bpf: signal error instead of silent drop for certain invalid asm insn

Currently, an invalid asm insn, either in an asm file or
in an inline asm format, might be silently dropped. This patch
fixed two places where this may happen by
signaling the error so user knows what goes wrong.

The following is an example to demonstrate error messages:

    -bash-4.2$ cat t.c
    int test(void *ctx) {
    #if defined(NO_ERROR)
      asm volatile("r0 = *(u16 *)skb[%0]" : : "i"(2));
    #elif defined(ERROR_1)
      asm volatile("r20 = *(u16 *)skb[%0]" : : "i"(2));
    #elif defined(ERROR_2)
      asm volatile("r0 = *(u16 *)(r1 + ?)" : :);
    #endif
      return 0;
    }
    -bash-4.2$ cat run.sh
    for macro in NO_ERROR ERROR_1 ERROR_2; do
      echo "===== compile for macro" $macro
      clang -D${macro} -O2 -target bpf -emit-llvm -S t.c
      echo "==llc=="
      llc -march=bpf -filetype=obj t.ll
    done
    -bash-4.2$ ./run.sh
    ===== compile for macro NO_ERROR
    ==llc==
    ===== compile for macro ERROR_1
    ==llc==
    <inline asm>:1:2: error: invalid register/token name
            r20 = *(u16 *)skb[2]
            ^
    note: !srcloc = 135
    ===== compile for macro ERROR_2
    ==llc==
    <inline asm>:1:21: error: unexpected token
            r0 = *(u16 *)(r1 + ?)
                               ^
    note: !srcloc = 210
    -bash-4.2$

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 329849

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/Target/BPF/AsmParser/BPFAsmParser.cpp b/llvm/lib/Target/BPF/AsmParser/BPFAsmParser.cpp
index deaa1132580..496f2befde5 100644
--- a/llvm/lib/Target/BPF/AsmParser/BPFAsmParser.cpp
+++ b/llvm/lib/Target/BPF/AsmParser/BPFAsmParser.cpp
@@ -460,7 +460,7 @@ bool BPFAsmParser::ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
   } else if (BPFOperand::isValidIdAtStart (Name))
     Operands.push_back(BPFOperand::createToken(Name, NameLoc));
   else
-    return true;
+    return Error(NameLoc, "invalid register/token name");
 
   while (!getLexer().is(AsmToken::EndOfStatement)) {
     // Attempt to parse token as operator
@@ -472,8 +472,10 @@ bool BPFAsmParser::ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
       continue;
 
     // Attempt to parse token as an immediate
-    if (parseImmediate(Operands) != MatchOperand_Success)
-      return true;
+    if (parseImmediate(Operands) != MatchOperand_Success) {
+      SMLoc Loc = getLexer().getLoc();
+      return Error(Loc, "unexpected token");
+    }
   }
 
   if (getLexer().isNot(AsmToken::EndOfStatement)) {