diff mbox series

[v5,bpf-next,3/4] bpf: Add cond_break macro

Message ID 20240305045219.66142-4-alexei.starovoitov@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Introduce may_goto and cond_break | expand

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netdev/cc_maintainers warning 15 maintainers not CCed: song@kernel.org haoluo@google.com llvm@lists.linux.dev jolsa@kernel.org mykolal@fb.com kpsingh@kernel.org ndesaulniers@google.com shuah@kernel.org nathan@kernel.org yonghong.song@linux.dev martin.lau@linux.dev justinstitt@google.com linux-kselftest@vger.kernel.org morbo@google.com sdf@google.com
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netdev/checkpatch warning WARNING: Avoid line continuations in quoted strings WARNING: Avoid unnecessary line continuations WARNING: Macros with flow control statements should be avoided WARNING: labels should not be indented
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Commit Message

Alexei Starovoitov March 5, 2024, 4:52 a.m. UTC 
From: Alexei Starovoitov <ast@kernel.org>

Use may_goto instruction to implement cond_break macro.
Ideally the macro should be written as:
  asm volatile goto(".byte 0xe5;
                     .byte 0;
                     .short %l[l_break] ...
                     .long 0;
but LLVM doesn't recognize fixup of 2 byte PC relative yet.
Hence use
  asm volatile goto(".byte 0xe5;
                     .byte 0;
                     .long %l[l_break] ...
                     .short 0;
that produces correct asm on little endian.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 tools/testing/selftests/bpf/bpf_experimental.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index 0d749006d107..bc9a0832ae72 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -326,6 +326,18 @@  l_true:												\
        })
 #endif
 
+#define cond_break					\
+	({ __label__ l_break, l_continue;		\
+	 asm volatile goto("1:.byte 0xe5;			\
+		      .byte 0;				\
+		      .long ((%l[l_break] - 1b - 8) / 8) & 0xffff;	\
+		      .short 0"				\
+		      :::: l_break);			\
+	goto l_continue;				\
+	l_break: break;					\
+	l_continue:;					\
+	})
+
 #ifndef bpf_nop_mov
 #define bpf_nop_mov(var) \
 	asm volatile("%[reg]=%[reg]"::[reg]"r"((short)var))