powerpc/bpf: Fix BPF_MOD when imm == 1

Only ignore the operation if dividing by 1.

Fixes: 156d0e2 ("powerpc/ebpf/jit: Implement JIT compiler for extended BPF")
Signed-off-by: Naveen N. Rao <[email protected]>
Tested-by: Johan Almbladh <[email protected]>
Reviewed-by: Christophe Leroy <[email protected]>
Acked-by: Song Liu <[email protected]>
Acked-by: Johan Almbladh <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/c674ca18c3046885602caebb326213731c675d06.1633464148.git.naveen.n.rao@linux.vnet.ibm.com

Author: rnav

arch/powerpc/net/bpf_jit_comp64.c

@@ -391,8 +391,14 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
 		case BPF_ALU64 | BPF_DIV | BPF_K: /* dst /= imm */
 			if (imm == 0)
 				return -EINVAL;
-			else if (imm == 1)
-				goto bpf_alu32_trunc;
+			if (imm == 1) {
+				if (BPF_OP(code) == BPF_DIV) {
+					goto bpf_alu32_trunc;
+				} else {
+					EMIT(PPC_RAW_LI(dst_reg, 0));
+					break;
+				}
+			}
 
 			PPC_LI32(b2p[TMP_REG_1], imm);
 			switch (BPF_CLASS(code)) {