Super simplified linux script to check if your kernel has been patched.
Either clone the repo
git clone https://github.com/TheNaterz/MeltdownKernelPatchCheck
cd MeltdownKernelPatchCheck
or simply
wget https://raw.githubusercontent.com/TheNaterz/MeltdownKernelPatchCheck/master/check.sh
Then run the script with
chmod +x check.sh
./check.sh