Author: jhb
Date: Sat Aug 12 18:42:54 2017
New Revision: 322437
URL: https://svnweb.freebsd.org/changeset/base/322437

Log:
  Reliably enable debug exceptions on all CPUs.
  
  Previously, debug exceptions were only enabled on the boot CPU if
  DDB was enabled in the dbg_monitor_init() function.  APs also called
  this function, but since mp_machdep.c doesn't include opt_ddb.h, the
  APs ended up calling an empty stub defined in <machine/debug_monitor.h>
  instead of the real function.  Also, if DDB was not enabled in the kernel,
  the boot CPU would not enable debug exceptions.
  
  Fix this by adding a new dbg_init() function that always clears the OS
  lock to enable debug exceptions which the boot CPU and the APs call.
  This function also calls dbg_monitor_init() to enable hardware breakpoints
  from DDB on all CPUs if DDB is enabled.  Eventually base support for
  hardware breakpoints/watchpoints will need to move out of the DDB-only
  debug_monitor.c for use by userland debuggers.
  
  Reviewed by:  andrew
  Differential Revision:        https://reviews.freebsd.org/D12001

Modified:
  head/sys/arm64/arm64/debug_monitor.c
  head/sys/arm64/arm64/machdep.c
  head/sys/arm64/arm64/mp_machdep.c
  head/sys/arm64/include/machdep.h

Modified: head/sys/arm64/arm64/debug_monitor.c
==============================================================================
--- head/sys/arm64/arm64/debug_monitor.c        Sat Aug 12 18:38:18 2017        
(r322436)
+++ head/sys/arm64/arm64/debug_monitor.c        Sat Aug 12 18:42:54 2017        
(r322437)
@@ -453,15 +453,12 @@ dbg_monitor_init(void)
 {
        u_int i;
 
-       /* Clear OS lock */
-       WRITE_SPECIALREG(OSLAR_EL1, 0);
-
        /* Find out many breakpoints and watchpoints we can use */
        dbg_watchpoint_num = ((READ_SPECIALREG(ID_AA64DFR0_EL1) >> 20) & 0xf) + 
1;
        dbg_breakpoint_num = ((READ_SPECIALREG(ID_AA64DFR0_EL1) >> 12) & 0xf) + 
1;
 
        if (bootverbose && PCPU_GET(cpuid) == 0) {
-               db_printf("%d watchpoints and %d breakpoints supported\n",
+               printf("%d watchpoints and %d breakpoints supported\n",
                    dbg_watchpoint_num, dbg_breakpoint_num);
        }
 

Modified: head/sys/arm64/arm64/machdep.c
==============================================================================
--- head/sys/arm64/arm64/machdep.c      Sat Aug 12 18:38:18 2017        
(r322436)
+++ head/sys/arm64/arm64/machdep.c      Sat Aug 12 18:42:54 2017        
(r322437)
@@ -1051,11 +1051,24 @@ initarm(struct arm64_bootparams *abp)
        mutex_init();
        init_param2(physmem);
 
-       dbg_monitor_init();
+       dbg_init();
        kdb_init();
        pan_enable();
 
        early_boot = 0;
+}
+
+void
+dbg_init(void)
+{
+
+       /* Clear OS lock */
+       WRITE_SPECIALREG(OSLAR_EL1, 0);
+
+       /* This permits DDB to use debug registers for watchpoints. */
+       dbg_monitor_init();
+
+       /* TODO: Eventually will need to initialize debug registers here. */
 }
 
 #ifdef DDB

Modified: head/sys/arm64/arm64/mp_machdep.c
==============================================================================
--- head/sys/arm64/arm64/mp_machdep.c   Sat Aug 12 18:38:18 2017        
(r322436)
+++ head/sys/arm64/arm64/mp_machdep.c   Sat Aug 12 18:42:54 2017        
(r322437)
@@ -52,7 +52,6 @@ __FBSDID("$FreeBSD$");
 #include <vm/vm_extern.h>
 #include <vm/vm_kern.h>
 
-#include <machine/debug_monitor.h>
 #include <machine/machdep.h>
 #include <machine/intr.h>
 #include <machine/smp.h>
@@ -272,7 +271,7 @@ init_secondary(uint64_t cpu)
        vfp_init();
 #endif
 
-       dbg_monitor_init();
+       dbg_init();
        pan_enable();
 
        /* Enable interrupts */

Modified: head/sys/arm64/include/machdep.h
==============================================================================
--- head/sys/arm64/include/machdep.h    Sat Aug 12 18:38:18 2017        
(r322436)
+++ head/sys/arm64/include/machdep.h    Sat Aug 12 18:42:54 2017        
(r322437)
@@ -48,6 +48,7 @@ extern enum arm64_bus arm64_bus_method;
 extern vm_paddr_t physmap[];
 extern u_int physmap_idx;
 
+void dbg_init(void);
 void initarm(struct arm64_bootparams *);
 extern void (*pagezero)(void *);
 
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