arch-arm: Add AArch32 HLT Semihosting interface

AArch32 HLT instruction is now able to issue Arm Semihosting commands as
the AArch64 counterpart in either Arm and Thumb mode.

Change-Id: I77da73d2e6a9288c704a5f646f4447022517ceb6
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/8372
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/src/arch/arm/isa/formats/breakpoint.isa b/src/arch/arm/isa/formats/breakpoint.isa
index a22f2de7a..4db470b1e 100644
--- a/src/arch/arm/isa/formats/breakpoint.isa
+++ b/src/arch/arm/isa/formats/breakpoint.isa
@@ -1,6 +1,6 @@
 // -*- mode:c++ -*-
 
-// Copyright (c) 2010 ARM Limited
+// Copyright (c) 2010,2018 ARM Limited
 // All rights reserved
 //
 // The license below extends only to copyright in the software and shall
@@ -87,7 +87,17 @@ output exec {{
     }
 }};
 
-def format Breakpoint() {{
-    decode_block = 'return new Breakpoint(machInst);\n'
+def format ArmBkptHlt() {{
+    decode_block = '''
+    {
+        if (bits(machInst, 21)) {
+            return new Breakpoint(machInst);
+        } else {
+            uint32_t imm16 = (bits(machInst, 19, 8) << 4) |
+                             (bits(machInst,  3, 0) << 0);
+            return new Hlt(machInst, imm16);
+        }
+    }
+    '''
 }};