On Fri, Mar 19, 2021 at 07:54:15AM +0800, Nicolas Boichat wrote:
> From: Thomas Gleixner <[email protected]>
>
> commit 6553896666433e7efec589838b400a2a652b3ffa upstream.
>
> Some code pathes, especially the low level entry code, must be protected
> against instrumentation for various reasons:
>
> - Low level entry code can be a fragile beast, especially on x86.
>
> - With NO_HZ_FULL RCU state needs to be established before using it.
>
> Having a dedicated section for such code allows to validate with tooling
> that no unsafe functions are invoked.
>
> Add the .noinstr.text section and the noinstr attribute to mark
> functions. noinstr implies notrace. Kprobes will gain a section check
> later.
>
> Provide also a set of markers: instrumentation_begin()/end()
>
> These are used to mark code inside a noinstr function which calls
> into regular instrumentable text section as safe.
>
> The instrumentation markers are only active when CONFIG_DEBUG_ENTRY is
> enabled as the end marker emits a NOP to prevent the compiler from merging
> the annotation points. This means the objtool verification requires a
> kernel compiled with this option.
>
> Signed-off-by: Thomas Gleixner <[email protected]>
> Reviewed-by: Alexandre Chartre <[email protected]>
> Acked-by: Peter Zijlstra <[email protected]>
> Link: https://lkml.kernel.org/r/[email protected]
>
> [Nicolas: context conflicts in:
> arch/powerpc/kernel/vmlinux.lds.S
> include/asm-generic/vmlinux.lds.h
> include/linux/compiler.h
> include/linux/compiler_types.h]
> Signed-off-by: Nicolas Boichat <[email protected]>
Did you build this on x86?
I get the following build error:
ld:./arch/x86/kernel/vmlinux.lds:20: syntax error
And that line looks like:
. = ALIGN(8); *(.text.hot .text.hot.*) *(.text .text.fixup) *(.text.unlikely
.text.unlikely.*) *(.text.unknown .text.unknown.*) . = ALIGN(8);
__noinstr_text_start = .; *(.__attribute__((noinline))
__attribute__((no_instrument_function))
__attribute((__section__(".noinstr.text"))).text) __noinstr_text_end = .;
*(.text..refcount) *(.ref.text) *(.meminit.text*) *(.memexit.text*)
So I'm going to drop both of these patches from the queue.
thanks,
greg k-h
