg;

        if (PE_parse_boot_arg("cpus", &wncpu)) {
                if (!((wncpu > 0) && (wncpu < NCPUS)))
                        wncpu = NCPUS;
        } else 
                wncpu = NCPUS;

        if( PE_get_hotkey( kPEControlKey ))
            halt_in_debugger = halt_in_debugger ? 0 : 1;

        if (PE_parse_boot_arg("debug", &boot_arg)) {
                if (boot_arg & DB_HALT) halt_in_debugger=1;
                if (boot_arg & DB_PRT) disableDebugOuput=FALSE; 
                if (boot_arg & DB_SLOG) systemLogDiags=TRUE; 
        }

        hw_lock_init(&debugger_lock);                           /* initialize debugger lock */
        hw_lock_init(&pbtlock);                                         /* initialize print backtrace lock */

#if     MACH_KDB
        /*
         * Initialize KDB
         */
#if     DB_MACHINE_COMMANDS
        db_machine_commands_install(ppc_db_commands);
#endif  /* DB_MACHINE_COMMANDS */
        ddb_init();

        if (boot_arg & DB_KDB)
                current_debugger = KDB_CUR_DB;

        /*
         * Cause a breakpoint trap to the debugger before proceeding
         * any further if the proper option bit was specified in
         * the boot flags.
         */
        if (halt_in_debugger && (current_debugger == KDB_CUR_DB)) {
                Debugger("inline call to debugger(machine_startup)");
                halt_in_debugger = 0;
                active_debugger =1;
        }
#endif /* MACH_KDB */
        if (PE_parse_boot_arg("preempt", &boot_arg)) {
                extern int default_preemption_rate;

                default_preemption_rate = boot_arg;
        }
        if (PE_parse_boot_arg("kpreempt", &boot_arg)) {
                extern int kernel_preemption_mode;
                extern boolean_t zone_gc_allowed;

                kernel_preemption_mode = boot_arg;
                zone_gc_allowed = FALSE; /* XXX: TO BE REMOVED  */
        }
        if (PE_parse_boot_arg("unsafe", &boot_arg)) {
                extern int max_unsafe_quanta;

                max_unsafe_quanta = boot_arg;
        }
        if (PE_parse_boot_arg("poll", &boot_arg)) {
                extern int max_poll_quanta;

                max_poll_quanta = boot_arg;
        }
        if (PE_parse_boot_arg("yield", &boot_arg)) {
                extern int sched_poll_yield_shift;

                sched_poll_yield_shift = boot_arg;
        }

        machine_conf();

        ml_thrm_init();                                                 /* Start thermal monitoring on this processor */

        /*
         * Start the system.
         */
        setup_main();

        /* Should never return */
}

char *
machine_boot_info(
        char *buf, 
        vm_size_t size)
{
        return(PE_boot_args());
}

void
machine_conf(void)
{
        machine_info.max_cpus = NCPUS;
        machine_info.avail_cpus = 1;
        machine_info.memory_size = mem_size;
}

void
machine_init(void)
{
        clock_config();
}

void slave_machine_init(void)
{
        (void) ml_set_interrupts_enabled(FALSE);        /* Make sure we are disabled */
        clock_init();                           /* Init the clock */
        cpu_machine_init();                     /* Initialize the processor */
}                               

void
halt_all_cpus(boolean_t reboot)
{
        if(reboot)
        {
                printf("MACH Reboot\n");
                PEHaltRestart(kPERestartCPU);
        }
        else
        {
                printf("CPU halted\n");
                PEHaltRestart(kPEHaltCPU);
        } 
        while(1);
}

void
halt_cpu(void)
{
        halt_all_cpus(FALSE);
}

#if     MACH_ASSERT
/*
 * Machine-dependent routine to fill in an array with up to callstack_max
 * levels of return pc information.
 */
void machine_callstack(
        natural_t       *buf,
        vm_size_t       callstack_max)
{
}
#endif  /* MACH_ASSERT */


void
print_backtrace(struct ppc_saved_state *ssp)
{
        unsigned int stackptr, *raddr, *rstack, trans, fence;
        int i, frames_cnt, skip_top_frames, frames_max;
        unsigned int store[8];                  /* Buffer for real storage reads */
        vm_offset_t backtrace_entries[32];
        thread_act_t *act;
        savearea *sv, *svssp;
        int cpu;

