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/* Copyright (c) 2020 Johannes Stoelp */
#include "thread.h"
#include "arch/x86_64/asm.h"
#include "executor.h"
#include <cassert>
#include <cstdint> // uintN_t
#include <sys/mman.h> // mmap
#include <unistd.h> // sysconf
namespace {
static long get_pagesize() { return ::sysconf(_SC_PAGESIZE); }
} // namespace
namespace nMatcha {
Thread::Thread() : mStackPtr(nullptr), mExecutor(nullptr) {
const long PAGE_SIZE = get_pagesize();
const long STACK_SIZE = 8 * PAGE_SIZE;
// Allocate new stack.
void* stack = ::mmap(nullptr, STACK_SIZE, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1 /* fd */, 0 /* offset */);
assert(stack != MAP_FAILED);
// Simple stack overflow detection by removing permissions from last
// stack page (lowest addr).
// In theory stack pointer could be decremented by more than one page
// and the page below last stack page could be used. However we don't
// take care of that now and risk the memory corruption.
int ret = ::mprotect(stack, PAGE_SIZE, PROT_NONE);
assert(ret == 0);
// Adjust stack pointer, as stack grows downwards.
mStackPtr = static_cast<uint8_t*>(stack) + STACK_SIZE;
{
static_assert(sizeof(uint64_t) == sizeof(std::uintptr_t), "Pointer must be 64bit!");
// Setup initial stack frame which will be popped when yielding
// first time into the thread.
// Basic idea is to yield into Thread::entry() function which will
// then call the user function.
uint64_t* stack = static_cast<uint64_t*>(mStackPtr);
// Arguments for `thread_create`.
*(--stack) = reinterpret_cast<uint64_t>(this);
*(--stack) = reinterpret_cast<uint64_t>(Thread::entry);
// Yield epilogue.
*(--stack) = reinterpret_cast<uint64_t>(thread_create); // Return address
*(--stack) = static_cast<uint64_t>(0); // rbp
// Callee saved registers.
*(--stack) = static_cast<uint64_t>(0); // rbx
*(--stack) = reinterpret_cast<uint64_t>(static_cast<uint64_t*>(mStackPtr) - 4); // rbp
*(--stack) = static_cast<uint64_t>(0); // r12
*(--stack) = static_cast<uint64_t>(0); // r13
*(--stack) = static_cast<uint64_t>(0); // r14
*(--stack) = static_cast<uint64_t>(0); // r15
mStackPtr = static_cast<void*>(stack);
}
}
void Thread::entry(void* obj) {
Thread* t = static_cast<Thread*>(obj);
t->threadFn();
}
void Thread::yield() {
assert(mExecutor);
::yield(mExecutor->getStackPtr(), &mStackPtr);
}
} // namespace nMatcha
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