FAILED: patch "[PATCH] s390/bpf: clear correct BPF accumulator register" failed to apply to 4.2-stable tree

The patch below does not apply to the 4.2-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Michael Holzheu <[email protected]>
Date: Wed, 29 Jul 2015 21:15:14 +0200
Subject: [PATCH] s390/bpf: clear correct BPF accumulator register

Currently we assumed the following BPF to eBPF register mapping:

- BPF_REG_A -> BPF_REG_7
- BPF_REG_X -> BPF_REG_8

Unfortunately this mapping is wrong. The correct mapping is:

- BPF_REG_A -> BPF_REG_0
- BPF_REG_X -> BPF_REG_7

So clear the correct registers and use the BPF_REG_A and BPF_REG_X macros instead of BPF_REG_0/7.

index 79c731e8d178..01ad16608f66 100644
@@ -448,13 +448,13 @@ 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 (%b7) and X (%b8) registers */
-	if (REG_SEEN(BPF_REG_7))
-		/* lghi %b7,0 */
-		EMIT4_IMM(0xa7090000, BPF_REG_7, 0);
-	if (REG_SEEN(BPF_REG_8))
-		/* lghi %b8,0 */
-		EMIT4_IMM(0xa7090000, BPF_REG_8, 0);
+	/* 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);
 }
 
 /*