On Thu, Jun 03, 2021 at 04:40:35PM +0100, Dave Martin wrote: > Do we know how libcs will detect that they don't need to do the > mprotect() calls? Do we need a detection mechanism at all? > Ignoring certain errors from mprotect() when ld.so is trying to set > PROT_BTI on the main executable's code pages is probably a reasonable, > backwards-compatible compromise here, but it seems a bit wasteful. I think the theory was that they would just do the mprotect() calls and ignore any errors as they currently do, or declare that they depend on a new enough kernel version I guess (not an option for glibc but might be for others which didn't do BTI yet). > > flexibility userspace has to disable BTI but it is expected that for cases > > where there are problems which require BTI to be disabled it is more likely > > that it will need to be disabled on a system level. > There's no flexibility impact unless MemoryDenyWriteExecute is in force, > right? Right, or some other mechanism that has the same effect.
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