Nios II R2 support for GDB.

2015-08-03  Sandra Loosemore  <sandra@codesourcery.com>

	gdb/
	* nios2-tdep.h: Include opcode/nios2.h here.
	(NIOS2_CDX_OPCODE_SIZE): New.
	(struct gdbarch_tdep): Add OP parameter to syscall_next_pc.
	* nios2-tdep.c: Don't include opcode/nios2.h here.
	(nios2_fetch_insn): For R2, try reading 2-byte instruction if
	4-byte read fails.
	(nios2_match_add, nios2_match_sub): Add cases for R2 encodings.
	(nios2_match_addi, nios2_match_orhi): Likewise.
	(nios2_match_stw, nios2_match_ldw): Likewise.
	(nios2_match_rdctl): Likewise.
	(nios2_match_stwm, nios2_match_ldwm): New.
	(nios2_match_branch): Add cases for R2 encodings.
	(nios2_match_jmpi, nios2_match_calli): Likewise.
	(nios2_match_jmpr, nios2_match_callr): Likewise.
	(nios2_match_break, nios2_match_trap): Likewise.
	(nios2_in_epilogue_p): Add R2 support.
	(nios2_analyze_prologue): Update comments.  Recognize R2 CDX
	prologues.
	(nios2_breakpoint_from_pc): Handle R2 instructions.
	(nios2_get_next_pc): Likewise.  Adjust call to
	tdep->syscall_next_pc.
	* nios2-linux-tdep.c (nios2_r1_linux_rt_sigreturn_tramp_frame):
	Renamed from nios2_linux_rt_sigreturn_tramp_frame.  Use
	instruction field macros instead of literal hex values.
	(nios2_r2_linux_rt_sigreturn_tramp_frame): New.
	(nios2_linux_syscall_next_pc): Adjust signature to pass OP.
	Use size field from OP instead of assuming all instructions
	are the same size.
	(nios2_linux_init_abi): Register appropriate unwinder for mach.

	gdb/gdbserver/
	* linux-nios2-low.c (NIOS2_BREAKPOINT): Conditionalize for
	arch variant.
	(CDX_BREAKPOINT): Define for R2.
	(nios2_breakpoint_at): Check for CDX_BREAKPOINT when R2.
	(the_low_target): Add comments.

2 files changed, 31 insertions, 2 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index e01fa46..8862a48 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,11 @@
+2015-08-03  Sandra Loosemore  <sandra@codesourcery.com>
+
+	* linux-nios2-low.c (NIOS2_BREAKPOINT): Conditionalize for
+	arch variant.
+	(CDX_BREAKPOINT): Define for R2.
+	(nios2_breakpoint_at): Check for CDX_BREAKPOINT when R2.
+	(the_low_target): Add comments.
+
 2015-07-30  Yao Qi  <yao.qi@linaro.org>
 
 	* linux-arm-low.c (arm_hwcap): Remove it.
diff --git a/gdb/gdbserver/linux-nios2-low.c b/gdb/gdbserver/linux-nios2-low.c
index 8a7ac28..71542b4 100644
--- a/gdb/gdbserver/linux-nios2-low.c
+++ b/gdb/gdbserver/linux-nios2-low.c
@@ -117,9 +117,17 @@ nios2_set_pc (struct regcache *regcache, CORE_ADDR pc)
   supply_register_by_name (regcache, "pc", newpc.buf);
 }
 
-/* Breakpoint support.  */
+/* Breakpoint support.  Also see comments on nios2_breakpoint_from_pc
+   in nios2-tdep.c.  */
+
+#if defined(__nios2_arch__) && __nios2_arch__ == 2
+#define NIOS2_BREAKPOINT 0xb7fd0020
+#define CDX_BREAKPOINT 0xd7c9
+#else
+#define NIOS2_BREAKPOINT 0x003b6ffa
+#endif
 
-static const unsigned int nios2_breakpoint = 0x003b6ffa;
+static const unsigned int nios2_breakpoint = NIOS2_BREAKPOINT;
 #define nios2_breakpoint_len 4
 
 /* Implement the breakpoint_reinsert_addr linux_target_ops method.  */
@@ -141,6 +149,13 @@ nios2_breakpoint_at (CORE_ADDR where)
 {
   unsigned int insn;
 
+  /* For R2, first check for the 2-byte CDX trap.n breakpoint encoding.  */
+#if defined(__nios2_arch__) && __nios2_arch__ == 2
+  (*the_target->read_memory) (where, (unsigned char *) &insn, 2);
+  if (insn == CDX_BREAKPOINT)
+    return 1;
+#endif
+
   (*the_target->read_memory) (where, (unsigned char *) &insn, 4);
   if (insn == nios2_breakpoint)
     return 1;
@@ -248,6 +263,12 @@ struct linux_target_ops the_low_target =
   NULL,
   nios2_get_pc,
   nios2_set_pc,
+
+  /* We only register the 4-byte breakpoint, even on R2 targets which also
+     support 2-byte breakpoints.  Since there is no supports_z_point_type
+     function provided, gdbserver never inserts software breakpoints itself
+     and instead relies on GDB to insert the breakpoint of the correct length
+     via a memory write.  */
   (const unsigned char *) &nios2_breakpoint,
   nios2_breakpoint_len,
   nios2_reinsert_addr,