[PATCH] Fix up --enable-initfini-array autodetection in configure (PR bootstrap/50237)

[Richard Guenther]

On Wed, Feb 15, 2012 at 6:09 PM, Rainer Orth
<ro@cebitec.uni-bielefeld.de> wrote:
> Paolo Bonzini <bonzini@gnu.org> writes:
>
>> This must be a separate macro in acinclude.m4 that is AC_REQUIREd from
>> gcc_AC_INITFINI_ARRAY.
>
> Here's an updated patch that does so.  During testing, I found one
> additional complication, though.  With the Sun as/GNU ld combination on
> Solaris 11/x86, after the bootstrap had completed, all programs linked
> against libgcc_s.so.1 SEGVed with a stacktrace like this:
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 1 (LWP 1)]
> 0x00002000 in ?? ()
> (gdb) where
> #0  0x00002000 in ?? ()
> #1  0xfefcd73f in call_array () from /usr/lib/ld.so.1
> #2  0xfefcd8bd in call_init () from /usr/lib/ld.so.1
> #3  0xfefcc8e1 in setup () from /usr/lib/ld.so.1
> #4  0xfefdcfd8 in _setup () from /usr/lib/ld.so.1
> #5  0xfefc0674 in _rt_boot () from /usr/lib/ld.so.1
> #6  0x0804796c in ?? ()
> #7  0x08047ab0 in ?? ()
> Backtrace stopped: previous frame inner to this frame (corrupt stack?)
>
> The problem turned out to be that with
>
>        .section        .init_array
>
> as generates
>
> Section Header[5]:  sh_name: .init_array
>    sh_addr:      0               sh_flags:   0
>    sh_size:      0x4             sh_type:    [ SHT_PROGBITS ]
>    sh_offset:    0x344           sh_entsize: 0
>    sh_link:      0               sh_info:    0
>    sh_addralign: 0x4
>
> i.e. empty sh_flags.  gld seems to mishandle this, since the
> corresponding .initarray entry is bad, as can be seen with runtime
> linker debugging:
>
> $ LD_DEBUG=init LD_PRELOAD=./libgcc_s.so.1 ls
> [...]
> 02032: 1: calling .initarray[0]:0xfed77100: ./libgcc_s.so.1
> 02032: 1: calling .initarray[1]:0x2000: ./libgcc_s.so.1
> Segmentation Fault
>
> If I change the above to
>
>        .section        .init_array,"aw",@progbits
>
> everything works fine with as/gld, but breaks again with gas/gld since
> gas warns about @progbits here.  It turned out that
>
>        .section        .init_array,"aw"
>
> is fine with both assemblers, while as doesn't understand @init_array.
> That's what the patch below uses.
>
>> Can you test Linux too?  The change of -e0 looks good, but I'd rather check
>> on the actual system.
>
> This patch has been bootstrapped on i386-pc-solaris2.{8, 9, 10, 11} with
> as/ld, gas/ld and gas/gld, i386-pc-solaris2.11 with as/gld, as well as
> x86_64-unknown-linux-gnu, correctly detecting .init_array etc. support
> on the gld configurations.  It was also included with
> sparc-sun-solaris2.* bootstraps, but even with gas/gld the configure
> test fails.  I've got to investigate that separately.

I'm not sure about the varasm.c change - it's definitely not a no-op
(callback will be not set, and the flags will be different).  Certainly
the current code is inconsistent wrt the priority != DEFAULT_INIT_PRIORITY
case, not sure why, but you don't make it consistent either because
you don't change that case to SECTION_NOTYPE either.  I'd be fine
with it with both calls using SECTION_NOTYPE, but would like to
know what the callback difference is about.

HJ, can you shed some light on this?

Thx,
Richard.

> Ok for mainline now?
>
> Thanks.
>        Rainer
>
>
> 2012-01-20  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
>
>        PR target/50166
>        * acinclude.m4 (gcc_AC_INITFINI_ARRAY): Require gcc_SUN_LD_VERSION.
>        Define _start.
>        Remove -e 0 from $gcc_cv_ld invocation.
>        Only use __GLIBC_PREREQ if defined.
>        Enable on Solaris since Solaris 8 patch.
>        (gcc_SUN_LD_VERSION): New macro.
>        * configure.ac (ld_ver) <*-*-solaris2*>: Refer to
>        gcc_SUN_LD_VERSION for version number format.
>        * configure: Regenerate.
>        * varasm.c (get_elf_initfini_array_priority_section): Use
>        get_section instead of get_unnamed_section to emit
>        .init_array/.fini_array with default priority.
>
>
>
> --
> -----------------------------------------------------------------------------
> Rainer Orth, Center for Biotechnology, Bielefeld University
>