[PATCH bpf-next] samples/bpf: fix build with new clang

[PATCH bpf-next] samples/bpf: fix build with new clang

[Alexei Starovoitov]

clang started to error on invalid asm clobber usage in x86 headers
and many bpf program samples failed to build with the message:

  CLANG-bpf  /data/users/ast/bpf-next/samples/bpf/xdp_redirect_kern.o
In file included from /data/users/ast/bpf-next/samples/bpf/xdp_redirect_kern.c:14:
In file included from ../include/linux/in.h:23:
In file included from ../include/uapi/linux/in.h:24:
In file included from ../include/linux/socket.h:8:
In file included from ../include/linux/uio.h:14:
In file included from ../include/crypto/hash.h:16:
In file included from ../include/linux/crypto.h:26:
In file included from ../include/linux/uaccess.h:5:
In file included from ../include/linux/sched.h:15:
In file included from ../include/linux/sem.h:5:
In file included from ../include/uapi/linux/sem.h:5:
In file included from ../include/linux/ipc.h:9:
In file included from ../include/linux/refcount.h:72:
../arch/x86/include/asm/refcount.h:72:36: error: asm-specifier for input or output variable conflicts with asm clobber list
                                         r->refs.counter, e, "er", i, "cx");
                                                                      ^
../arch/x86/include/asm/refcount.h:86:27: error: asm-specifier for input or output variable conflicts with asm clobber list
                                         r->refs.counter, e, "cx");
                                                             ^
2 errors generated.

Override volatile() to workaround the problem.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 samples/bpf/asm_goto_workaround.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/samples/bpf/asm_goto_workaround.h b/samples/bpf/asm_goto_workaround.h
index 5cd7c1d1a5d5..7409722727ca 100644
--- a/samples/bpf/asm_goto_workaround.h
+++ b/samples/bpf/asm_goto_workaround.h
@@ -13,4 +13,5 @@
 #define asm_volatile_goto(x...) asm volatile("invalid use of asm_volatile_goto")
 #endif
 
+#define volatile(x...) volatile("")
 #endif
-- 
2.20.0

Re: [PATCH bpf-next] samples/bpf: fix build with new clang

[Daniel Borkmann]

On 04/04/2019 11:37 PM, Alexei Starovoitov wrote:
> clang started to error on invalid asm clobber usage in x86 headers
> and many bpf program samples failed to build with the message:
> 
>   CLANG-bpf  /data/users/ast/bpf-next/samples/bpf/xdp_redirect_kern.o
> In file included from /data/users/ast/bpf-next/samples/bpf/xdp_redirect_kern.c:14:
> In file included from ../include/linux/in.h:23:
> In file included from ../include/uapi/linux/in.h:24:
> In file included from ../include/linux/socket.h:8:
> In file included from ../include/linux/uio.h:14:
> In file included from ../include/crypto/hash.h:16:
> In file included from ../include/linux/crypto.h:26:
> In file included from ../include/linux/uaccess.h:5:
> In file included from ../include/linux/sched.h:15:
> In file included from ../include/linux/sem.h:5:
> In file included from ../include/uapi/linux/sem.h:5:
> In file included from ../include/linux/ipc.h:9:
> In file included from ../include/linux/refcount.h:72:
> ../arch/x86/include/asm/refcount.h:72:36: error: asm-specifier for input or output variable conflicts with asm clobber list
>                                          r->refs.counter, e, "er", i, "cx");
>                                                                       ^
> ../arch/x86/include/asm/refcount.h:86:27: error: asm-specifier for input or output variable conflicts with asm clobber list
>                                          r->refs.counter, e, "cx");
>                                                              ^
> 2 errors generated.
> 
> Override volatile() to workaround the problem.
> 
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Applied, thanks!