[patch/asan] Use lvm.global_ctors instead of symbol name matching to find constructors

[Alexey Samsonov]

On Tue, May 13, 2014 at 1:30 AM, Nico Weber <thakis at chromium.org> wrote:

> samsonov, do you want to try shepherding this in?
>

Definitely. I'll try to test/land it this week.


> The patch should work as-is and it's better than what's currently there,
> but maybe it should happen behind a flag at first (as it might find more
> stuff than the current logic) – not sure about this. And there should
> probably some integration test, like Reid mentioned.
>



>
> On Wed, May 7, 2014 at 11:41 PM, Reid Kleckner <rnk at google.com> wrote:
>
>> No, it's more basic.
>>
>> If I understand the current ASan init-order instrumentation, it only
>> poisons globals of other TUs during _GLOBAL__*.  Initializers of static
>> data members of class templates get their own llvm.global_ctors entry, so
>> other globals are not poisoned, and we get false negatives.
>>
>>
>> On Wed, May 7, 2014 at 12:46 AM, Kostya Serebryany <kcc at google.com>wrote:
>>
>>> This is https://code.google.com/p/address-sanitizer/issues/detail?id=215,
>>> isn't it?
>>>
>>>
>>> On Wed, May 7, 2014 at 4:07 AM, Reid Kleckner <rnk at google.com> wrote:
>>>
>>>> This is a good idea, because it will catch more bugs.  Consider this
>>>> C++:
>>>>
>>>> int foo();
>>>> template <int N> struct X { static int x; };
>>>> template <int N> int X<N>::x = foo();
>>>> int main() { return X<0>::x + X<2>::x + X<3>::x + X<4>::x; }
>>>>
>>>> This will put 4 entries into llvm.global_ctors, none of which are
>>>> called _GLOBAL__*.  We should probably have an ASan integration test in
>>>> compiler-rt for this, when foo accesses some global in a different TU.
>>>>
>>>> On the other hand, all this poisoning and unpoisoning may be expensive.
>>>>  We could batch up all the initializers of equal priority and merge them
>>>> into one initializer bracketed by calls to poison and unpoison.
>>>>
>>>>
>>>> On Tue, May 6, 2014 at 4:55 PM, Nico Weber <thakis at chromium.org> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> here's how the global_ctors version would look. I haven't tested this
>>>>> much (it's different in that it could now instrument multiple
>>>>> constructors per module).
>>>>>
>>>>> Feel free to play with this, and then land this with tweaks, land it
>>>>> as-is, or don't land it, up to you :-)
>>>>>
>>>>> Nico
>>>>>
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>>>>>
>>>>>
>>>>
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>>>>
>>>
>>
>


-- 
Alexey Samsonov, Mountain View, CA
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