On Wed, Nov 2, 2016 at 12:51 AM, steven shi <[email protected]> wrote:
> Hello,
>
> I like to use the -fsanitize=kernel-address option, and I believe it better
> fit my firmware scenario rather than -fsanitize=address. I but after take a
> look at the current LLVM Asan implementation, I have some concerns that
> kernel-address might disable the global and stack instrumentations by
> default as below code. Does LLVM Asan really support
> -fsanitize=kernel-address to check glabal and stack buffer issues?
>
>
>
> http://llvm.org/svn/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
>
> line 1723:
>
> // TODO(glider): temporarily disabled globals instrumentation for KASan.
>
> if (ClGlobals && !CompileKernel) {
>
> Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
>
> assert(CtorFunc);
>
> IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
>
> Changed |= InstrumentGlobals(IRB, M);
>
> }
>
>
>
> Line2287:
>
> bool DoStackMalloc = ClUseAfterReturn && !ASan.CompileKernel &&
>
> LocalStackSize <= kMaxStackMallocSize;
>
>
> The original and complete background is in below email thread:
> http://lists.llvm.org/pipermail/llvm-dev/2016-November/106746.html
Hi Steven,
We need to remove "!CompileKernel" from this condition as the TODO
says. It was just a temporary workaround:
// TODO(glider): temporarily disabled globals instrumentation for KASan.
if (ClGlobals && !CompileKernel) {
Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
assert(CtorFunc);
IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
Changed |= InstrumentGlobals(IRB, M);
}
However, we also need to remove "CompileKernel" from this condition:
bool UseCalls =
CompileKernel ||
(ClInstrumentationWithCallsThreshold >= 0 &&
ToInstrument.size() > (unsigned)ClInstrumentationWithCallsThreshold);
Then -fsanitize=kernel-address will not give you calls by default,
only if you add the threshold flag. But you can also get calls with
-fsanitize=address and the threshold flag, and it will also give you
stack and globals today without any changes in llvm.
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