Re: [PATCH] disable ptrace BookE interface for PowerPC server processors

[Edjunior Barbosa Machado <emachado at linux dot vnet dot ibm dot com>]

On 05/22/2012 02:34 PM, Mark Kettenis wrote:

> But how are you going to handle this when that functionality does
> become available?  


Thanks for the feedback and sorry for the late reply. I was discussing
with the kernel developer responsible for the next version of the ptrace
booke interface and he proposed that the 'features' field from the
struct ppc_debug_info returned by ptrace PPC_PTRACE_GETHWDBGINFO call
could be used to check if its availability. According to him, this field
is currently 0 for servers, but once the new ptrace interface becomes
functional, it will return the flag PPC_DEBUG_FEATURE_DATA_BP_RANGE
enabled. Moreover, this change will not affect the behavior on embedded
processors (which already has PPC_DEBUG_FEATURE_DATA_BP_RANGE and
PPC_DEBUG_FEATURE_DATA_BP_MASK enabled).

Please consider the new version of the patch below.

Thanks,
-- 
Edjunior Barbosa Machado
IBM Linux Technology Center

gdb/
2012-25-05  Edjunior Machado  <emachado@linux.vnet.ibm.com>

	* ppc-linux-nat.c (have_ptrace_booke_interface): disable ptrace booke
	interface for powerpc server processors if not available in kernel.

diff --git a/gdb/ppc-linux-nat.c b/gdb/ppc-linux-nat.c
index 34c40b4..9ffcf88 100644
--- a/gdb/ppc-linux-nat.c
+++ b/gdb/ppc-linux-nat.c
@@ -1421,17 +1421,18 @@ have_ptrace_booke_interface (void)
       /* Check for kernel support for BOOKE debug registers.  */
       if (ptrace (PPC_PTRACE_GETHWDBGINFO, tid, 0, &booke_debug_info) >= 0)
 	{
-	  have_ptrace_booke_interface = 1;
-	  max_slots_number = booke_debug_info.num_instruction_bps
-	    + booke_debug_info.num_data_bps
-	    + booke_debug_info.num_condition_regs;
-	}
-      else
-	{
-	  /* Old school interface and no BOOKE debug registers support.  */
-	  have_ptrace_booke_interface = 0;
-	  memset (&booke_debug_info, 0, sizeof (struct ppc_debug_info));
+	  if (booke_debug_info.features)
+	    {
+	      have_ptrace_booke_interface = 1;
+	      max_slots_number = booke_debug_info.num_instruction_bps
+	        + booke_debug_info.num_data_bps
+	        + booke_debug_info.num_condition_regs;
+	      return have_ptrace_booke_interface;
+	    }
 	}
+      /* Old school interface and no BOOKE debug registers support.  */
+      have_ptrace_booke_interface = 0;
+      memset (&booke_debug_info, 0, sizeof (struct ppc_debug_info));
     }
 
   return have_ptrace_booke_interface;