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Date: Fri, 16 Apr 2021 15:29:53 +0200
From: Harald Hoyer <harald@...hat.com>
To: Andy Caldwell <andy.caldwell@...rosoft.com>, musl@...ts.openwall.com
Subject: Re: [PATCH] Add static-pie support to musl-gcc
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:
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@...rosoft.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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