This adds two atomic opcodes BPF_XCHG and BPF_CMPXCHG on ppc64, both of which include the BPF_FETCH flag. The kernel's atomic_cmpxchg operation fundamentally has 3 operands, but we only have two register fields. Therefore the operand we compare against (the kernel's API calls it 'old') is hard-coded to be BPF_REG_R0. Also, kernel's atomic_cmpxchg returns the previous value at dst_reg + off. JIT the same for BPF too with return value put in BPF_REG_0. BPF_REG_R0 = atomic_cmpxchg(dst_reg + off, BPF_REG_R0, src_reg); Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxx> --- arch/powerpc/net/bpf_jit_comp64.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index 504fa459f9f3..df9e20b22ccb 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -783,6 +783,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * */ case BPF_STX | BPF_ATOMIC | BPF_W: case BPF_STX | BPF_ATOMIC | BPF_DW: + u32 save_reg = tmp2_reg; + u32 ret_reg = src_reg; + /* Get offset into TMP_REG_1 */ EMIT(PPC_RAW_LI(tmp1_reg, off)); tmp_idx = ctx->idx * 4; @@ -813,6 +816,24 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * case BPF_XOR | BPF_FETCH: EMIT(PPC_RAW_XOR(tmp2_reg, tmp2_reg, src_reg)); break; + case BPF_CMPXCHG: + /* + * Return old value in BPF_REG_0 for BPF_CMPXCHG & + * in src_reg for other cases. + */ + ret_reg = bpf_to_ppc(BPF_REG_0); + + /* Compare with old value in BPF_R0 */ + if (size == BPF_DW) + EMIT(PPC_RAW_CMPD(bpf_to_ppc(BPF_REG_0), tmp2_reg)); + else + EMIT(PPC_RAW_CMPW(bpf_to_ppc(BPF_REG_0), tmp2_reg)); + /* Don't set if different from old value */ + PPC_BCC_SHORT(COND_NE, (ctx->idx + 3) * 4); + fallthrough; + case BPF_XCHG: + save_reg = src_reg; + break; default: pr_err_ratelimited( "eBPF filter atomic op code %02x (@%d) unsupported\n", @@ -822,15 +843,14 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * /* store new value */ if (size == BPF_DW) - EMIT(PPC_RAW_STDCX(tmp2_reg, tmp1_reg, dst_reg)); + EMIT(PPC_RAW_STDCX(save_reg, tmp1_reg, dst_reg)); else - EMIT(PPC_RAW_STWCX(tmp2_reg, tmp1_reg, dst_reg)); + EMIT(PPC_RAW_STWCX(save_reg, tmp1_reg, dst_reg)); /* we're done if this succeeded */ PPC_BCC_SHORT(COND_NE, tmp_idx); - /* For the BPF_FETCH variant, get old value into src_reg */ if (imm & BPF_FETCH) - EMIT(PPC_RAW_MR(src_reg, _R0)); + EMIT(PPC_RAW_MR(ret_reg, _R0)); break; /* -- 2.35.1
