Re: [PATCH v4 04/29] objtool: Add a pass for generating __mcount_loc

[Miroslav Benes]

Hi Sami,

On Tue, 29 Sep 2020, Sami Tolvanen wrote:

> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> 
> Add the --mcount option for generating __mcount_loc sections
> needed for dynamic ftrace. Using this pass requires the kernel to
> be compiled with -mfentry and CC_USING_NOP_MCOUNT to be defined
> in Makefile.
> 
> Link: https://lore.kernel.org/lkml/20200625200235.GQ4781@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> [Sami: rebased to mainline, dropped config changes, fixed to actually use
>        --mcount, and wrote a commit message.]
> Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

I am sorry to reply on v4. Should have been sooner.

Julien has been sending patches to make objtool's check functionality 
arch-agnostic as much as possible. So it seems to me that the patch should 
be based on the effort

I also wonder about making 'mcount' command separate from 'check'. Similar 
to what is 'orc' now. But that could be done later.

See tip-tree/objtool/core for both.

Thanks
Miroslav