/*
 *      We need this lock to make sure we don't hang up when we double panic on an MP.
 */

        cpu  = cpu_number();                                    /* Just who are we anyways? */
        if(pbtcpu != cpu) {                                             /* Allow recursion */
                hw_atomic_add(&pbtcnt, 1);                      /* Remember we are trying */
                while(!hw_lock_try(&pbtlock));          /* Spin here until we can get in. If we never do, well, we're crashing anyhow... */     
                pbtcpu = cpu;                                           /* Mark it as us */     
        }       

        svssp = (savearea *)ssp;                                /* Make this easier */
        sv = 0;
        if(current_thread()) sv = (savearea *)current_act()->mact.pcb;  /* Find most current savearea if system has started */

        fence = 0xFFFFFFFF;                                             /* Show we go all the way */
        if(sv) fence = sv->save_r1;                             /* Stop at previous exception point */
        
        if(!svssp) {                                                    /* Should we start from stack? */
                printf("Latest stack backtrace for cpu %d:\n", cpu_number());
                __asm__ volatile("mr %0,r1" : "=r" (stackptr)); /* Get current stack */
                dump_backtrace(stackptr, fence);        /* Dump the backtrace */
                if(!sv) {                                                       /* Leave if no saveareas */
                        printf("\nKernel version:\n%s\n",version);      /* Print kernel version */
                        hw_lock_unlock(&pbtlock);               /* Allow another back trace to happen */
                        return; 
                }
        }
        else {                                                                  /* Were we passed an exception? */
                fence = 0xFFFFFFFF;                                     /* Show we go all the way */
                if(svssp->save_prev) fence = svssp->save_prev->save_r1;         /* Stop at previous exception point */
        
                printf("Latest crash info for cpu %d:\n", cpu_number());
                printf("   Exception state (sv=0x%08x)\n", sv);
                dump_savearea(svssp, fence);            /* Dump this savearea */        
        }

        if(!sv) {                                                               /* Leave if no saveareas */
                printf("\nKernel version:\n%s\n",version);      /* Print kernel version */
                hw_lock_unlock(&pbtlock);                       /* Allow another back trace to happen */
                return; 
        }
        
        printf("Proceeding back via exception chain:\n");

        while(sv) {                                                             /* Do them all... */
                printf("   Exception state (sv=0x%08x)\n", sv);
                if(sv == svssp) {                                       /* Did we dump it already? */
                        printf("      previously dumped as \"Latest\" state. skipping...\n");
                }
                else {
                        fence = 0xFFFFFFFF;                             /* Show we go all the way */
                        if(sv->save_prev) fence = sv->save_prev->save_r1;       /* Stop at previous exception point */
                        dump_savearea(sv, fence);               /* Dump this savearea */        
                }       
                
                sv = sv->save_prev;                                     /* Back chain */
        }
        
        printf("\nKernel version:\n%s\n",version);      /* Print kernel version */

        pbtcpu = -1;                                                    /* Mark as unowned */
        hw_lock_unlock(&pbtlock);                               /* Allow another back trace to happen */
        hw_atomic_sub(&pbtcnt, 1);                              /* Show we are done */

        while(pbtcnt);                                                  /* Wait for completion */

        return;
}

void dump_savearea(savearea *sv, unsigned int fence) {

        char *xcode;
        
        if(sv->save_exception > T_MAX) xcode = invxcption;      /* Too big for table */
        else xcode = trap_type[sv->save_exception / 4];         /* Point to the type */
        
