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202 行
4.9 KiB
202 行
4.9 KiB
#include <array>
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#include <span>
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#include <memory>
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#include <list>
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#include <functional>
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#include <iostream>
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#if defined(__x86_64__)
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#if defined(__GNUG__)
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constexpr bool is_x86_64_linux = true;
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#else
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#if defined(__clang__)
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constexpr bool is_x86_64_linux = true;
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#else
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constexpr bool is_x86_64_linux = false;
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#endif
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#endif
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#else
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constexpr bool is_x86_64_linux = false;
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#endif
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static_assert(is_x86_64_linux, "This code probably only works on x86_64 GNU Extensions C++");
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struct platform_data {
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platform_data() = default;
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platform_data(std::span<char> stack_str)
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: stack_ptr(&*(stack_str.end()-16))
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, base_ptr(stack_ptr)
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{}
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uint64_t rbx, r12, r13, r14, r15;
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void* stack_ptr;
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void* base_ptr;
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void pull() __attribute__((always_inline))
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{
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__asm__ __volatile__(
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"movq %%rsp, %0\n"
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"movq %%rbp, %1\n"
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"movq %%rbx, %2\n"
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"movq %%r12, %3\n"
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"movq %%r13, %4\n"
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"movq %%r14, %5\n"
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"movq %%r15, %6\n"
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: "=m"(stack_ptr)
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, "=m"(base_ptr)
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, "=m"(rbx)
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, "=m"(r12)
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, "=m"(r13)
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, "=m"(r14)
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, "=m"(r15)
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);
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}
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void* push(void* location) __attribute__((always_inline))
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{
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volatile void* volatile tmp = static_cast<char*>(stack_ptr) - sizeof(void*);
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*static_cast<volatile void* volatile * volatile>(tmp) = location;
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__asm__ __volatile__(
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"movq %1, %%rsp\n"
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"movq %2, %%rbp\n"
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"movq %3, %%rbx\n"
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"movq %4, %%r12\n"
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"movq %5, %%r13\n"
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"movq %6, %%r14\n"
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"movq %7, %%r15\n"
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"popq %0\n"
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: "+r"(location)
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: "m"(tmp)
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, "m"(base_ptr)
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, "m"(rbx)
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, "m"(r12)
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, "m"(r13)
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, "m"(r14)
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, "m"(r15)
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: "memory"
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);
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return location;
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}
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};
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enum class process_status {
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inactive = 0,
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running = 1,
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waiting = 2,
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finished = 3,
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zombie = 4
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};
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struct process {
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char* stack;
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size_t sz;
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platform_data scheduling_swapper;
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process_status state = process_status::inactive;
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std::function<void()> fn;
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process(std::function<void()> _fn, size_t _sz = 16384)
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: stack(new char[_sz])
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, sz(_sz)
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, scheduling_swapper(std::span<char>(stack, sz))
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, fn(_fn)
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{}
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process(char* stack_base)
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: stack(stack_base)
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, sz(0)
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{}
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process(const process&) = delete;
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~process() {
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if(sz) delete[] stack;
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}
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};
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__attribute__((noinline)) struct system* spawner (struct system* sys);
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struct system {
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static system sys;
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std::list<std::unique_ptr<process>>
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running,
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waiting,
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naughty;
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std::unique_ptr<process> previous;
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std::unique_ptr<process> current;
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std::unique_ptr<process> one() {
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auto v = std::move(running.back());
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running.pop_back();
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return v;
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}
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void rid(std::unique_ptr<process> current) {
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switch(current->state) {
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case process_status::inactive:
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case process_status::running:
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running.push_front(std::move(current));
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break;
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case process_status::finished:
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clean(std::move(current));
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break;
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case process_status::zombie:
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naughty.push_front(std::move(current));
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break;
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case process_status::waiting:
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waiting.push_front(std::move(current));
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break;
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}
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}
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void clean(std::unique_ptr<process>) {}
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void yield_to(std::unique_ptr<process> target) noexcept {
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current->scheduling_swapper.pull();
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sys.rid(std::move(current));
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current = std::move(target);
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current->scheduling_swapper.push(this);
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spawner(&sys);
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}
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void yield() noexcept {
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current->scheduling_swapper.pull();
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sys.rid(std::move(current));
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current = one();
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current->scheduling_swapper.push(this);
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spawner(&sys);
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}
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};
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// Needs to return the system one way or another
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__attribute__((noinline)) struct system* spawner (struct system* sys) {
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auto& proc = *system::sys.current;
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if(proc.state == process_status::inactive) {
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proc.state = process_status::running;
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proc.fn();
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proc.state = process_status::finished;
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sys->current->scheduling_swapper.pull();
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sys->yield();
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}
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return sys;
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}
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struct system system::sys;
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int main() {
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char c;
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system::sys.current = std::make_unique<process>(&c);
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std::cout << "1";
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system::sys.current->state = process_status::running;
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system::sys.yield_to(std::make_unique<process>([](){
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std::cout << "2";
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}));
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std::cout << "3\n";
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return 0;
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}
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