[RFC arm64] samples/bpf: explicitly exclude sysreg sections with asm macros

[Mark Rutland]

Hi,

On Wed, Mar 15, 2017 at 02:31:30PM -0400, Andy Gospodarek wrote:
> On Fri, Mar 10, 2017 at 08:41:13PM +0000, Mark Rutland wrote:
> > On Fri, Mar 10, 2017 at 02:26:56PM -0500, Andy Gospodarek wrote:
> > > On Fri, Mar 10, 2017 at 05:52:30PM +0000, Will Deacon wrote:
> > > > On Thu, Mar 09, 2017 at 06:18:12PM -0500, Andy Gospodarek wrote:

> > > > Why does asm cause compilation to fail?
> > > 
> > > It isn't the ASM itself that causes the compilation to fail, it's the
> > > ASM macros included inside the new ifdef that are problematic.  Here is
> > > what is seen per object file:
> > 
> > > ./arch/arm64/include/asm/barrier.h:62:23: note: expanded from macro
> > > '__smp_store_release'
> > >                 asm volatile ("stlr %1, %0"
> > > \
> > >                                     ^
> > > 1 warning generated.
> > > LLVM ERROR: Inline asm not supported by this streamer because we don't  <----  THIS LINE
> > > have an asm parser for this target
> > 
> > ... so as far as I can see it's the presence of any inline assembly that
> > the tool cannot handle, as LLVM tells us.

> > So why isn't this a problem on other architectures? They're going to
> > have equivalent inline asm getting pulled in, and these samples
> > presumably compiled on at least on architecture in the past.

> As far as I can tell (hoping my regex is proper), x86 doesn't have any
> inline assembly that introduces macros like this in any h-files.

Just to be clear, is the error quoted above at all relevant here?

The error is for an asm statement which does not use assembly macros, in
a different file.

In the error message, LLVM explicitly states that it does not have a
parser for this target's assembly -- which would be a problem for *any*
inline assembly.

How does that specific error relate to the use of assembly macros within
sysreg.h?

... has the wrong error been quoted above?

... does LLVM dump a misleading error message after seeing an assembly
macro (which it presumably can't handle)?

Thanks,
Mark.