On 11/25/20 7:17 PM, Thomas Gleixner wrote: > Carlos, Petr, > > On Wed, Nov 25 2020 at 15:37, Carlos O'Donell wrote: >> On 11/19/20 7:14 PM, Thomas Gleixner wrote: >>> So from my point of view asking for distorted time still _is_ a request >>> for ponies. >> >> I'm happy if you say it's more work than the value it provides. > > Thinking more about it. Would a facility which provides: > > CLOCK_FAKE_MONOTONIC|BOOTTIME|REALTIME > > where you can go wild on setting time to whatever you want solve > your problem?
We would need a way to inject CLOCK_FAKE_* in lieu of the real constants. There are only two straight forward ways I know how to do that and they aren't very useful e.g. alternative build, syscall hot-path debug code to alter the constant. We might write a syscall interception framework using seccomp and SECCOMP_RET_TRACE, but that involves ptrace'ing the process under test, and is equivalent to a micro-sandbox. I'm not against that idea for testing; we would test what we ship. I don't think eBPF can modify the incoming arguments. I need to go check if systemtap can modify incoming arguments; I've never done that in any script. In what other ways can we inject the new constants? -- Cheers, Carlos.
