Hi,

I am experiencing the following error (verbose log attached) when 
building the wireguard module on my Arch Linux running 4.20-rc4:

% make -C /usr/lib/modules/4.20.0-rc4-1-git/build/ M=$(pwd) modules 
 
 

make: Entering directory '/usr/lib/modules/4.20.0-rc4-1-git/build' 
 
 

   CC [M]  /home/martin/projects/wireguard/git/src/main.o 
 
 

   CC [M]  /home/martin/projects/wireguard/git/src/noise.o 
 
 

./arch/x86/include/asm/refcount.h: Assembler messages: 
 
 

./arch/x86/include/asm/refcount.h:90: Error: no such instruction: 
`lock_prefix decl 680(%rbx)' 
 

./arch/x86/include/asm/refcount.h:91: Error: no such instruction: 
`refcount_check_lt_zero counter="680(%rbx)"' 
 

./arch/x86/include/asm/refcount.h:90: Error: no such instruction: 
`lock_prefix decl 680(%rbx)' 
 

./arch/x86/include/asm/refcount.h:91: Error: no such instruction: 
`refcount_check_lt_zero counter="680(%rbx)"' 
 

./arch/x86/include/asm/atomic.h:200: Error: no such instruction: 
`lock_prefix cmpxchgl %ecx,(%rdx)' 
 

./arch/x86/include/asm/refcount.h:109: Error: no such instruction: 
`refcount_error counter="(%rdx)"' 
 

./arch/x86/include/asm/refcount.h:90: Error: no such instruction: 
`lock_prefix decl 680(%rbx)' 
 

./arch/x86/include/asm/refcount.h:91: Error: no such instruction: 
`refcount_check_lt_zero counter="680(%rbx)"' 
 

./arch/x86/include/asm/atomic64_64.h:160: Error: no such instruction: 
`lock_prefix xaddq %rax,keypair_counter(%rip)' 
 

make[1]: *** [scripts/Makefile.build:294: 
/home/martin/projects/wireguard/git/src/noise.o] Error 1 
 
 

make: *** [Makefile:1565: 
_module_/home/martin/projects/wireguard/git/src] Error 2 
 
 

make: Leaving directory '/usr/lib/modules/4.20.0-rc4-1-git/build'

The issue seems to be caused by this series:
https://lkml.org/lkml/2018/10/4/25

The compilation succeeds when building against a full checkout of the 
kernel, so I suspect that something is missing in the linux-headers 
package on my distro.

Can you point me any direction to make this work? Let me know if any 
testing/logging is needed.

Thanks.

-- 
Kind regards,
Martin Hundebøll
Embedded Linux Consultant

+45 61 65 54 61
martin@geanix.com

Geanix IVS
https://geanix.com
DK39600706