Messages in this thread | | | Date | Fri, 29 Oct 2021 15:51:09 -0700 | From | Pawan Gupta <> | Subject | Re: [PATCH v2 1/2] arch/Kconfig: Make CONFIG_CPU_SPECTRE available for all architectures |
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On 29.10.2021 11:08, Russell King (Oracle) wrote: >On Thu, Oct 28, 2021 at 12:36:58PM -0700, Pawan Gupta wrote: >> Isn't ARM already using CPU_SPECTRE for selecting things: >> >> config HARDEN_BRANCH_PREDICTOR >> bool "Harden the branch predictor against aliasing attacks" if EXPERT >> depends on CPU_SPECTRE >> >> This was the whole motivation for doing the same for x86. >> >> Adding a condition for all architectures is also okay, but its going to >> a little messier: >> >> config BPF_UNPRIV_DEFAULT_OFF >> default y if X86 || ARM || ... > >It doesn't have to be (but sadly we end up repeating "DEFAULT"): > >config BPF_UNPRIV_DEFAULT_OFF_DEFAULT > bool > >config BPF_UNPRIV_DEFAULT_OFF > bool "Disable unprivileged BPF by default" > default BPF_UNPRIV_DEFAULT_OFF_DEFAULT > >Then architectures can select BPF_UNPRIV_DEFAULT_OFF_DEFAULT if they >wish this to be defaulted to "yes".
Looks like we are settling on unconditional 'default y' for now [1]. I have sent a v3 with 'default y' [2].
>However, please note that this has limited use given that the >BPF_UNPRIV_DEFAULT_OFF option has been around for a while now. Any >existing configuration that mentions this symbol will override any >default specified in the Kconfig files if the option is user-visible.
Yes, existing configurations will have to toggle this manually. However, many distros already have BPF_UNPRIV_DEFAULT_OFF=y in their configuration.
>So, IMHO, defaults need to be set correctly from the point in time >that the option is introduced.
Agree.
[1] https://lore.kernel.org/lkml/6130e55f-4d84-5ada-4e86-5b678e3eaf5e@iogearbox.net/ [2] https://lore.kernel.org/lkml/0ace9ce3f97656d5f62d11093ad7ee81190c3c25.1635535215.git.pawan.kumar.gupta@linux.intel.com/
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