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Re: [PATCH v3 09/16] elf: Move vDSO setup to rtld (BZ#24967) - regression found

From: Lukasz Majewski <lukma at denx dot de>
To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
Cc: Siddhesh Poyarekar <siddhesh at gotplt dot org>, libc-alpha at sourceware dot org, Szabolcs Nagy <Szabolcs dot Nagy at arm dot com>, Florian Weimer <fweimer at redhat dot com>
Date: Tue, 7 Jan 2020 17:13:08 +0100
Subject: Re: [PATCH v3 09/16] elf: Move vDSO setup to rtld (BZ#24967) - regression found
References: <20191217214728.2886-1-adhemerval.zanella@linaro.org> <20191217214728.2886-9-adhemerval.zanella@linaro.org> <d0cafb1b-d000-9ac7-af19-24a17e711384@gotplt.org> <24cb9107-0d17-54c8-f169-fbfdebd0099a@linaro.org>

Hi Adhemerval, Siddhesh

> On 02/01/2020 09:55, Siddhesh Poyarekar wrote:
> > On 18/12/19 3:17 am, Adhemerval Zanella wrote:  
> >> Changes from previous version:
> >>
> >>   - Do not GLRO access on ifunc resolver, ut rather call the vDSO
> >>     resolve function instead (dl_vdso_vsym).
> >>
> >> --
> >>
> >> This patch moves the vDSO setup from libc to loader code, just
> >> after the vDSO link_map setup.  For static case the initialization
> >> is moved to _dl_non_dynamic_init instead.
> >>
> >> Instead of using the mangled pointer, the vDSO data is set as
> >> attribute_relro (on _rtld_global_ro for shared or _dl_vdso_* for
> >> static).  It is read-only even with partial relro.
> >>
> >> It fixes BZ#24967 now that the vDSO pointer is setup earlier than
> >> malloc interposition is called.
> >>
> >> Also, vDSO calls should not be a problem for static dlopen as
> >> indicated by BZ#20802.  The vDSO pointer would be zero-initialized
> >> and the syscall will be issued instead.
> >>
> >> Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu,
> >> arm-linux-gnueabihf, powerpc64le-linux-gnu, powerpc64-linux-gnu,
> >> powerpc-linux-gnu, s390x-linux-gnu, sparc64-linux-gnu, and
> >> sparcv9-linux-gnu.  I also run some tests on mips.
> >> ---
> >>  csu/init-first.c                              |  4 -
> >>  elf/dl-support.c                              |  7 ++
> >>  elf/rtld.c                                    |  7 +-
> >>  malloc/tst-interpose-aux.c                    |  5 ++
> >>  sysdeps/generic/dl-vdso-setup.c               |  1 +
> >>  sysdeps/generic/dl-vdso-setup.h               | 28 ++++++
> >>  sysdeps/generic/dl-vdso.h                     | 30 +++++++
> >>  sysdeps/generic/ldsodefs.h                    |  6 ++
> >>  sysdeps/powerpc/powerpc32/backtrace.c         | 16 ++--
> >>  sysdeps/powerpc/powerpc64/backtrace.c         |  8 +-
> >>  sysdeps/unix/sysv/linux/aarch64/Makefile      |  1 -
> >>  sysdeps/unix/sysv/linux/arm/Makefile          |  1 -
> >>  sysdeps/unix/sysv/linux/dl-vdso-setup.c       | 81
> >> +++++++++++++++++ sysdeps/unix/sysv/linux/dl-vdso-setup.h       |
> >> 55 ++++++++++++ sysdeps/unix/sysv/linux/dl-vdso.c             | 48
> >> ---------- sysdeps/unix/sysv/linux/dl-vdso.h             | 30
> >> ++++--- sysdeps/unix/sysv/linux/gettimeofday.c        |  3 +-
> >>  sysdeps/unix/sysv/linux/init-first.c          | 90
> >> ------------------- sysdeps/unix/sysv/linux/libc-vdso.h
