Luna/kernel/src/sys/file.cpp

#include "Log.h"
#include "fs/Pipe.h"
#include "fs/VFS.h"
#include "memory/MemoryManager.h"
#include "sys/Syscall.h"
#include "thread/Scheduler.h"
#include <bits/fcntl.h>
#include <bits/open-flags.h>
#include <bits/seek.h>
#include <luna/SafeArithmetic.h>
#include <sys/types.h>

Result<u64> sys_read(Registers*, SyscallArgs args)
{
    int fd = (int)args[0];
    u8* buf = (u8*)args[1];
    usize size = (usize)args[2];

    if (!MemoryManager::validate_user_write(buf, size)) return err(EFAULT);

    Thread* current = Scheduler::current();

    auto& descriptor = *TRY(current->resolve_fd(fd));

    if (!descriptor.is_readable()) return err(EBADF);

    while (descriptor.inode->blocking())
    {
        if (descriptor.should_block()) kernel_sleep(10);
        else
            return err(EAGAIN);
    }

    usize nread = TRY(descriptor.inode->read(buf, descriptor.offset, size));

    descriptor.offset += nread;

    return nread;
}

Result<u64> sys_write(Registers*, SyscallArgs args)
{
    int fd = (int)args[0];
    const u8* buf = (const u8*)args[1];
    usize size = (usize)args[2];

    if (!MemoryManager::validate_user_read(buf, size)) return err(EFAULT);

    Thread* current = Scheduler::current();

    auto& descriptor = *TRY(current->resolve_fd(fd));

    if (!descriptor.is_writable()) return err(EBADF);

    if (descriptor.should_append()) descriptor.offset = descriptor.inode->size();

    usize nwritten = TRY(descriptor.inode->write(buf, descriptor.offset, size));

    descriptor.offset += nwritten;

    return nwritten;
}

Result<u64> sys_lseek(Registers*, SyscallArgs args)
{
    int fd = (int)args[0];
    off_t offset = (long)args[1];
    int whence = (int)args[2];

    Thread* current = Scheduler::current();

    auto& descriptor = *TRY(current->resolve_fd(fd));

    off_t new_offset;

    switch (whence)
    {
    case SEEK_SET: new_offset = offset; break;
    case SEEK_CUR: new_offset = TRY(safe_add((long)descriptor.offset, offset)); break;
    case SEEK_END: new_offset = TRY(safe_add((long)descriptor.inode->size(), offset)); break;
    default: return err(EINVAL);
    }

    if (new_offset < 0) return err(EINVAL);

    descriptor.offset = (usize)new_offset;

    return (u64)new_offset;
}

Result<u64> sys_fcntl(Registers*, SyscallArgs args)
{
    int fd = (int)args[0];
    int cmd = (int)args[1];

    Thread* current = Scheduler::current();

    auto& descriptor = *TRY(current->resolve_fd(fd));

    bool is_cloexec = true;

    switch (cmd)
    {
    case F_DUPFD: is_cloexec = false; [[fallthrough]];
    case F_DUPFD_CLOEXEC: {
        int arg = (int)args[2];
        int new_fd = TRY(current->allocate_fd(arg));

        current->fd_table[new_fd] = descriptor;

        if (is_cloexec) current->fd_table[new_fd]->flags |= O_CLOEXEC;
        else
            current->fd_table[new_fd]->flags &= ~O_CLOEXEC;

        return (u64)new_fd;
    }
    case F_GETFD: return (u64) !!(descriptor.flags & O_CLOEXEC);
    case F_SETFD: {
        int arg = (int)args[2];
        if (arg == FD_CLOEXEC) descriptor.flags |= O_CLOEXEC;
        else
            descriptor.flags &= ~O_CLOEXEC;
        return 0;
    }
    case F_GETFL: return (u64)(descriptor.flags & ~O_CLOEXEC);
    case F_SETFL: {
        int arg = (int)args[2];

        descriptor.flags &= ~(O_APPEND | O_NONBLOCK);
        arg &= (O_APPEND | O_NONBLOCK);

        descriptor.flags |= arg;

        return 0;
    }
    default: return err(EINVAL);
    }
}

Result<u64> sys_ioctl(Registers*, SyscallArgs args)
{
    int fd = (int)args[0];
    int request = (int)args[1];
    void* arg = (void*)args[2];

    Thread* current = Scheduler::current();
    auto& descriptor = *TRY(current->resolve_fd(fd));

    return descriptor.inode->ioctl(request, arg);
}

Result<u64> sys_dup2(Registers*, SyscallArgs args)
{
    int oldfd = (int)args[0];
    int newfd = (int)args[1];

    Thread* current = Scheduler::current();

    if (newfd < 0 || newfd >= FD_MAX) return err(EBADF);

    auto descriptor = *TRY(current->resolve_fd(oldfd));

    if (newfd == oldfd) return (u64)newfd;

    current->fd_table[newfd] = descriptor;
    current->fd_table[newfd]->flags &= ~O_CLOEXEC;

    return (u64)newfd;
}

Result<u64> sys_pipe(Registers*, SyscallArgs args)
{
    int* pfds = (int*)args[0];

    Thread* current = Scheduler::current();

    int rfd = TRY(current->allocate_fd(0));
    int wfd = TRY(current->allocate_fd(rfd + 1));

    if (!MemoryManager::copy_to_user_typed(pfds, &rfd)) return err(EFAULT);
    if (!MemoryManager::copy_to_user_typed(pfds + 1, &wfd)) return err(EFAULT);

    SharedPtr<VFS::Inode> rpipe;
    SharedPtr<VFS::Inode> wpipe;

    TRY(Pipe::create(rpipe, wpipe));

    current->fd_table[rfd] = FileDescriptor { rpipe, 0, O_RDONLY };
    current->fd_table[wfd] = FileDescriptor { wpipe, 0, O_WRONLY };

    return 0;
}