From cde66c2d88da1d73d755109c80ce4c34b917596b Mon Sep 17 00:00:00 2001
From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Date: Wed, 29 Jul 2015 21:15:17 +0200
Subject: [PATCH] s390/bpf: Only clear A and X for converted BPF programs
Only classic BPF programs that have been converted to eBPF need to clear
the A and X registers. We can check for converted programs with:
bpf_prog->type == BPF_PROG_TYPE_UNSPEC
So add the check and skip initialization for real eBPF programs.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
arch/s390/net/bpf_jit_comp.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 04af36728a18..3dd01637f83a 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -387,7 +387,7 @@ static void save_restore_regs(struct bpf_jit *jit, int op)
* Save registers and create stack frame if necessary.
* See stack frame layout desription in "bpf_jit.h"!
*/
-static void bpf_jit_prologue(struct bpf_jit *jit)
+static void bpf_jit_prologue(struct bpf_jit *jit, bool is_classic)
{
if (jit->seen & SEEN_TAIL_CALL) {
/* xc STK_OFF_TCCNT(4,%r15),STK_OFF_TCCNT(%r15) */
@@ -440,13 +440,15 @@ static void bpf_jit_prologue(struct bpf_jit *jit)
EMIT6_DISP_LH(0xe3000000, 0x0004, REG_SKB_DATA, REG_0,
BPF_REG_1, offsetof(struct sk_buff, data));
}
- /* BPF compatibility: clear A (%b0) and X (%b7) registers */
- if (REG_SEEN(BPF_REG_A))
- /* lghi %ba,0 */
- EMIT4_IMM(0xa7090000, BPF_REG_A, 0);
- if (REG_SEEN(BPF_REG_X))
- /* lghi %bx,0 */
- EMIT4_IMM(0xa7090000, BPF_REG_X, 0);
+ /* Clear A (%b0) and X (%b7) registers for converted BPF programs */
+ if (is_classic) {
+ if (REG_SEEN(BPF_REG_A))
+ /* lghi %ba,0 */
+ EMIT4_IMM(0xa7090000, BPF_REG_A, 0);
+ if (REG_SEEN(BPF_REG_X))
+ /* lghi %bx,0 */
+ EMIT4_IMM(0xa7090000, BPF_REG_X, 0);
+ }
}
/*
@@ -1232,7 +1234,7 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp)
jit->lit = jit->lit_start;
jit->prg = 0;
- bpf_jit_prologue(jit);
+ bpf_jit_prologue(jit, fp->type == BPF_PROG_TYPE_UNSPEC);
for (i = 0; i < fp->len; i += insn_count) {
insn_count = bpf_jit_insn(jit, fp, i);
if (insn_count < 0)
--
2.42.0