[PATCH bpf-next] selftests/bpf: Using llvm may_goto inline asm for cond_break macro

[PATCH bpf-next] selftests/bpf: Using llvm may_goto inline asm for cond_break macro

[Yonghong Song]

Currently, cond_break macro uses bytes to encode the may_goto insn.
Patch [1] in llvm implemented may_goto insn in BPF backend.
Replace byte-level encoding with llvm inline asm for better usability.
Using llvm may_goto insn is controlled by macro __BPF_FEATURE_MAY_GOTO.

  [1] https://github.com/llvm/llvm-project/commit/0e0bfacff71859d1f9212205f8f873d47029d3fb

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
 tools/testing/selftests/bpf/bpf_experimental.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index a5b9df38c162..3329ea080865 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -326,6 +326,16 @@ l_true:												\
        })
 #endif
 
+#ifdef __BPF_FEATURE_MAY_GOTO
+#define cond_break					\
+	({ __label__ l_break, l_continue;		\
+	 asm volatile goto("may_goto %l[l_break]"	\
+		      :::: l_break);			\
+	goto l_continue;				\
+	l_break: break;					\
+	l_continue:;					\
+	})
+#else
 #define cond_break					\
 	({ __label__ l_break, l_continue;		\
 	 asm volatile goto("1:.byte 0xe5;			\
@@ -337,6 +347,7 @@ l_true:												\
 	l_break: break;					\
 	l_continue:;					\
 	})
+#endif
 
 #ifndef bpf_nop_mov
 #define bpf_nop_mov(var) \
-- 
2.43.0

RE: [PATCH bpf-next] selftests/bpf: Using llvm may_goto inline asm for cond_break macro

[John Fastabend]

Yonghong Song wrote:
> Currently, cond_break macro uses bytes to encode the may_goto insn.
> Patch [1] in llvm implemented may_goto insn in BPF backend.
> Replace byte-level encoding with llvm inline asm for better usability.
> Using llvm may_goto insn is controlled by macro __BPF_FEATURE_MAY_GOTO.
> 
>   [1] https://github.com/llvm/llvm-project/commit/0e0bfacff71859d1f9212205f8f873d47029d3fb
> 
> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
> ---
>  tools/testing/selftests/bpf/bpf_experimental.h | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
> index a5b9df38c162..3329ea080865 100644
> --- a/tools/testing/selftests/bpf/bpf_experimental.h
> +++ b/tools/testing/selftests/bpf/bpf_experimental.h
> @@ -326,6 +326,16 @@ l_true:												\
>         })
>  #endif
>  
> +#ifdef __BPF_FEATURE_MAY_GOTO
> +#define cond_break					\
> +	({ __label__ l_break, l_continue;		\
> +	 asm volatile goto("may_goto %l[l_break]"	\
> +		      :::: l_break);			\
> +	goto l_continue;				\
> +	l_break: break;					\
> +	l_continue:;					\
> +	})
> +#else
>  #define cond_break					\
>  	({ __label__ l_break, l_continue;		\
>  	 asm volatile goto("1:.byte 0xe5;			\
> @@ -337,6 +347,7 @@ l_true:												\
>  	l_break: break;					\
>  	l_continue:;					\
>  	})
> +#endif
>  
>  #ifndef bpf_nop_mov
>  #define bpf_nop_mov(var) \
> -- 
> 2.43.0
> 
> 

Acked-by: John Fastabend <john.fastabend@gmail.com>

Re: [PATCH bpf-next] selftests/bpf: Using llvm may_goto inline asm for cond_break macro

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:

On Mon,  1 Apr 2024 19:54:46 -0700 you wrote:
> Currently, cond_break macro uses bytes to encode the may_goto insn.
> Patch [1] in llvm implemented may_goto insn in BPF backend.
> Replace byte-level encoding with llvm inline asm for better usability.
> Using llvm may_goto insn is controlled by macro __BPF_FEATURE_MAY_GOTO.
> 
>   [1] https://github.com/llvm/llvm-project/commit/0e0bfacff71859d1f9212205f8f873d47029d3fb
> 
> [...]

Here is the summary with links:
  - [bpf-next] selftests/bpf: Using llvm may_goto inline asm for cond_break macro
    https://git.kernel.org/bpf/bpf-next/c/965c6167c93f

You are awesome, thank you!
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