On Wed, May 27, 2020 at 08:46:59AM +0100, Will Deacon wrote: > On Fri, May 15, 2020 at 06:16:01PM +0100, Catalin Marinas wrote: > > By default, even if PROT_MTE is set on a memory range, there is no tag > > check fault reporting (SIGSEGV). Introduce a set of option to the > > exiting prctl(PR_SET_TAGGED_ADDR_CTRL) to allow user control of the tag > > check fault mode: > > > > PR_MTE_TCF_NONE - no reporting (default) > > PR_MTE_TCF_SYNC - synchronous tag check fault reporting > > PR_MTE_TCF_ASYNC - asynchronous tag check fault reporting > > > > These options translate into the corresponding SCTLR_EL1.TCF0 bitfield, > > context-switched by the kernel. Note that uaccess done by the kernel is > > not checked and cannot be configured by the user. > > > > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> > > Cc: Will Deacon <will@xxxxxxxxxx> > > --- > > > > Notes: > > v3: > > - Use SCTLR_EL1_TCF0_NONE instead of 0 for consistency. > > - Move mte_thread_switch() in this patch from an earlier one. In > > addition, it is called after the dsb() in __switch_to() so that any > > asynchronous tag check faults have been registered in the TFSR_EL1 > > registers (to be added with the in-kernel MTE support. > > > > v2: > > - Handle SCTLR_EL1_TCF0_NONE explicitly for consistency with PR_MTE_TCF_NONE. > > - Fix SCTLR_EL1 register setting in flush_mte_state() (thanks to Peter > > Collingbourne). > > - Added ISB to update_sctlr_el1_tcf0() since, with the latest > > architecture update/fix, the TCF0 field is used by the uaccess > > routines. > > > > arch/arm64/include/asm/mte.h | 14 ++++++ > > arch/arm64/include/asm/processor.h | 3 ++ > > arch/arm64/kernel/mte.c | 77 ++++++++++++++++++++++++++++++ > > arch/arm64/kernel/process.c | 26 ++++++++-- > > include/uapi/linux/prctl.h | 6 +++ > > 5 files changed, 123 insertions(+), 3 deletions(-) > > Dave is working on man pages for prctl() (and I think also ptrace). I think > it would be /very/ useful for us to have some RFC patches on top of his work > adding documentation for the MTE interactions, as we found some other minor > issues/inconsistencies as a direct result of writing and reviewing the man > page for our existing interfaces. I have a local draft for the address tagging and MTE prctls already btw. I hadn't posted them yet so as to focus on nailing the "easy" stuff down ;) If I have time I'll try and get them posted today so that people can take a look before next week. Cheers ---Dave
