binder: add functions to copy to/from binder buffers

Avoid vm_area when copying to or from binder buffers.
Instead, new copy functions are added that copy from
kernel space to binder buffer space. These use
kmap_atomic() and kunmap_atomic() to create temporary
mappings and then memcpy() is used to copy within
that page.

Also, kmap_atomic() / kunmap_atomic() use the appropriate
cache flushing to support VIVT cache architectures.
Allow binder to build if CPU_CACHE_VIVT is defined.

Several uses of the new functions are added here. More
to follow in subsequent patches.

Signed-off-by: Todd Kjos <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/android/Kconfig

···
 
 config ANDROID_BINDER_IPC
 	bool "Android Binder IPC Driver"
-	depends on MMU && !CPU_CACHE_VIVT
+	depends on MMU
 	default n
 	---help---
 	  Binder is used in Android for both communication between processes,

drivers/android/binder.c

···
 		off_end = (void *)off_start + buffer->offsets_size;
 	for (offp = off_start; offp < off_end; offp++) {
 		struct binder_object_header *hdr;
-		size_t object_size = binder_validate_object(buffer, *offp);
+		size_t object_size;
+		binder_size_t object_offset;
+		binder_size_t buffer_offset = (uintptr_t)offp -
+			(uintptr_t)buffer->data;
 
+		binder_alloc_copy_from_buffer(&proc->alloc, &object_offset,
+					      buffer, buffer_offset,
+					      sizeof(object_offset));
+		object_size = binder_validate_object(buffer, object_offset);
 		if (object_size == 0) {
 			pr_err("transaction release %d bad object at offset %lld, size %zd\n",
-			       debug_id, (u64)*offp, buffer->data_size);
+			       debug_id, (u64)object_offset, buffer->data_size);
 			continue;
 		}
-		hdr = (struct binder_object_header *)(buffer->data + *offp);
+		hdr = (struct binder_object_header *)
+			(buffer->data + object_offset);
 		switch (hdr->type) {
 		case BINDER_TYPE_BINDER:
 		case BINDER_TYPE_WEAK_BINDER: {
···
 				continue;
 			}
 			fd_array = (u32 *)(parent_buffer + (uintptr_t)fda->parent_offset);
-			for (fd_index = 0; fd_index < fda->num_fds; fd_index++)
-				binder_deferred_fd_close(fd_array[fd_index]);
+			for (fd_index = 0; fd_index < fda->num_fds;
+			     fd_index++) {
+				u32 fd;
+				binder_size_t offset =
+					(uintptr_t)&fd_array[fd_index] -
+					(uintptr_t)buffer->data;
+
+				binder_alloc_copy_from_buffer(&proc->alloc,
+							      &fd,
+							      buffer,
+							      offset,
+							      sizeof(fd));
+				binder_deferred_fd_close(fd);
+			}
 		} break;
 		default:
 			pr_err("transaction release %d bad object type %x\n",
···
 	return ret;
 }
 
-static int binder_translate_fd(u32 *fdp,
+static int binder_translate_fd(u32 fd, binder_size_t fd_offset,
 			       struct binder_transaction *t,
 			       struct binder_thread *thread,
 			       struct binder_transaction *in_reply_to)
···
 	struct file *file;
 	int ret = 0;
 	bool target_allows_fd;
-	int fd = *fdp;
 
 	if (in_reply_to)
 		target_allows_fd = !!(in_reply_to->flags & TF_ACCEPT_FDS);
···
 		goto err_alloc;
 	}
 	fixup->file = file;
-	fixup->offset = (uintptr_t)fdp - (uintptr_t)t->buffer->data;
+	fixup->offset = fd_offset;
 	trace_binder_transaction_fd_send(t, fd, fixup->offset);
 	list_add_tail(&fixup->fixup_entry, &t->fd_fixups);
 
