SharedBuffer: Split the creation and share steps

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.

4 files changed, 24 insertions, 6 deletions

diff --git a/Libraries/LibC/SharedBuffer.cpp b/Libraries/LibC/SharedBuffer.cpp
index ef7e31e621..1a0c3a9701 100644
--- a/Libraries/LibC/SharedBuffer.cpp
+++ b/Libraries/LibC/SharedBuffer.cpp
@@ -3,10 +3,10 @@
 #include <stdio.h>
 #include <unistd.h>
 
-RefPtr<SharedBuffer> SharedBuffer::create(pid_t peer, int size)
+RefPtr<SharedBuffer> SharedBuffer::create_with_size(int size)
 {
     void* data;
-    int shared_buffer_id = create_shared_buffer(peer, size, &data);
+    int shared_buffer_id = create_shared_buffer(size, &data);
     if (shared_buffer_id < 0) {
         perror("create_shared_buffer");
         return nullptr;
@@ -14,6 +14,16 @@ RefPtr<SharedBuffer> SharedBuffer::create(pid_t peer, int size)
     return adopt(*new SharedBuffer(shared_buffer_id, size, data));
 }
 
+bool SharedBuffer::share_with(pid_t peer)
+{
+    int ret = share_buffer_with(shared_buffer_id(), peer);
+    if (ret < 0) {
+        perror("share_buffer_with");
+        return false;
+    }
+    return true;
+}
+
 RefPtr<SharedBuffer> SharedBuffer::create_from_shared_buffer_id(int shared_buffer_id)
 {
     void* data = get_shared_buffer(shared_buffer_id);
diff --git a/Libraries/LibC/SharedBuffer.h b/Libraries/LibC/SharedBuffer.h
index aec7ab3047..2d1cdfc423 100644
--- a/Libraries/LibC/SharedBuffer.h
+++ b/Libraries/LibC/SharedBuffer.h
@@ -5,10 +5,11 @@
 
 class SharedBuffer : public RefCounted<SharedBuffer> {
 public:
-    static RefPtr<SharedBuffer> create(pid_t peer, int);
+    static RefPtr<SharedBuffer> create_with_size(int);
     static RefPtr<SharedBuffer> create_from_shared_buffer_id(int);
     ~SharedBuffer();
 
+    bool share_with(pid_t);
     int shared_buffer_id() const { return m_shared_buffer_id; }
     void seal();
     int size() const { return m_size; }
diff --git a/Libraries/LibC/unistd.cpp b/Libraries/LibC/unistd.cpp
index d4622bba1f..b2307f1f7c 100644
--- a/Libraries/LibC/unistd.cpp
+++ b/Libraries/LibC/unistd.cpp
@@ -423,9 +423,15 @@ int read_tsc(unsigned* lsw, unsigned* msw)
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
-int create_shared_buffer(pid_t peer_pid, int size, void** buffer)
+int create_shared_buffer(int size, void** buffer)
 {
-    int rc = syscall(SC_create_shared_buffer, peer_pid, size, buffer);
+    int rc = syscall(SC_create_shared_buffer, size, buffer);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
+int share_buffer_with(int shared_buffer_id, pid_t peer_pid)
+{
+    int rc = syscall(SC_share_buffer_with, shared_buffer_id, peer_pid);
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
diff --git a/Libraries/LibC/unistd.h b/Libraries/LibC/unistd.h
index 42235b0e63..806efbebe0 100644
--- a/Libraries/LibC/unistd.h
+++ b/Libraries/LibC/unistd.h
@@ -21,7 +21,8 @@ int gettid();
 int donate(int tid);
 int create_thread(int (*)(void*), void*);
 void exit_thread(int);
-int create_shared_buffer(pid_t peer_pid, int, void** buffer);
+int create_shared_buffer(int, void** buffer);
+int share_buffer_with(int, pid_t peer_pid);
 void* get_shared_buffer(int shared_buffer_id);
 int release_shared_buffer(int shared_buffer_id);
 int seal_shared_buffer(int shared_buffer_id);