kernel/device_manager: Implement B_GET_DRIVER_FOR_DEVICE

for legacy and new drivers.

This is an opcode for ioctl that can be used on almost any device entry found in /dev.
When used, ioctl will fill a buffer with the absolute path to the driver file that is
being used by the device.

This opcode was available in BeOS R5, though remained unimplemented in Haiku since
the introduction of the Device Manager almost two decades ago.

Original change by Jacob Secunda.

Change-Id: Ic49141b677b4158a63918459d4048450c825447c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5078
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

headers/private/kernel/kmodule.h

@@ -32,6 +32,7 @@ extern status_t load_module(const char *path, module_info ***_modules);
 extern status_t module_init(struct kernel_args *args);
 extern status_t module_init_post_threads(void);
 extern status_t module_init_post_boot_device(bool bootingFromBootLoaderVolume);
+extern status_t module_get_path(const char* moduleName, char** path);
 
 #ifdef __cplusplus
 }

src/system/kernel/device_manager/devfs.cpp

@@ -1534,21 +1534,6 @@ devfs_ioctl(fs_volume* _volume, fs_vnode* _vnode, void* _cookie, uint32 op,
 				return status;
 			}
 
-			case B_GET_DRIVER_FOR_DEVICE:
-			{
-#if 0
-				const char* path;
-				if (!vnode->stream.u.dev.driver)
-					return B_ENTRY_NOT_FOUND;
-				path = vnode->stream.u.dev.driver->path;
-				if (path == NULL)
-					return B_ENTRY_NOT_FOUND;
-
-				return user_strlcpy((char*)buffer, path, B_FILE_NAME_LENGTH);
-#endif
-				return B_ERROR;
-			}
-
 			case B_GET_PARTITION_INFO:
 			{
 				struct devfs_partition* partition

src/system/kernel/device_manager/device_manager.cpp

@@ -21,8 +21,9 @@
 #include <device_manager_defs.h>
 #include <fs/devfs.h>
 #include <fs/KPath.h>
-#include <kernel.h>
 #include <generic_syscall.h>
+#include <kernel.h>
+#include <kmodule.h>
 #include <util/AutoLock.h>
 #include <util/DoublyLinkedList.h>
 #include <util/Stack.h>
@@ -91,6 +92,8 @@ public:
 
 	virtual void			Removed();
 
+	virtual	status_t		Control(void* cookie, int32 op, void* buffer, size_t length);
+
 			void			SetRemovedFromParent(bool removed)
 								{ fRemovedFromParent = removed; }
 
@@ -1251,6 +1254,28 @@ Device::Removed()
 }
 
 
+status_t
+Device::Control(void* _cookie, int32 op, void* buffer, size_t length)
+{
+	switch (op) {
+		case B_GET_DRIVER_FOR_DEVICE:
+		{
+			char* path = NULL;
+			status_t status = module_get_path(ModuleName(), &path);
+			if (status != B_OK)
+				return status;
+			if (length != 0 && length <= strlen(path))
+				return ERANGE;
+			status = user_strlcpy(static_cast<char*>(buffer), path, length);
+			free(path);
+			return status;
+		}
+		default:
+			return AbstractModuleDevice::Control(_cookie, op, buffer, length);;
+	}
+}
+
+
 //	#pragma mark - device_node
 
 

src/system/kernel/device_manager/legacy_drivers.cpp

@@ -71,6 +71,8 @@ public:
 								void** _cookie);
 	virtual	status_t		Select(void* cookie, uint8 event, selectsync* sync);
 
+	virtual	status_t		Control(void* cookie, int32 op, void* buffer, size_t length);
+
 			bool			Republished() const { return fRepublished; }
 			void			SetRepublished(bool republished)
 								{ fRepublished = republished; }
@@ -1323,6 +1325,20 @@ LegacyDevice::Removed()
 }
 
 
+status_t
+LegacyDevice::Control(void* _cookie, int32 op, void* buffer, size_t length)
+{
+	switch (op) {
+		case B_GET_DRIVER_FOR_DEVICE:
+			if (length != 0 && length <= strlen(fDriver->path))
+				return ERANGE;
+			return user_strlcpy(static_cast<char*>(buffer), fDriver->path, length);
+		default:
+			return AbstractModuleDevice::Control(_cookie, op, buffer, length);
+	}
+}
+
+
 void
 LegacyDevice::SetHooks(device_hooks* hooks)
 {

src/system/kernel/module.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2008, Haiku Inc. All rights reserved.
+ * Copyright 2002-2022, Haiku Inc. All rights reserved.
  * Distributed under the terms of the MIT License.
  *
  * Copyright 2001, Thomas Kurschel. All rights reserved.
@@ -1742,6 +1742,28 @@ load_module(const char* path, module_info*** _modules)
 }
 
 
+status_t
+module_get_path(const char* moduleName, char** filePath)
+{
+	if (moduleName == NULL || filePath == NULL)
+		return B_BAD_VALUE;
+
+	RecursiveLocker _(sModulesLock);
+
+	// Check if the module and its image are already cached in the module system.
+	module* foundModule = sModulesHash->Lookup(moduleName);
+	if (foundModule != NULL) {
+		if (foundModule->module_image == NULL)
+			return ENOTSUP;
+				// The module is built-in and has no associated image.
+		*filePath = strdup(foundModule->module_image->path);
+		return *filePath != NULL ? B_OK : B_NO_MEMORY;
+	}
+
+	return B_NAME_NOT_FOUND;
+}
+
+
 status_t
 start_watching_modules(const char* prefix, NotificationListener& listener)
 {