[ARM] Make thumb2_breakpoint static again

This patch makes thumb2_breakpoint static.  When writing this patch,
I find the only reason we keep thumb2_breakpoint extern is that it
is used as an argument passed to arm_gdbserver_get_next_pcs.  However,
field arm_thumb2_breakpoint is only used in a null check in
thumb_get_next_pcs_raw, so I wonder why do need to pass thumb2_breakpoint
to arm_gdbserver_get_next_pcs.

thumb2_breakpoint was added by Daniel Jacobowitz in order to support
single-step IT block
https://sourceware.org/ml/gdb-patches/2010-01/msg00624.html  the logic
there was if we have 32-bit thumb-2 breakpoint defined, we can safely
single-step IT block, otherwise, we can't.  Daniel didn't want to use
16-bit thumb BKPT instruction, because it triggers even on instruction
which should be executed.  Secondly, using 16-bit thumb illegal
instruction on top of 32-bit thumb instruction may break the meaning of
original IT blocks, because the other 16-bit can be regarded as an
instruction.  See more explanations from Daniel's kernel patch
http://www.spinics.net/lists/arm-kernel/msg80476.html

Let us back to this patch, GDB/GDBserver can safely single step
IT block if thumb2_breakpoint is defined, but the single step logic
doesn't have to know the thumb-2 breakpoint instruction.  Only
breakpoint insertion mechanism decides to use which breakpoint
instruction.  In the software single step code, instead of pass
thumb2_breakpoint, we can pass a boolean variable
has_thumb2_breakpoint indicate whether the target has thumb-2
breakpoint defined, which is equivalent to the original code.

Regression tested on arm-linux.  No regression.

gdb:

2016-01-14  Yao Qi  <yao.qi@linaro.org>

	* arch/arm-get-next-pcs.c (arm_get_next_pcs_ctor): Change
	argument arm_thumb2_breakpoint to has_thumb2_breakpoint.
	(thumb_get_next_pcs_raw): Check has_thumb2_breakpoint
	instead.
	* arch/arm-get-next-pcs.h (struct arm_get_next_pcs)
	<arm_thumb2_breakpoint>: Remove.
	<has_thumb2_breakpoint>: New field.
	(arm_get_next_pcs_ctor): Update declaration.
	* arm-linux-tdep.c (arm_linux_software_single_step): Pass
	1 to arm_get_next_pcs_ctor.
	* arm-tdep.c (arm_software_single_step): Pass 0 to
	arm_get_next_pcs_ctor.

gdb/gdbserver:

2016-01-14  Yao Qi  <yao.qi@linaro.org>

	* linux-aarch32-low.c (thumb2_breakpoint): Make it static.
	* linux-aarch32-low.h (thumb2_breakpoint): Remove declaration.
	* linux-arm-low.c (arm_gdbserver_get_next_pcs): Pass 1 to
	arm_get_next_pcs_ctor.

4 files changed, 9 insertions, 4 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 757424c..a76bb14 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,10 @@
+2016-01-14  Yao Qi  <yao.qi@linaro.org>
+
+	* linux-aarch32-low.c (thumb2_breakpoint): Make it static.
+	* linux-aarch32-low.h (thumb2_breakpoint): Remove declaration.
+	* linux-arm-low.c (arm_gdbserver_get_next_pcs): Pass 1 to
+	arm_get_next_pcs_ctor.
+
 2016-01-12  Josh Stone  <jistone@redhat.com>
 	    Philippe Waroquiers  <philippe.waroquiers@skynet.be>
 
diff --git a/gdb/gdbserver/linux-aarch32-low.c b/gdb/gdbserver/linux-aarch32-low.c
index ed66e08..2bbbb24 100644
--- a/gdb/gdbserver/linux-aarch32-low.c
+++ b/gdb/gdbserver/linux-aarch32-low.c
@@ -45,7 +45,7 @@ static const unsigned long arm_breakpoint = arm_abi_breakpoint;
 #define arm_breakpoint_len 4
 static const unsigned short thumb_breakpoint = 0xde01;
 #define thumb_breakpoint_len 2
-const unsigned short thumb2_breakpoint[] = { 0xf7f0, 0xa000 };
+static const unsigned short thumb2_breakpoint[] = { 0xf7f0, 0xa000 };
 #define thumb2_breakpoint_len 4
 
 /* Some older versions of GNU/Linux and Android do not define
diff --git a/gdb/gdbserver/linux-aarch32-low.h b/gdb/gdbserver/linux-aarch32-low.h
index 5c68454..434a523 100644
--- a/gdb/gdbserver/linux-aarch32-low.h
+++ b/gdb/gdbserver/linux-aarch32-low.h
@@ -15,8 +15,6 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
-extern const unsigned short thumb2_breakpoint[];
-
 extern struct regs_info regs_info_aarch32;
 
 void arm_fill_gregset (struct regcache *regcache, void *buf);
diff --git a/gdb/gdbserver/linux-arm-low.c b/gdb/gdbserver/linux-arm-low.c
index d967e58..927a6fa 100644
--- a/gdb/gdbserver/linux-arm-low.c
+++ b/gdb/gdbserver/linux-arm-low.c
@@ -942,7 +942,7 @@ arm_gdbserver_get_next_pcs (CORE_ADDR pc, struct regcache *regcache)
 			 /* Byte order is ignored assumed as host.  */
 			 0,
 			 0,
-			 (const gdb_byte *) &thumb2_breakpoint,
+			 1,
 			 regcache);
 
   next_pcs = arm_get_next_pcs (&next_pcs_ctx, pc);