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 <hbath...@linux.ibm.com>
---
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
