ld.gold error unsupported -mbss-plt code

[Peter Bergner]

On 7/24/24 3:24 AM, Chris Packham wrote:
> On Wed, Jul 24, 2024 at 2:00 PM Alan Modra <amodra@gmail.com> wrote:
>> Around 2007, the powerpc ABI (and gcc and binutils) gained what I
>> called secure-plt.  Prior to that, the powerpc plt section was a bss
>> section that was written with code generated by ld.so.  This required
>> a section that was both writable and executable, and therefore
>> somewhat of a target for malicious code.  The new secure-plt ABI
>> doesn't use an executable plt, but the code generated to make a call
>> via the plt is a little slower than bss-plt in moderately sized
>> executables and libraries.  Your gcc might be configured to generate
>> bss-plt code by default, so to use ld.gold when linking shared
>> libraries or PIEs you'd need to pass -msecure-plt to gcc when
>> compiling.  If your project has assembly that makes bss-plt style
>> calls then more work will be needed.
> 
> Thanks for the explanation. I think specifying -msecure-plt helps
> reduce the number of errors but I still have the problem that
> crtbeginS.o from the toolchain obviously still has the bss-plt style.
> There might be some incantation I can pass to change how that's
> generated but I'll take the easy way out and just disable ld.gold in
> that configuration.

I think you need to configure gcc with --enable-secureplt to get crtbeginS.o
built with non bss-plt style calls.  To be honest, I'm not sure why we
don't default to that after all of the years since Alan's change.
Alan, do you remember why we didn't make --enable-secureplt a default option?

Peter