[PATCH v1] [powerpc] Remove 512 bytes region limit if using 2nd DAWR.

[Rogerio Alves via Gdb-patches <gdb-patches@sourceware.org>]

Power 10 introduces the 2nd DAWR (second watchpoint) and also removed
a restriction that limit the watch region to 512 bytes.

2020-11-08  Rogerio A. Cardoso  <rcardoso@linux.ibm.com>

gdb/

* ppc-linux-nat.c: (PPC_DEBUG_FEATURE_DATA_BP_ARCH_31): New define.
(region_ok_for_hw_watchpoint): Check if 2nd DAWR is avaliable before set
region.

---
 gdb/ppc-linux-nat.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/gdb/ppc-linux-nat.c b/gdb/ppc-linux-nat.c
index 7131134c10..643400eac5 100644
--- a/gdb/ppc-linux-nat.c
+++ b/gdb/ppc-linux-nat.c
@@ -138,6 +138,11 @@ struct ppc_hw_breakpoint
 #define PPC_DEBUG_FEATURE_DATA_BP_DAWR	0x10
 #endif /* PPC_DEBUG_FEATURE_DATA_BP_DAWR */
 
+/* Feature defined on Linux kernel v5.1: Second watchpoint support.  */
+#ifndef PPC_DEBUG_FEATURE_DATA_BP_ARCH_31
+#define PPC_DEBUG_FEATURE_DATA_BP_ARCH_31 0x20
+#endif /* PPC_DEBUG_FEATURE_DATA_BP_ARCH_31 */
+
 /* The version of the PowerPC HWDEBUG kernel interface that we will use, if
    available.  */
 #define PPC_DEBUG_CURRENT_VERSION 1
@@ -2111,7 +2116,6 @@ ppc_linux_nat_target::region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
       int region_size;
       const struct ppc_debug_info &hwdebug_info = (m_dreg_interface
 						   .hwdebug_info ());
-
       /* 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
@@ -2121,9 +2125,11 @@ ppc_linux_nat_target::region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
 	  && linux_get_hwcap (current_top_target ()) & PPC_FEATURE_BOOKE)
 	return 2;
       /* Check if the processor provides DAWR interface.  */
-      if (hwdebug_info.features & PPC_DEBUG_FEATURE_DATA_BP_DAWR)
+      if (hwdebug_info.features & PPC_DEBUG_FEATURE_DATA_BP_DAWR
+	  && !(hwdebug_info.features & PPC_DEBUG_FEATURE_DATA_BP_ARCH_31))
 	/* DAWR interface allows to watch up to 512 byte wide ranges which
-	   can't cross a 512 byte boundary.  */
+	   can't cross a 512 byte boundary unless it uses a second DARW
+	   ISA 3.1 (P10) which has no such restriction.  */
 	region_size = 512;
       else
 	region_size = hwdebug_info.data_bp_alignment;
-- 
2.17.1