static int allocate_user_kernel_buffer(size_t size, void **buf) {
int err = 0;
// The user space daemon is requesting a new circular queue.
// Make sure the requested size is within sane size bounds.
if (size > MAX_KMEM || size < MIN_KMEM) {
err = -EINVAL;
goto error_exit;
}
// Record the requested buffer size.
osquery.buf_size = size;
// Allocate a contiguous region of memory.
osquery.buffer = IOMallocAligned(osquery.buf_size, PAGE_SIZE);
// Cannot proceed if no memory to back the circular queue is available.
if (osquery.buffer == NULL) {
err = -EINVAL;
goto error_exit;
}
// Zero memory for safety, this memory will be shared with user space.
bzero(osquery.buffer, osquery.buf_size);
// This buffer will be shared, create a descriptor.
osquery.md =
IOMemoryDescriptor::withAddressRange((mach_vm_address_t)osquery.buffer,
osquery.buf_size,
kIODirectionInOut,
kernel_task);
if (osquery.md == NULL) {
err = -EINVAL;
goto error_exit;
}
// Now map the buffer into the user space process as read only.
osquery.mm = osquery.md->createMappingInTask(
current_task(), NULL, kIOMapAnywhere | kIOMapReadOnly);
if (osquery.mm == NULL) {
err = -EINVAL;
goto error_exit;
}
// The virtual address will be shared back to the user space queue manager.
*buf = (void *)osquery.mm->getAddress();
// Initialize the kernel space queue manager with the new buffer.
osquery_cqueue_init(&osquery.cqueue, osquery.buffer, osquery.buf_size);
return 0;
error_exit:
// A drop-through error handler will clean up any intermediate allocations.
cleanup_user_kernel_buffer();
return err;
}
static int allocate_user_kernel_buffer(size_t size, void **buf) {
int err = 0;
if (size > MAX_KMEM || size < MIN_KMEM) {
err = -EINVAL;
goto error_exit;
}
osquery.buf_size = size;
osquery.buffer = IOMallocAligned(osquery.buf_size, PAGE_SIZE);
if (osquery.buffer == NULL) {
err = -EINVAL;
goto error_exit;
}
bzero(osquery.buffer, osquery.buf_size); // Zero memory for safety.
osquery.md
= IOMemoryDescriptor::withAddressRange((mach_vm_address_t)osquery.buffer,
osquery.buf_size,
kIODirectionInOut, kernel_task);
if (osquery.md == NULL) {
err = -EINVAL;
goto error_exit;
}
osquery.mm = osquery.md->createMappingInTask(current_task(), NULL,
kIOMapAnywhere | kIOMapReadOnly);
if (osquery.mm == NULL) {
err = -EINVAL;
goto error_exit;
}
*buf = (void *)osquery.mm->getAddress();
osquery_cqueue_init(&osquery.cqueue, osquery.buffer, osquery.buf_size);
return 0;
error_exit:
cleanup_user_kernel_buffer();
return err;
}