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NightMonkey
Guru
Joined: 21 Mar 2003
Posts: 356
Location: Philadelphia, PA
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 Posted: Wed Jan 17, 2018 11:48 pm Post subject: Which gccs support new kernel option CONFIG_RETPOLINE? |
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| Code: | Avoid speculative indirect branches in kernel (RETPOLINE) [Y/n/?] (NEW) ?
CONFIG_RETPOLINE:
Compile kernel with the retpoline compiler options to guard against
kernel-to-user data leaks by avoiding speculative indirect
branches. Requires a compiler with -mindirect-branch=thunk-extern
support for full protection. The kernel may run slower.
Without compiler support, at least indirect branches in assembler
code are eliminated. Since this includes the syscall entry path,
it is not entirely pointless.
Symbol: RETPOLINE [=y]
Type : boolean
Prompt: Avoid speculative indirect branches in kernel
Location:
-> Processor type and features
Defined at arch/x86/Kconfig:432 |
Thanks! 
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mike155
Advocate
Joined: 17 Sep 2010
Posts: 4438
Location: Frankfurt, Germany
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| Posted: Thu Jan 18, 2018 1:41 am Post subject: |
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Any recent GCC (5, 6, 7) compiler will compile your kernel if you set CONFIG_RETPOLINE=Y.
But only "indirect branches in assembler code" will be eliminated.
To get full protection, you'll need a GCC compiler with -mindirect-branch=thunk-extern support. So far no such compiler has been released.
GCC 7.3.0 will probably be released next week. It will be the first GCC compiler to support -mindirect-branch=thunk-extern.
If you're lion-hearted, you could also try the latest GCC 7 or 8 snapshots from GCC git server. They already contain support for -mindirect-branch=thunk-extern. |
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