s390/bpf,jit: fix 32 bit divisions, use unsigned divide instructions

[ Upstream commit 3af57f78c38131b7a66e2b01e06fdacae01992a3 ]

The s390 bpf jit compiler emits the signed divide instructions "dr" and "d"
for unsigned divisions.
This can cause problems: the dividend will be zero extended to a 64 bit value
and the divisor is the 32 bit signed value as specified A or X accumulator,
even though A and X are supposed to be treated as unsigned values.

The divide instrunctions will generate an exception if the result cannot be
expressed with a 32 bit signed value.
This is the case if e.g. the dividend is 0xffffffff and the divisor either 1
or also 0xffffffff (signed: -1).

To avoid all these issues simply use unsigned divide instructions.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index b7792d499da6..1919db6c0607 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -335,16 +335,16 @@ static int bpf_jit_insn(struct bpf_jit *jit, struct sock_filter *filter,
                 EMIT4_PCREL(0xa7840000, (jit->ret0_ip - jit->prg));
                 /* lhi %r4,0 */
                 EMIT4(0xa7480000);
-                /* dr %r4,%r12 */
-                EMIT2(0x1d4c);
+                /* dlr %r4,%r12 */
+                EMIT4(0xb997004c);
                 break;
         case BPF_S_ALU_DIV_K: /* A /= K */
                 if (K == 1)
                         break;
                 /* lhi %r4,0 */
                 EMIT4(0xa7480000);
-                /* d %r4,<d(K)>(%r13) */
-                EMIT4_DISP(0x5d40d000, EMIT_CONST(K));
+                /* dl %r4,<d(K)>(%r13) */
+                EMIT6_DISP(0xe340d000, 0x0097, EMIT_CONST(K));
                 break;
         case BPF_S_ALU_MOD_X: /* A %= X */
                 jit->seen |= SEEN_XREG | SEEN_RET0;
@@ -354,8 +354,8 @@ static int bpf_jit_insn(struct bpf_jit *jit, struct sock_filter *filter,
                 EMIT4_PCREL(0xa7840000, (jit->ret0_ip - jit->prg));
                 /* lhi %r4,0 */
                 EMIT4(0xa7480000);
-                /* dr %r4,%r12 */
-                EMIT2(0x1d4c);
+                /* dlr %r4,%r12 */
+                EMIT4(0xb997004c);
                 /* lr %r5,%r4 */
                 EMIT2(0x1854);
                 break;
@@ -367,8 +367,8 @@ static int bpf_jit_insn(struct bpf_jit *jit, struct sock_filter *filter,
                 }
                 /* lhi %r4,0 */
                 EMIT4(0xa7480000);
-                /* d %r4,<d(K)>(%r13) */
-                EMIT4_DISP(0x5d40d000, EMIT_CONST(K));
+                /* dl %r4,<d(K)>(%r13) */
+                EMIT6_DISP(0xe340d000, 0x0097, EMIT_CONST(K));
                 /* lr %r5,%r4 */
                 EMIT2(0x1854);
                 break;