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.
