[v2,4/4] powerpc64: Enable static-pie
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Commit Message
* sysdeps/powerpc/powerpc64/configure.ac (SUPPORT_STATIC_PIE): Define.
(PI_STATIC_AND_HIDDEN): Define.
* sysdeps/powerpc/powerpc64/configure: Regenerate.
Comments
Alan Modra via Libc-alpha <libc-alpha@sourceware.org> writes:
> * sysdeps/powerpc/powerpc64/configure.ac (SUPPORT_STATIC_PIE): Define.
> (PI_STATIC_AND_HIDDEN): Define.
> * sysdeps/powerpc/powerpc64/configure: Regenerate.
While the code in this patch is perfect, I'm slightly inclined to think its
merge should be delayed until the failures on both powerpc64-linux and
powerpc64le-linux are fixed.
Another option would be to restrict this code to powerpc64le-linux only,
although I haven't had the success you mentioned in the cover letter.
Anyway, in one of my tests in particular (powerpc64le-linux, GCC 8, Binutils
2.30, without --enable-static-pie) I noticed many tests failing. I'm still
investigating what happened.
On Fri, Apr 08, 2022 at 07:49:05PM -0300, Tulio Magno Quites Machado Filho wrote:
> Alan Modra via Libc-alpha <libc-alpha@sourceware.org> writes:
>
> > * sysdeps/powerpc/powerpc64/configure.ac (SUPPORT_STATIC_PIE): Define.
> > (PI_STATIC_AND_HIDDEN): Define.
> > * sysdeps/powerpc/powerpc64/configure: Regenerate.
>
> While the code in this patch is perfect, I'm slightly inclined to think its
> merge should be delayed until the failures on both powerpc64-linux and
> powerpc64le-linux are fixed.
>
> Another option would be to restrict this code to powerpc64le-linux only,
> although I haven't had the success you mentioned in the cover letter.
>
> Anyway, in one of my tests in particular (powerpc64le-linux, GCC 8, Binutils
> 2.30, without --enable-static-pie) I noticed many tests failing. I'm still
> investigating what happened.
binutils-2.30 is too old. You'll find __rela_iplt_start and
__rela_iplt_end symbols being defined in PIEs. Those symbols are
supposed to mark out IFUNC relocs in ET_EXEC static binaries. Their
presence in ET_DYN static binaries is bad, especially since it seems
they have garbage values not pointing at the correct set of
relocations. I suspect, but haven't checked, that the garbage values
are due to -z combreloc. This bug in ld was fixed with commit
795e3bb7de9, so you'll need at least binutils-2.33 for static-pie.
I'll note that static-pie is enabled in glibc without any user
--enable-static-pie, ie. it is the default if SUPPORT_STATIC_PIE is
set. SUPPORT_STATIC_PIE is enabled unconditionally for x86 and
aarch64 without any toolchain checks, and I foolishly followed that
precedent. Likely x86 would fail the glibc testsuite all over the
place with an old binutils too.
On 2022-04-14, Alan Modra via Libc-alpha wrote:
>On Fri, Apr 08, 2022 at 07:49:05PM -0300, Tulio Magno Quites Machado Filho wrote:
>> Alan Modra via Libc-alpha <libc-alpha@sourceware.org> writes:
>>
>> > * sysdeps/powerpc/powerpc64/configure.ac (SUPPORT_STATIC_PIE): Define.
>> > (PI_STATIC_AND_HIDDEN): Define.
>> > * sysdeps/powerpc/powerpc64/configure: Regenerate.
>>
>> While the code in this patch is perfect, I'm slightly inclined to think its
>> merge should be delayed until the failures on both powerpc64-linux and
>> powerpc64le-linux are fixed.
>>
>> Another option would be to restrict this code to powerpc64le-linux only,
>> although I haven't had the success you mentioned in the cover letter.
>>
>> Anyway, in one of my tests in particular (powerpc64le-linux, GCC 8, Binutils
>> 2.30, without --enable-static-pie) I noticed many tests failing. I'm still
>> investigating what happened.
>
>binutils-2.30 is too old. You'll find __rela_iplt_start and
>__rela_iplt_end symbols being defined in PIEs. Those symbols are
>supposed to mark out IFUNC relocs in ET_EXEC static binaries. Their
>presence in ET_DYN static binaries is bad, especially since it seems
>they have garbage values not pointing at the correct set of
>relocations. I suspect, but haven't checked, that the garbage values
>are due to -z combreloc. This bug in ld was fixed with commit
>795e3bb7de9, so you'll need at least binutils-2.33 for static-pie.
I think conditional definition of __rela_iplt_start depending on
-no-pie/-pie is inelegant: it makes __rela_iplt_start the only symbol
with -no-pie/-pie internal linker script difference.
-no-pie/-pie internal linker scripts could otherwise be very similar,
with just the image base difference.
@@ -1,6 +1,12 @@
# This file is generated from configure.ac by Autoconf. DO NOT EDIT!
# Local configure fragment for sysdeps/powerpc/powerpc64.
+$as_echo "#define PI_STATIC_AND_HIDDEN 1" >>confdefs.h
+
+
+$as_echo "#define SUPPORT_STATIC_PIE 1" >>confdefs.h
+
+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for support for overlapping .opd entries" >&5
$as_echo_n "checking for support for overlapping .opd entries... " >&6; }
if ${libc_cv_overlapping_opd+:} false; then :
@@ -1,6 +1,15 @@
GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
# Local configure fragment for sysdeps/powerpc/powerpc64.
+dnl It is possible to access static and hidden symbols in a position
+dnl independent way requiring no relocation on powerpc64. The linker
+dnl edits medium and large model code that uses GOT/TOC entries (which
+dnl would require relocation) to r2 relative accesses.
+AC_DEFINE(PI_STATIC_AND_HIDDEN)
+
+dnl Static PIE is supported.
+AC_DEFINE(SUPPORT_STATIC_PIE)
+
AC_CACHE_CHECK(for support for overlapping .opd entries,
libc_cv_overlapping_opd, [dnl
libc_cv_overlapping_opd=no