[4/7] Add --early-cflags configure option

---
 config.make.in      |  1 +
 configure           | 13 +++++++++++++
 configure.ac        |  6 ++++++
 elf/Makefile        |  8 ++++++++
 manual/install.texi |  7 +++++++
 5 files changed, 35 insertions(+)

On Fri, Jan 14, 2022 at 4:43 AM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> ---
>  config.make.in      |  1 +
>  configure           | 13 +++++++++++++
>  configure.ac        |  6 ++++++
>  elf/Makefile        |  8 ++++++++
>  manual/install.texi |  7 +++++++
>  5 files changed, 35 insertions(+)
>
> diff --git a/config.make.in b/config.make.in
> index e8630a8d0c..e06f1ff49f 100644
> --- a/config.make.in
> +++ b/config.make.in
> @@ -110,6 +110,7 @@ CFLAGS = @CFLAGS@
>  CPPFLAGS-config = @CPPFLAGS@
>  CPPUNDEFS = @CPPUNDEFS@
>  extra-nonshared-cflags = @extra_nonshared_cflags@
> +early-cflags = @early_cflags@
>  ASFLAGS-config = @ASFLAGS_config@
>  AR = @AR@
>  NM = @NM@
> diff --git a/configure b/configure
> index 3f956cf777..6eedd8c3a7 100755
> --- a/configure
> +++ b/configure
> @@ -681,6 +681,7 @@ force_install
>  bindnow
>  hardcoded_path_in_tests
>  enable_timezone_tools
> +early_cflags
>  extra_nonshared_cflags
>  use_default_link
>  sysheaders
> @@ -761,6 +762,7 @@ with_selinux
>  with_headers
>  with_default_link
>  with_nonshared_cflags
> +with_early_cflags
>  with_timeoutfactor
>  enable_sanity_checks
>  enable_shared
> @@ -1480,6 +1482,8 @@ Optional Packages:
>    --with-default-link     do not use explicit linker scripts
>    --with-nonshared-cflags=CFLAGS
>                            build nonshared libraries with additional CFLAGS
> +  --with-early-cflags=CFLAGS
> +                          build early initialization with additional CFLAGS
>    --with-timeoutfactor=NUM
>                            specify an integer to scale the timeout
>    --with-cpu=CPU          select code for CPU variant
> @@ -3386,6 +3390,15 @@ fi
>
>
>
> +# Check whether --with-early-cflags was given.
> +if test "${with_early_cflags+set}" = set; then :
> +  withval=$with_early_cflags; early_cflags=$withval
> +else
> +  early_cflags=
> +fi
> +
> +
> +
>
>  # Check whether --with-timeoutfactor was given.
>  if test "${with_timeoutfactor+set}" = set; then :
> diff --git a/configure.ac b/configure.ac
> index 277d3527d2..445b0b7f15 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -162,6 +162,12 @@ AC_ARG_WITH([nonshared-cflags],
>             [extra_nonshared_cflags=$withval],
>             [extra_nonshared_cflags=])
>  AC_SUBST(extra_nonshared_cflags)
> +AC_ARG_WITH([early-cflags],
> +           AS_HELP_STRING([--with-early-cflags=CFLAGS],
> +                          [build early initialization with additional CFLAGS]),
> +           [early_cflags=$withval],
> +           [early_cflags=])
> +AC_SUBST(early_cflags)
>
>  AC_ARG_WITH([timeoutfactor],
>             AS_HELP_STRING([--with-timeoutfactor=NUM],
> diff --git a/elf/Makefile b/elf/Makefile
> index 0c4be43deb..9fcb4ebd13 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -99,6 +99,14 @@ CFLAGS-.o += $(call elide-stack-protector,.o,$(elide-routines.os))
>  CFLAGS-.op += $(call elide-stack-protector,.op,$(elide-routines.os))
>  CFLAGS-.os += $(call elide-stack-protector,.os,$(all-rtld-routines))
>
> +# Add the requested compiler flags to the early startup code.
> +CFLAGS-dl-printf.os += $(early-cflags)
> +CFLAGS-dl-sysdep.os += $(early-cflags)
> +CFLAGS-dl-tunables.os += $(early-cflags)
> +CFLAGS-dl-write.os += $(early-cflags)
> +CFLAGS-dl-writev.os += $(early-cflags)
> +CFLAGS-rtld.os += $(early-cflags)
> +
>  ifeq ($(unwind-find-fde),yes)
>  routines += unwind-dw2-fde-glibc
>  shared-only-routines += unwind-dw2-fde-glibc
> diff --git a/manual/install.texi b/manual/install.texi
> index b1afc56f5a..27d5893c5e 100644
> --- a/manual/install.texi
> +++ b/manual/install.texi
> @@ -131,6 +131,13 @@ that the objects in @file{libc_nonshared.a} are compiled with this flag
>  (although this will not affect the generated code in this particular
>  case and potentially change debugging information and metadata only).
>
> +@item --with-early-cflags=@var{cflags}
> +Use additional compiler flags @var{cflags} to build the early startup
> +code of the dynamic linker.  These flags can be used to enable early
> +dynamic linker diagnostics to run on CPUs which are not compatible with
> +the rest of @theglibc{}, for example, due to compiler flags which target
> +a later instruction set architecture (ISA).
> +

