Windows.cpp

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#include "Common.h"
#include "CothreadPrivate.h"
 
#include "SysV.S"
 
#include <cstddef>
#include <stdexcept>
 
using namespace libcommunism;
using namespace libcommunism::internal;
 
const size_t Amd64::kNumSavedRegisters{ 8 + (10 * 2) };
 
void Amd64::ValidateStackSize(const size_t size) {
    if (!size) throw std::runtime_error("Size may not be nil");
    if (size % kStackAlignment) throw std::runtime_error("Stack is misaligned");
}
 
void* Amd64::AllocStack(const size_t bytes) {
    auto ret = _aligned_malloc(bytes, kStackAlignment);
    if (!ret) {
        throw std::runtime_error("failed to allocate stack");
    }
    return ret;
}
 
void Amd64::DeallocStack(void* stack) {
    _aligned_free(stack);
}
 
void Amd64::Prepare(Amd64 *wrap, const Cothread::Entry& entry) {
    static_assert(offsetof(Amd64, stackTop) == COTHREAD_OFF_CONTEXT_TOP, "cothread stack top is invalid");
 
    // build the context structure we pass to our "fake" entry point
    auto info = new CallInfo{ entry };
    if (!info) throw std::runtime_error("Failed to allocate call info");
 
    // NOLINTBEGIN(cppcoreguidelines-pro-type-reinterpret-cast)
    // prepare some space for a stack frame (zeroed registers; four function call params)
    auto& stackBuf = wrap->stack;
    auto stackFrame = reinterpret_cast<std::byte*>(stackBuf.data());
    stackFrame += ((stackBuf.size() * sizeof(uintptr_t)) & ~(0x10 - 1))
        - (sizeof(uintptr_t) * (4 + kNumSavedRegisters));
    auto stack = reinterpret_cast<uintptr_t*>(stackFrame);
 
    // method to execute if main method returns
    *--stack = reinterpret_cast<uintptr_t>(&Amd64::EntryReturnedStub);
 
    // and then jump to the stub that calls the entry point
    *--stack = reinterpret_cast<uintptr_t>(info);
    *--stack = reinterpret_cast<uintptr_t>(&Amd64::DereferenceCallInfo);
    *--stack = reinterpret_cast<uintptr_t>(&Amd64::JumpToEntry);
    // NOLINTEND(cppcoreguidelines-pro-type-reinterpret-cast)
 
    // clear the region that registers are written into (so they're all zeroed)
    for (size_t i = 0; i < kNumSavedRegisters; i++) {
        *--stack = 0;
    }
 
    // restore the stack pointer to the correct point
    wrap->stackTop = stack;
}