factor/vm/callbacks.cpp

#include "master.hpp"

namespace factor
{

callback_heap::callback_heap(cell size, factor_vm *parent_) :
	seg(new segment(size,true)),
	here(seg->start),
	parent(parent_) {}

callback_heap::~callback_heap()
{
	delete seg;
	seg = NULL;
}

void factor_vm::init_callbacks(cell size)
{
	callbacks = new callback_heap(size,this);
}

void callback_heap::store_callback_operand(code_block *stub, cell index, cell value)
{
	tagged<array> code_template(parent->special_objects[CALLBACK_STUB]);

	cell rel_class = untag_fixnum(array_nth(code_template.untagged(),3 * index + 1));
	cell rel_type  = untag_fixnum(array_nth(code_template.untagged(),3 * index + 2));
	cell offset    = untag_fixnum(array_nth(code_template.untagged(),3 * index + 3));

	relocation_entry rel(
		(relocation_type)rel_type,
		(relocation_class)rel_class,
		offset);

	instruction_operand op(rel,stub,0);
	op.store_value(value);
}

void callback_heap::update(code_block *stub)
{
	store_callback_operand(stub,1,(cell)callback_entry_point(stub));
	stub->flush_icache();
}

code_block *callback_heap::add(cell owner, cell return_rewind)
{
	tagged<array> code_template(parent->special_objects[CALLBACK_STUB]);
	tagged<byte_array> insns(array_nth(code_template.untagged(),0));
	cell size = array_capacity(insns.untagged());

	cell bump = align(size + sizeof(code_block),data_alignment);
	if(here + bump > seg->end) fatal_error("Out of callback space",0);

	free_heap_block *free_block = (free_heap_block *)here;
	free_block->make_free(bump);
	here += bump;

	code_block *stub = (code_block *)free_block;
	stub->owner = owner;
	stub->parameters = false_object;
	stub->relocation = false_object;

	memcpy(stub->entry_point(),insns->data<void>(),size);

	/* Store VM pointer */
	store_callback_operand(stub,0,(cell)parent);

	/* On x86, the RET instruction takes an argument which depends on
	the callback's calling convention */
#if defined(FACTOR_X86) || defined(FACTOR_AMD64)
	store_callback_operand(stub,2,return_rewind);
#endif

	update(stub);

	return stub;
}

struct callback_updater {
	callback_heap *callbacks;

	explicit callback_updater(callback_heap *callbacks_) : callbacks(callbacks_) {}

	void operator()(code_block *stub)
	{
		callbacks->update(stub);
	}
};

void callback_heap::update()
{
	callback_updater updater(this);
	each_callback(updater);
}

void factor_vm::primitive_callback()
{
	cell return_rewind = to_cell(ctx->pop());
	tagged<word> w(ctx->pop());

	w.untag_check(this);
	ctx->push(allot_alien(callbacks->add(w.value(),return_rewind)->entry_point()));
}

}