[Buildroot] [PATCH v2, 1/1] toolchain/toolchain-wrapper: fix gcc -v with relro

Fabrice Fontaine fontaine.fabrice at gmail.com
Fri Dec 25 21:16:01 UTC 2020


Hi Yann,

Le ven. 25 déc. 2020 à 18:10, Yann E. MORIN <yann.morin.1998 at free.fr> a écrit :
>
> Fabrice, All,
>
> On 2020-12-24 11:18 +0100, Fabrice Fontaine spake thusly:
> > rhash in version 1.4.0 with relro fails to build because gcc -v raises
> > the following build failure:
> >
> > /data/buildroot-test/instance-1/output-1/host/mips64el-buildroot-linux-gnu/sysroot/soft-float/el/usr/lib64/Scrt1.o: In function `__start':
> > (.text+0x20): undefined reference to `main'
> > collect2: error: ld returned 1 exit status
> > Run result: 1
> >
> > This build failure is raised because the toolchain-wrapper calls gcc with
> > -Wl,-z,relro and as a result gcc wrongly assumes that some linking must
> > be done.
>
> Although I do undesrstand the problem, I am not sure this is a good
> solution.
>
> Indeed, it is perfectly legit to call gcc -v while doing an acutal
> compile or link:
>
>     $ echo 'main() { return 0; }' |gcc -v -Wl,-z,relro -o ess -x c -
>
> Indeed, using -v is a good way to see the actual programs gcc calls in
> the various steps, and has already helped me debug some difficult
> issues...
>
> So, I think we need to be a little bit smarter in how we detect whether
> an actual link is attempted. It is however not trivial to come up with
> such a heuristic.
>
> But it might be simpler to "fix" rhash itself, with something like:
>
>     diff -durN rhash-1.4.0.orig/configure rhash-1.4.0/configure
>     --- rhash-1.4.0.orig/configure2020-07-14 21:35: 11.000000000 +0200
>     +++ rhash-1.4.0/configure2020-12-25 18:07:15.52 9581029 +0100
>     @@ -513,8 +513,13 @@
>        CC_TMP="$CC"
>        test -n "$OPT_CC" && OTHER_CC= || OTHER_CC="gcc cc"
>        for CC in "$CC_TMP" $OTHER_CC; do
>     +    cc_name_tmp=
>          if run_cmd "$CC -v"; then
>            cc_name_tmp=$($CC -v 2>&1 | tail -n 1 | cut -d ' ' -f 1)
>     +    elif run_cmd "$CC --version"; then
>     +      cc_name_tmp=$($CC --version 2>&1 | head -n 1 | cut -d ' ' -f 1)
>     +    fi
>     +    if test "${cc_name_tmp}"; then
>            if test "$cc_name_tmp" = "gcc"; then
>              cc_name=$cc_name_tmp
>              start_check "$CC version"
>
> This should also be hopefully accpetable upstream (too bad they do not
> want to switch a common, well-known buildsystem, and that the cmake
> suppot has languished without any comment for more than a year now...)
I already sent a patch to "fix" rhash here:
https://patchwork.ozlabs.org/project/buildroot/patch/20201203202853.616174-1-fontaine.fabrice@gmail.com/
I'll send it to upstream as soon as I got an answer on a previous PR.
>
> Regards,
> Yann E. MORIN.
>
> > Fixes:
> >  - http://autobuild.buildroot.org/results/8605c16cc28316954ce8b9dcc266974390c5da20
> >
> > Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>
> > Tested-by: Peter Seiderer <ps.report at gmx.net>
> > ---
> > Changes v1 -> v2 (after review of Peter Seiderer):
> >  - Fix typos in commit log and update comment in source code
> >
> >  toolchain/toolchain-wrapper.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/toolchain/toolchain-wrapper.c b/toolchain/toolchain-wrapper.c
> > index 0fb6064b1c..2a7dd61729 100644
> > --- a/toolchain/toolchain-wrapper.c
> > +++ b/toolchain/toolchain-wrapper.c
> > @@ -453,10 +453,11 @@ int main(int argc, char **argv)
> >                       *cur++ = "-pie";
> >       }
> >  #endif
> > -     /* Are we building the Linux Kernel or U-Boot? */
> > +     /* Are we building the Linux Kernel or U-Boot or displaying the programs invoked by the compiler? */
> >       for (i = 1; i < argc; i++) {
> >               if (!strcmp(argv[i], "-D__KERNEL__") ||
> > -                 !strcmp(argv[i], "-D__UBOOT__"))
> > +                 !strcmp(argv[i], "-D__UBOOT__") ||
> > +                 !strcmp(argv[i], "-v"))
> >                       break;
> >       }
> >       if (i == argc) {
> > --
> > 2.29.2
> >
> > _______________________________________________
> > buildroot mailing list
> > buildroot at busybox.net
> > http://lists.busybox.net/mailman/listinfo/buildroot
>
> --
> .-----------------.--------------------.------------------.--------------------.
> |  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
> | +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
> | +33 561 099 427 `------------.-------:  X  AGAINST      |  \e/  There is no  |
> | http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
> '------------------------------^-------^------------------^--------------------'
Best Regards,

Fabrice



More information about the buildroot mailing list