[PATCH] Enable hw watchpoint with longer ranges using DAWR on Power

[Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>]

Hi,

The new DAWR interface provided by the next generation of Power processors
(Power ISA Version 2.07) included in the kernel this year allows gdb to use
hardware watchpoint with longer ranges (up to 512 bytes wide), which can't cross
a 512 byte boundary [1]. The patch below enables the usage of this new feature,
currently exported to the userspace as PPC_DEBUG_FEATURE_DATA_BP_DAWR via struct
ppc_debug_info [2]. Ok?

Thanks and regards,
--
Edjunior

[1] http://patchwork.ozlabs.org/patch/215520/
[2] http://patchwork.ozlabs.org/patch/229888/

gdb/ChangeLog
2013-07-02  Edjunior Barbosa Machado  <emachado@linux.vnet.ibm.com>

	* ppc-linux-nat.c (PPC_DEBUG_FEATURE_DATA_BP_DAWR): New define.
	(ppc_linux_region_ok_for_hw_watchpoint): Add checking to use the new
	DAWR interface for longer ranges hardware watchpoint (up to 512 bytes).

---
 gdb/ppc-linux-nat.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/gdb/ppc-linux-nat.c b/gdb/ppc-linux-nat.c
index 65d4f4a..dd35624 100644
--- a/gdb/ppc-linux-nat.c
+++ b/gdb/ppc-linux-nat.c
@@ -177,7 +177,11 @@ struct ppc_hw_breakpoint
         (1<<((n)+PPC_BREAKPOINT_CONDITION_BE_SHIFT))
 #endif /* PPC_PTRACE_GETHWDBGINFO */
 
-
+/* New feature defined on Linux kernel v3.9: DAWR interface, that enables
+   wider watchpoint (up to 512 bytes).  */
+#ifndef PPC_DEBUG_FEATURE_DATA_BP_DAWR
+#define PPC_DEBUG_FEATURE_DATA_BP_DAWR	0x10
+#endif /* PPC_DEBUG_FEATURE_DATA_BP_DAWR */
 
 /* Similarly for the general-purpose (gp0 -- gp31)
    and floating-point registers (fp0 -- fp31).  */
@@ -1502,6 +1506,7 @@ ppc_linux_region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
      to determine the hardcoded watchable region for watchpoints.  */
   if (have_ptrace_booke_interface ())
     {
+      int region_size;
       /* Embedded DAC-based processors, like the PowerPC 440 have ranged
 	 watchpoints and can watch any access within an arbitrary memory
 	 region. This is useful to watch arrays and structs, for instance.  It
@@ -1510,11 +1515,17 @@ ppc_linux_region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
 	  && booke_debug_info.features & PPC_DEBUG_FEATURE_DATA_BP_RANGE
 	  && ppc_linux_get_hwcap () & PPC_FEATURE_BOOKE)
 	return 2;
+      /* Check if the processor provides DAWR interface.  */
+      if (booke_debug_info.features & PPC_DEBUG_FEATURE_DATA_BP_DAWR)
+	/* DAWR interface allows to watch up to 512 byte wide ranges which
+ 	   can't cross a 512 byte boundary.  */
+        region_size = 512;
+      else
+	region_size = booke_debug_info.data_bp_alignment;
       /* Server processors provide one hardware watchpoint and addr+len should
          fall in the watchable region provided by the ptrace interface.  */
-      if (booke_debug_info.data_bp_alignment
-	  && (addr + len > (addr & ~(booke_debug_info.data_bp_alignment - 1))
-	      + booke_debug_info.data_bp_alignment))
+      if (region_size
+	  && (addr + len > (addr & ~(region_size - 1)) + region_size))
 	return 0;
     }
   /* addr+len must fall in the 8 byte watchable region for DABR-based
-- 
1.8.2.1