        printf("      PC=0x%08X; MSR=0x%08x; DAR=0x%08x; DSISR=0x%08x; LR=0x%08x; R1=0x%08x; XCP=0x%08x (%s)\n",
                sv->save_srr0, sv->save_srr1, sv->save_dar, sv->save_dsisr,
                sv->save_lr, sv->save_r1, sv->save_exception, xcode);
        
        if(!(sv->save_srr1 & MASK(MSR_PR))) {           /* Are we in the kernel? */
                dump_backtrace(sv->save_r1, fence);             /* Dump the stack back trace from  here if not user state */
        }
        
        return;
}



#define DUMPFRAMES 32
#define LRindex 2

void dump_backtrace(unsigned int stackptr, unsigned int fence) {

        unsigned int bframes[DUMPFRAMES];
        unsigned int  sframe[8], raddr, dumbo;
        int i;
        
        printf("      Backtrace:\n");
        for(i = 0; i < DUMPFRAMES; i++) {                       /* Dump up to max frames */
        
                if(!stackptr || (stackptr == fence)) break;             /* Hit stop point or end... */
                
                if(stackptr & 0x0000000f) {                             /* Is stack pointer valid? */
                        printf("\n         backtrace terminated - unaligned frame address: 0x%08x\n", stackptr);        /* No, tell 'em */
                        break;
                }

                raddr = (unsigned int)LRA(PPC_SID_KERNEL, (void *)stackptr);    /* Get physical frame address */
                if(!raddr) {                                                    /* Is it mapped? */
                        printf("\n         backtrace terminated - frame not mapped: 0x%08x\n", stackptr);       /* No, tell 'em */
                        break;
                }
        
                if(raddr >= mem_actual) {                               /* Is it within physical RAM? */
                        printf("\n         backtrace terminated - frame outside of RAM: v=0x%08x, p=%08X\n", stackptr, raddr);  /* No, tell 'em */
                        break;
                }
        
                ReadReal(raddr, &sframe[0]);                    /* Fetch the stack frame */

                bframes[i] = sframe[LRindex];                   /* Save the link register */
                
                if(!i) printf("         ");                             /* Indent first time */
                else if(!(i & 7)) printf("\n         ");        /* Skip to new line every 8 */
                printf("0x%08x ", bframes[i]);                  /* Dump the link register */
                
                stackptr = sframe[0];                                   /* Chain back */
        }
        printf("\n");
        if(i >= DUMPFRAMES) printf("      backtrace continues...\n");   /* Say we terminated early */
        if(i) kmod_dump((vm_offset_t *)&bframes[0], i); /* Show what kmods are in trace */
        
}
        


void 
Debugger(const char     *message) {

        int i;
        unsigned int store[8];
        spl_t spl;
        
        spl = splhigh();                                                                /* No interruptions from here on */
        
/*
 *      backtrace for Debugger() call  from panic() if no current debugger
 *      backtrace and return for double panic() call
 */
        if ((panicstr != (char *)0) && 
          (((nestedpanic != 0) && (current_debugger == 1)) || (active_debugger == 0))) {
                print_backtrace(NULL);
                if (nestedpanic != 0)  {
                        splx(spl);
                        return;                                                                 /* Yeah, don't enter again... */
                }
        }
        
        if (debug_mode && debugger_active[cpu_number()]) {      /* Are we already on debugger on this processor? */
                splx(spl);
                return;                                                                         /* Yeah, don't do it again... */
        }

        if ((current_debugger != NO_CUR_DB)) {                  /* If there is a debugger configured, enter it */
                printf("Debugger(%s)\n", message);
                TRAP_DEBUGGER;
                splx(spl);
                return;                                                                         /* Done debugging for a while */
        }

        printf("\nNo debugger configured - dumping debug information\n");
        printf("MSR=%08X\n",mfmsr());
        print_backtrace(NULL);
        splx(spl);
        return;
}

