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[llvm-mc-fuzzer] Support untested instruction discovery for variable length instruction sets like microMIPS.

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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

llvm-svn: 248253
This commit is contained in:
Daniel Sanders 2015-09-22 09:22:53 +00:00
parent f4315577b8
commit d1efb60150
1 changed files with 11 additions and 0 deletions
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11
tools/llvm-mc-fuzzer/llvm-mc-fuzzer.cpp
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@ -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 *Data, size_t Size) {
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);
}