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

[Robin Murphy]

On 17/03/17 13:58, Andy Gospodarek wrote:
> On Fri, Mar 17, 2017 at 11:11:59AM +0000, Robin Murphy wrote:
>> On 16/03/17 21:04, Andy Gospodarek wrote:
>>>
>>> While I generally agree isn't the entire reason this inline asm exists
>>> -- to fix a binutils issue?  :-)
>>
>> Binutils is required to build the arm64 kernel; if certain versions of
>> binutils packaged by arm64 distros can't cope with certain instructions
>> we need to use, we have to do what we can to make it build. However, if
>> LLVM cannot cope with inline assembly on arm64, then it's pretty clear
>> that the kernel cannot be built with LLVM anyway, thus there is nothing
>> to work around in that regard. Sorry, you've got a straw man there ;)
> 
> I know, right?  I'll see if I can come up with something that appears to
> be less fragile and/or intrusive to the arm64 arch code as I'd really
> like to stop carrying a patch in my devel tree for this.

I'm honestly not sure if I'm serious or not, but:

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 72c58675973e..f52ebad7b096 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -154,6 +154,6 @@ $(src)/*.c: verify_target_bpf
 # useless for BPF samples.
 $(obj)/%.o: $(src)/%.c
        $(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) \
-               -D__KERNEL__ -D__ASM_SYSREG_H -Wno-unused-value
-Wno-pointer-sign \
+               -D__KERNEL__ -D'asm(...)' -Wno-unused-value
-Wno-pointer-sign \
                -Wno-compare-distinct-pointer-types \
                -O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf
-filetype=obj -o $@


?

Robin.