Re: powerpc help needed: Defining hidden alias for __sigsetjmp

[Andreas Schwab <schwab at suse dot de>]

On Nov 14 2016, Florian Weimer <fweimer@redhat.com> wrote:

> This patch adds a reference to __longjmp to libc.so.  With it, libc_pic.os
> has this:
>
>  8296: 00017024    492 FUNC    GLOBAL HIDDEN         2
> __longjmp@@GLIBC_2.3.4
>  9342: 00017210    184 FUNC    GLOBAL DEFAULT        2 __longjmp@GLIBC_2.0
>
> And libc.so has this:
>
>  5208: 00039c04    492 FUNC    LOCAL  DEFAULT       11
> __longjmp@@GLIBC_2.3.4
>  5758: 00039df0    184 FUNC    LOCAL  DEFAULT       11 __longjmp@GLIBC_2.0
>
> It turns out that libc.map lists _longjmp only, based on the entry in
> sysdeps/powerpc/Versions.

So it looks like a linker bug that the symbol was exported before,
probably related to the fact that it is a default version.  But it is
also a bug that __longjmp has a version in the first place.

> setjmp/__longjmp.os has:
>
>    11: 00000000    492 FUNC    GLOBAL DEFAULT        1 __vmx__longjmp
>    14: 000001ec    184 FUNC    GLOBAL DEFAULT        1 __novmx__longjmp
>    15: 00000000    492 FUNC    GLOBAL DEFAULT        1
> __longjmp@@GLIBC_2.3.4
>    16: 000001ec    184 FUNC    GLOBAL DEFAULT        1 __longjmp@GLIBC_2.0
>
> setjmp/longjmp.os has:
>
>    21: 00000000    116 FUNC    GLOBAL DEFAULT        1 __vmx__libc_longjmp
>    22: 00000000    116 FUNC    GLOBAL DEFAULT        1
> __vmx__libc_siglongjmp
>    23: 00000000    116 FUNC    WEAK   DEFAULT        1 __vmx_longjmp
>    24: 00000000    116 FUNC    WEAK   DEFAULT        1 __vmxlongjmp
>    25: 00000000    116 FUNC    WEAK   DEFAULT        1 __vmxsiglongjmp
>    30: 00000000    116 FUNC    GLOBAL HIDDEN         1
> __GI___vmx__libc_longjmp
>    31: 00000000    116 FUNC    GLOBAL DEFAULT        1
> __libc_longjmp@@GLIBC_PRIVATE
>    32: 00000000    116 FUNC    GLOBAL DEFAULT        1
> __libc_siglongjmp@@GLIBC_PRIVATE
>    33: 00000000    116 FUNC    WEAK   DEFAULT        1
> _longjmp@@GLIBC_2.3.4
>    34: 00000000    116 FUNC    WEAK   DEFAULT        1 longjmp@@GLIBC_2.3.4
>    35: 00000000    116 FUNC    WEAK   DEFAULT        1
> siglongjmp@@GLIBC_2.3.4

The version is coming from sysdeps/powerpc/powerpc32/fpu/__longjmp.S,
and was added in commit 5c76ff279f.  Clearly this was a genuine error,
and the versioned alias in sysdeps/powerpc/powerpc32/__longjmp.S has
later been removed in commit 9b9ef82358 (without fixing the fpu
version).

> So the __GI_* aliases are missing there, too.

There is no hidden_proto for __longjmp, only attribute_hidden, so this
is correct.  It is already an internal-only function.

> I wonder if this indeed the root cause.  It would mean this is a spurious
> ABI addition.  Can we drop __longjmp from the ABI in this way? Or do we
> have to fix this up using a powerpc-specific alias?

I'm not sure.  Nobody should be using __longjmp, it's not declared or
used in any public header.

> This happens on no other architecture for which we have abilist files. It
> was introduced into the abilist file here:
>
> commit 0741d64c9140aa205f9df8ebee80ca0bcb018445
> Author: Andreas Schwab <schwab@linux-m68k.org>
> Date:   Tue May 1 01:12:54 2012 +0200
>
>     Update powerpc ABI data

It's unfortunate that Jakub didn't fix the fpu version back in 2004.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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