From b43a06011e0a4606504391ffb94762276c95610d Mon Sep 17 00:00:00 2001

From: Serhei Makarov <smakarov@redhat.com>

Date: Wed, 7 Nov 2018 13:07:51 -0500

Subject: [PATCH 23/32] pr23860 verifier workaround :: be sure to delete all

 mov rN,rN

An apparent bug in the eBPF verifier fails to preserve register state

when MOVing a register to itself, marking rN as 'unknown scalar'.

Previously bpf-opt.cxx failed to remove spurious MOVs if they were the

final instruction in a basic block. This would fail verification if

the register holds a pointer.

---

 bpf-opt.cxx | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/bpf-opt.cxx b/bpf-opt.cxx

index 904b33b46..8b9a6ea60 100644

--- a/bpf-opt.cxx

+++ b/bpf-opt.cxx

@@ -909,7 +909,7 @@ post_alloc_cleanup (program &p)

 	  n = j->next;

 	  if (j->is_move()

 	      && j->src1->is_reg()

-	      && j->dest->reg() == j->src1->reg() && n)

+	      && j->dest->reg() == j->src1->reg())

 	    {

 	      // Delete no-op moves created by partition merging.

 	      insn *p = j->prev;

-- 

2.14.5