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From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 13 Jan 2021 05:06:12 -0800
Message-ID: <CAMe9rOpW8_1mjYdG9kbH3u4h9YNrshKv1Xi+3DQ1XDjM0qOY-Q@mail.gmail.com>
Subject: [BACKPORT] [PATCH] x86: Set header.feature_1 in TCB for always-on CET
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>, 
 Libc-stable Mailing List <libc-stable@sourceware.org>
Cc: GNU C Library <libc-alpha@sourceware.org>, 
 Adhemerval Zanella <adhemerval.zanella@linaro.com>
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On Wed, Jan 13, 2021 at 4:58 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 13/01/2021 09:14, H.J. Lu wrote:
> > On Wed, Jan 13, 2021 at 4:09 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >>
> >> Update dl_cet_check() to set header.feature_1 in TCB when both IBT and
> >> SHSTK are always on.
> >> ---
> >>  sysdeps/x86/Makefile         | 6 ++++++
> >>  sysdeps/x86/dl-cet.c         | 5 ++++-
> >>  sysdeps/x86/tst-setjmp-cet.c | 1 +
> >>  3 files changed, 11 insertions(+), 1 deletion(-)
> >>  create mode 100644 sysdeps/x86/tst-setjmp-cet.c
> >>
> >> diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
> >> index c814d5a195..adaa2a92cd 100644
> >> --- a/sysdeps/x86/Makefile
> >> +++ b/sysdeps/x86/Makefile
> >> @@ -48,6 +48,12 @@ endif # $(subdir) == math
> >>  ifeq ($(subdir),setjmp)
> >>  gen-as-const-headers += jmp_buf-ssp.sym
> >>  sysdep_routines += __longjmp_cancel
> >> +ifneq ($(enable-cet),no)
> >> +ifneq ($(have-tunables),no)
> >> +tests += tst-setjmp-cet
> >> +tst-setjmp-cet-ENV = GLIBC_TUNABLES=glibc.cpu.x86_ibt=on:glibc.cpu.x86_shstk=on
> >> +endif
> >> +endif
> >>  endif
> >>
> >>  ifeq ($(subdir),string)
> >> diff --git a/sysdeps/x86/dl-cet.c b/sysdeps/x86/dl-cet.c
> >> index ed7fd6d10d..a63b9c7164 100644
> >> --- a/sysdeps/x86/dl-cet.c
> >> +++ b/sysdeps/x86/dl-cet.c
> >> @@ -47,7 +47,10 @@ dl_cet_check (struct link_map *m, const char *program)
> >>    /* No legacy object check if both IBT and SHSTK are always on.  */
> >>    if (enable_ibt_type == cet_always_on
> >>        && enable_shstk_type == cet_always_on)
> >> -    return;
> >> +    {
> >> +      THREAD_SETMEM (THREAD_SELF, header.feature_1, GL(dl_x86_feature_1));
> >> +      return;
> >> +    }
> >>
> >>    /* Check if IBT is enabled by kernel.  */
> >>    bool ibt_enabled
> >> diff --git a/sysdeps/x86/tst-setjmp-cet.c b/sysdeps/x86/tst-setjmp-cet.c
> >> new file mode 100644
> >> index 0000000000..42c795d2a8
> >> --- /dev/null
> >> +++ b/sysdeps/x86/tst-setjmp-cet.c
> >> @@ -0,0 +1 @@
> >> +#include <setjmp/tst-setjmp.c>
> >> --
> >> 2.29.2
> >>
> >
> > This fixed:
> >
> > https://sourceware.org/bugzilla/show_bug.cgi?id=27177
> >
> > I'd like to fix it for 2.33.
> >
> > Thanks.
> >
>
> Ok for 2.33.

I am backporting it to release branches.

Thanks.

-- 
H.J.