Re: [PATCH v3 00/12] signal: sort out si_trapno and si_perf

[Marco Elver]

On Tue, 4 May 2021 at 23:13, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote:
> This set of changes sorts out the ABI issues with SIGTRAP TRAP_PERF, and
> hopefully will can get merged before any userspace code starts using the
> new ABI.
>
> The big ideas are:
> - Placing the asserts first to prevent unexpected ABI changes
> - si_trapno becomming ordinary fault subfield.
> - struct signalfd_siginfo is almost full
>
> This set of changes starts out with Marco's static_assert changes and
> additional one of my own that enforces the fact that the alignment of
> siginfo_t is also part of the ABI.  Together these build time
> checks verify there are no unexpected ABI changes in the changes
> that follow.
>
> The field si_trapno is changed to become an ordinary extension of the
> _sigfault member of siginfo.
>
> The code is refactored a bit and then si_perf_type is added along side
> si_perf_data in the _perf subfield of _sigfault of siginfo_t.
>
> Finally the signalfd_siginfo fields are removed as they appear to be
> filling up the structure without userspace actually being able to use
> them.
>
> v2: https://lkml.kernel.org/r/m14kfjh8et.fsf_-_@xxxxxxxxxxxxxxxxx
> v1: https://lkml.kernel.org/r/m1zgxfs7zq.fsf_-_@xxxxxxxxxxxxxxxxx
>
> Eric W. Biederman (9):
>       signal: Verify the alignment and size of siginfo_t
>       siginfo: Move si_trapno inside the union inside _si_fault
>       signal: Implement SIL_FAULT_TRAPNO
>       signal: Use dedicated helpers to send signals with si_trapno set
>       signal: Remove __ARCH_SI_TRAPNO
>       signal: Rename SIL_PERF_EVENT SIL_FAULT_PERF_EVENT for consistency
>       signal: Factor force_sig_perf out of perf_sigtrap
>       signal: Deliver all of the siginfo perf data in _perf
>       signalfd: Remove SIL_FAULT_PERF_EVENT fields from signalfd_siginfo
>
> Marco Elver (3):
>       sparc64: Add compile-time asserts for siginfo_t offsets
>       arm: Add compile-time asserts for siginfo_t offsets
>       arm64: Add compile-time asserts for siginfo_t offsets
>
>  arch/alpha/include/uapi/asm/siginfo.h              |   2 -
>  arch/alpha/kernel/osf_sys.c                        |   2 +-
>  arch/alpha/kernel/signal.c                         |   4 +-
>  arch/alpha/kernel/traps.c                          |  24 ++---
>  arch/alpha/mm/fault.c                              |   4 +-
>  arch/arm/kernel/signal.c                           |  39 +++++++
>  arch/arm64/kernel/signal.c                         |  39 +++++++
>  arch/arm64/kernel/signal32.c                       |  39 +++++++
>  arch/mips/include/uapi/asm/siginfo.h               |   2 -
>  arch/sparc/include/uapi/asm/siginfo.h              |   3 -
>  arch/sparc/kernel/process_64.c                     |   2 +-
>  arch/sparc/kernel/signal32.c                       |  37 +++++++
>  arch/sparc/kernel/signal_64.c                      |  36 +++++++
>  arch/sparc/kernel/sys_sparc_32.c                   |   2 +-
>  arch/sparc/kernel/sys_sparc_64.c                   |   2 +-
>  arch/sparc/kernel/traps_32.c                       |  22 ++--
>  arch/sparc/kernel/traps_64.c                       |  44 ++++----
>  arch/sparc/kernel/unaligned_32.c                   |   2 +-
>  arch/sparc/mm/fault_32.c                           |   2 +-
>  arch/sparc/mm/fault_64.c                           |   2 +-
>  arch/x86/kernel/signal_compat.c                    |  15 ++-
>  fs/signalfd.c                                      |  23 ++---
>  include/linux/compat.h                             |  10 +-
>  include/linux/sched/signal.h                       |  13 +--
>  include/linux/signal.h                             |   3 +-
>  include/uapi/asm-generic/siginfo.h                 |  20 ++--
>  include/uapi/linux/signalfd.h                      |   4 +-
>  kernel/events/core.c                               |  11 +-
>  kernel/signal.c                                    | 113 +++++++++++++--------
>  .../selftests/perf_events/sigtrap_threads.c        |  12 +--
>  30 files changed, 373 insertions(+), 160 deletions(-)

Looks good, thanks a lot! I ran selftests/perf_events on x86-64, and
build-tested x86-32, arm, arm64, sparc, alpha.

I added my Reviewed/Acked-by to the various patches.

Thanks,
-- Marco