Messages in this thread | | | Date | Wed, 17 Apr 2024 05:59:42 +0200 | Subject | Re: [PATCH -v2] x86/retpoline: Ensure default return thunk isn't used at runtime | From | Klara Modin <> |
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On 2024-04-16 11:27, Borislav Petkov wrote: > On Wed, Apr 03, 2024 at 07:10:17PM +0200, Klara Modin wrote: >> With this patch/commit, one of my machines (older P4 Xeon, 32-bit only) >> hangs on boot with CONFIG_RETHUNK=y / CONFIG_MITIGATION_RETHUNK=y. > > Ok, this should fix it: > > --- > From: "Borislav Petkov (AMD)" <bp@alien8.de> > Date: Mon, 15 Apr 2024 18:15:43 +0200 > Subject: [PATCH] x86/retpolines: Enable the default thunk warning only on relevant configs > > The using-default-thunk warning check makes sense only with > configurations which actually enable the special return thunks. > > Otherwise, it fires on unrelated 32-bit configs on which the special > return thunks won't even work (they're 64-bit only) and, what is more, > those configs even go off into the weeds when booting in the > alternatives patching code, leading to a dead machine. > > Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> > Link: https://lore.kernel.org/r/78e0d19c-b77a-4169-a80f-2eef91f4a1d6@gmail.com > Link: https://lore.kernel.org/r/20240413024956.488d474e@yea > --- > arch/x86/lib/retpoline.S | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S > index e674ccf720b9..391059b2c6fb 100644 > --- a/arch/x86/lib/retpoline.S > +++ b/arch/x86/lib/retpoline.S > @@ -382,8 +382,15 @@ SYM_FUNC_END(call_depth_return_thunk) > SYM_CODE_START(__x86_return_thunk) > UNWIND_HINT_FUNC > ANNOTATE_NOENDBR > +#if defined(CONFIG_MITIGATION_UNRET_ENTRY) || \ > + defined(CONFIG_MITIGATION_SRSO) || \ > + defined(CONFIG_MITIGATION_CALL_DEPTH_TRACKING) > ALTERNATIVE __stringify(ANNOTATE_UNRET_SAFE; ret), \ > "jmp warn_thunk_thunk", X86_FEATURE_ALWAYS > +#else > + ANNOTATE_UNRET_SAFE > + ret > +#endif > int3 > SYM_CODE_END(__x86_return_thunk) > EXPORT_SYMBOL(__x86_return_thunk)
Thanks, Tested-by: Klara Modin <klarasmodin@gmail.com>
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