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SharedBuffer: Split the creation and share steps

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This allows us to seal a buffer *before* anyone else has access to it
(well, ok, the creating process still does, but you can't win them all).

It also means that a SharedBuffer can be shared with multiple clients:
all you need is to have access to it to share it on again.
This commit is contained in:
Robin Burchell 2019-07-18 09:52:22 +02:00 • committed by Andreas Kling
parent f60d7e5d1f
commit b907608e46
12 changed files with 58 additions and 22 deletions
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30
Kernel/Process.cpp
View file

@ -2377,28 +2377,19 @@ void Process::disown_all_shared_buffers()
shared_buffer->disown(m_pid);
}
int Process::sys$create_shared_buffer(pid_t peer_pid, int size, void** buffer)
int Process::sys$create_shared_buffer(int size, void** buffer)
{
if (!size || size < 0)
return -EINVAL;
size = PAGE_ROUND_UP(size);
if (!peer_pid || peer_pid < 0 || peer_pid == m_pid)
return -EINVAL;
if (!validate_write_typed(buffer))
return -EFAULT;
{
InterruptDisabler disabler;
auto* peer = Process::from_pid(peer_pid);
if (!peer)
return -ESRCH;
}
LOCKER(shared_buffers().lock());
static int s_next_shared_buffer_id;
int shared_buffer_id = ++s_next_shared_buffer_id;
auto shared_buffer = make<SharedBuffer>(shared_buffer_id, size);
shared_buffer->share_with(m_pid);
shared_buffer->share_with(peer_pid);
*buffer = shared_buffer->get_address(*this);
ASSERT((int)shared_buffer->size() >= size);
#ifdef SHARED_BUFFER_DEBUG
@ -2409,6 +2400,25 @@ int Process::sys$create_shared_buffer(pid_t peer_pid, int size, void** buffer)
return shared_buffer_id;
}
int Process::sys$share_buffer_with(int shared_buffer_id, pid_t peer_pid)
{
if (!peer_pid || peer_pid < 0 || peer_pid == m_pid)
return -EINVAL;
LOCKER(shared_buffers().lock());
auto it = shared_buffers().resource().find(shared_buffer_id);
if (it == shared_buffers().resource().end())
return -EINVAL;
auto& shared_buffer = *(*it).value;
{
InterruptDisabler disabler;
auto* peer = Process::from_pid(peer_pid);
if (!peer)
return -ESRCH;
}
shared_buffer.share_with(peer_pid);
return 0;
}
int Process::sys$release_shared_buffer(int shared_buffer_id)
{
LOCKER(shared_buffers().lock());