Luna/kernel/src/sys/waitpid.cpp

#include "memory/MemoryManager.h"
#include "sys/Syscall.h"
#include "thread/Scheduler.h"
#include <bits/waitpid.h>

Result<u64> sys_waitpid(Registers*, SyscallArgs args)
{
    pid_t pid = (pid_t)args[0];
    int* status_ptr = (int*)args[1];
    int options = (int)args[2];

    Thread* current = Scheduler::current();

    Thread* thread;

    if (pid > 0)
    {
        thread = TRY(Result<Thread*>::from_option(Scheduler::find_by_pid(pid), ESRCH));

        if (thread->parent_id != current->id) return err(ECHILD);

        while (thread->state != ThreadState::Exited)
        {
            if (options & WNOHANG) return err(EAGAIN);
            kernel_sleep(10);
        }
    }
    else if (pid == -1)
    {
        if (!Scheduler::has_children((pid_t)current->id)) return err(ECHILD);

        Option<Thread*> child;

        while (child = Scheduler::find_exited_child((pid_t)current->id), !child.has_value())
        {
            if (options & WNOHANG) return err(EAGAIN);
            kernel_sleep(10);
        }

        thread = child.value();
    }
    else
        return err(ENOTSUP);

    int status = (int)thread->status;
    u64 id = thread->id;

    thread->state = ThreadState::Dying;

    if (status_ptr)
        if (!MemoryManager::copy_to_user_typed(status_ptr, &status)) return err(EFAULT);

    return id;
}