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

[Florian Weimer]

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.

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

Thanks,
Florian