c/c++实现有栈协程

有栈协程

有栈协程通过切换执行上下文实现，核心是切换栈寄存器和跳转ip代码地址，同时需要保存切换当前编译器ABI规定的 非易失寄存器。

System V AMD64 ABI 和 MSVC x64 ABI 的非易失性寄存器RBX、RBP、RSP、R12、R13、R14、R15
XMM6-XMM15RDI、RSI、仅MSVC

MSVC比GCC多了两个RDI、RSI，这些寄存器在切换时是必须要保存的。更多详情参考官方文档。

MSVC x64 ABI

切换核心汇编如下

linux amd 64extern "C" __attribute__((sysv_abi, naked, noinline)) void
switch_jmp(context_amd64 *save_, context_amd64 *jmp_);.text
.globl switch_jmpswitch_jmp:// rdi = save_, rsi = jmp_// 保存上下文到save_movq %rbx, 0x000(%rdi)    // RBXmovq %rbp, 0x008(%rdi)    // RBPmovq %rsp, 0x010(%rdi)    // RSPmovq %r12, 0x018(%rdi)    // R12movq %r13, 0x020(%rdi)    // R13movq %r14, 0x028(%rdi)    // R14movq %r15, 0x030(%rdi)    // R15#ifdef SAVE_FLOATmovaps %xmm6, 0x040(%rdi)   // XMM6movaps %xmm7, 0x050(%rdi)   // XMM7movaps %xmm8, 0x060(%rdi)   // XMM8movaps %xmm9, 0x070(%rdi)   // XMM9movaps %xmm10, 0x080(%rdi)  // XMM10movaps %xmm11, 0x090(%rdi)  // XMM11movaps %xmm12, 0x0A0(%rdi)  // XMM12movaps %xmm13, 0x0B0(%rdi)  // XMM13movaps %xmm14, 0x0C0(%rdi)  // XMM14movaps %xmm15, 0x0D0(%rdi)  // XMM15
#endif// 从jmp_恢复上下文movq 0x000(%rsi), %rbx  // RBXmovq 0x008(%rsi), %rbp  // RBPmovq 0x010(%rsi), %rsp  // RSPmovq 0x018(%rsi), %r12  // R12movq 0x020(%rsi), %r13  // R13movq 0x028(%rsi), %r14  // R14movq 0x030(%rsi), %r15  // R15
#ifdef SAVE_FLOATmovaps 0x040(%rsi), %xmm6movaps 0x050(%rsi), %xmm7movaps 0x060(%rsi), %xmm8movaps 0x070(%rsi), %xmm9movaps 0x080(%rsi), %xmm10movaps 0x090(%rsi), %xmm11movaps 0x0A0(%rsi), %xmm12movaps 0x0B0(%rsi), %xmm13movaps 0x0C0(%rsi), %xmm14movaps 0x0D0(%rsi), %xmm15
#endifret

c++异常在windows下的有栈协程里失效

实际情况可能很复杂，msvc c++实现在SEH(结构化异常处理)机制之上，如上的上下文切换在windows会让协程的c++异常无法被catch拦截，会直接崩溃。

借鉴了boost.context的实现，hack了线程gs:[030h] NT_TIB结构，切换了栈base地址，msvc c++异常就可以被拦截 成功运行，但MINGW下异常还是无法被正常catch!!

    ; load NT_TIBmov  r10,  gs:[030h]mov  rax, [r10+01478h]mov  [rcx+048h], raxmov  rax, [r10+010h]mov  [rcx+050h], raxmov  rax,  [r10+08h]mov  [rcx+058h], raxmov  r10,  gs:[030h]mov  rax, [rdx+048h]mov  [r10+01478h], raxmov  rax, [rdx+050h]mov  [r10+010h], raxmov  rax, [rdx+058h]mov  [r10+08h], rax

