Re: [PATCH 6/9] powerpc/bpf: Fix BPF_SUB when imm == 0x80000000
From: Christophe Leroy <hidden>
Date: 2021-10-03 08:07:43
Also in:
bpf
Le 01/10/2021 à 23:14, Naveen N. Rao a écrit :
quoted hunk ↗ jump to hunk
We aren't handling subtraction involving an immediate value of 0x80000000 properly. Fix the same. Fixes: 156d0e290e969c ("powerpc/ebpf/jit: Implement JIT compiler for extended BPF") Signed-off-by: Naveen N. Rao <redacted> --- arch/powerpc/net/bpf_jit_comp64.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index ffb7a2877a8469..4641a50e82d50d 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c@@ -333,15 +333,15 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */ case BPF_ALU64 | BPF_ADD | BPF_K: /* dst += imm */ case BPF_ALU64 | BPF_SUB | BPF_K: /* dst -= imm */ - if (BPF_OP(code) == BPF_SUB) - imm = -imm; - if (imm) { - if (imm >= -32768 && imm < 32768) - EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(imm))); - else { - PPC_LI32(b2p[TMP_REG_1], imm); + if (imm > -32768 && imm < 32768) { + EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, + BPF_OP(code) == BPF_SUB ? IMM_L(-imm) : IMM_L(imm))); + } else { + PPC_LI32(b2p[TMP_REG_1], imm); + if (BPF_OP(code) == BPF_SUB) + EMIT(PPC_RAW_SUB(dst_reg, dst_reg, b2p[TMP_REG_1])); + else EMIT(PPC_RAW_ADD(dst_reg, dst_reg, b2p[TMP_REG_1])); - } } goto bpf_alu32_trunc;
There is now so few code common to both BPF_ADD and BPF_SUB that you should make them different cases. While at it, why not also use ADDIS if imm is 32 bits ? That would be an ADDIS/ADDI instead of LIS/ORI/ADD
case BPF_ALU | BPF_MUL | BPF_X: /* (u32) dst *= (u32) src */