From: Alexei Starovoitov <ast@xxxxxxxxxx>
bpf_nop_mov(var) asm macro emits nop register move: rX = rX.
If 'var' is a scalar and not a fixed constant the verifier will assign ID to it.
If it's later spilled the stack slot will carry that ID as well.
Hence the range refining comparison "if rX < const" will update all copies
including spilled slot.
This macro is a temporary workaround until the verifier gets smarter.
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
tools/testing/selftests/bpf/bpf_experimental.h | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index 4c5ba91fa55a..6ecee9866970 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -323,6 +323,11 @@ l_true:\
})
#endif
+#ifndef bpf_nop_mov
+#define bpf_nop_mov(var) \
+ asm volatile("%[reg]=%[reg]"::[reg]"r"((short)var))
+#endif
+
/* Description
* Assert that a conditional expression is true.
* Returns
--
2.34.1
