Q: After updating to IOS8 on iPhone 4S I can't open the  text messages all I can see is white screen?

Hey Kar.M,

Thanks for the question. After reviewing your post, it sounds like you have a white screen. I would recommend that you read this article, it may be able to help you resolve or isolate the issue.

iPhone: Hardware troubleshooting

Display shows a white screen

1. Try turning iPhone off and then on again.
2. If the iPhone will not turn off, try to reset it.
3. If that doesn't work, try restoring the device.

Thanks for using Apple Support Communities.

Have a nice day,

Mario

Hey Kar.M,

Since the Messages App wont open follow this article. 

Turn your iOS device off and on (restart) and reset

If after that the Messages app still wont open correctly you may need to restore the iPhone. 

Use iTunes to restore your iOS device to factory settings

Thanks for using Apple Support Communities.

Have a nice day,

Mario