[llvm-dev] [PPC] Linker fails on -fstack-protector

Hal Finkel via llvm-dev
Thu, 11 Feb 2016 01:04:00 -0000

----- Original Message -----

> From: "Eric Christopher" <echristo at gmail.com>
> To: "Tim Shen" <timshen at google.com>, llvm-dev at
lists.llvm.org, "Hal
> Finkel" <hfinkel at anl.gov>, "Kit Barton" <kbarton
at ca.ibm.com>
> Sent: Wednesday, February 10, 2016 6:59:50 PM
> Subject: Re: [llvm-dev] [PPC] Linker fails on -fstack-protector

> On Mon, Jan 25, 2016 at 11:58 AM Tim Shen via llvm-dev <
> llvm-dev at lists.llvm.org > wrote:

> > When -fstack-protector is turned on, linker fails to find the
> > symbol
> > " __stack_chk_guard" because at least for powerpc64le, glibc
> > doesn't
> > provide this symbol. Instead, they put the stack guard into TCB.
>

> > x86 fixed this issue by injecting a special address space (which is
> > later translated to TCB register access) and hard code the offset
> > of
> > stack_guard, but I don't see a easy way to handle address spaces
in
> > ppc.
>
Why is handling address spaces in ppc any more difficult than doing so for x86?

-Hal

> > A cleaner solution could be adding an IR intrinsic
> > llvm.get_tcb_address() and hard code the offset of stack_guard
> > member, since they aren't supposed to change.
>

> > Details are in the bug: https://llvm.org/bugs/show_bug.cgi?id=26226
>

> > Any ideas?
>

> Not a huge fan of a ppc specific intrinsic (which it should be, so
> llvm.ppc... if we go that route) to do this. I actually rather liked
> the cleanliness of the address space solution for x86. How much work
> would it be to do that? Alternately: Hal, Kit, what do you two think
> as far as the ppc backend?

> The other solution you mentioned - combining the slot load into the
> existing intrinsic might work, we'd just need to figure out how to
> autoupgrade everything into it which might be a bit more difficult
> than fixing the backends and dealing. Have you looked into how the
> autoupgrade would work?

> Thanks!

> -eric

> > Thanks! _______________________________________________
>
> > LLVM Developers mailing list
>
> > llvm-dev at lists.llvm.org
>
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>

--

Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory
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