Messages in this thread | | | Date | Mon, 24 Oct 2022 12:56:03 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH V6 04/11] compiler_types.h: Add __noinstr_section() for noinstr |
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On Thu, Oct 20, 2022 at 08:29:28PM +0800, Guo Ren wrote: > Hi Mark and Lai, > > On Thu, Oct 20, 2022 at 5:15 PM Mark Rutland <mark.rutland@arm.com> wrote: > > > > On Sat, Oct 08, 2022 at 09:54:39AM +0800, Guo Ren wrote: > > > On Mon, Oct 3, 2022 at 7:39 PM Mark Rutland <mark.rutland@arm.com> wrote: > > > > > > > > On Sat, Oct 01, 2022 at 09:24:44PM -0400, guoren@kernel.org wrote: > > > > > From: Lai Jiangshan <laijs@linux.alibaba.com> > > > > > > > > > > And it will be extended for C entry code. > > > > > > > > > > Cc: Borislav Petkov <bp@alien8.de> > > > > > Reviewed-by: Miguel Ojeda <ojeda@kernel.org> > > > > > Reviewed-by: Kees Cook <keescook@chromium.org> > > > > > Suggested-by: Nick Desaulniers <ndesaulniers@google.com> > > > > > Suggested-by: Peter Zijlstra <peterz@infradead.org> > > > > > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> > > > > > --- > > > > > include/linux/compiler_types.h | 8 +++++--- > > > > > 1 file changed, 5 insertions(+), 3 deletions(-) > > > > > > > > > > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > > > > > index 4f2a819fd60a..e9ce11ea4d8b 100644 > > > > > --- a/include/linux/compiler_types.h > > > > > +++ b/include/linux/compiler_types.h > > > > > @@ -227,9 +227,11 @@ struct ftrace_likely_data { > > > > > #endif > > > > > > > > > > /* Section for code which can't be instrumented at all */ > > > > > -#define noinstr \ > > > > > - noinline notrace __attribute((__section__(".noinstr.text"))) \ > > > > > - __no_kcsan __no_sanitize_address __no_profile __no_sanitize_coverage > > > > > +#define __noinstr_section(section) \ > > > > > + noinline notrace __section(section) __no_profile \ > > > > > + __no_kcsan __no_sanitize_address __no_sanitize_coverage > > > > > + > > > > > +#define noinstr __noinstr_section(".noinstr.text") > > > > > > > > One thing proably worth noting here is that while KPROBES will avoid > > > > instrumenting `.noinstr.text`, that won't happen automatically for other > > > > __noinstr_section() sections, and that will need to be inhibited through other > > > > means (e.g. the kprobes blacklist, explicit NOKPROBE_SYMBOL() annotation, or > > > > otherwise). > > > > > > In riscv, "we select HAVE_KPROBES if !XIP_KERNEL", so don't worry > > > about that. I don't think we could enable kprobe for XIP_KERNEL in the > > > future. > > > > Sure; but someone else might use __noinstr_section() elsewhere where this could > > matter, and I was suggesting that we could add a comment as above. > Okay, how about: > > /* Be care KPROBES will avoid instrumenting .noinstr.text, not > __noinstr_section(). */ > #define __noinstr_section(section) \ > noinline notrace __section(section) __no_profile \ > __no_kcsan __no_sanitize_address __no_sanitize_coverage
How about we split this like:
| /* | * Prevent the compiler from instrumenting this code in any way | * This does not prevent instrumentation via KPROBES, which must be | * prevented through other means if necessary. | */ | #define __no_compiler_instrument \ | noinline notrace noinline notrace __no_kcsan \ | __no_sanitize_address __no_sanitize_coverage | | /* | * Section for code which can't be instrumented at all. | * Any code in this section cannot be instrumented with KPROBES. | */ | #define noinstr __no_compiler_instrument section(".noinstr.text")
... then we don't need __noinstr_section(), and IMO the split is clearer.
Peter?
Thanks, Mark.
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