关于TLS，不推荐自己hack gs fs寄存器实现TLS，在原有TLS上封装协程的TLS就好。

关于栈切换保存在哪儿？有的实现是直接在当前栈压入，但这种实现是需要返回值的。还是采取了非压入栈的，在独立的地方存储上下文。

封装相关：协程挂起时，应该跳出到调度器，保持干净的栈，所以挂起时时返回到调度器的resume后。

有栈协程实现demo，全部源码：

//allocate.h
#include <cstddef>
#include <cassert>#ifdef _WIN32
#include <Windows.h>
std::size_t page_size() {SYSTEM_INFO si;::GetSystemInfo(&si);return static_cast<std::size_t>(si.dwPageSize);
}
void *allocate_stack(size_t size_, size_t &out_size) {size_t page_size_ = page_size();const std::size_t pages = (size_ + page_size_ - 1) / page_size_;const std::size_t size__ = (pages + 1) * page_size_;out_size = size__;void *vp = ::VirtualAlloc(0, size__, MEM_COMMIT, PAGE_READWRITE);assert(vp != nullptr && "VirtualAlloc NULL");DWORD old_options;// 增加一个PAGE_GUARD保护页，拦截栈溢出const BOOL result = ::VirtualProtect(vp, page_size_, PAGE_READWRITE | PAGE_GUARD, &old_options);assert(FALSE != result && "VirtualProtect false");return vp;
}void free_stack(void *ptr, size_t size) { ::VirtualFree(ptr, 0, MEM_RELEASE); }
#elif __linux__
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>std::size_t page_size() {return static_cast<std::size_t>(::sysconf(_SC_PAGESIZE));
}void *allocate_stack(size_t size_, size_t &out_size) {size_t page_size_ = page_size();const std::size_t pages = (size_ + page_size_ - 1) / page_size_;const std::size_t size__ = (pages + 1) * page_size_;out_size = size__;void *vp = ::mmap(0, size__, PROT_READ | PROT_WRITE,MAP_PRIVATE | MAP_ANON | MAP_STACK, -1, 0);assert(vp != nullptr && "::mmap return null!");const int result(::mprotect(vp, page_size_, PROT_NONE));assert(0 == result && "::mprotect faild!");return vp;
}
void free_stack(void *ptr, size_t size) { ::munmap(ptr, size); }#endif

