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Message-ID: <20190530031727.GL23599@brightrain.aerifal.cx> Date: Wed, 29 May 2019 23:17:27 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: [PATCH] fix musl-gcc.specs.sh to correctly handle -static-pie 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 <theferdi265@...il.com> > 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 <<EOF > 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? Rich
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