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Kernel+LibC+Tests: Implement pwritev(2)

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While this isn't really POSIX, it's needed by the Zig port and was
simple enough to implement.
This commit is contained in:
sin-ack 2022-10-01 13:21:20 +00:00 • committed by Andrew Kaster
parent 70337f3a4b
commit 9b425b860c
6 changed files with 28 additions and 12 deletions
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18
Kernel/Syscalls/write.cpp
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@ -11,7 +11,9 @@
namespace Kernel {
ErrorOr<FlatPtr> Process::sys$writev(int fd, Userspace<const struct iovec*> iov, int iov_count)
// NOTE: The offset is passed by pointer because off_t is 64bit,
// hence it can't be passed by register on 32bit platforms.
ErrorOr<FlatPtr> Process::sys$pwritev(int fd, Userspace<const struct iovec*> iov, int iov_count, Userspace<off_t const*> userspace_offset)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
TRY(require_promise(Pledge::stdio));
@ -31,26 +33,32 @@ ErrorOr<FlatPtr> Process::sys$writev(int fd, Userspace<const struct iovec*> iov,
return EINVAL;
}
// NOTE: Negative offset means "operate like writev" which seeks the file.
auto base_offset = TRY(copy_typed_from_user(userspace_offset));
auto description = TRY(open_file_description(fd));
if (!description->is_writable())
return EBADF;
if (base_offset >= 0 && !description->file().is_seekable())
return EINVAL;
int nwritten = 0;
off_t current_offset = base_offset;
for (auto& vec : vecs) {
auto buffer = TRY(UserOrKernelBuffer::for_user_buffer((u8*)vec.iov_base, vec.iov_len));
auto result = do_write(*description, buffer, vec.iov_len);
auto result = do_write(*description, buffer, vec.iov_len, base_offset >= 0 ? current_offset : Optional<off_t> {});
if (result.is_error()) {
if (nwritten == 0)
return result.release_error();
return nwritten;
}
nwritten += result.value();
current_offset += result.value();
}
return nwritten;
}
ErrorOr<FlatPtr> Process::do_write(OpenFileDescription& description, UserOrKernelBuffer const& data, size_t data_size)
ErrorOr<FlatPtr> Process::do_write(OpenFileDescription& description, UserOrKernelBuffer const& data, size_t data_size, Optional<off_t> offset)
{
size_t total_nwritten = 0;
@ -72,7 +80,9 @@ ErrorOr<FlatPtr> Process::do_write(OpenFileDescription& description, UserOrKerne
}
// TODO: handle exceptions in unblock_flags
}
auto nwritten_or_error = description.write(data.offset(total_nwritten), data_size - total_nwritten);
auto nwritten_or_error = offset.has_value()
? description.write(offset.value() + total_nwritten, data.offset(total_nwritten), data_size - total_nwritten)
: description.write(data.offset(total_nwritten), data_size - total_nwritten);
if (nwritten_or_error.is_error()) {
if (total_nwritten > 0)
return total_nwritten;