Upgrade Linux to 4.8 and adjust our kernel tweaks accordingly

Originally created by @intrigeri on #11886 (Redmine)

https://ftp-master.debian.org/new/linux_4.8.4-1~exp1.html reads:

       * [amd64] Enable LEGACY_VSYSCALL_NONE instead of LEGACY_VSYSCALL_EMULATE.
         This breaks (e)glibc 2.13 and earlier, and can be reverted using the kernel
         parameter: vsyscall=emulate
       * Enable SLAB_FREELIST_RANDOM
       * security,printk: Enable SECURITY_DMESG_RESTRICT, preventing non-root users
         reading the kernel log by default (sysctl: kernel.dmesg_restrict)

Likely we can drop a couple tweaks we do, and should check if at least our slab_nomerge is still the best we can do.

Feature Branch: feature/11886-linux-4.8

Attachments

• noats.patch

Related issues

• Related to #11840 (closed)
• Related to #12090 (closed)
• Related to #12025 (closed)
• Related to #12122 (closed)