/*
 *              Here's where we attempt to get some diagnostic information dumped out
 *              when the system is really confused.  We will try to get into the 
 *              debugger as well.
 *
 *              We are here with interrupts disabled and on the debug stack.  The savearea
 *              that was passed in is NOT chained to the activation.
 *
 *              save_r3 contains the failure reason code.
 */

void SysChoked(int type, savearea *sv) {                        /* The system is bad dead */

        unsigned int failcode;
        
        mp_disable_preemption();
        disableDebugOuput = FALSE;
        debug_mode = TRUE;

        failcode = sv->save_r3;                                                 /* Get the failure code */
        if(failcode > failUnknown) failcode = failUnknown;      /* Set unknown code code */
        
        kprintf("System Failure: cpu=%d; code=%08X (%s)\n", cpu_number(), sv->save_r3, failNames[failcode]);
        printf("System Failure: cpu=%d; code=%08X (%s)\n", cpu_number(), sv->save_r3, failNames[failcode]);

        print_backtrace((struct ppc_saved_state *)sv);  /* Attempt to print backtrace */
        Call_DebuggerC(type, sv);                                               /* Attempt to get into debugger */

        if ((current_debugger != NO_CUR_DB)) Call_DebuggerC(type, sv);  /* Attempt to get into debugger */

}



/*
 *      When we get here, interruptions are disabled and we are on the debugger stack
 *      Never, ever, ever, ever enable interruptions from here on
 */

int Call_DebuggerC(
        int     type,
        struct ppc_saved_state *saved_state)
{
        int                             directcall, wait;
        vm_offset_t             instr_ptr;
        unsigned int    instr;
        int                     my_cpu, tcpu;

        my_cpu = cpu_number();                                                          /* Get our CPU */

#if     MACH_KDB
        if((debugger_cpu == my_cpu) &&                                          /* Do we already own debugger? */
          debugger_active[my_cpu] &&                                            /* and are we really active? */
          db_recover &&                                                                         /* and have we set up recovery? */
          (current_debugger == KDB_CUR_DB)) {                           /* and are we in KDB (only it handles recovery) */
                kdb_trap(type, saved_state);                                    /* Then reenter it... */
        }
#endif
        
        hw_atomic_add(&debug_mode, 1);                                          /* Indicate we are in debugger */
        debugger_active[my_cpu]++;                                                      /* Show active on our CPU */
        lock_debugger();                                                                        /* Insure that only one CPU is in debugger */

        if(db_im_stepping == my_cpu) {                                          /* Are we just back from a step? */
                enable_preemption_no_check();                                   /* Enable preemption now */
                db_im_stepping = 0xFFFFFFFF;                                    /* Nobody stepping right now */
        }

        if (debugger_debug) {
#if 0
                kprintf("Call_DebuggerC(%d): %08X %08X, debact = %d\n", my_cpu, type, saved_state, debug_mode); /* (TEST/DEBUG) */
#endif
                printf("Call_Debugger: enter - cpu %d, is_slave %d, debugger_cpu %d, pc %08X\n",
                   my_cpu, debugger_is_slave[my_cpu], debugger_cpu, saved_state->srr0);
        }
        
        if (instr_ptr = (vm_offset_t)LRA(PPC_SID_KERNEL, (void *)(saved_state->srr0))) {
                instr = ml_phys_read(instr_ptr);                                /* Get the trap that caused entry */
        } 
        else instr = 0;