> >> | 30 +------ sysdeps/unix/sysv/linux/mips/Makefile         |  2 -
> >>  sysdeps/unix/sysv/linux/powerpc/Makefile      |  1 -
> >>  .../sysv/linux/powerpc/get_timebase_freq.c    |  5 +-
> >>  sysdeps/unix/sysv/linux/powerpc/init-first.c  | 50 -----------
> >>  sysdeps/unix/sysv/linux/powerpc/libc-vdso.h   | 10 ---
> >>  sysdeps/unix/sysv/linux/riscv/Makefile        |  4 -
> >>  sysdeps/unix/sysv/linux/riscv/flush-icache.c  |  2 +-
> >>  sysdeps/unix/sysv/linux/s390/Makefile         |  4 -
> >>  sysdeps/unix/sysv/linux/sparc/Makefile        |  4 -
> >>  sysdeps/unix/sysv/linux/sysdep-vdso.h         |  6 +-
> >>  sysdeps/unix/sysv/linux/time.c                |  3 +-
> >>  sysdeps/unix/sysv/linux/x86/Makefile          |  4 -
> >>  31 files changed, 257 insertions(+), 289 deletions(-)
> >>  create mode 100644 sysdeps/generic/dl-vdso-setup.c
> >>  create mode 100644 sysdeps/generic/dl-vdso-setup.h
> >>  create mode 100644 sysdeps/generic/dl-vdso.h
> >>  create mode 100644 sysdeps/unix/sysv/linux/dl-vdso-setup.c
> >>  create mode 100644 sysdeps/unix/sysv/linux/dl-vdso-setup.h
> >>  delete mode 100644 sysdeps/unix/sysv/linux/dl-vdso.c
> >>  delete mode 100644 sysdeps/unix/sysv/linux/init-first.c
> >>  delete mode 100644 sysdeps/unix/sysv/linux/powerpc/init-first.c
> >>  
> > 
> > OK with some minor nits fixed, see below.
> > 
> > Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>  
> 
> >> diff --git a/sysdeps/generic/dl-vdso-setup.h
> >> b/sysdeps/generic/dl-vdso-setup.h new file mode 100644
> >> index 0000000000..3d79bae317
> >> --- /dev/null
> >> +++ b/sysdeps/generic/dl-vdso-setup.h
> >> @@ -0,0 +1,28 @@
> >> +/* ELF symbol initialization functions for VDSO objects.
> >> +   Copyright (C) 2019 Free Software Foundation, Inc.  
> > 
> > Update copyright year.  
> 
> Ack.
> 
> >   
> >> +   This file is part of the GNU C Library.
> >> +
> >> +   The GNU C Library is free software; you can redistribute it
> >> and/or
> >> +   modify it under the terms of the GNU Lesser General Public
> >> +   License as published by the Free Software Foundation; either
> >> +   version 2.1 of the License, or (at your option) any later
> >> version. +
> >> +   The GNU C Library is distributed in the hope that it will be
> >> useful,
> >> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> >> GNU
> >> +   Lesser General Public License for more details.
> >> +
> >> +   You should have received a copy of the GNU Lesser General
> >> Public
> >> +   License along with the GNU C Library; if not, see
> >> +   <https://www.gnu.org/licenses/>.  */
> >> +
> >> +#ifndef _DL_VDSO_INIT_H
> >> +#define _DL_VDSO_INIT_H
> >> +
> >> +/* Initialize the VDSO functions pointers.  */
> >> +static inline void __attribute__ ((always_inline))
> >> +setup_vdso_pointers (void)
> >> +{
> >> +}
> >> +
> >> +#endif
> >> diff --git a/sysdeps/generic/dl-vdso.h b/sysdeps/generic/dl-vdso.h
> >> new file mode 100644
> >> index 0000000000..5651f49a1a
> >> --- /dev/null
> >> +++ b/sysdeps/generic/dl-vdso.h
> >> @@ -0,0 +1,30 @@
> >> +/* ELF symbol resolve functions for VDSO objects.
> >> +   Copyright (C) 2019 Free Software Foundation, Inc.  
> > 
> > Update copyright year.  
> 
> Ack.
> 
