FS#62524 : Consider building with -fno-jump-tables to reduce retpoline impact

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FS#62524 - Consider building with -fno-jump-tables to reduce retpoline impact

Attached to Project: Arch Linux
Opened by Kerin Millar (kerframil) - Wednesday, 01 May 2019, 22:52 GMT
Last edited by Evangelos Foutras (foutrelis) - Thursday, 02 May 2019, 20:01 GMT

Task Type	Feature Request
Category	Kernel
Status	Closed
Assigned To	No-one
Architecture	All
Severity	Low
Priority	Normal
Reported Version
Due in Version	Undecided
Due Date	Undecided
Percent Complete
Votes	0
Private	No

Details

Description:

Commit a9d57ef15cbe327fe54416dd194ee0ea66ae53a4 adds -fno-jump-tables as an option for gcc in the case that CONFIG_RETPOLINE is enabled. Doing so results in switch statements generally executing more quickly than they otherwise would. This behaviour is already a default in clang, and will become the default behaviour once gcc-8.4.0 lands. In the meantime, backporting this trivial patch would be beneficial.

Additional info:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a9d57ef15cbe327fe54416dd194ee0ea66ae53a4
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86952#c19
https://twitter.com/grsecurity/status/1112668594863853568

This task depends upon

Closed by Evangelos Foutras (foutrelis)
Thursday, 02 May 2019, 20:01 GMT
Reason for closing: Upstream
Additional comments about closing: Patch is included in upstream 5.0.11 and 4.19.38 kernels.