Re: [PATCH] x86: Ignore protected visibility in shared libraries on Solaris

[Alan Modra <amodra@gmail.com>]

On Wed, Aug 24, 2022 at 09:46:32AM +0930, Alan Modra wrote:
> On Tue, Aug 23, 2022 at 10:34:32AM -0700, H.J. Lu via Binutils wrote:
> > On x86, the PLT entry in executable may be used as function address for
> > functions in shared libraries.  If functions are protected, the function
> > address used in executable can be different from the function address
> > used in shared library.  This will lead to incorrect run-time behavior
> > if function pointer equality is needed.  By default, x86 linker issues
> > an error in this case.
> > 
> > On Solaris, linker issued an error for
> > 
> > struct tm *tb = (kind == CPP_time_kind::FIXED ? gmtime : localtime) (&tt);
> > 
> > where gmtime is a protected function in libc.so.  Use gmtime's PLT entry
> > in executable as function address is safe since function pointer equality
> > isn't needed.
> 
> I'm curious as to how pointer_equality_needed came to be set for
> gmtime.

Hmm, I figure it was -fno-PIC code with a R_X86_64_32 or R_X86_64_64
referencing gmtime.  And yes, -fno-PIC -mcmodel=medium will generate
R_X86_64_32 in a testcase like

extern int f1 (int);
extern int f2 (int);
int foo (int what, int val) { return (what ? f1 : f2) (val); }

So why exclude R_X86_64_32 with an ABI_64_P test before setting
func_pointer_ref in elf_x86_64_scan_relocs?

-- 
Alan Modra
Australia Development Lab, IBM