Re: [PATCH] Properly handle --disable-default-pie [BZ #28780]

["H.J. Lu" <hjl.tools@gmail.com>]

On Mon, Jan 17, 2022 at 6:35 AM Siddhesh Poyarekar
<siddhesh@sourceware.org> wrote:
>
> OK review time since we're now on the same page as to what's going on.
> Mostly minor nits below.
>
> On 16/01/2022 03:59, H.J. Lu via Libc-alpha wrote:
> > When --disable-default-pie is used, glibc programs and the testsuite
> > should be built as position dependent executables (non-PIE), regardless
> > if the build compiler supports PIE or static PIE.
> >
> > When --disable-default-pie is used, don't build PIE nor static PIE.
> > by default.
>
> Please update the commit message to reflect the latest status on the
> bug, i.e. it's static pie that doesn't honour default-pie, not all PIE.

Fixed.

> >
> > This fixes BZ #28780.
> > ---
> >   configure    | 47 +++++++++++++++++++++++++++++------------------
> >   configure.ac | 40 ++++++++++++++++++++++++++--------------
> >   2 files changed, 55 insertions(+), 32 deletions(-)
> >
> > diff --git a/configure b/configure
> > index 6a7e5c6164..a12f66fa58 100755
> > --- a/configure
> > +++ b/configure
> > @@ -7035,32 +7035,35 @@ cc-pie-default = $libc_cv_cc_pie_default"
> >
> >   { $as_echo "$as_me:${as_lineno-$LINENO}: checking if we can build programs as PIE" >&5
> >   $as_echo_n "checking if we can build programs as PIE... " >&6; }
> > -if test "x$default_pie" != xno; then
> > -  # Disable build-pie-default if target does not support it.
> > -  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> > +cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> >   /* end confdefs.h.  */
> >   #ifdef PIE_UNSUPPORTED
> >   # error PIE is not supported
> >   #endif
> >   _ACEOF
> >   if ac_fn_c_try_compile "$LINENO"; then :
> > -  libc_cv_pie_default=yes
> > +  libc_cv_pie_supported=yes
> >   else
> > -  libc_cv_pie_default=no
> > +  libc_cv_pie_supported=no
> >   fi
> >   rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
> > +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_pie_supported" >&5
> > +$as_echo "$libc_cv_pie_supported" >&6; }
> > +# Disable build-pie-default if target does not support it or glibc is
> > +# configured with --disable-default-pie.
> > +if test "x$default_pie" = xno; then
> > +  build_pie_default=no
> > +else
> > +  build_pie_default=$libc_cv_pie_supported
> >   fi
> > -{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_pie_default" >&5
> > -$as_echo "$libc_cv_pie_default" >&6; }
> >   config_vars="$config_vars
> > -build-pie-default = $libc_cv_pie_default"
> > +build-pie-default = $build_pie_default"
> >
> >   { $as_echo "$as_me:${as_lineno-$LINENO}: checking if we can build static PIE programs" >&5
> >   $as_echo_n "checking if we can build static PIE programs... " >&6; }
> > -libc_cv_static_pie=$libc_cv_pie_default
> > -if test "x$libc_cv_pie_default" != xno \
> > +libc_cv_static_pie_supported=$libc_cv_pie_supported
> > +if test "x$libc_cv_pie_supported" != xno \
> >      -a "$libc_cv_no_dynamic_linker" = yes; then
> > -  # Enable static-pie if available
> >     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> >   /* end confdefs.h.  */
> >   #ifndef SUPPORT_STATIC_PIE
> > @@ -7068,18 +7071,26 @@ if test "x$libc_cv_pie_default" != xno \
> >   #endif
> >   _ACEOF
> >   if ac_fn_c_try_compile "$LINENO"; then :
> > -  libc_cv_static_pie=yes
> > +  libc_cv_static_pie_supported=yes
> >   else
> > -  libc_cv_static_pie=no
> > +  libc_cv_static_pie_supported=no
> >   fi
