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Date: Thu, 12 May 2022 13:15:46 +0530 From: Hari Bathini <hbathini@...ux.ibm.com> To: bpf@...r.kernel.org, linuxppc-dev <linuxppc-dev@...ts.ozlabs.org> Cc: Michael Ellerman <mpe@...erman.id.au>, "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>, Christophe Leroy <christophe.leroy@...roup.eu>, netdev@...r.kernel.org, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, Jordan Niethe <jniethe5@...il.com> Subject: [PATCH 5/5] bpf ppc32: Add instructions for atomic_[cmp]xchg This adds two atomic opcodes BPF_XCHG and BPF_CMPXCHG on ppc32, 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@...ux.ibm.com> --- arch/powerpc/net/bpf_jit_comp32.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c index 5604ae1b60ab..4690fd6e9e52 100644 --- a/arch/powerpc/net/bpf_jit_comp32.c +++ b/arch/powerpc/net/bpf_jit_comp32.c @@ -829,6 +829,23 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * /* we're done if this succeeded */ PPC_BCC_SHORT(COND_NE, tmp_idx); break; + case BPF_CMPXCHG: + /* Compare with old value in BPF_REG_0 */ + EMIT(PPC_RAW_CMPW(bpf_to_ppc(BPF_REG_0), _R0)); + /* Don't set if different from old value */ + PPC_BCC_SHORT(COND_NE, (ctx->idx + 3) * 4); + fallthrough; + case BPF_XCHG: + /* store new value */ + EMIT(PPC_RAW_STWCX(src_reg, tmp_reg, dst_reg)); + PPC_BCC_SHORT(COND_NE, tmp_idx); + /* + * Return old value in src_reg for BPF_XCHG & + * BPF_REG_0 for BPF_CMPXCHG. + */ + EMIT(PPC_RAW_MR(imm == BPF_XCHG ? src_reg : bpf_to_ppc(BPF_REG_0), + _R0)); + break; default: pr_err_ratelimited("eBPF filter atomic op code %02x (@%d) unsupported\n", code, i); -- 2.35.1
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