adder.cpp

//
// adder.cpp
//
// CXXFLAGS="-std=c++14 -O3 -ggdb -ggdb3" make adder
//

#include <iostream>
#include <cstdint>

#include <sys/mman.h>

class Adder final {
public:
	Adder(uint32_t value)
		: _push_rbp(0x55),
		  _mov_rbp_rsp{0x48, 0x89, 0xe5},
		  _lea_eax_rdi_{0x8d, 0x47},
		  _value(value),
		  _pop_rbp(0x5d),
		  _ret(0xc3) {
	}

	int (*entry())(int) {
		return reinterpret_cast<int(*)(int)>(this);
	}

private:
	uint8_t const _push_rbp;        // push rbp
	uint8_t const _mov_rbp_rsp[3];  // mov rbp, rsp
	uint8_t const _lea_eax_rdi_[2];
	uint8_t const _value;           // lea eax, [rdi + value]
	uint8_t const _pop_rbp;         // pop rbp
	uint8_t const _ret;             // ret
} __attribute__((packed));

int main() {
	Adder* adder_heap = reinterpret_cast<Adder*>(::mmap(nullptr, 4096, PROT_EXEC|PROT_READ|PROT_WRITE, MAP_ANON | MAP_PRIVATE, 0, 0));
	auto adder1 = new (adder_heap) Adder(1);
	auto adder2 = new (adder_heap + 1) Adder(2);
	auto add1 = adder1->entry();
	auto add2 = adder2->entry();
	for (int i = 0; i < 10; i++) {
		std::cout << add1(i) << std::endl;
		std::cout << add2(i) << std::endl;
	}
	::munmap(adder_heap, 4096);
	
	return 0;
}