[llvm] r329849 - bpf: signal error instead of silent drop for certain invalid asm insn

[Yonghong Song via llvm-commits]

Author: yhs
Date: Wed Apr 11 13:24:52 2018
New Revision: 329849

URL: http://llvm.org/viewvc/llvm-project?rev=329849&view=rev
Log:
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 at kernel.org>
Signed-off-by: Yonghong Song <yhs at fb.com>

Modified:
    llvm/trunk/lib/Target/BPF/AsmParser/BPFAsmParser.cpp

Modified: llvm/trunk/lib/Target/BPF/AsmParser/BPFAsmParser.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/BPF/AsmParser/BPFAsmParser.cpp?rev=329849&r1=329848&r2=329849&view=diff
==============================================================================
--- llvm/trunk/lib/Target/BPF/AsmParser/BPFAsmParser.cpp (original)
+++ llvm/trunk/lib/Target/BPF/AsmParser/BPFAsmParser.cpp Wed Apr 11 13:24:52 2018
@@ -460,7 +460,7 @@ bool BPFAsmParser::ParseInstruction(Pars
   } 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(Pars
       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)) {