Directly link libcapstone for easier development

This lets us use libcapstone directly from miniruby so we don't need a
Ruby Gem to to dev work.

Example usage:

```ruby
def foo(x)
  if x < 1
    "wow"
  else
    "neat"
  end
end

iseq = RubyVM::InstructionSequence.of(method(:foo))
puts UJIT.disasm(iseq)
100.times { foo 1 }
puts UJIT.disasm(iseq)
```

Then in the terminal

```
$ ./miniruby test.rb

== disasm: #<ISeq:foo@test.rb:1 (1,0)-(7,3)> (catch: FALSE)
local table (size: 1, argc: 1 [opts: 0, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 1] x@0<Arg>
0000 getlocal_WC_0                          x@0                       (   2)[LiCa]
0002 putobject_INT2FIX_1_
0003 opt_lt                                 <calldata!mid:<, argc:1, ARGS_SIMPLE>
0005 branchunless                           10
0007 putstring                              "wow"                     (   3)[Li]
0009 leave                                                            (   7)[Re]
0010 putstring                              "neat"                    (   5)[Li]
0012 leave                                                            (   7)[Re]

== ISEQ RANGE: 10 -> 10 ========================================================
        0x0:    movabs  rax, 0x7fe816e2d1a0
        0xa:    mov     qword ptr [rdi], rax
        0xd:    mov     r8, rax
        0x10:   mov     r9, rax
        0x13:   mov     r11, r12
        0x16:   jmp     qword ptr [rax]
== ISEQ RANGE: 0 -> 7 ==========================================================
        0x0:    mov     rax, qword ptr [rdi + 0x20]
        0x4:    mov     rax, qword ptr [rax - 0x18]
        0x8:    mov     qword ptr [rdx], rax
        0xb:    mov     qword ptr [rdx + 8], 3
        0x13:   movabs  rax, 0x7fe817808200
        0x1d:   test    byte ptr [rax + 0x3e6], 1
        0x24:   jne     0x3ffff7b
        0x2a:   test    byte ptr [rdx], 1
        0x2d:   je      0x3ffff7b
        0x33:   test    byte ptr [rdx + 8], 1
        0x37:   je      0x3ffff7b
        0x3d:   mov     rax, qword ptr [rdx]
        0x40:   cmp     rax, qword ptr [rdx + 8]
        0x44:   movabs  rax, 0
        0x4e:   movabs  rcx, 0x14
        0x58:   cmovl   rax, rcx
        0x5c:   mov     qword ptr [rdx], rax
        0x5f:   test    qword ptr [rdx], -9
        0x66:   jne     0x3ffffd5
```

Make sure to `brew install pkg-config capstone`

6 files changed, 93 insertions, 35 deletions

diff --git a/common.mk b/common.mk
index 9cab62b60a..73f4c57473 100644
--- a/common.mk
+++ b/common.mk
@@ -1063,6 +1063,7 @@ BUILTIN_RB_SRCS = \
 		$(srcdir)/nilclass.rb \
 		$(srcdir)/prelude.rb \
 		$(srcdir)/gem_prelude.rb \
+		$(srcdir)/ujit.rb \
 		$(empty)
 BUILTIN_RB_INCS = $(BUILTIN_RB_SRCS:.rb=.rbinc)
 
@@ -15641,6 +15642,7 @@ ujit_core.$(OBJEXT): {$(VPATH)}vm_core.h
 ujit_core.$(OBJEXT): {$(VPATH)}vm_debug.h
 ujit_core.$(OBJEXT): {$(VPATH)}vm_opts.h
 ujit_core.$(OBJEXT): {$(VPATH)}vm_sync.h
+ujit_iface.$(OBJEXT): {$(VPATH)}ujit.rbinc
 ujit_iface.$(OBJEXT): $(CCAN_DIR)/check_type/check_type.h
 ujit_iface.$(OBJEXT): $(CCAN_DIR)/container_of/container_of.h
 ujit_iface.$(OBJEXT): $(CCAN_DIR)/list/list.h
diff --git a/configure.ac b/configure.ac
index fa844eb7cd..b34004da1e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1229,6 +1229,17 @@ AC_CHECK_LIB(dl, dlopen)	# Dynamic linking for SunOS/Solaris and SYSV
 AC_CHECK_LIB(dld, shl_load)	# Dynamic linking for HP-UX
 AC_CHECK_LIB(socket, shutdown)  # SunOS/Solaris
 
