On Thu, Aug 27, 2020 at 11:56:49AM +0100, Vincenzo Frascino wrote: > On 8/27/20 11:38 AM, Catalin Marinas wrote: > > On Fri, Aug 14, 2020 at 07:27:06PM +0200, Andrey Konovalov wrote: > >> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c > >> index 7717ea9bc2a7..cfac7d02f032 100644 > >> --- a/arch/arm64/kernel/mte.c > >> +++ b/arch/arm64/kernel/mte.c > >> @@ -18,10 +18,14 @@ > >> > >> #include <asm/barrier.h> > >> #include <asm/cpufeature.h> > >> +#include <asm/kasan.h> > >> +#include <asm/kprobes.h> > >> #include <asm/mte.h> > >> #include <asm/ptrace.h> > >> #include <asm/sysreg.h> > >> > >> +u64 gcr_kernel_excl __read_mostly; > > > > Could we make this __ro_after_init? > > Yes, it makes sense, it should be updated only once through mte_init_tags(). > > Something to consider though here is that this might not be the right approach > if in future we want to add stack tagging. In such a case we need to know the > kernel exclude mask before any C code is executed. Initializing the mask via > mte_init_tags() it is too late. It depends on how stack tagging ends up in the kernel, whether it uses ADDG/SUBG or not. If it's only IRG, I think it can cope with changing the GCR_EL1.Excl in the middle of a function. > I was thinking to add a compilation define instead of having gcr_kernel_excl in > place. This might not work if the kernel excl mask is meant to change during the > execution. A macro with the default value works for me. That's what it basically is currently, only that it ends up in a variable. -- Catalin
