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arm64: bpf: fix 32bit unconditional bswap
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BugLink: https://bugs.launchpad.net/bugs/2065400

[ Upstream commit a51cd6b ]

In case when is64 == 1 in emit(A64_REV32(is64, dst, dst), ctx) the
generated insn reverses byte order for both high and low 32-bit words,
resuling in an incorrect swap as indicated by the jit test:

[ 9757.262607] test_bpf: torvalds#312 BSWAP 16: 0x0123456789abcdef -> 0xefcd jited:1 8 PASS
[ 9757.264435] test_bpf: torvalds#313 BSWAP 32: 0x0123456789abcdef -> 0xefcdab89 jited:1 ret 1460850314 != -271733879 (0x5712ce8a != 0xefcdab89)FAIL (1 times)
[ 9757.266260] test_bpf: torvalds#314 BSWAP 64: 0x0123456789abcdef -> 0x67452301 jited:1 8 PASS
[ 9757.268000] test_bpf: torvalds#315 BSWAP 64: 0x0123456789abcdef >> 32 -> 0xefcdab89 jited:1 8 PASS
[ 9757.269686] test_bpf: torvalds#316 BSWAP 16: 0xfedcba9876543210 -> 0x1032 jited:1 8 PASS
[ 9757.271380] test_bpf: torvalds#317 BSWAP 32: 0xfedcba9876543210 -> 0x10325476 jited:1 ret -1460850316 != 271733878 (0xa8ed3174 != 0x10325476)FAIL (1 times)
[ 9757.273022] test_bpf: torvalds#318 BSWAP 64: 0xfedcba9876543210 -> 0x98badcfe jited:1 7 PASS
[ 9757.274721] test_bpf: torvalds#319 BSWAP 64: 0xfedcba9876543210 >> 32 -> 0x10325476 jited:1 9 PASS

Fix this by forcing 32bit variant of rev32.

Fixes: 1104247 ("bpf, arm64: Support unconditional bswap")
Signed-off-by: Artem Savkov <asavkov@redhat.com>
Tested-by: Puranjay Mohan <puranjay12@gmail.com>
Acked-by: Puranjay Mohan <puranjay12@gmail.com>
Acked-by: Xu Kuohai <xukuohai@huawei.com>
Message-ID: <20240321081809.158803-1-asavkov@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>
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@sm00th @smb49
sm00th authored and smb49 committed Jun 7, 2024
1 parent 869918d commit 9192c10
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion arch/arm64/net/bpf_jit_comp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -876,7 +876,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
emit(A64_UXTH(is64, dst, dst), ctx);
break;
case 32:
emit(A64_REV32(is64, dst, dst), ctx);
emit(A64_REV32(0, dst, dst), ctx);
/* upper 32 bits already cleared */
break;
case 64:
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