This patch series introduces a mechanism to inherit hardware capabilities
(AT_HWCAP, AT_HWCAP2, etc.) from a parent process when they have been
modified via prctl.

To support C/R operations (snapshots, live migration) in heterogeneous
clusters, we must ensure that processes utilize CPU features available
on all potential target nodes. To solve this, we need to advertise a
common feature set across the cluster.

Initially, a cgroup-based approach was considered, but it was decided
that inheriting HWCAPs from a parent process that has set its own
auxiliary vector via prctl is a simpler and more flexible solution.

This implementation adds a new mm flag MMF_USER_HWCAP, which is set when the
auxiliary vector is modified via prctl(PR_SET_MM_AUXV). When execve() is
called, if the current process has MMF_USER_HWCAP set, the HWCAP values are
extracted from the current auxiliary vector and inherited by the new process.

The first patch fixes AUXV size calculation for ELF_HWCAP3 and ELF_HWCAP4
in binfmt_elf_fdpic and updates AT_VECTOR_SIZE_BASE.

The second patch implements the core inheritance logic in execve().

The third patch adds a selftest to verify that HWCAPs are correctly
inherited across execve().

v4: minor fixes based on feedback from the previous version.
v3: synchronize saved_auxv access with arg_lock

v1: https://lkml.org/lkml/2025/12/5/65
v2: https://lkml.org/lkml/2026/1/8/219
v3: https://lkml.org/lkml/2026/2/9/1233

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chen Ridong <chenridong@huawei.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>

Andrei Vagin (3):
  binfmt_elf_fdpic: fix AUXV size calculation for ELF_HWCAP3 and ELF_HWCAP4
  exec: inherit HWCAPs from the parent process
  mm: synchronize saved_auxv access with arg_lock
  selftests/exec: add test for HWCAP inheritance

 fs/binfmt_elf.c                              |   8 +-
 fs/binfmt_elf_fdpic.c                        |  14 ++-
 fs/exec.c                                    |  64 ++++++++++++
 fs/proc/base.c                               |  12 ++-
 include/linux/auxvec.h                       |   2 +-
 include/linux/binfmts.h                      |  11 ++
 include/linux/mm_types.h                     |   2 +
 kernel/fork.c                                |   8 ++
 kernel/sys.c                                 |  30 +++---
 tools/testing/selftests/exec/.gitignore      |   1 +
 tools/testing/selftests/exec/Makefile        |   1 +
 tools/testing/selftests/exec/hwcap_inherit.c | 104 +++++++++++++++++++
 12 files changed, 231 insertions(+), 26 deletions(-)
 create mode 100644 tools/testing/selftests/exec/hwcap_inherit.c

-- 
2.52.0.351.gbe84eed79e-goog

On Tue, Feb 17, 2026 at 10:01 AM Andrei Vagin <avagin@google.com> wrote:
>
> This patch series introduces a mechanism to inherit hardware capabilities
> (AT_HWCAP, AT_HWCAP2, etc.) from a parent process when they have been
> modified via prctl.
>
> To support C/R operations (snapshots, live migration) in heterogeneous
> clusters, we must ensure that processes utilize CPU features available
> on all potential target nodes. To solve this, we need to advertise a
> common feature set across the cluster.
>
> Initially, a cgroup-based approach was considered, but it was decided
> that inheriting HWCAPs from a parent process that has set its own
> auxiliary vector via prctl is a simpler and more flexible solution.
>
> This implementation adds a new mm flag MMF_USER_HWCAP, which is set when the
> auxiliary vector is modified via prctl(PR_SET_MM_AUXV). When execve() is
> called, if the current process has MMF_USER_HWCAP set, the HWCAP values are
> extracted from the current auxiliary vector and inherited by the new process.
>
> The first patch fixes AUXV size calculation for ELF_HWCAP3 and ELF_HWCAP4
> in binfmt_elf_fdpic and updates AT_VECTOR_SIZE_BASE.
>
> The second patch implements the core inheritance logic in execve().
>
> The third patch adds a selftest to verify that HWCAPs are correctly
> inherited across execve().
>
> v4: minor fixes based on feedback from the previous version.

