[llvm] r248253 - [llvm-mc-fuzzer] Support untested instruction discovery for variable length instruction sets like microMIPS.
Daniel Sanders via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 22 02:22:54 PDT 2015
Author: dsanders
Date: Tue Sep 22 04:22:53 2015
New Revision: 248253
URL: http://llvm.org/viewvc/llvm-project?rev=248253&view=rev
Log:
[llvm-mc-fuzzer] Support untested instruction discovery for variable length instruction sets like microMIPS.
Summary:
For fixed length instructions, we can use -max_len to limit the fuzzer to a
single instruction. This doesn't work for variable length instruction sets
since a 4-byte input could consist of one 4-byte instruction or two 2-byte
instructions.
This patch adds a --insn-limit to llvm-mc-fuzzer to limit the input in
terms of instructions processed.
Reviewers: kcc
Subscribers: kcc, llvm-commits
Differential Revision: http://reviews.llvm.org/D12960
Modified:
llvm/trunk/tools/llvm-mc-fuzzer/llvm-mc-fuzzer.cpp
Modified: llvm/trunk/tools/llvm-mc-fuzzer/llvm-mc-fuzzer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-mc-fuzzer/llvm-mc-fuzzer.cpp?rev=248253&r1=248252&r2=248253&view=diff
==============================================================================
--- llvm/trunk/tools/llvm-mc-fuzzer/llvm-mc-fuzzer.cpp (original)
+++ llvm/trunk/tools/llvm-mc-fuzzer/llvm-mc-fuzzer.cpp Tue Sep 22 04:22:53 2015
@@ -44,6 +44,12 @@ static cl::opt<std::string>
cl::desc("Target a specific cpu type (-mcpu=help for details)"),
cl::value_desc("cpu-name"), cl::init(""));
+// This is useful for variable-length instruction sets.
+static cl::opt<unsigned> InsnLimit(
+ "insn-limit",
+ cl::desc("Limit the number of instructions to process (0 for no limit)"),
+ cl::value_desc("count"), cl::init(0));
+
static cl::list<std::string>
MAttrs("mattr", cl::CommaSeparated,
cl::desc("Target specific attributes (-mattr=help for details)"),
@@ -67,11 +73,16 @@ void DisassembleOneInput(const uint8_t *
assert(Ctx);
uint8_t *p = DataCopy.data();
unsigned Consumed;
+ unsigned InstructionsProcessed = 0;
do {
Consumed = LLVMDisasmInstruction(Ctx, p, Size, 0, AssemblyText,
AssemblyTextBufSize);
Size -= Consumed;
p += Consumed;
+
+ InstructionsProcessed ++;
+ if (InsnLimit != 0 && InstructionsProcessed < InsnLimit)
+ break;
} while (Consumed != 0);
LLVMDisasmDispose(Ctx);
}
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