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Subject: [MODERATED] Re: [PATCH 5/5] SSB extra v2 5
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From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <1ae07e8f-636f-0cbd-399c-e5d538dc93ea@linux.intel.com>
Date: Mon, 7 May 2018 17:46:20 -0700
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To: speck@linutronix.de
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On 05/07/2018 05:36 PM, speck for Andi Kleen wrote:
>> +	/* To mitigate speculative-store-bypass, we only need
>> +	 * mitigation for programs that write to memory.  Mark that
>> +	 * the program needs mitigation if loaded without
>> +	 * CAP_SYS_ADMIN:
>> +	 */
>> +	if (env->saw_memory_write && !capable(CAP_SYS_ADMIN))
>> +		env->prog->need_mitigation = true;
> Flag should have a more descriptive name specific to SSB. 
> I bet this won't be the last mitigation needed for EBPF :|

For now, it *is* generic, though.  It's whether the mitigation function
gets injected into the call path or not.

Once we have multiple things we have to mitigate for at entry/exit, we
may need to add some other flags to the bpf_prog that say exactly what
mitigations we need, like a "bfp_prog->does_memory_write" that
explicitly tells us if we need the SSB mitigation.