On Tue, Feb 15, 2022 at 10:39:46AM +0100, Arnd Bergmann wrote: > On Tue, Feb 15, 2022 at 10:21 AM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > On Tue, 15 Feb 2022 at 10:13, Arnd Bergmann <arnd@xxxxxxxxxx> wrote: > > > > arm64 also has this leading up to the range check, and I think we'd no > > longer need it: > > > > if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) && > > (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR))) > > addr = untagged_addr(addr); > > I suspect the expensive part here is checking the two flags, as untagged_addr() > seems to always just add a sbfx instruction. Would this work? > > #ifdef CONFIG_ARM64_TAGGED_ADDR_ABI > #define access_ok(ptr, size) __access_ok(untagged_addr(ptr), (size)) > #else // the else path is the default, this can be left out. > #define access_ok(ptr, size) __access_ok((ptr), (size)) > #endif This would be an ABI change, e.g. for tasks without TIF_TAGGED_ADDR. I don't think we should change this as part of this series. Thanks, Mark.
