debug: add interactive debug mode

Introduce a new interactive debug cli which can be started by invoking the
ucode interpreter with the `-x` flag.

The main debugger functionality resides in the debug library while the cli
frontend just gains some minimal amount of code to load and instantiate the
debug library when the `-x` option is passed.

As a precondition for the new debug functionality, the ucode VM has been
extended with low level breakpoint support.

Signed-off-by: Jo-Philipp Wich <[email protected]>

include/ucode/types.h

@@ -290,8 +290,14 @@ typedef struct {
 	bool mcall, strict;
 } uc_callframe_t;
 
+typedef struct uc_breakpoint {
+	uint8_t *ip;
+	void (*cb)(uc_vm_t *, struct uc_breakpoint *);
+} uc_breakpoint_t;
+
 uc_declare_vector(uc_callframes_t, uc_callframe_t);
 uc_declare_vector(uc_stack_t, uc_value_t *);
+uc_declare_vector(uc_breakpoints_t, uc_breakpoint_t *);
 
 typedef struct printbuf uc_stringbuf_t;
 
@@ -308,7 +314,7 @@ struct uc_vm {
 	uc_source_t *sources;
 	uc_weakref_t values;
 	uc_resource_types_t restypes;
-	char _reserved[sizeof(uc_modexports_t)];
+	uc_breakpoints_t breakpoints;
 	union {
 		uint32_t u32;
 		int32_t s32;

include/ucode/vm.h

@@ -122,7 +122,7 @@ typedef enum {
 
 #define GC_DEFAULT_INTERVAL 1000
 
-extern uint32_t insns[__I_MAX];
+extern const int8_t insn_operand_bytes[__I_MAX];
 
 void uc_vm_init(uc_vm_t *vm, uc_parse_config_t *config);
 void uc_vm_free(uc_vm_t *vm);