//stackfull.cpp
#include <cassert>
#include <cstddef>
#include <iostream>
#include <cstdint>
#include <functional>
#include <iomanip>
#include <memory>
#include <list>
#include <algorithm>
#include <atomic>
#include <string.h>#include "allocate.h"#if !(defined(__x86_64__) || defined(_M_X64) || defined(__amd64__) ||          \defined(__amd64))
#error "此程序仅支持 AMD64 (x86-64) 架构平台，不支持当前平台编译。"
#endifnamespace co {struct context_amd64;
#ifdef _WIN64
#if defined(_MSC_VER)
extern "C" __declspec(noinline) void switch_jmp(context_amd64 *save_,context_amd64 *jmp_);
#elif __MINGW64__
extern "C" __attribute__((ms_abi, naked, noinline)) void
switch_jmp(context_amd64 *save_, context_amd64 *jmp_);
#endif
#elif __linux__
extern "C" __attribute__((sysv_abi, naked, noinline)) void
switch_jmp(context_amd64 *save_, context_amd64 *jmp_);
#endif// System V AMD64 ABI 和 MSVC x64 ABI 的非易失性寄存器
// RDI、RSI、仅MSVC
// RBX、RBP、RSP、R12、R13、R14、R15
// XMM6-XMM15constexpr size_t rbp_index = 1;
constexpr size_t rsp_index = 2;
// xmm align 16
struct xmm_regs {uint64_t _1;uint64_t _2;
};
struct alignas(16) context_amd64 {uint64_t regs[7]{}; // RBX、RBP、RSP、R12、R13、R14、R15
#ifdef _WIN64uint64_t rdi_rsi[2]{}; // RDI、RSI、uint64_t tib_info[3];  // fc_dealloc  limit  base     windows tib
#elseuint64_t alignas__ = 0;//仅对齐
#endif // _WIN64_// cmakelist中启用SAVE_FLOAT
#ifdef SAVE_FLOATxmm_regs regs_xmm[10]{}; // XMM6-XMM15 它需要16对齐
#endif
};struct coroutine_base;
struct context_tls {context_amd64 break_{};struct coroutine_base *co_current_ = nullptr;
};constexpr size_t STACK_SIZE = 1024 * 1024 * 2;
thread_local context_tls switch_;void co_suspend();void debug_print(const char *action, const char *name) {std::cout << std::right << std::setfill('=');std::string action_;action_.append("[");action_.append(action);action_.append("]");std::cout << std::setw(15) << action_;std::cout << std::setw(10) << name << std::endl;
};struct coroutine_base {static void entry() noexcept {context_tls &tls_ = switch_;coroutine_base *this_ = tls_.co_current_;debug_print("start", this_->name());try {this_->invoke();} catch (...) {this_->except_ptr = std::current_exception();}this_->done_ = true;debug_print("end", this_->name());switch_jmp(&this_->context_,&tls_.break_); // 没有ret地址，不能继续必须跳转};public:void resume() {if (done_)return;context_tls &tls_ = switch_;tls_.co_current_ = this;debug_print("resume", this->name());switch_jmp(&tls_.break_, &this->context_);debug_print("suspend", this->name());}bool done() { return done_; }template <typename R> R get() {return std::move(*std::launder(static_cast<R *>(result())));}std::exception_ptr &except() { return except_ptr; }template <typename R> void set(R &&r) {using type = std::remove_reference_t<R>;*std::launder(static_cast<type *>(result())) = r;}template <typename RR> static void current_yield(RR &r) {context_tls &tls_ = switch_;tls_.co_current_->set(std::forward<RR>(r));co::co_suspend();}const char *name() { return name_.c_str(); }void set_name(const char *_name) { name_ = _name; }virtual ~coroutine_base() { free_stack(stack_m_, stack_size_); }protected:coroutine_base(size_t stack_size) {stack_m_ = (uint8_t *)allocate_stack(stack_size, stack_size_);stack_ = stack_m_ + stack_size_; // 逆行增长// 压入一个空地址 对齐16 重要 这是默认call的压栈stack_ = stack_ - sizeof(uintptr_t);// 压入entry，配合switch_jmpstack_ = stack_ - sizeof(uintptr_t);*static_cast<uintptr_t *>((void *)stack_) =(uintptr_t)&coroutine_base::entry;context_.regs[rsp_index] = (uintptr_t)(void *)stack_;context_.regs[rbp_index] = (uintptr_t)(void *)stack_;
#ifdef _WIN64//  c++ 异常 msvc windowscontext_.tib_info[0] = (uintptr_t)(stack_ - stack_size);context_.tib_info[1] = (uintptr_t)(stack_ - stack_size);context_.tib_info[2] = (uintptr_t)stack_;
#endif};virtual void invoke() = 0;virtual void *result() = 0;context_amd64 context_{};uint8_t *stack_m_ = nullptr;uint8_t *stack_ = nullptr;size_t stack_size_ = 0;std::atomic_bool done_ = false;std::exception_ptr except_ptr{};std::string name_;friend void co_suspend();
};void co_suspend() {context_tls &tls_ = switch_;coroutine_base *this_ = tls_.co_current_;switch_jmp(&this_->context_, &tls_.break_);
};template <typename R> struct result_storage {alignas(std::max_align_t) uint8_t ret_s[sizeof(R)]{};void *get_addr() { return static_cast<void *>(&this->ret_s[0]); }
};
template <> struct result_storage<void> {void *get_addr() {throw std::runtime_error("void null!");return nullptr;}
};template <typename R, typename... Args>
struct coroutine : public coroutine_base {public:template <typename F, typename... Args2>coroutine(F &&_func, Args2 &&..._args) noexcept: coroutine_base(STACK_SIZE), args_(std::forward<Args2>(_args)...) {coro_main_ = _func;}private:result_storage<R> ret{};std::tuple<Args...> args_{};std::function<R(Args...)> coro_main_;void invoke() override {if constexpr (std::is_void_v<R>) {std::apply(coro_main_, args_);} else {new (ret.get_addr()) R(std::apply(coro_main_, args_));}}void *result() override { return ret.get_addr(); }
};template <typename F, typename... Args>
co::coroutine_base *create_co(const char *name, F &&_func, Args &&..._args) {using R = std::invoke_result_t<F, Args...>;auto *ptr = new co::coroutine<R, Args...>(std::forward<F>(_func),std::forward<Args>(_args)...);ptr->set_name(name);return ptr;
};
} // namespace coint main() {std::cout << 1.132 << std::endl;using coro_unptr = std::unique_ptr<co::coroutine_base>;std::list<coro_unptr> task_;task_.emplace_back(co::create_co("co_1", []() {std::cout << "hello " << std::endl;co::co_suspend();std::cout << "world~" << std::endl;}));task_.emplace_back(co::create_co("co_2",[](int x) {int my_value = 123;int other = 200;other += 100;double f64 = 1.23;f64 = f64 + 2.222;co::co_suspend();double ret = (my_value + other + x) + f64;std::cout << "co_r value:" << ret << std::endl;return ret;},10000));while (task_.size() > 0) {for (auto &t : task_) {if (!t->done()) {t->resume();}}std::erase_if(task_, [](const auto &x) { return x->done(); });}coro_unptr generator_test(co::create_co("co_3",[](size_t x) -> size_t {for (size_t i = 0; i < x; i++) {co::coroutine_base::current_yield(i);}return 0;},10));while (true) {if (!generator_test->done()) {generator_test->resume();size_t v = generator_test->get<size_t>();std::cout << "generator:" << v << std::endl;} elsebreak;}coro_unptr throw_test(co::create_co("co_test", []() { throw std::runtime_error("error !!!"); }));try {throw_test->resume();if (throw_test->except())std::rethrow_exception(throw_test->except());} catch (const std::exception &e) {std::cout << "exception: " << e.what() << std::endl;}std::cout << "end####" << std::endl;return 0;
}

