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Re: [PATCH 1/2] Add private_function for private functions within glibc

On Thu, Jun 22, 2017 at 6:40 AM, Florian Weimer <> wrote:
> On 06/17/2017 03:59 PM, H.J. Lu wrote:
>> Here parameters are passed to _dl_init in registers.  I want to minimize
>> changes to avoid any potential issues.
> Well, as a rule of thumb, if we do something that breaks our own code,
> it is pretty much guaranteed to wreak havoc across the board (because
> our test coverage is somewhat poor).
> I see a lot of use of regparm (3).  For example:
> $ echo '#include <Qt/qchar.h>' | g++ -m32 -E -x c++ - | grep regparm
>     static Category __attribute__((regparm(3))) category(uint ucs4);
>     static Category __attribute__((regparm(3))) category(ushort ucs2);
>     static Direction __attribute__((regparm(3))) direction(uint ucs4);
>     static Direction __attribute__((regparm(3))) direction(ushort ucs2);
>     static Joining __attribute__((regparm(3))) joining(uint ucs4);
> …
> I think these calls actually cross DSO boundaries.

I don't think so.  See "static ...".

> So I really think you should make the use of %ecx conditional on whether
> shadow stacks are enabled.
> Thanks,
> Florian


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