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List:       musl
Subject:    Re: [musl] [PATCH] Add static-pie support to musl-gcc
From:       Fangrui Song <i () maskray ! me>
Date:       2021-04-16 23:33:41
Message-ID: 20210416233341.r3puy5jkxzofhupm () gmail ! com
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On 2021-04-16, Harald Hoyer wrote:
> Yeah, I have been suggesting this, too \
> <https://www.openwall.com/lists/musl/2020/04/07/2>. 
> Final suggestion was:
> 
> tools/musl-gcc.specs.sh | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
> mode change 100644 => 100755 tools/musl-gcc.specs.sh
> 
> diff --git a/tools/musl-gcc.specs.sh b/tools/musl-gcc.specs.sh
> old mode 100644
> new mode 100755
> index 30492574..ed584ed3
> --- 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} $libdir/crti.o crtbeginS.o%s
> +%{shared:;static-pie:$libdir/rcrt1.o; :$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} +-dynamic-linker $ldso -nostdlib %{shared:-shared} \
> %{static:-static} %{static-pie:-static -pie --no-dynamic-linker} \
> %{rdynamic:-export-dynamic} 
> *esp_link:

If there is a change, will be good to restrict the --dynamic-linker
option to !shared !static !static-pie only.

> 
> Am 15.04.21 um 22:14 schrieb Andy Caldwell:
> > Hello all,
> > 
> > I've been using musl as the libc backend for rustc for various and  I also wanted
> > to build some C executables against musl (using the `musl-gcc` wrapper since I'm
> > compiling on Ubuntu/Centos).  For various (security and other) reasons we want
> > to build `-static-pie` executables but the existing `musl-gcc.specs` file doesn't
> > handle that flag.  I found https://www.openwall.com/lists/musl/2019/05/28/1
> > which seemed like a good start, but also seems to have stalled.
> > 
> > Starting from that patch, I've applied the various suggestions in the following
> > emails in the thread (adding `-z text` and handling `-eh-frame-hdr`).  I've also
> > make a few other changes:
> > 
> > * Pass `-pie` to the linker when `-static-pie` is requested (this might be
> > passed automatically if gcc was built `-default-pie` but it doesn't hurt to
> > pass it in and it's certainly needed in some cases)
> > * Don't pass `-dynamic-linker ...` when `-static` is requested (which mirror's
> > gcc's standard behaviour)
> > 
> > Using this specfile, I was able to build and run the OpenSSL command line tools
> > (which seem to be a decent stress-test of a compiler/linker) both as `-static` \
> > and as `-static-pie`, as well as building the compiling the following example
> > executable to check that PIE is being applied appropriately (compare the
> > outputs with `-static` vs. `-static-pie` across multiple runs).
> > 
> > ```
> > #include <stdio.h>
> > 
> > static int static_int = 42;
> > static int *static_ptr = &static_int;
> > 
> > int main(int argc, char** argv) {
> > printf("main: %p, stack: %p, statics: %p\n", main, &argc, static_ptr);
> > return 0;
> > }
> > ```
> > 
> > Thanks,
> > 
> > Andy Caldwell
> > 
> > --- PATCH BELOW ---
> > 
> > From 2953e1dc837cd81cac059ea0fa7b4f7bb11c568a Mon Sep 17 00:00:00 2001
> > From: Andy Caldwell <andy.caldwell@microsoft.com>
> > Date: Thu, 15 Apr 2021 21:05:38 +0100
> > Subject: [PATCH] Add static-pie support to musl-gcc
> > 
> > ---
> > 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..0e5a9035 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; !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 -pie; !static: \
> > -dynamic-linker $ldso} -nostdlib -z text %{shared} %{static-pie|static:-static} \
> > %{rdynamic:-export-dynamic} %{!static: -eh-frame-hdr} 
> > *esp_link:
> > 
> > 
> 


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