netdev - [PATCH 2/5] bpf ppc64: add support for atomic fetch operations

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Date:   Thu, 12 May 2022 13:15:43 +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 2/5] bpf ppc64: add support for atomic fetch operations

Adding instructions for ppc64 for

atomic[64]_fetch_add
atomic[64]_fetch_and
atomic[64]_fetch_or
atomic[64]_fetch_xor

Signed-off-by: Hari Bathini <hbathini@...ux.ibm.com>
---
 arch/powerpc/net/bpf_jit_comp64.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index b34ed88167f0..504fa459f9f3 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -792,17 +792,25 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
 			else
 				EMIT(PPC_RAW_LWARX(tmp2_reg, tmp1_reg, dst_reg, 0));
 
+			/* Save old value in _R0 */
+			if (imm & BPF_FETCH)
+				EMIT(PPC_RAW_MR(_R0, tmp2_reg));
+
 			switch (imm) {
 			case BPF_ADD:
+			case BPF_ADD | BPF_FETCH:
 				EMIT(PPC_RAW_ADD(tmp2_reg, tmp2_reg, src_reg));
 				break;
 			case BPF_AND:
+			case BPF_AND | BPF_FETCH:
 				EMIT(PPC_RAW_AND(tmp2_reg, tmp2_reg, src_reg));
 				break;
 			case BPF_OR:
+			case BPF_OR | BPF_FETCH:
 				EMIT(PPC_RAW_OR(tmp2_reg, tmp2_reg, src_reg));
 				break;
 			case BPF_XOR:
+			case BPF_XOR | BPF_FETCH:
 				EMIT(PPC_RAW_XOR(tmp2_reg, tmp2_reg, src_reg));
 				break;
 			default:
@@ -812,13 +820,17 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
 				return -EOPNOTSUPP;
 			}
 
-			/* store result back */
+			/* store new value */
 			if (size == BPF_DW)
 				EMIT(PPC_RAW_STDCX(tmp2_reg, tmp1_reg, dst_reg));
 			else
 				EMIT(PPC_RAW_STWCX(tmp2_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));
 			break;
 
 		/*
-- 
2.35.1