Re: [RFA] procfs.c: TARGET_CAN_USE_HARDWARE_WATCHPOINT via target vector

[Michael Snyder <msnyder@redhat.com>]

Kevin Buettner wrote:
> 
> On Irix, it's possible to debug processes using the o32, n32, and n64
> ABIs from a single gdb.  Unfortunately, due to some limitations with
> the watchpoint support in procfs.c, it is not possible to use hardware
> watchpoints in all cases.  (See patch comments for details.)
> 
> My first cut at a patch simply changed the macro in
> config/mips/nm-irix5.h.  However, since this same solution will be
> required for each platform requiring procfs.c, I decided to use the
> newly added hardware breakpoint facilities in the target vector.
> 
> Okay to commit?

Sure -- but don't you think it should default to zero?
Or is being able to do it the norm?  (I don't remember).

> 
> Kevin
> 
>         * procfs.c (procfs_can_use_hw_breakpoint): New function.
>         (init_procfs_ops): Define ``to_can_use_hw_breakpoint'' for procfs
>         target vector.
>         * config/mips/nm-irix5.h (TARGET_CAN_USE_HARDWARE_WATCHPOINT):
>         Delete.  Add comment regarding this now-deleted target method.
> 
> Index: procfs.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/procfs.c,v
> retrieving revision 1.38
> diff -u -p -r1.38 procfs.c
> --- procfs.c    11 Jul 2002 13:50:49 -0000      1.38
> +++ procfs.c    12 Aug 2002 21:18:34 -0000
> @@ -136,6 +136,8 @@ static int proc_find_memory_regions (int
> 
>  static char * procfs_make_note_section (bfd *, int *);
> 
> +static int procfs_can_use_hw_breakpoint (int, int, int);
> +
>  struct target_ops procfs_ops;          /* the target vector */
> 
>  static void
> @@ -183,6 +185,7 @@ init_procfs_ops (void)
>    procfs_ops.to_has_thread_control  = tc_schedlock;
>    procfs_ops.to_find_memory_regions = proc_find_memory_regions;
>    procfs_ops.to_make_corefile_notes = procfs_make_note_section;
> +  procfs_ops.to_can_use_hw_breakpoint = procfs_can_use_hw_breakpoint;
>    procfs_ops.to_magic               = OPS_MAGIC;
>  }
> 
> @@ -5136,6 +5139,37 @@ procfs_set_watchpoint (ptid_t ptid, CORE
>  #endif /* AIX5 */
>  #endif /* UNIXWARE */
>    return 0;
> +}
> +
> +/* Return non-zero if we can set a hardware watchpoint of type TYPE.  TYPE
> +   is one of bp_hardware_watchpoint, bp_read_watchpoint, bp_write_watchpoint,
> +   or bp_hardware_watchpoint.  CNT is the number of watchpoints used so
> +   far.
> +
> +   Note:  procfs_can_use_hw_breakpoint() is not yet used by all
> +   procfs.c targets due to the fact that some of them still define
> +   TARGET_CAN_USE_HARDWARE_WATCHPOINT.  */
> +
> +static int
> +procfs_can_use_hw_breakpoint (int type, int cnt, int othertype)
> +{
> +#ifndef TARGET_HAS_HARDWARE_WATCHPOINTS
> +  return 0;
> +#else
> +  /* Due to the way that proc_set_watchpoint() is implemented, host
> +     and target pointers must be of the same size.  If they are not,
> +     we can't use hardware watchpoints.  This limitation is due to the
> +     fact that proc_set_watchpoint() calls address_to_host_pointer();
> +     a close inspection of address_to_host_pointer will reveal that
> +     an internal error will be generated when the host and target
> +     pointer sizes are different.  */
> +  if (sizeof (void *) != TYPE_LENGTH (builtin_type_void_data_ptr))
> +    return 0;
> +
> +  /* Other tests here???  */
> +
> +  return 1;
> +#endif
>  }
> 
>  /*
> Index: config/mips/nm-irix5.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/config/mips/nm-irix5.h,v
> retrieving revision 1.5
> diff -u -p -r1.5 nm-irix5.h
> --- config/mips/nm-irix5.h      5 Jun 2002 19:18:24 -0000       1.5
> +++ config/mips/nm-irix5.h      12 Aug 2002 21:18:34 -0000
> @@ -24,7 +24,9 @@
> 
>  #define TARGET_HAS_HARDWARE_WATCHPOINTS
> 
> -#define TARGET_CAN_USE_HARDWARE_WATCHPOINT(type, cnt, ot) 1
> +/* TARGET_CAN_USE_HARDWARE_WATCHPOINT is now defined to go through
> +   the target vector.  For Irix5, procfs_can_use_hw_watchpoint()
> +   should be invoked.  */
> 
>  /* When a hardware watchpoint fires off the PC will be left at the
>     instruction which caused the watchpoint.  It will be necessary for