#if 0
        if (debugger_debug) kprintf("Call_DebuggerC(%d): instr_ptr = %08X, instr = %08X\n", my_cpu, instr_ptr, instr);  /* (TEST/DEBUG) */
#endif

        if (db_breakpoints_inserted) cpus_holding_bkpts++;      /* Bump up the holding count */
        if (debugger_cpu == -1 && !debugger_is_slave[my_cpu]) {
#if 0
                if (debugger_debug) kprintf("Call_DebuggerC(%d): lasttrace = %08X\n", my_cpu, lastTrace);       /* (TEST/DEBUG) */
#endif
                debugger_cpu = my_cpu;                                                  /* Show that we are debugger */
                lastTrace = LLTraceSet(0);                                              /* Disable low-level tracing */

                for(tcpu = 0; tcpu < NCPUS; tcpu++) {                   /* Stop all the other guys */
                        if(tcpu == my_cpu) continue;                            /* Don't diddle ourselves */
                        hw_atomic_add(&debugger_sync, 1);                       /* Count signal sent */
                        (void)cpu_signal(tcpu, SIGPdebug, 0 ,0);        /* Tell 'em to enter debugger */
                }
                (void)hw_cpu_sync(&debugger_sync, LockTimeOut); /* Wait for the other processors to enter debug */
                debugger_sync = 0;                                                              /* We're done with it */
        } 
        else if (debugger_cpu != my_cpu)  goto debugger_exit;   /* We are not debugger, don't continue... */
        

        if (instr == TRAP_DIRECT_INST) {
                disableDebugOuput = FALSE;
                print_backtrace(saved_state);
        }

        switch_debugger = 0;                                                            /* Make sure switch request is off */
        directcall = 1;                                                                         /* Assume direct call */

        if (saved_state->srr1 & MASK(SRR1_PRG_TRAP)) {          /* Trap instruction? */
                
                directcall = 0;                                                                 /* We had a trap not a direct call */

                switch (instr) {                                                                /* Select trap type */

#if     MACH_KDP
                        case BREAK_TO_KDP0:                                                     /* Breakpoint into KDP? */
                        case BREAK_TO_KDP1:                                                     /* Breakpoint into KDP? */
                                current_debugger = KDP_CUR_DB;                  /* Yes, set KDP */
                                kdp_trap(type, saved_state);                    /* Enter it */
                                break;
#endif
        
#if     MACH_KDB
                        case BREAK_TO_KDB0:                                             /* Breakpoint to KDB (the "good" debugger)? */
                                current_debugger = KDB_CUR_DB;                  /* Yes, set it */
                                kdb_trap(type, saved_state);                    /* Enter it */
                                break;
#endif
                                
                        case TRAP_DEBUGGER_INST:                                        /* Should we enter the current debugger? */
                        case TRAP_DIRECT_INST:                                          /* Should we enter the current debugger? */
                                if (current_debugger == KDP_CUR_DB)     /* Is current KDP? */
                                        kdp_trap(type, saved_state);            /* Yes, enter it */
                                else if (current_debugger == KDB_CUR_DB)        /* Is this KDB? */
                                        kdb_trap(type, saved_state);            /* Yes, go ahead and enter */
                                else goto debugger_error;                               /* No debugger active */
                                break;
                                
                        default:                                                                        /* Unknown/bogus trap type */
                                goto debugger_error;
                }
        }

        while(1) {                                                                                      /* We are here to handle debugger switches */
                
                if(!directcall) {                                                               /* Was this a direct call? */
                        if(!switch_debugger) break;                                     /* No, then leave if no switch requested... */

/*
 *                      Note: we can only switch to a debugger we have.  Ignore bogus switch requests.
 */
#if 0
                        if (debugger_debug) kprintf("Call_DebuggerC(%d): switching debuggers\n", my_cpu);       /* (TEST/DEBUG) */
#endif
#if MACH_KDB
                        if(current_debugger == KDP_CUR_DB) current_debugger = KDB_CUR_DB; /* Switch to KDB */
#if MACH_KDP
                        else 
#endif
#endif
#if MACH_KDP
                        if(current_debugger == KDB_CUR_DB) current_debugger = KDP_CUR_DB;               /* Switch to KDP */
#endif
                }
                
                switch_debugger = 0;                                                    /* Clear request */
                directcall = 0;                                                                 /* Clear first-time direct call indication */

                switch (current_debugger) {                                             /* Enter correct debugger */
                