+if pkg-config --exists capstone; then
+   CAPSTONE_CFLAGS=`pkg-config --cflags capstone`
+   CAPSTONE_LIB_L=`pkg-config --libs-only-L capstone`
+   LDFLAGS="$LDFLAGS $CAPSTONE_LIB_L"
+   CFLAGS="$CFLAGS $CAPSTONE_CFLAGS"
+else
+   AC_MSG_ERROR(Please install capstone and pkg-config)
+fi
+
+AC_CHECK_LIB(capstone, cs_open) # Capstone
+
 dnl Checks for header files.
 AC_HEADER_DIRENT
 dnl AC_HEADER_STDC has been checked in AC_USE_SYSTEM_EXTENSIONS
diff --git a/inits.c b/inits.c
index f69ee73a89..059055246a 100644
--- a/inits.c
+++ b/inits.c
@@ -99,6 +99,7 @@ rb_call_builtin_inits(void)
     BUILTIN(timev);
     BUILTIN(nilclass);
     BUILTIN(marshal);
+    BUILTIN(ujit);
     Init_builtin_prelude();
 }
 #undef CALL
diff --git a/misc/ujit_disasm.rb b/misc/ujit_disasm.rb
deleted file mode 100644
index 38eb139c33..0000000000
--- a/misc/ujit_disasm.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-begin
-    require "crabstone"
-    require "stringio"
-rescue LoadError => e
-  puts "Please install crabstone, which is needed by the disassembler:"
-  puts "  $ brew install capstone"
-  puts "  $ gem install capstone"
-  raise e
-end
-
-module UJIT
-  def self.disasm(iseq)
-    blocks = UJIT.blocks_for(iseq)
-    return if blocks.empty?
-
-    io = StringIO.new
-
-    cs = Crabstone::Disassembler.new(Crabstone::ARCH_X86, Crabstone::MODE_64)
-
-    io.puts iseq.disasm
-
-    blocks.sort_by(&:address).reverse.each do |block|
-      io.puts "== ISEQ RANGE: #{block.iseq_start_index} -> #{block.iseq_end_index} ".ljust(80, "=")
-      cs.disasm(block.code, 0).each do |i|
-        io.printf(
-          "\t0x%<address>x:\t%<instruction>s\t%<details>s\n",
-          address: i.address,
-          instruction: i.mnemonic,
-          details: i.op_str
-        )
-      end
-    end
-    io.string
-  end
-end
diff --git a/ujit.rb b/ujit.rb
new file mode 100644
index 0000000000..cdfb886795
--- /dev/null
+++ b/ujit.rb
@@ -0,0 +1,31 @@
+module UJIT
+  def omg
+  end
+
+  def self.disasm(iseq)
+    blocks = UJIT.blocks_for(iseq)
+    return if blocks.empty?
+
+    str = ""
+
+    cs = UJIT::Disasm.open(UJIT::Disasm::ARCH_X86, UJIT::Disasm::MODE_64)
+
+    str << iseq.disasm
+    str << "\n"
+
+    blocks.sort_by(&:address).reverse.each do |block|
+      str << "== ISEQ RANGE: #{block.iseq_start_index} -> #{block.iseq_end_index} ".ljust(80, "=")
+      str << "\n"
+
+      cs.disasm(block.code, 0).each do |i|
+        str << sprintf(
+          "\t0x%<address>x:\t%<instruction>s\t%<details>s\n",
+          address: i.address,
+          instruction: i.mnemonic,
+          details: i.op_str
+        )
+      end
+    end
+    str
+  end
+end
diff --git a/ujit_iface.c b/ujit_iface.c
index fac401a7b2..349aa40b1b 100644
--- a/ujit_iface.c
+++ b/ujit_iface.c
@@ -13,8 +13,12 @@
 #include "ujit_codegen.h"
 #include "ujit_core.h"
 #include "ujit_hooks.inc"
+#include "ujit.rbinc"
+#include <capstone/capstone.h>
 
 VALUE cUjitBlock;
+VALUE cUjitDisasm;
+VALUE cUjitDisasmInsn;
 
 extern st_table * version_tbl;
 extern codeblock_t *cb;
@@ -25,6 +29,12 @@ static const rb_data_type_t ujit_block_type = {
     0, 0, RUBY_TYPED_FREE_IMMEDIATELY
 };
 
+static const rb_data_type_t ujit_disasm_type = {
+    "UJIT/Disasm",
+    {0, (void(*)(void *))cs_close, 0, },
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+};
+
 bool rb_ujit_enabled;
 
 // Hash table of encoded instructions
@@ -366,6 +376,36 @@ iseq_end_index(VALUE self)
     return INT2NUM(block->end_idx);
 }
 
+static VALUE
+ujit_disasm_open(VALUE mod, VALUE arch, VALUE mode)
+{
+    csh * handle;
+    VALUE disasm = TypedData_Make_Struct(cUjitDisasm, csh, &ujit_disasm_type, handle);
+    cs_open(NUM2INT(arch), NUM2INT(mode), handle);
+    return disasm;
+}
+
+static VALUE
+ujit_disasm(VALUE self, VALUE code, VALUE from)
+{
+    size_t count;
+    csh * handle;
+    cs_insn *insns;
+
+    TypedData_Get_Struct(self, csh, &ujit_disasm_type, handle);
+    count = cs_disasm(*handle, StringValuePtr(code), RSTRING_LEN(code), NUM2INT(from), 0, &insns);
+    VALUE insn_list = rb_ary_new_capa(count);
+
+    for (size_t i = 0; i < count; i++) {
+        VALUE vals = rb_ary_new_from_args(3, LONG2NUM(insns[i].address),
+                rb_str_new2(insns[i].mnemonic),
+                rb_str_new2(insns[i].op_str));
+        rb_ary_push(insn_list, rb_struct_alloc(cUjitDisasmInsn, vals));
+    }
+    cs_free(insns, count);
+    return insn_list;
+}
+
 void
 rb_ujit_init(void)
 {
@@ -389,6 +429,14 @@ rb_ujit_init(void)
     rb_define_method(cUjitBlock, "iseq_start_index", iseq_start_index, 0);
     rb_define_method(cUjitBlock, "iseq_end_index", iseq_end_index, 0);
 
+    cUjitDisasm = rb_define_class_under(mUjit, "Disasm", rb_cObject);
+    rb_define_const(cUjitDisasm, "ARCH_X86", INT2NUM(CS_ARCH_X86));
+    rb_define_const(cUjitDisasm, "MODE_64", INT2NUM(CS_MODE_64));
+    rb_define_module_function(cUjitDisasm, "open", ujit_disasm_open, 2);
+    rb_define_method(cUjitDisasm, "disasm", ujit_disasm, 2);
+
+    cUjitDisasmInsn = rb_struct_define_under(cUjitDisasm, "Insn", "address", "mnemonic", "op_str", NULL);
+
     // Initialize the GC hooks
     method_lookup_dependency = st_init_numtable();
     struct ujit_root_struct *root;