From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/14157 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Fangrui Song Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH] fix musl-gcc.specs.sh to correctly handle -static-pie Date: Thu, 30 May 2019 14:20:44 +0800 Message-ID: <20190530062044.i7lkjrwfvcdyvfm6@gmail.com> References: <9ea47b05-2298-dc48-d938-f1593c1d0d3c@gmail.com> <20190530031727.GL23599@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="252175"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: NeoMutt/20180223-112-0c5bf3 Cc: musl@lists.openwall.com To: Rich Felker Original-X-From: musl-return-14173-gllmg-musl=m.gmane.org@lists.openwall.com Thu May 30 08:21:12 2019 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.89) (envelope-from ) id 1hWER6-0013U0-8I for gllmg-musl@m.gmane.org; Thu, 30 May 2019 08:21:12 +0200 Original-Received: (qmail 1276 invoked by uid 550); 30 May 2019 06:21:09 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 1252 invoked from network); 30 May 2019 06:21:08 -0000 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=pIFxhLOsYkVdpgPO87wGu9HeWJyg4JbjYn6fNXmSfZg=; b=tBjr+fy/REaaW1vEQzR7ZwPHHLqaLwPY7i5d0tsUcB8XEn8loW2wUHeFxUqezA+h5Z 06fOUKHcbYN/9+jcAtg/J19VwJvJOTuwTpcxTfgW7/sLwVYKIzNPTdXkCezUu+6XpHRb 7C4EvsFUo1pRPYiNPv04ZO7n9HBwDD5/7FkQR5U2IczA5zvm/VsgzHbQfs4gWbT1xtUD zcqZMvRbkwAkSm6PiSyiWdAcsWt/iXnSNcBZ2DIYa/U3RWwaEw5i33n4Ujs4NBGxWh/p 3ezOt6qbIqW3xSjlLb1bDqiZ0kwzQdVj15I+VRiwVTgGCXp3U68DI9kjgi2PYnf2HE0+ lrlQ== X-Gm-Message-State: APjAAAX6ZmTzgaL5Irop/IQFTYMbeTX43F3+gTJ/Kp64PPf5cVjhcJXn +8egRd69kmgF4MQxfabb7SA= X-Google-Smtp-Source: APXvYqx4zyfRR9jwGgejW/tsymmdCDuvWWbB7R+yUJPjGQqeINm30tLBQE9DqFDhD5LRk7HzejJfOw== X-Received: by 2002:a63:cd4c:: with SMTP id a12mr2254134pgj.362.1559197256913; Wed, 29 May 2019 23:20:56 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20190530031727.GL23599@brightrain.aerifal.cx> Xref: news.gmane.org gmane.linux.lib.musl.general:14157 Archived-At: On 2019-05-29, Rich Felker wrote: >On Tue, May 28, 2019 at 10:19:18PM +0200, Ferdi265 wrote: >> Hello, >> >> Today I wanted to use musl-gcc to build -static-pie binaries. I noticed >> that this does not work (musl-libc is still linked as a shared library >> and is also still requested as an interpreter). >> >> Looking into the musl-gcc.specs file the bug was obvious: rcrt1.o was >> not used as a startfile, and neither -no-dynamic-linker nor -static were >> passed to the linker. >> >> This patch fixes this by actually using rcrt1.o and passing the linker >> options when -static-pie is given. >> >> I don't have much experience with the specifics of gcc .spec files and >> which options need to be passed, but this seems to work with all >> variations of -shared, -static, and -static-pie that I've tried. >> >> Here (https://github.com/Ferdi265/musl) is the repository with the patch >> on GitHub, and I've also attached the patch below. >> >> Greetings, >> Ferdinand "Ferdi265" Bachmann >> >> --- PATCH BELOW --- >> >> From 070bce8f7e508a951d3b65da227b2fca3a65f37b Mon Sep 17 00:00:00 2001 >> From: Ferdinand Bachmann >> Date: Tue, 28 May 2019 21:53:25 +0200 >> Subject: [PATCH] fix musl-gcc.specs.sh to correctly handle -static-pie >> >> --- >> tools/musl-gcc.specs.sh | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/tools/musl-gcc.specs.sh b/tools/musl-gcc.specs.sh >> index 30492574..7206cb25 100644 >> --- a/tools/musl-gcc.specs.sh >> +++ b/tools/musl-gcc.specs.sh >> @@ -17,13 +17,13 @@ cat <> libgcc.a%s %:if-exists(libgcc_eh.a%s) >> >> *startfile: >> -%{!shared: $libdir/Scrt1.o} $libdir/crti.o crtbeginS.o%s >> +%{static-pie: $libdir/rcrt1.o} %{!static-pie: %{!shared: >> $libdir/Scrt1.o}} $libdir/crti.o crtbeginS.o%s >> >> *endfile: >> crtendS.o%s $libdir/crtn.o >> >> *link: >> --dynamic-linker $ldso -nostdlib %{shared:-shared} %{static:-static} >> %{rdynamic:-export-dynamic} >> +%{static-pie:-no-dynamic-linker -static} %{!static-pie:-dynamic-linker >> $ldso} -nostdlib %{shared:-shared} %{static:-static} >> %{rdynamic:-export-dynamic} >> >> *esp_link: >> > >This looks okay-ish, but could be improved. GCC spec syntax doesn't >require separate static-pie and !static-pie conditions; it supports >"else" with notation: > > %{static-pie:-no-dynamic-linker -static;-dynamic-linker $ldso} > >There's also the question of whether we should make -static -pie work >like it's intended to by us, or like gcc does it upstream (ignoring >-pie). I think it's hard to duplicate the behavior we want since it >depends on knowing if the compiler was built as default-pie, so the >way you've done it is probably the best we can easily do, and at least >non-broken. > >Anyone else have comments on this? gcc -dumpspecs says: %{static-pie:-static -pie --no-dynamic-linker -z text} Do we want to specify -z text? In ld.bfd and gold, -z notext is the default. If text relocations are needed: -z notext: allow and emit DF_TEXTREL. DF_TEXTREL is not emitted if there is no text relocation. -z text: error In lld, -z text is the default (this change is a no-op). -z text: error on text relocations -z notext: allow text relocations, and emit DF_TEXTREL no matter whether text relocations exist. While comparing the differences, I also came across this rule: %{!static|static-pie:--eh-frame-hdr} > It means "pass --eh-frame-hdr to ld if -static isn't used or -static-pie > is used since -static-pie needs PT_GNU_EH_FRAME segment. This is related to PT_GNU_EH_FRAME (it is produced if .eh_frame_hdr exists) and various unwinders. I'm not particularly clear about the internals. Some related links: https://reviews.llvm.org/D19029 FreeBSD folk said LLVM's libunwind needed this on ARM I think this piece of code is relevant https://github.com/llvm-mirror/libunwind/blob/master/src/AddressSpace.hpp#L532 https://reviews.llvm.org/D43203 clang -static adds --eh-frame-hdr unconditionally https://www.openwall.com/lists/musl/2014/06/16/2 Re: gcc'c crtstuff.c: a musl-related experience