Messages in this thread | | | Date | Fri, 17 May 2024 17:27:39 +0200 | Subject | Re: [PATCH] x86/kvm/tdx: Save %rbp in TDX_MODULE_CALL | From | Jürgen Groß <> |
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On 17.05.24 17:16, Dave Hansen wrote: > On 5/17/24 07:44, Juergen Gross wrote: >> Just another data point: Before using this machine I was testing on >> another one with older firmware. That one really didn't support NOM_RBP_MOD >> and I needed to build the kernel with CONFIG_FRAME_POINTER enabled to get >> past the check you are mentioning above. > > For all intents and purposes, the modules that intentionally clobber RBP > don't support Linux. If buggy modules are accidentally clobbering RBP, > we can debate how much the kernel should bend over to accommodate them, > but my preference would be to ignore them. > > I'd much rather put a deny list in the kernel than try to tolerate RBP > clobbering universally.
Would you be fine with adding a new X86_FEATURE (or BUG?) allowing to switch RBP save/restore via ALTERNATIVE, controlled by a command line option?
Or maybe by adding a new CONFIG_TDX_MODULE_CAN_CLOBBER_RBP (probably using a shorter name) option?
TBH I'm slightly puzzled that the firmware I'm using could make it outside Intel. I'm fearing this might happen again.
Juergen
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