;win_msvc.asm
.codeswitch_jmp proc frame.endprolog;RCX save_,RDX jmp_;-----------保存到上下文到save_-------------mov [rcx + 000h], rbx   ; RBXmov [rcx + 008h], rbp   ; RBPmov [rcx + 010h], rsp   ; RSPmov [rcx + 018h], r12   ; R12mov [rcx + 020h], r13   ; R13mov [rcx + 028h], r14   ; R14mov [rcx + 030h], r15   ; R15mov [rcx + 038h], rdi   ; RDImov [rcx + 040h], rsi   ; RSI; load NT_TIBmov  r10,  gs:[030h]mov  rax, [r10+01478h]mov  [rcx+048h], raxmov  rax, [r10+010h]mov  [rcx+050h], raxmov  rax,  [r10+08h]mov  [rcx+058h], raxIFDEF SAVE_FLOATmovaps [rcx + 0060h], xmm6    ; XMM6movaps [rcx + 0070h], xmm7    ; XMM7movaps [rcx + 0080h], xmm8    ; XMM8movaps [rcx + 0090h], xmm9    ; XMM9movaps [rcx + 00A0h], xmm10   ; XMM10movaps [rcx + 00B0h], xmm11   ; XMM11movaps [rcx + 00C0h], xmm12   ; XMM12movaps [rcx + 00D0h], xmm13   ; XMM13movaps [rcx + 00E0h], xmm14   ; XMM14movaps [rcx + 00F0h], xmm15   ; XMM15
ENDIF;-----------从jmp_恢复上下文-------------; 恢复整数寄存器mov rbx, [rdx + 000h] ; RBXmov rbp, [rdx + 008h] ; RBPmov rsp, [rdx + 010h] ; RSPmov r12, [rdx + 018h] ; R12mov r13, [rdx + 020h] ; R13mov r14, [rdx + 028h] ; R14mov r15, [rdx + 030h] ; R15mov rdi, [rdx + 038h] ; RDImov rsi, [rdx + 040h] ; RSI; load NT_TIBmov  r10,  gs:[030h]mov  rax, [rdx+048h]mov  [r10+01478h], raxmov  rax, [rdx+050h]mov  [r10+010h], raxmov  rax, [rdx+058h]mov  [r10+08h], raxIFDEF SAVE_FLOATmovaps  xmm6,  [rdx+0060h]movaps  xmm7,  [rdx+0070h]movaps  xmm8,  [rdx+0080h]movaps  xmm9,  [rdx+0090h]movaps  xmm10, [rdx+00A0h]movaps  xmm11, [rdx+00B0h]movaps  xmm12, [rdx+00C0h]movaps  xmm13, [rdx+00D0h]movaps  xmm14, [rdx+00E0h]movaps  xmm15, [rdx+00F0h]
ENDIFretswitch_jmp endp
end    

