linux-kernel - [PATCH] nfp: bpf: Fix bitwise vs. logical OR warning

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Message-Id: <20211018193101.2340261-1-nathan@kernel.org>
Date:   Mon, 18 Oct 2021 12:31:01 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Simon Horman <simon.horman@...igine.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        oss-drivers@...igine.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        llvm@...ts.linux.dev, Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] nfp: bpf: Fix bitwise vs. logical OR warning

A new warning in clang points out two places in this driver where
boolean expressions are being used with a bitwise OR instead of a
logical one:

drivers/net/ethernet/netronome/nfp/nfp_asm.c:199:20: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
        reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                             ||
drivers/net/ethernet/netronome/nfp/nfp_asm.c:199:20: note: cast one or both operands to int to silence this warning
drivers/net/ethernet/netronome/nfp/nfp_asm.c:280:20: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
        reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                             ||
drivers/net/ethernet/netronome/nfp/nfp_asm.c:280:20: note: cast one or both operands to int to silence this warning
2 errors generated.

The motivation for the warning is that logical operations short circuit
while bitwise operations do not. In this case, it does not seem like
short circuiting is harmful so implement the suggested fix of changing
to a logical operation to fix the warning.

Link: https://github.com/ClangBuiltLinux/linux/issues/1479
Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 drivers/net/ethernet/netronome/nfp/nfp_asm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_asm.c b/drivers/net/ethernet/netronome/nfp/nfp_asm.c
index 2643ea5948f4..154399c5453f 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_asm.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_asm.c
@@ -196,7 +196,7 @@ int swreg_to_unrestricted(swreg dst, swreg lreg, swreg rreg,
 	}
 
 	reg->dst_lmextn = swreg_lmextn(dst);
-	reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
+	reg->src_lmextn = swreg_lmextn(lreg) || swreg_lmextn(rreg);
 
 	return 0;
 }
@@ -277,7 +277,7 @@ int swreg_to_restricted(swreg dst, swreg lreg, swreg rreg,
 	}
 
 	reg->dst_lmextn = swreg_lmextn(dst);
-	reg->src_lmextn = swreg_lmextn(lreg) | swreg_lmextn(rreg);
+	reg->src_lmextn = swreg_lmextn(lreg) || swreg_lmextn(rreg);
 
 	return 0;
 }

base-commit: 041c61488236a5a84789083e3d9f0a51139b6edf
-- 
2.33.1.637.gf443b226ca