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Re: [PATCH 0/2] nptl: Update struct pthread_unwind_buf

On Fri, Feb 9, 2018 at 4:11 AM, Florian Weimer <> wrote:
> * H. J. Lu:
>>> My proposal is still rather hackish, but so is the existing code (the
>> A pointer to a buffer in user program is passed to libpthread.
>> There is a jmp buf in the buffer followed by other fields.  Since
>> the size of jmp buf is increased in glibc 2.28, we need to know the
>> offset of other fields. Otherwise libpthread may write beyond the
>> buffer in user program.  I don't see how symbol versioning can help
>> us here since the INTERNAL libpthread functions don't know the
>> layout of __pthread_unwind_buf_t of USER programs.
> I suggest *not* to increase the size of the jump buffer.

Where do we save shadow stack pointer?

> CET markup will not be correct for static libraries compiled against
> 2.27 or earlier with a CET-enabled toolchain, so this is the only
> completely safe approach.

I don't believe so.  As long as there is a single input .o file which
isn't marked
with CET, the output static binary won't be marked with CET.  If what
you said is true, please file a glibc bug report.


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