Messages in this thread Patch in this message | | | From | Xi Wang <> | Subject | [PATCH] arm64: bpf: fix signedness bug in loading 64-bit immediate | Date | Fri, 8 May 2015 01:39:51 -0400 |
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Consider "(u64)insn1.imm << 32 | imm" in the arm64 JIT. Since imm is signed 32-bit, it is sign-extended to 64-bit, losing the high 32 bits. The fix is to convert imm to u32 first and zero-extend it to u64.
Also extend test_bpf to catch this JIT bug; the interpreter is correct.
Before: test_bpf: #58 load 64-bit immediate ret -1 != 1 FAIL (1 times)
After: test_bpf: #58 load 64-bit immediate 74 PASS
Fixes: 30d3d94cc3d5 ("arm64: bpf: add 'load 64-bit immediate' instruction") Cc: Zi Shen Lim <zlim.lnx@gmail.com> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Xi Wang <xi.wang@gmail.com> --- arch/arm64/net/bpf_jit_comp.c | 2 +- lib/test_bpf.c | 3 ++- 2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index edba042b2325..14cdc099fda0 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -487,7 +487,7 @@ emit_cond_jmp: return -EINVAL; } - imm64 = (u64)insn1.imm << 32 | imm; + imm64 = ((u64)(u32)insn1.imm) << 32 | (u64)(u32)imm; emit_a64_mov_i64(dst, imm64, ctx); return 1; diff --git a/lib/test_bpf.c b/lib/test_bpf.c index 80d78c51f65f..9f6849891b5f 100644 --- a/lib/test_bpf.c +++ b/lib/test_bpf.c @@ -1755,7 +1755,8 @@ static struct bpf_test tests[] = { BPF_EXIT_INSN(), BPF_JMP_IMM(BPF_JEQ, R3, 0x1234, 1), BPF_EXIT_INSN(), - BPF_ALU64_IMM(BPF_MOV, R0, 1), + BPF_LD_IMM64(R0, 0x1ffffffffLL), + BPF_ALU64_IMM(BPF_RSH, R0, 32), /* R0 = 1 */ BPF_EXIT_INSN(), }, INTERNAL, -- 1.9.1
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