> >   rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
> > -  if test "$libc_cv_static_pie" = "yes"; then
> > -    $as_echo "#define ENABLE_STATIC_PIE 1" >>confdefs.h
> > +fi
> > +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_static_pie_supported" >&5
> > +$as_echo "$libc_cv_static_pie_supported" >&6; }
> > +
> > +# Enable static-pie only if it is available and glibc isn't configured
> > +# with --disable-default-pie.
> > +if test "x$default_pie" == xno; then
> > +  libc_cv_static_pie=no
> > +else
> > +  libc_cv_static_pie=$libc_cv_static_pie_supported
> > +fi
> > +if test "$libc_cv_static_pie" = "yes"; then
> > +  $as_echo "#define ENABLE_STATIC_PIE 1" >>confdefs.h
> >
> > -  fi
> >   fi
> > -{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_static_pie" >&5
> > -$as_echo "$libc_cv_static_pie" >&6; }
> >   config_vars="$config_vars
> >   enable-static-pie = $libc_cv_static_pie"
> >
> > diff --git a/configure.ac b/configure.ac
> > index 40f2de1661..cacf00140d 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -1868,28 +1868,40 @@ rm -f conftest.*])
> >   LIBC_CONFIG_VAR([cc-pie-default], [$libc_cv_cc_pie_default])
> >
> >   AC_MSG_CHECKING(if we can build programs as PIE)
> > -if test "x$default_pie" != xno; then
> > -  # Disable build-pie-default if target does not support it.
> > -  AC_COMPILE_IFELSE([AC_LANG_SOURCE([[#ifdef PIE_UNSUPPORTED
> > +AC_COMPILE_IFELSE([AC_LANG_SOURCE([[#ifdef PIE_UNSUPPORTED
> >   # error PIE is not supported
> > -#endif]])], [libc_cv_pie_default=yes], [libc_cv_pie_default=no])
> > +#endif]])], [libc_cv_pie_supported=yes], [libc_cv_pie_supported=no])
> > +AC_MSG_RESULT($libc_cv_pie_supported)
> > +# Disable build-pie-default if target does not support it or glibc is
> > +# configured with --disable-default-pie.
> > +if test "x$default_pie" = xno; then
> > +  build_pie_default=no
> > +else
> > +  build_pie_default=$libc_cv_pie_supported
> >   fi
> > -AC_MSG_RESULT($libc_cv_pie_default)
> > -LIBC_CONFIG_VAR([build-pie-default], [$libc_cv_pie_default])
> > +LIBC_CONFIG_VAR([build-pie-default], [$build_pie_default])
> >
> >   AC_MSG_CHECKING(if we can build static PIE programs)
> > -libc_cv_static_pie=$libc_cv_pie_default
> > -if test "x$libc_cv_pie_default" != xno \
> > +libc_cv_static_pie_supported=$libc_cv_pie_supported
> > +if test "x$libc_cv_pie_supported" != xno \
> >      -a "$libc_cv_no_dynamic_linker" = yes; then
> > -  # Enable static-pie if available
> >     AC_COMPILE_IFELSE([AC_LANG_SOURCE([[#ifndef SUPPORT_STATIC_PIE
> >   # error static PIE is not supported
> > -#endif]])], [libc_cv_static_pie=yes], [libc_cv_static_pie=no])
> > -  if test "$libc_cv_static_pie" = "yes"; then
> > -    AC_DEFINE(ENABLE_STATIC_PIE)
> > -  fi
> > +#endif]])], [libc_cv_static_pie_supported=yes],
> > +         [libc_cv_static_pie_supported=no])
> > +fi
> > +AC_MSG_RESULT($libc_cv_static_pie_supported)
> > +
> > +# Enable static-pie only if it is available and glibc isn't configured
> > +# with --disable-default-pie.
> > +if test "x$default_pie" == xno; then
>
> Single '=' here?

Fixed.

> > +  libc_cv_static_pie=no
> > +else
> > +  libc_cv_static_pie=$libc_cv_static_pie_supported
> > +fi
> > +if test "$libc_cv_static_pie" = "yes"; then
> > +  AC_DEFINE(ENABLE_STATIC_PIE)
> >   fi
> > -AC_MSG_RESULT($libc_cv_static_pie)
> >   LIBC_CONFIG_VAR([enable-static-pie], [$libc_cv_static_pie])
> >
> >   # Set the `multidir' variable by grabbing the variable from the compiler.
>

I just sent out the v2 patch.

-- 
H.J.