On Fri, Jan 22, 2021 at 3:41 PM Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > > While this patch didn't land upstream, we need an MTE kill-switch for > > Android GKI. Is this patch OK to take as is? Is it still valid? > > As you noticed, this code no longer exists. The CPUID is checked early > during boot in proc.S, before the MMU is enabled, as you need to set up > the MAIR register. > > Now, what do you mean by kill switch? There are multiple levels at which > one can disable MTE or some of its effects: memory type (MAIR) level, > tag allocation (TCR_EL1.ATA), tag checking (SCTLR_EL1.TCF). Apart from > the latter, all the other bits are cached in the TLB which make them > more problematic to toggle at run-time. > > For the kernel, we can currently disable tag checking via the kasan > command line options. For user-space, we don't have a kill switch > specific to MTE, however one can disable the tagged addr ABI and > presumably the C library will avoid generating tagged heap pointers. Just FTR: As discussed off-the-list, there won't be any need for a kill-switch for userspace MTE. Thanks!