                        case KDP_CUR_DB:                                                        /* Enter KDP */
                                kdp_trap(type, saved_state);
                                break;
                                
                        case KDB_CUR_DB:                                                        /* Enter KDB */
                                kdb_trap(type, saved_state);
                                break;
                                
                        default:                                                                        /* No debugger installed */
                                goto debugger_error;
                                break;
                }
        }

debugger_exit:
#if 0
        if (debugger_debug) kprintf("Call_DebuggerC(%d): exit - inst = %08X, cpu=%d(%d), run=%d\n", my_cpu, 
                instr, my_cpu, debugger_cpu, db_run_mode);      /* (TEST/DEBUG) */
#endif
        if ((instr == TRAP_DEBUGGER_INST) ||                            /* Did we trap to enter debugger? */
                (instr == TRAP_DIRECT_INST)) saved_state->srr0 += TRAP_INST_SIZE;       /* Yes, point past trap */

        if(debugger_cpu == my_cpu) LLTraceSet(lastTrace);       /* Enable tracing on the way out if we are debugger */

        wait = FALSE;                                                                           /* Assume we are not going to wait */
        if (db_run_mode == STEP_CONTINUE) {                                     /* Are we going to run? */
                wait = TRUE;                                                                    /* Yeah, remember to wait for breakpoints to clear */
                debugger_cpu = -1;                                                              /* Release other processor's debuggers */
                debugger_pending[0] = 0;                                                /* Release request (this is a HACK) */
                debugger_pending[1] = 0;                                                /* Release request (this is a HACK) */
                NMIss = 0;                                                                              /* Let NMI bounce */
        }
        
        if(db_run_mode == STEP_ONCE) {                                          /* Are we about to step? */
                disable_preemption();                                                   /* Disable preemption for the step */
                db_im_stepping = my_cpu;                                                /* Remember that I am about to step */
        }

        if (db_breakpoints_inserted) cpus_holding_bkpts--;      /* If any breakpoints, back off count */
        if (debugger_is_slave[my_cpu]) debugger_is_slave[my_cpu]--;     /* If we were a slove, uncount us */
        if (debugger_debug)
                printf("Call_Debugger: exit - cpu %d, debugger_cpu %d, run_mode %d holds %d\n",
                          my_cpu, debugger_cpu, db_run_mode,
                          cpus_holding_bkpts);

        unlock_debugger();                                                                      /* Release the lock */
        debugger_active[my_cpu]--;                                                      /* Say we aren't active anymore */

        if (wait) while(cpus_holding_bkpts);                            /* Wait for breakpoints to clear */

        hw_atomic_sub(&debug_mode, 1);                                          /* Set out of debug now */

        return(1);                                                                                      /* Exit debugger normally */

debugger_error:
        if(db_run_mode != STEP_ONCE) enable_preemption_no_check();      /* Enable preemption, but don't preempt here */
        hw_atomic_sub(&debug_mode, 1);                                          /* Set out of debug now */
        return(0);                                                                                      /* Return in shame... */

}

void lock_debugger(void) {
        int             my_cpu;
        register int    i;

        my_cpu = cpu_number();                                                          /* Get our CPU number */

        while(1) {                                                                                      /* Check until we get it */

                if (debugger_cpu != -1 && debugger_cpu != my_cpu) continue;     /* Someone, not us, is debugger... */
                if (hw_lock_try(&debugger_lock)) {                              /* Get the debug lock */                        
                        if (debugger_cpu == -1 || debugger_cpu == my_cpu) break;        /* Is it us? */
                        hw_lock_unlock(&debugger_lock);                         /* Not us, release lock */
                }
        } 
}

void unlock_debugger(void) {

        hw_lock_unlock(&debugger_lock);

}