···
 		return -EINVAL;
 	}
 	for (fdi = 0; fdi < fda->num_fds; fdi++) {
-		int ret = binder_translate_fd(&fd_array[fdi], t, thread,
-						in_reply_to);
+		u32 fd;
+		int ret;
+		binder_size_t offset =
+			(uintptr_t)&fd_array[fdi] -
+			(uintptr_t)t->buffer->data;
+
+		binder_alloc_copy_from_buffer(&target_proc->alloc,
+					      &fd, t->buffer,
+					      offset, sizeof(fd));
+		ret = binder_translate_fd(fd, offset, t, thread,
+					  in_reply_to);
 		if (ret < 0)
 			return ret;
 	}
···
 
 		t->security_ctx = (uintptr_t)kptr +
 		    binder_alloc_get_user_buffer_offset(&target_proc->alloc);
-		memcpy(kptr, secctx, secctx_sz);
+		binder_alloc_copy_to_buffer(&target_proc->alloc,
+					    t->buffer, buf_offset,
+					    secctx, secctx_sz);
 		security_release_secctx(secctx, secctx_sz);
 		secctx = NULL;
 	}
···
 	off_min = 0;
 	for (; offp < off_end; offp++) {
 		struct binder_object_header *hdr;
-		size_t object_size = binder_validate_object(t->buffer, *offp);
+		size_t object_size;
+		binder_size_t object_offset;
+		binder_size_t buffer_offset =
+			(uintptr_t)offp - (uintptr_t)t->buffer->data;
 
-		if (object_size == 0 || *offp < off_min) {
+		binder_alloc_copy_from_buffer(&target_proc->alloc,
+					      &object_offset,
+					      t->buffer,
+					      buffer_offset,
+					      sizeof(object_offset));
+		object_size = binder_validate_object(t->buffer, object_offset);
+		if (object_size == 0 || object_offset < off_min) {
 			binder_user_error("%d:%d got transaction with invalid offset (%lld, min %lld max %lld) or object.\n",
-					  proc->pid, thread->pid, (u64)*offp,
+					  proc->pid, thread->pid,
+					  (u64)object_offset,
 					  (u64)off_min,
 					  (u64)t->buffer->data_size);
 			return_error = BR_FAILED_REPLY;
···
 			goto err_bad_offset;
 		}
 
-		hdr = (struct binder_object_header *)(t->buffer->data + *offp);
-		off_min = *offp + object_size;
+		hdr = (struct binder_object_header *)
+			(t->buffer->data + object_offset);
+		off_min = object_offset + object_size;
 		switch (hdr->type) {
 		case BINDER_TYPE_BINDER:
 		case BINDER_TYPE_WEAK_BINDER: {
···
 
 		case BINDER_TYPE_FD: {
 			struct binder_fd_object *fp = to_binder_fd_object(hdr);
-			int ret = binder_translate_fd(&fp->fd, t, thread,
-						      in_reply_to);
+			binder_size_t fd_offset = object_offset +
+				(uintptr_t)&fp->fd - (uintptr_t)fp;
+			int ret = binder_translate_fd(fp->fd, fd_offset, t,
+						      thread, in_reply_to);
 
 			if (ret < 0) {
 				return_error = BR_FAILED_REPLY;
···
 
 /**
  * binder_apply_fd_fixups() - finish fd translation
+ * @proc:         binder_proc associated @t->buffer
  * @t:	binder transaction with list of fd fixups
  *
  * Now that we are in the context of the transaction target
···
  * fput'ing files that have not been processed and ksys_close'ing
  * any fds that have already been allocated.
  */
-static int binder_apply_fd_fixups(struct binder_transaction *t)
+static int binder_apply_fd_fixups(struct binder_proc *proc,
+				  struct binder_transaction *t)
 {
 	struct binder_txn_fd_fixup *fixup, *tmp;
 	int ret = 0;
 
 	list_for_each_entry(fixup, &t->fd_fixups, fixup_entry) {
 		int fd = get_unused_fd_flags(O_CLOEXEC);
-		u32 *fdp;
 