Kees,

I think it is ready to be merged. Let me know if you have any other
comments/concerns/questions.

Thanks,
Andrei

On Mon, Feb 23, 2026 at 10:29:00AM -0800, Andrei Vagin wrote:
> On Tue, Feb 17, 2026 at 10:01 AM Andrei Vagin <avagin@google.com> wrote:
> >
> > This patch series introduces a mechanism to inherit hardware capabilities
> > (AT_HWCAP, AT_HWCAP2, etc.) from a parent process when they have been
> > modified via prctl.
> >
> > To support C/R operations (snapshots, live migration) in heterogeneous
> > clusters, we must ensure that processes utilize CPU features available
> > on all potential target nodes. To solve this, we need to advertise a
> > common feature set across the cluster.
> >
> > Initially, a cgroup-based approach was considered, but it was decided
> > that inheriting HWCAPs from a parent process that has set its own
> > auxiliary vector via prctl is a simpler and more flexible solution.
> >
> > This implementation adds a new mm flag MMF_USER_HWCAP, which is set when the
> > auxiliary vector is modified via prctl(PR_SET_MM_AUXV). When execve() is
> > called, if the current process has MMF_USER_HWCAP set, the HWCAP values are
> > extracted from the current auxiliary vector and inherited by the new process.
> >
> > The first patch fixes AUXV size calculation for ELF_HWCAP3 and ELF_HWCAP4
> > in binfmt_elf_fdpic and updates AT_VECTOR_SIZE_BASE.
> >
> > The second patch implements the core inheritance logic in execve().
> >
> > The third patch adds a selftest to verify that HWCAPs are correctly
> > inherited across execve().
> >
> > v4: minor fixes based on feedback from the previous version.
> 
> Kees,
> 
> I think it is ready to be merged. Let me know if you have any other
> comments/concerns/questions.

Yeah, I think it's looking good. I'll land this in for-next/execve after
rc2 (a week from now).

Thanks!

-- 
Kees Cook

On Mon, Feb 23, 2026 at 2:29 PM Kees Cook <kees@kernel.org> wrote:
>
> On Mon, Feb 23, 2026 at 10:29:00AM -0800, Andrei Vagin wrote:
> > On Tue, Feb 17, 2026 at 10:01 AM Andrei Vagin <avagin@google.com> wrote:
> > >
> > > This patch series introduces a mechanism to inherit hardware capabilities
> > > (AT_HWCAP, AT_HWCAP2, etc.) from a parent process when they have been
> > > modified via prctl.
> > >
> > > To support C/R operations (snapshots, live migration) in heterogeneous
> > > clusters, we must ensure that processes utilize CPU features available
> > > on all potential target nodes. To solve this, we need to advertise a
> > > common feature set across the cluster.
> > >
> > > Initially, a cgroup-based approach was considered, but it was decided
> > > that inheriting HWCAPs from a parent process that has set its own
> > > auxiliary vector via prctl is a simpler and more flexible solution.
> > >
> > > This implementation adds a new mm flag MMF_USER_HWCAP, which is set when the
> > > auxiliary vector is modified via prctl(PR_SET_MM_AUXV). When execve() is
> > > called, if the current process has MMF_USER_HWCAP set, the HWCAP values are
> > > extracted from the current auxiliary vector and inherited by the new process.
> > >
> > > The first patch fixes AUXV size calculation for ELF_HWCAP3 and ELF_HWCAP4
> > > in binfmt_elf_fdpic and updates AT_VECTOR_SIZE_BASE.
> > >
> > > The second patch implements the core inheritance logic in execve().
> > >
> > > The third patch adds a selftest to verify that HWCAPs are correctly
> > > inherited across execve().
> > >
> > > v4: minor fixes based on feedback from the previous version.
> >
> > Kees,
> >
> > I think it is ready to be merged. Let me know if you have any other
> > comments/concerns/questions.
>
> Yeah, I think it's looking good. I'll land this in for-next/execve after
> rc2 (a week from now).

Hi Kees, just a friendly ping in case this slipped off your radar.

Thanks,
Andrei