> >> diff --git a/sysdeps/unix/sysv/linux/dl-vdso-setup.c
> >> b/sysdeps/unix/sysv/linux/dl-vdso-setup.c new file mode 100644
> >> index 0000000000..1069879f1a
> >> --- /dev/null
> >> +++ b/sysdeps/unix/sysv/linux/dl-vdso-setup.c
> >> @@ -0,0 +1,81 @@
> >> +/* Data for vDSO support.  Linux version.
> >> +   Copyright (C) 2019 Free Software Foundation, Inc.  
> > 
> > Update copyright year.  
> 
> Ack.
> 
> >   
> >> +   This file is part of the GNU C Library.
> >> +
> >> +   The GNU C Library is free software; you can redistribute it
> >> and/or
> >> +   modify it under the terms of the GNU Lesser General Public
> >> +   License as published by the Free Software Foundation; either
> >> +   version 2.1 of the License, or (at your option) any later
> >> version. +
> >> +   The GNU C Library is distributed in the hope that it will be
> >> useful,
> >> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> >> GNU
> >> +   Lesser General Public License for more details.
> >> +
> >> +   You should have received a copy of the GNU Lesser General
> >> Public
> >> +   License along with the GNU C Library; if not, see
> >> +   <https://www.gnu.org/licenses/>.  */
> >> +
> >> +/* This file is included in three different modes for both static
> >> (libc.a)
> >> +   and shared (rtld) modes:
> >> +
> >> +   1. PROCINFO_DECL is defined, meaning we are only interested in
> >> +      declarations.  For static it requires use the extern
> >> keywork along with
> >> +      the attribute_relro while for shared it will be embedded in
> >> the
> >> +      rtld_global_ro.
> >> +
> >> +   2. PROCINFO_DECL and SHARED are not defined.  Nothing to do,
> >> the default
> >> +      zero initializion is suffice.
> >> +
> >> +   3. PROCINFO_DECL is not defined while SHARED is.  Similar to
> >> 2., the zero
> >> +      initialization of rtld_global_ro is suffice.  */
> >> +
> >> +#ifndef PROCINFO_CLASS
> >> +# define PROCINFO_CLASS
> >> +#endif
> >> +
> >> +#ifndef SHARED
> >> +# define RELRO attribute_relro
> >> +#else
> >> +# define RELRO
> >> +#endif
> >> +
> >> +#if defined PROCINFO_DECL || !defined SHARED
> >> +# ifdef HAVE_CLOCK_GETTIME_VSYSCALL
> >> +PROCINFO_CLASS int (*_dl_vdso_clock_gettime) (clockid_t,
> >> +					      struct timespec *)
> >> RELRO; +#endif  
> > 
> > Fix indentation.  
> 
> Ack.
> 
> >   
> >> +# ifdef HAVE_GETTIMEOFDAY_VSYSCALL
> >> +PROCINFO_CLASS int (*_dl_vdso_gettimeofday) (struct timeval *,
> >> void *) RELRO; +#endif  
> > 
> > Fix indentation.  
> 
> Ack.

Unfortunately this patch caused regression on my ARMv7 32 bit setup.
Please find filled in bugzilla entry:

https://sourceware.org/bugzilla/show_bug.cgi?id=25352


Best regards,

Lukasz Majewski

--

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HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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Follow-Ups:
- Re: [PATCH v3 09/16] elf: Move vDSO setup to rtld (BZ#24967) - regression found
  - From: Adhemerval Zanella

References:
- Re: [PATCH v3 09/16] elf: Move vDSO setup to rtld (BZ#24967)
  - From: Siddhesh Poyarekar
- Re: [PATCH v3 09/16] elf: Move vDSO setup to rtld (BZ#24967)
  - From: Adhemerval Zanella

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