 		if (fd < 0) {
 			binder_debug(BINDER_DEBUG_TRANSACTION,
···
 		trace_binder_transaction_fd_recv(t, fd, fixup->offset);
 		fd_install(fd, fixup->file);
 		fixup->file = NULL;
-		fdp = (u32 *)(t->buffer->data + fixup->offset);
-		/*
-		 * This store can cause problems for CPUs with a
-		 * VIVT cache (eg ARMv5) since the cache cannot
-		 * detect virtual aliases to the same physical cacheline.
-		 * To support VIVT, this address and the user-space VA
-		 * would both need to be flushed. Since this kernel
-		 * VA is not constructed via page_to_virt(), we can't
-		 * use flush_dcache_page() on it, so we'd have to use
-		 * an internal function. If devices with VIVT ever
-		 * need to run Android, we'll either need to go back
-		 * to patching the translated fd from the sender side
-		 * (using the non-standard kernel functions), or rework
-		 * how the kernel uses the buffer to use page_to_virt()
-		 * addresses instead of allocating in our own vm area.
-		 *
-		 * For now, we disable compilation if CONFIG_CPU_CACHE_VIVT.
-		 */
-		*fdp = fd;
+		binder_alloc_copy_to_buffer(&proc->alloc, t->buffer,
+					    fixup->offset, &fd,
+					    sizeof(u32));
 	}
 	list_for_each_entry_safe(fixup, tmp, &t->fd_fixups, fixup_entry) {
 		if (fixup->file) {
 			fput(fixup->file);
 		} else if (ret) {
-			u32 *fdp = (u32 *)(t->buffer->data + fixup->offset);
+			u32 fd;
 
-			binder_deferred_fd_close(*fdp);
+			binder_alloc_copy_from_buffer(&proc->alloc, &fd,
+						      t->buffer, fixup->offset,
+						      sizeof(fd));
+			binder_deferred_fd_close(fd);
 		}
 		list_del(&fixup->fixup_entry);
 		kfree(fixup);
···
 			trd->sender_pid = 0;
 		}
 
-		ret = binder_apply_fd_fixups(t);
+		ret = binder_apply_fd_fixups(proc, t);
 		if (ret) {
 			struct binder_buffer *buffer = t->buffer;
 			bool oneway = !!(t->flags & TF_ONE_WAY);

drivers/android/binder_alloc.c

···
 	}
 	return 0;
 }
+
+static void binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
+					bool to_buffer,
+					struct binder_buffer *buffer,
+					binder_size_t buffer_offset,
+					void *ptr,
+					size_t bytes)
+{
+	/* All copies must be 32-bit aligned and 32-bit size */
+	BUG_ON(!check_buffer(alloc, buffer, buffer_offset, bytes));
+
+	while (bytes) {
+		unsigned long size;
+		struct page *page;
+		pgoff_t pgoff;
+		void *tmpptr;
+		void *base_ptr;
+
+		page = binder_alloc_get_page(alloc, buffer,
+					     buffer_offset, &pgoff);
+		size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
+		base_ptr = kmap_atomic(page);
+		tmpptr = base_ptr + pgoff;
+		if (to_buffer)
+			memcpy(tmpptr, ptr, size);
+		else
+			memcpy(ptr, tmpptr, size);
+		/*
+		 * kunmap_atomic() takes care of flushing the cache
+		 * if this device has VIVT cache arch
+		 */
+		kunmap_atomic(base_ptr);
+		bytes -= size;
+		pgoff = 0;
+		ptr = ptr + size;
+		buffer_offset += size;
+	}
+}
+
+void binder_alloc_copy_to_buffer(struct binder_alloc *alloc,
+				 struct binder_buffer *buffer,
+				 binder_size_t buffer_offset,
+				 void *src,
+				 size_t bytes)
+{
+	binder_alloc_do_buffer_copy(alloc, true, buffer, buffer_offset,
+				    src, bytes);
+}
+
+void binder_alloc_copy_from_buffer(struct binder_alloc *alloc,
+				   void *dest,
+				   struct binder_buffer *buffer,
+				   binder_size_t buffer_offset,
+				   size_t bytes)
+{
+	binder_alloc_do_buffer_copy(alloc, false, buffer, buffer_offset,
+				    dest, bytes);
+}
+

drivers/android/binder_alloc.h

···
 				 const void __user *from,
 				 size_t bytes);
 
+void binder_alloc_copy_to_buffer(struct binder_alloc *alloc,
+				 struct binder_buffer *buffer,
+				 binder_size_t buffer_offset,
+				 void *src,
+				 size_t bytes);
+
+void binder_alloc_copy_from_buffer(struct binder_alloc *alloc,
+				   void *dest,
+				   struct binder_buffer *buffer,
+				   binder_size_t buffer_offset,
+				   size_t bytes);
+
 #endif /* _LINUX_BINDER_ALLOC_H */