From 7b8a9050aa8666e29d19f2eea9917afa72fe00ae Mon Sep 17 00:00:00 2001

From: Serhei Makarov <smakarov@redhat.com>

Date: Mon, 5 Nov 2018 16:58:21 -0500

Subject: [PATCH 20/32] PR23860 partial fix: fix BPF_NEG opcode generation.

Plus some improved diagnostics on malformed code.

* bpf-base.cxx (value::print): Don't abort() on unknown operand.

(opcode_name): Don't abort() on unknown opcode.

(insn::print): Don't abort() on malformed insn.

(program::mk_binary): Ensure BPF_NEG src==dest, don't use BPF_X.

---

 bpf-base.cxx | 15 ++++++++++-----

 1 file changed, 10 insertions(+), 5 deletions(-)

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

index 210efa9aa..24b610cf3 100644

--- a/bpf-base.cxx

+++ b/bpf-base.cxx

@@ -32,7 +32,7 @@ value::print(std::ostream &o) const

     case TMPREG:

       return o << "t" << reg_val;

     default:

-      abort();

+      return o << "<BUG:unknown operand>";

     }

 }

@@ -359,7 +359,7 @@ opcode_name(opcode op)

     case BPF_JMP | BPF_JSET | BPF_K:	opn = "jsetk"; break;

     default:

-      abort();

+      opn = "<BUG:unknown opcode>";

     }

   return opn;

@@ -457,7 +457,7 @@ insn::print(std::ostream &o) const

       return o << opn << "\t" << *src0 << "," << *src1;

     default:

-      abort ();

+      return o << "<BUG:unknown instruction format>";

     }

 }

@@ -705,10 +705,15 @@ program::mk_binary(insn_inserter &ins, opcode op, value *dest,

 void

 program::mk_unary(insn_inserter &ins, opcode op, value *dest, value *src)

 {

+  assert (op == BPF_NEG); // XXX: BPF_NEG is the only unary operator so far.

+

+  if (dest != src) // src is not used for BPF_NEG. BPF negates in-place.

+    mk_mov(ins, dest, src);

+

   insn *i = ins.new_insn();

-  i->code = BPF_ALU64 | BPF_X | op;

+  i->code = BPF_ALU64 | op; // BPF_X is not used for BPF_NEG.

   i->dest = dest;

-  i->src0 = src;

+  i->src0 = dest; // XXX: dest as an ersatz 'source'.

 }

 void

-- 

2.14.5