disas: Implement disassembly output for A64

Use libvixl to implement disassembly output in debug
logs for A64, for use with both AArch64 hosts and targets.

Signed-off-by: Claudio Fontana <claudio.fontana@linaro.org>
[PMM:
 * added support for target disassembly
 * switched to custom QEMUDisassembler so the output format
   matches what QEMU expects
 * make sure we correctly fall back to "just print hex"
   if we didn't build the AArch64 disassembler because of
   lack of a C++ compiler
 * rename from 'aarch64' to 'arm-a64' because this is a
   disassembler for the A64 instruction set
 * merge aarch64.c and aarch64-cxx.cc into one C++ file
 * simplify the aarch64.c<->aarch64-cxx.cc interface]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 87 insertions, 0 deletions

diff --git a/disas/arm-a64.cc b/disas/arm-a64.cc
new file mode 100644
index 0000000..162be0c
--- /dev/null
+++ b/disas/arm-a64.cc
@@ -0,0 +1,87 @@
+/*
+ * ARM A64 disassembly output wrapper to libvixl
+ * Copyright (c) 2013 Linaro Limited
+ * Written by Claudio Fontana
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "a64/disasm-a64.h"
+
+extern "C" {
+#include "disas/bfd.h"
+}
+
+using namespace vixl;
+
+static Decoder *vixl_decoder = NULL;
+static Disassembler *vixl_disasm = NULL;
+
+/* We don't use libvixl's PrintDisassembler because its output
+ * is a little unhelpful (trailing newlines, for example).
+ * Instead we use our own very similar variant so we have
+ * control over the format.
+ */
+class QEMUDisassembler : public Disassembler {
+public:
+    explicit QEMUDisassembler(FILE *stream) : stream_(stream) { }
+    ~QEMUDisassembler() { }
+
+protected:
+    void ProcessOutput(Instruction *instr) {
+        fprintf(stream_, "%08" PRIx32 "      %s",
+                instr->InstructionBits(), GetOutput());
+    }
+
+private:
+    FILE *stream_;
+};
+
+static int vixl_is_initialized(void)
+{
+    return vixl_decoder != NULL;
+}
+
+static void vixl_init(FILE *f) {
+    vixl_decoder = new Decoder();
+    vixl_disasm = new QEMUDisassembler(f);
+    vixl_decoder->AppendVisitor(vixl_disasm);
+}
+
+#define INSN_SIZE 4
+
+/* Disassemble ARM A64 instruction. This is our only entry
+ * point from QEMU's C code.
+ */
+int print_insn_arm_a64(uint64_t addr, disassemble_info *info)
+{
+    uint8_t bytes[INSN_SIZE];
+    uint32_t instr;
+    int status;
+
+    status = info->read_memory_func(addr, bytes, INSN_SIZE, info);
+    if (status != 0) {
+        info->memory_error_func(status, addr, info);
+        return -1;
+    }
+
+    if (!vixl_is_initialized()) {
+        vixl_init(info->stream);
+    }
+
+    instr = bytes[0] | bytes[1] << 8 | bytes[2] << 16 | bytes[3] << 24;
+    vixl_decoder->Decode(reinterpret_cast<Instruction*>(&instr));
+
+    return INSN_SIZE;
+}