Kernel: Merge the shbuf_get_size() syscall into shbuf_get()

Add an extra out-parameter to shbuf_get() that receives the size of the
shared buffer. That way we don't need to make a separate syscall to
get the size, which we always did immediately after.

AK/SharedBuffer.cpp

@@ -67,16 +67,12 @@ bool SharedBuffer::share_globally()
 
 RefPtr<SharedBuffer> SharedBuffer::create_from_shbuf_id(int shbuf_id)
 {
- void* data = shbuf_get(shbuf_id);
+ size_t size = 0;
+ void* data = shbuf_get(shbuf_id, &size);
  if (data == (void*)-1) {
  perror("shbuf_get");
  return nullptr;
  }
- int size = shbuf_get_size(shbuf_id);
- if (size < 0) {
- perror("shbuf_get_size");
- return nullptr;
- }
  return adopt(*new SharedBuffer(shbuf_id, size, data));
 }
 

Kernel/Process.cpp

@@ -3634,9 +3634,11 @@ int Process::sys$shbuf_release(int shbuf_id)
  return 0;
 }
 
-void* Process::sys$shbuf_get(int shbuf_id)
+void* Process::sys$shbuf_get(int shbuf_id, size_t* user_size)
 {
  REQUIRE_PROMISE(shared_buffer);
+ if (user_size && !validate_write_typed(user_size))
+ return (void*)-EFAULT;
  LOCKER(shared_buffers().lock());
  auto it = shared_buffers().resource().find(shbuf_id);
  if (it == shared_buffers().resource().end())
@@ -3647,6 +3649,10 @@ void* Process::sys$shbuf_get(int shbuf_id)
 #ifdef SHARED_BUFFER_DEBUG
  kprintf("%s(%u): Retaining shared buffer %d, buffer count: %u\n", name().characters(), pid(), shbuf_id, shared_buffers().resource().size());
 #endif
+ if (user_size) {
+ size_t size = shared_buffer.size();
+ copy_to_user(user_size, &size);
+ }
  return shared_buffer.ref_for_process_and_get_address(*this);
 }
 
@@ -3667,22 +3673,6 @@ int Process::sys$shbuf_seal(int shbuf_id)
  return 0;
 }
 
-int Process::sys$shbuf_get_size(int shbuf_id)
-{
- REQUIRE_PROMISE(shared_buffer);
- LOCKER(shared_buffers().lock());
- auto it = shared_buffers().resource().find(shbuf_id);
- if (it == shared_buffers().resource().end())
- return -EINVAL;
- auto& shared_buffer = *(*it).value;
- if (!shared_buffer.is_shared_with(m_pid))
- return -EPERM;
-#ifdef SHARED_BUFFER_DEBUG
- kprintf("%s(%u): Get shared buffer %d size: %u\n", name().characters(), pid(), shbuf_id, shared_buffers().resource().size());
-#endif
- return shared_buffer.size();
-}
-
 int Process::sys$shbuf_set_volatile(int shbuf_id, bool state)
 {
  REQUIRE_PROMISE(shared_buffer);

Kernel/Process.h

@@ -276,10 +276,9 @@ class Process : public InlineLinkedListNode<Process> {
  int sys$shbuf_create(int, void** buffer);
  int sys$shbuf_allow_pid(int, pid_t peer_pid);
  int sys$shbuf_allow_all(int);
- void* sys$shbuf_get(int shbuf_id);
+ void* sys$shbuf_get(int shbuf_id, size_t* size);
  int sys$shbuf_release(int shbuf_id);
  int sys$shbuf_seal(int shbuf_id);
- int sys$shbuf_get_size(int shbuf_id);
  int sys$shbuf_set_volatile(int shbuf_id, bool);
  int sys$halt();
  int sys$reboot();

Kernel/Syscall.h

@@ -121,7 +121,6 @@ namespace Kernel {
  __ENUMERATE_SYSCALL(chown) \
  __ENUMERATE_SYSCALL(fchmod) \
  __ENUMERATE_SYSCALL(symlink) \
- __ENUMERATE_SYSCALL(shbuf_get_size) \
  __ENUMERATE_SYSCALL(shbuf_seal) \
  __ENUMERATE_SYSCALL(sendto) \
  __ENUMERATE_SYSCALL(recvfrom) \

Libraries/LibC/serenity.h

@@ -34,10 +34,9 @@ __BEGIN_DECLS
 int shbuf_create(int, void** buffer);
 int shbuf_allow_pid(int, pid_t peer_pid);
 int shbuf_allow_all(int);
-void* shbuf_get(int shbuf_id);
+void* shbuf_get(int shbuf_id, size_t* size);
 int shbuf_release(int shbuf_id);
 int shbuf_seal(int shbuf_id);
-int shbuf_get_size(int shbuf_id);
 
 int module_load(const char* path, size_t path_length);
 int module_unload(const char* name, size_t name_length);

Libraries/LibC/unistd.cpp

@@ -553,9 +553,9 @@ int set_process_icon(int icon_id)
  __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
-void* shbuf_get(int shbuf_id)
+void* shbuf_get(int shbuf_id, size_t* size)
 {
- int rc = syscall(SC_shbuf_get, shbuf_id);
+ int rc = syscall(SC_shbuf_get, shbuf_id, size);
  if (rc < 0 && -rc < EMAXERRNO) {
  errno = -rc;
  return (void*)-1;
@@ -569,12 +569,6 @@ int shbuf_release(int shbuf_id)
  __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
-int shbuf_get_size(int shbuf_id)
-{
- int rc = syscall(SC_shbuf_get_size, shbuf_id);
- __RETURN_WITH_ERRNO(rc, rc, -1);
-}
-
 int shbuf_seal(int shbuf_id)
 {
  int rc = syscall(SC_shbuf_seal, shbuf_id);