[libphobos] Work around lack of dlpi_tls_modid before Solaris 11.5

Rainer Orth ro@CeBiTec.Uni-Bielefeld.DE
Tue Apr 9 19:31:00 GMT 2019


Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> writes:

> Before Solaris 11.5, struct dl_phdr_info lacked the dlpi_tls_modid
> member.  While the support might be backported to Solaris 11.4, it
> certainly won't to previous Solaris releases.  To work around this, I've
> used the following patch.  Again, it's pretty straightforward.
>
> Point of note:
>
> * On Solaris, FreeBSD and NetBSD, dl_phdr_info is always visible in
>   <link.h>, while on Linux one needs to define _GNU_SOURCE.
>   AC_USE_SYSTEM_EXTENSION takes care of this, but needs to be called
>   early (i.e. not in DRUNTIME_OS_DLPI_TLS_MODID) to avoid an autoconf
>   warning:
>
> configure.ac:129: warning: AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS
> m4/druntime/os.m4:190: DRUNTIME_OS_DLPI_TLS_MODID is expanded from...
> configure.ac:129: the top level
>
> Tested on i386-pc-solaris2.11 (Solaris 11.4) and x86_64-pc-linux-gnu.
>
> Not unexpectedly, there are a couple of regressions compared to the
> Solaris 11.5/x86 results:
>
> +FAIL: gdc.test/runnable/testaa.d   execution test
> +FAIL: gdc.test/runnable/testaa.d -fPIC   execution test
> +FAIL: gdc.test/runnable/testaa.d -fPIC -shared-libphobos   execution test
> +FAIL: gdc.test/runnable/testaa.d -shared-libphobos   execution test
>
>   32 and 64-bit
>
> +FAIL: gdc.test/runnable/xtest55.d   execution test
> +FAIL: gdc.test/runnable/xtest55.d -shared-libphobos   execution test
>
>   64-bit only
>
> +FAIL: libphobos.shared/link_linkdep.d -I/vol/gcc/src/hg/trunk/local/libphobos/t
> estsuite/libphobos.shared liblinkdep.so lib.so -shared-libphobos execution test
>
> +FAIL: libphobos.shared/load_linkdep.d -shared-libphobos -ldl execution test
> +FAIL: libphobos.shared/load_loaddep.d -shared-libphobos -ldl execution test
>
> +FAIL: libphobos.shared/linkDR.c -shared-libphobos -ldl -pthread execution test
> +FAIL: libphobos.shared/host.c -ldl -pthread execution test
> +FAIL: libphobos.shared/loadDR.c -ldl -pthread -g execution test
>
>   32 and 64-bit
>
> +FAIL: libphobos.shared/link.d -I/vol/gcc/src/hg/trunk/local/libphobos/testsuite/libphobos.shared lib.so -shared-libphobos execution test
>
>   64-bit only
>
> I haven't looked much closer yet, just posting this to see if anything
> along those lines could be acceptable at all.

Fortunately, Iain just discovered a way better way to work around the
lack of dlpi_tls_modid: dlinfo(RTLD_DI_LINKMAP) returns not only a
pointer to a Link_map * as documented in the man page, but rather a
pointer to a struct Rt_map which also includes a rt_tlsmodid member.
It has been this way since at least Solaris 9 and the Solaris/Illumos
sources ($SRC/cmd/sgs/include/rtld.h) explicitly have a comment around
the start of the structure stateing

	Exposed to rtld_db - don't move, don't delete

which pretty much guarantees that this can be relied on.

The only other quirk of note is that before dlpi_tls_modid got added,
tlsmodid started at 0 for the main executable, not 1 as the glibc spec
required and libdruntime assumes.  I account for this by adjusting
_tlsMod on dlinfo and undoing the adjustment before passing it to
__tls_get_adddr, the only consumer.

With the revised patch below, I get clean gdc testresults on Solaris
11.3 and 11.4 (and still on 11.5 which uses the dlpi_tls_modid path),
and almost identical libphobos testresults on all three versions.

I hope this is good to go in (the sections_elf_shared.d part via
upstream, the rest directly) now?

Thanks a lot to Iain for discovering this.

	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University


2019-01-22  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
	    Iain Buclaw  <ibuclaw@gdcproject.org>

	PR d/88150
	* m4/druntime/os.m4 (DRUNTIME_OS_DLPI_TLS_MODID): New macro.
	* configure.ac: Use it.
	Call AC_USE_SYSTEM_EXTENSIONS.
	* configure: Regenerate.
	* Makefile.in, libdruntime/Makefile.in, src/Makefile.in,
	testsuite/Makefile.in: Regenerate.
	* libdruntime/gcc/config.d.in (OS_Have_Dlpi_Tls_Modid): Define.
	* libdruntime/rt/sections_elf_shared.d (scanSegments) <PT_TLS>:
	[OS_Have_Dlpi_Tls_Modid]: Use dlpi_tls_modid.
	[Solaris]: Use dlinfo(RTLD_DI_LINKMAP) to get rt_tlsmodid.
	Otherwise clear pdso._tlsMod, pdso._tlsSize.
	(getTLSRange) [Solaris && !OS_Have_Dlpi_Tls_Modid]: Readjust mod.

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