Re: [musl] Re: [PATCH v2] configure: define TARGET_LIBC_GNUSTACK on musl

[Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>]

On Tue, Nov 16, 2021 at 8:41 AM Rich Felker <dalias@libc.org> wrote:
>
> On Tue, Nov 16, 2021 at 03:40:00PM +0100, Dragan Mladjenovic wrote:
> > Hi,
> >
> > Looks fine to me. If possible, maybe it should even be back-ported
> > to stable branches.
The change cherry-picks fine onto 10.x and 11.x branches. Should I
send out separate patches or can the committer of this patch apply it
to 10.x and 11.x?
> >
> > Not sure if MIPS assembly sources (if any) in musl would need
> > explicit ..note.GNU-stack
> >
> > to complement this?
>
> What are the actual consequences of making this change, and what is
> the goal? I'm concerned that it might produce object files which don't
> include annotation that they don't need executable stack, in which
> case the final executable file will be marked as executable-stack and
> the kernel will load it as such. That would be very bad.
It is actually the other way around - for MIPS hard-float targets on
non-glibc (or glibc < 2.31) without this change the .note.GNU-stack
annotation is not emitted by GCC.

Ilya
>
> Rich
>
>
> > On 16-Nov-21 06:13, Ilya Lipnitskiy wrote:
> > >musl only uses PT_GNU_STACK to set default thread stack size and has no
> > >executable stack support[0], so there is no reason not to emit the
> > >.note.GNU-stack section on musl builds.
> > >
> > >[0]: https://lore.kernel.org/all/20190423192534.GN23599@brightrain.aerifal.cx/T/#u
> > >
> > >gcc/ChangeLog:
> > >
> > >     * configure: Regenerate.
> > >     * configure.ac: define TARGET_LIBC_GNUSTACK on musl
> > >
> > >Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
> > >---
> > >  gcc/configure    | 3 +++
> > >  gcc/configure.ac | 3 +++
> > >  2 files changed, 6 insertions(+)
> > >
> > >diff --git a/gcc/configure b/gcc/configure
> > >index 74b9d9be4c85..7091a838aefa 100755
> > >--- a/gcc/configure
> > >+++ b/gcc/configure
> > >@@ -31275,6 +31275,9 @@ fi
> > >  # Check if the target LIBC handles PT_GNU_STACK.
> > >  gcc_cv_libc_gnustack=unknown
> > >  case "$target" in
> > >+  mips*-*-linux-musl*)
> > >+    gcc_cv_libc_gnustack=yes
> > >+    ;;
> > >    mips*-*-linux*)
> > >  if test $glibc_version_major -gt 2 \
> > >diff --git a/gcc/configure.ac b/gcc/configure.ac
> > >index c9ee1fb8919e..8a2d34179a75 100644
> > >--- a/gcc/configure.ac
> > >+++ b/gcc/configure.ac
> > >@@ -6961,6 +6961,9 @@ fi
> > >  # Check if the target LIBC handles PT_GNU_STACK.
> > >  gcc_cv_libc_gnustack=unknown
> > >  case "$target" in
> > >+  mips*-*-linux-musl*)
> > >+    gcc_cv_libc_gnustack=yes
> > >+    ;;
> > >    mips*-*-linux*)
> > >      GCC_GLIBC_VERSION_GTE_IFELSE([2], [31], [gcc_cv_libc_gnustack=yes], )
> > >      ;;