Isn't it limited to rtld?  If yes, I prefer --with-early-rtld-cflags

>  @item --with-timeoutfactor=@var{NUM}
>  Specify an integer @var{NUM} to scale the timeout of test programs.
>  This factor can be changed at run time using @env{TIMEOUTFACTOR}
> --
> 2.34.1
>
>

* H. J. Lu:

>> +@item --with-early-cflags=@var{cflags}
>> +Use additional compiler flags @var{cflags} to build the early startup
>> +code of the dynamic linker.  These flags can be used to enable early
>> +dynamic linker diagnostics to run on CPUs which are not compatible with
>> +the rest of @theglibc{}, for example, due to compiler flags which target
>> +a later instruction set architecture (ISA).
>
> Isn't it limited to rtld?  If yes, I prefer --with-early-rtld-cflags

It's currently restricted to ld.so.  But we might enhance it to cover
static linking in the future, too.

Thanks,
Florian

On Fri, Jan 14, 2022 at 6:29 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu:
>
> >> +@item --with-early-cflags=@var{cflags}
> >> +Use additional compiler flags @var{cflags} to build the early startup
> >> +code of the dynamic linker.  These flags can be used to enable early
> >> +dynamic linker diagnostics to run on CPUs which are not compatible with
> >> +the rest of @theglibc{}, for example, due to compiler flags which target
> >> +a later instruction set architecture (ISA).
> >
> > Isn't it limited to rtld?  If yes, I prefer --with-early-rtld-cflags
>
> It's currently restricted to ld.so.  But we might enhance it to cover
> static linking in the future, too.

But static linking may need a different early CFLAGS.

* H. J. Lu:

> On Fri, Jan 14, 2022 at 6:29 AM Florian Weimer <fweimer@redhat.com> wrote:
>>
>> * H. J. Lu:
>>
>> >> +@item --with-early-cflags=@var{cflags}
>> >> +Use additional compiler flags @var{cflags} to build the early startup
>> >> +code of the dynamic linker.  These flags can be used to enable early
>> >> +dynamic linker diagnostics to run on CPUs which are not compatible with
>> >> +the rest of @theglibc{}, for example, due to compiler flags which target
>> >> +a later instruction set architecture (ISA).
>> >
>> > Isn't it limited to rtld?  If yes, I prefer --with-early-rtld-cflags
>>
>> It's currently restricted to ld.so.  But we might enhance it to cover
>> static linking in the future, too.
>
> But static linking may need a different early CFLAGS.

Fair point, I will send an updated patch.

Thanks,
Florian