powerpc/bpf: use unsigned division instruction for 64-bit operations

BPF_ALU64 div/mod operations are currently using signed division, unlike
BPF_ALU32 operations. Fix the same. DIV64 and MOD64 overflow tests pass
with this fix.

Fixes: 156d0e2 ("powerpc/ebpf/jit: Implement JIT compiler for extended BPF")
Cc: [email protected] # v4.8+
Signed-off-by: Naveen N. Rao <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>

Author: rnav

arch/powerpc/include/asm/ppc-opcode.h

@@ -338,6 +338,7 @@
 #define PPC_INST_MADDLD			0x10000033
 #define PPC_INST_DIVWU			0x7c000396
 #define PPC_INST_DIVD			0x7c0003d2
+#define PPC_INST_DIVDU			0x7c000392
 #define PPC_INST_RLWINM			0x54000000
 #define PPC_INST_RLWINM_DOT		0x54000001
 #define PPC_INST_RLWIMI			0x50000000

arch/powerpc/net/bpf_jit.h

@@ -116,7 +116,7 @@
 				     ___PPC_RA(a) | IMM_L(i))
 #define PPC_DIVWU(d, a, b)	EMIT(PPC_INST_DIVWU | ___PPC_RT(d) |	      \
 				     ___PPC_RA(a) | ___PPC_RB(b))
-#define PPC_DIVD(d, a, b)	EMIT(PPC_INST_DIVD | ___PPC_RT(d) |	      \
+#define PPC_DIVDU(d, a, b)	EMIT(PPC_INST_DIVDU | ___PPC_RT(d) |	      \
 				     ___PPC_RA(a) | ___PPC_RB(b))
 #define PPC_AND(d, a, b)	EMIT(PPC_INST_AND | ___PPC_RA(d) |	      \
 				     ___PPC_RS(a) | ___PPC_RB(b))

arch/powerpc/net/bpf_jit_comp64.c

@@ -399,12 +399,12 @@ static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
 		case BPF_ALU64 | BPF_DIV | BPF_X: /* dst /= src */
 		case BPF_ALU64 | BPF_MOD | BPF_X: /* dst %= src */
 			if (BPF_OP(code) == BPF_MOD) {
-				PPC_DIVD(b2p[TMP_REG_1], dst_reg, src_reg);
+				PPC_DIVDU(b2p[TMP_REG_1], dst_reg, src_reg);
 				PPC_MULD(b2p[TMP_REG_1], src_reg,
 						b2p[TMP_REG_1]);
 				PPC_SUB(dst_reg, dst_reg, b2p[TMP_REG_1]);
 			} else
-				PPC_DIVD(dst_reg, dst_reg, src_reg);
+				PPC_DIVDU(dst_reg, dst_reg, src_reg);
 			break;
 		case BPF_ALU | BPF_MOD | BPF_K: /* (u32) dst %= (u32) imm */
 		case BPF_ALU | BPF_DIV | BPF_K: /* (u32) dst /= (u32) imm */
@@ -432,15 +432,15 @@ static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
 				break;
 			case BPF_ALU64:
 				if (BPF_OP(code) == BPF_MOD) {
-					PPC_DIVD(b2p[TMP_REG_2], dst_reg,
+					PPC_DIVDU(b2p[TMP_REG_2], dst_reg,
 							b2p[TMP_REG_1]);
 					PPC_MULD(b2p[TMP_REG_1],
 							b2p[TMP_REG_1],
 							b2p[TMP_REG_2]);
 					PPC_SUB(dst_reg, dst_reg,
 							b2p[TMP_REG_1]);
 				} else
-					PPC_DIVD(dst_reg, dst_reg,
+					PPC_DIVDU(dst_reg, dst_reg,
 							b2p[TMP_REG_1]);
 				break;
 			}