On Fri, Dec 13, 2019 at 10:05:10AM -0800, Peter Collingbourne wrote: > On Wed, Dec 11, 2019 at 10:40 AM Catalin Marinas > <catalin.marinas@xxxxxxx> wrote: > > This series proposes the initial user-space support for the ARMv8.5 > > Memory Tagging Extension [1]. > > Thanks for sending out this series. I have been testing it on Android > with the FVP model and my in-development scudo changes that add memory > tagging support [1], and have not noticed any problems so far. Thanks for the comments so far and the testing. I'll post a v2 next week. > > - Clarify whether mmap(tagged_addr, PROT_MTE) pre-tags the memory with > > the tag given in the tagged_addr hint. Strong justification is > > required for this as it would force arm64 to disable the zero page. > > We would like to use this feature in scudo to tag large (>128KB on > Android) allocations, which are currently allocated via mmap rather > than from an allocation pool. Otherwise we would need to pay the cost > (perf and RSS) of faulting all of their pages at allocation time > instead of on demand, if we want to tag them. Would the default tag of 0 be sufficient here? We disable match-all for user-space already, so 0 is not a wildcard. -- Catalin
