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>

configure

@@ -4641,6 +4641,10 @@ for i in $ARCH $TARGET_BASE_ARCH ; do
   arm)
     echo "CONFIG_ARM_DIS=y"  >> $config_target_mak
     echo "CONFIG_ARM_DIS=y"  >> config-all-disas.mak
+    if test -n "${cxx}"; then
+      echo "CONFIG_ARM_A64_DIS=y"  >> $config_target_mak
+      echo "CONFIG_ARM_A64_DIS=y"  >> config-all-disas.mak
+    fi
   ;;
   cris)
     echo "CONFIG_CRIS_DIS=y"  >> $config_target_mak

disas.c

@@ -190,7 +190,7 @@ static int print_insn_od_target(bfd_vma pc, disassemble_info *info)
 /* Disassemble this for me please... (debugging). 'flags' has the following
    values:
     i386 - 1 means 16 bit code, 2 means 64 bit code
-    arm  - bit 0 = thumb, bit 1 = reverse endian
+    arm  - bit 0 = thumb, bit 1 = reverse endian, bit 2 = A64
     ppc  - nonzero means little endian
     other targets - unused
  */
@@ -225,7 +225,15 @@ void target_disas(FILE *out, CPUArchState *env, target_ulong code,
     }
     print_insn = print_insn_i386;
 #elif defined(TARGET_ARM)
-    if (flags & 1) {
+    if (flags & 4) {
+        /* We might not be compiled with the A64 disassembler
+         * because it needs a C++ compiler; in that case we will
+         * fall through to the default print_insn_od case.
+         */
+#if defined(CONFIG_ARM_A64_DIS)
+        print_insn = print_insn_arm_a64;
+#endif
+    } else if (flags & 1) {
         print_insn = print_insn_thumb1;
     } else {
         print_insn = print_insn_arm;
@@ -356,6 +364,8 @@ void disas(FILE *out, void *code, unsigned long size)
 #elif defined(_ARCH_PPC)
     s.info.disassembler_options = (char *)"any";
     print_insn = print_insn_ppc;
+#elif defined(__aarch64__) && defined(CONFIG_ARM_A64_DIS)
+    print_insn = print_insn_arm_a64;
 #elif defined(__alpha__)
     print_insn = print_insn_alpha;
 #elif defined(__sparc__)

disas/Makefile.objs

@@ -1,5 +1,10 @@
+
 common-obj-$(CONFIG_ALPHA_DIS) += alpha.o
 common-obj-$(CONFIG_ARM_DIS) += arm.o
+common-obj-$(CONFIG_ARM_A64_DIS) += arm-a64.o
+common-obj-$(CONFIG_ARM_A64_DIS) += libvixl/
+libvixldir = $(SRC_PATH)/disas/libvixl
+$(obj)/arm-a64.o: QEMU_CFLAGS += -I$(libvixldir)
 common-obj-$(CONFIG_CRIS_DIS) += cris.o
 common-obj-$(CONFIG_HPPA_DIS) += hppa.o
 common-obj-$(CONFIG_I386_DIS) += i386.o

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;
+}

disas/libvixl/Makefile.objs

@@ -0,0 +1,8 @@
+libvixl_OBJS = utils.o \
+               a64/instructions-a64.o \
+               a64/decoder-a64.o \
+               a64/disasm-a64.o
+
+$(addprefix $(obj)/,$(libvixl_OBJS)): QEMU_CFLAGS += -I$(SRC_PATH)/disas/libvixl
+
+common-obj-$(CONFIG_ARM_A64_DIS) += $(libvixl_OBJS)

include/disas/bfd.h

@@ -379,6 +379,7 @@ int print_insn_h8300            (bfd_vma, disassemble_info*);
 int print_insn_h8300h           (bfd_vma, disassemble_info*);
 int print_insn_h8300s           (bfd_vma, disassemble_info*);
 int print_insn_h8500            (bfd_vma, disassemble_info*);
+int print_insn_arm_a64          (bfd_vma, disassemble_info*);
 int print_insn_alpha            (bfd_vma, disassemble_info*);
 disassembler_ftype arc_get_disassembler (int, int);
 int print_insn_arm              (bfd_vma, disassemble_info*);

target-arm/translate-a64.c

@@ -8105,7 +8105,7 @@ done_generating:
         qemu_log("----------------\n");
         qemu_log("IN: %s\n", lookup_symbol(pc_start));
         log_target_disas(env, pc_start, dc->pc - pc_start,
-                         dc->thumb | (dc->bswap_code << 1));
+                         4 | (dc->bswap_code << 1));
         qemu_log("\n");
     }
 #endif