Messages in this thread | | | Date | Wed, 17 Apr 2024 10:57:23 -0700 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v3] x86/bugs: Only harden syscalls when needed |
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On Wed, Apr 17, 2024 at 09:45:14AM -0700, Pawan Gupta wrote: > On Wed, Apr 17, 2024 at 04:14:26PM +0100, Andrew Cooper wrote: > > On 17/04/2024 12:02 am, Josh Poimboeuf wrote: > > > diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c > > > index ca295b0c1eee..dcb97cc2758f 100644 > > > --- a/arch/x86/kernel/cpu/bugs.c > > > +++ b/arch/x86/kernel/cpu/bugs.c > > > @@ -1678,6 +1687,21 @@ static void __init spectre_v2_select_mitigation(void) > > > enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline(); > > > enum spectre_v2_mitigation mode = SPECTRE_V2_NONE; > > > > > > + /* > > > + * X86_FEATURE_INDIRECT_SAFE indicates whether indirect calls can be > > > + * considered safe. That means either: > > > + * > > > + * - the CPU isn't vulnerable to Spectre v2 or its variants; > > > + * > > > + * - a hardware mitigation is in place (e.g., IBRS, BHI_DIS_S); or > > > + * > > > + * - the user turned off mitigations altogether. > > > + * > > > + * Assume innocence until proven guilty: set the cap bit now, then > > > + * clear it later if/when needed. > > > + */ > > > + setup_force_cpu_cap(X86_FEATURE_INDIRECT_SAFE); > > > > Following on from the (re)discovery that X86_FEATURE_RETPOLINE is a poor > > name given what it *actually* does, can I recommend s/SAFE/OK/ here? > > Or simply X86_FEATURE_USE_INDIRECT_BRANCH. > > > This flag really is "do I want indirect branches or not", which - as > > noted here - is more than just a judgement of whether indirect branches > > are "safe".
X86_FEATURE_USE_INDIRECT_BRANCH sounds good. It's a bit long but does describe it better.
-- Josh
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