//linux_gas.S
.text
.globl switch_jmpswitch_jmp:// rdi = save_, rsi = jmp_// 保存上下文到save_movq %rbx, 0x000(%rdi)    // RBXmovq %rbp, 0x008(%rdi)    // RBPmovq %rsp, 0x010(%rdi)    // RSPmovq %r12, 0x018(%rdi)    // R12movq %r13, 0x020(%rdi)    // R13movq %r14, 0x028(%rdi)    // R14movq %r15, 0x030(%rdi)    // R15#ifdef SAVE_FLOATmovaps %xmm6, 0x040(%rdi)   // XMM6movaps %xmm7, 0x050(%rdi)   // XMM7movaps %xmm8, 0x060(%rdi)   // XMM8movaps %xmm9, 0x070(%rdi)   // XMM9movaps %xmm10, 0x080(%rdi)  // XMM10movaps %xmm11, 0x090(%rdi)  // XMM11movaps %xmm12, 0x0A0(%rdi)  // XMM12movaps %xmm13, 0x0B0(%rdi)  // XMM13movaps %xmm14, 0x0C0(%rdi)  // XMM14movaps %xmm15, 0x0D0(%rdi)  // XMM15
#endif// 从jmp_恢复上下文movq 0x000(%rsi), %rbx  // RBXmovq 0x008(%rsi), %rbp  // RBPmovq 0x010(%rsi), %rsp  // RSPmovq 0x018(%rsi), %r12  // R12movq 0x020(%rsi), %r13  // R13movq 0x028(%rsi), %r14  // R14movq 0x030(%rsi), %r15  // R15
#ifdef SAVE_FLOATmovaps 0x040(%rsi), %xmm6movaps 0x050(%rsi), %xmm7movaps 0x060(%rsi), %xmm8movaps 0x070(%rsi), %xmm9movaps 0x080(%rsi), %xmm10movaps 0x090(%rsi), %xmm11movaps 0x0A0(%rsi), %xmm12movaps 0x0B0(%rsi), %xmm13movaps 0x0C0(%rsi), %xmm14movaps 0x0D0(%rsi), %xmm15
#endifret

cmake_minimum_required (VERSION 3.10)project ("stackfull")
set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)add_compile_definitions(SAVE_FLOAT)if (UNIX AND NOT APPLE)message(STATUS "Platform: Linux")enable_language(ASM)set(ASM_SOURCES linux_gas.S)
elseif (WIN32)if (MSVC)message(STATUS "Platform: Windows MSVC")enable_language(ASM_MASM)set(ASM_SOURCES win_msvc.asm)elseif (MINGW)message(STATUS "Platform: Windows MinGW")enable_language(ASM)set_source_files_properties(win_gas.S PROPERTIESCOMPILE_FLAGS "-x assembler-with-cpp"
)set(ASM_SOURCES win_gas.S)add_compile_options(-fexceptions)endif ()
else()message(FATAL_ERROR "Unsupported platform")
endif()add_executable (stackfull "stackfull.cpp" "allocate.h" ${ASM_SOURCES})