Re: [Xen-devel] [PATCH v2 02/10] x86: assembly, FUNC_START for fn, DATA_START for data

[Ingo Molnar <mingo@xxxxxxxxxx>]

* Jiri Slaby <jslaby@xxxxxxx> wrote:

> On 03/22/2017, 08:25 AM, Ingo Molnar wrote:
> > 
> > * Pavel Machek <pavel@xxxxxx> wrote:
> > 
> >> Hi!
> >>
> >>> -ENTRY(saved_rbp) .quad   0
> >>> -ENTRY(saved_rsi) .quad   0
> >>> -ENTRY(saved_rdi) .quad   0
> >>> -ENTRY(saved_rbx) .quad   0
> >>> +SYM_DATA_START(saved_rbp)                .quad   0
> >>> +SYM_DATA_START(saved_rsi)                .quad   0
> >>> +SYM_DATA_START(saved_rdi)                .quad   0
> >>> +SYM_DATA_START(saved_rbx)                .quad   0
> >>
> >> Does it make sense to call it SYM_DATA_*START* when there's no
> >> corresponding end?
> > 
> > That looks like a bug - I think we should strive for them to always be in 
> > pairs.
> > 
> > Jiri, Josh, could objtool help here perhaps, to detect 'non-terminated' 
> > SYM_*_START() uses? This could be done by emitting debug data into a 
> > special 
> > section and then analyzing that section for unpaired entries. The section 
> > can be 
> > discarded in the final link, it won't show up in the kernel image.
> 
> It should be easier than that. No introduction of other info needed --
> every global symbol without a ".type" or ".size" (i.e. SYM_*_END) should
> be a bug now.

I'm all for that!

Can we detect double ends as well - i.e. do a build check of the full syntax of 
these symbol definition primitives?

Thanks,

        Ingo

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