RFC Dealing with the aliases of SI_USER

Linus,

Would you consider the patchset below for -rc2?

Dealing with the aliases of SI_USER has been a challenge as we have had a b0rked ABI in some cases since 2.5.

So far no one except myself has suggested that changing the si_code of from 0 to something else for those problematic aliases of SI_USER is going to be a problem. So it looks like just fixing the issue is a real possibility.

Fixing the cases that do kill(SIGFPE, ...) because at least test cases care seems important.

The best fixes to backport appear to be the real architecture fixes that remove the aliases for SI_USER as those are deep fixes that fundamentally fix the problems, and are also very small changes.

I am not yet brave enough to merge architectural fixes like that without
arch maintainers buy-in. Getting at least an ack if nothing else takes
a little bit of time.

Still we have a arm fix upthread and David Miller has given his nod to a sparc fix that uses FPE_FLTUNK. So it appears real architecture fixes are progressing. Further I have looked and that leaves only
powerpc, parisc, ia64, and alpha. The new si_code FPE_FLTUNK appears
to address most of those, and there is an untested patch for parisc.

So real progress appears possible.

The generic code can do better, and that is what this rfc patchset is about. It ensures siginfo is fully initialized and uses copy_to_user to copy siginfo to userspace. This takes siginfo_layout out of the picture and so for non-compat non-signalfd siginfos the status quo returns to what it was before I introduced siginfo_layout (AKA regressions go bye-bye).

I believe given the issues these changes are a candiate for -rc2. Otherwise I will keep these changes for the next merge window.

Eric W. Biederman (3):
signal: Ensure every siginfo we send has all bits initialized
signal: Reduce copy_siginfo_to_user to just copy_to_user
signal: Stop special casing TRAP_FIXME and FPE_FIXME in siginfo_layout

 arch/alpha/kernel/osf_sys.c               |  1 +
 arch/alpha/kernel/signal.c                |  2 +
 arch/alpha/kernel/traps.c                 |  5 ++
 arch/alpha/mm/fault.c                     |  2 +
 arch/arc/mm/fault.c                       |  2 +
 arch/arm/kernel/ptrace.c                  |  1 +
 arch/arm/kernel/swp_emulate.c             |  1 +
 arch/arm/kernel/traps.c                   |  5 ++
 arch/arm/mm/alignment.c                   |  1 +
 arch/arm/mm/fault.c                       |  5 ++
 arch/arm/vfp/vfpmodule.c                  |  3 +-
 arch/arm64/kernel/fpsimd.c                |  2 +-
 arch/arm64/kernel/sys_compat.c            |  1 +
 arch/arm64/kernel/traps.c                 |  1 +
 arch/arm64/mm/fault.c                     | 18 ++++--
 arch/c6x/kernel/traps.c                   |  1 +
 arch/hexagon/kernel/traps.c               |  1 +
 arch/hexagon/mm/vm_fault.c                |  1 +
 arch/ia64/kernel/brl_emu.c                |  1 +
 arch/ia64/kernel/signal.c                 |  2 +
 arch/ia64/kernel/traps.c                  | 27 ++++++++-
 arch/ia64/kernel/unaligned.c              |  1 +
 arch/ia64/mm/fault.c                      |  4 +-
 arch/m68k/kernel/traps.c                  |  2 +
 arch/microblaze/kernel/exceptions.c       |  1 +
 arch/microblaze/mm/fault.c                |  4 +-
 arch/mips/mm/fault.c                      |  1 +
 arch/nds32/kernel/traps.c                 |  6 +-
 arch/nds32/mm/fault.c                     |  1 +
 arch/nios2/kernel/traps.c                 |  1 +
 arch/openrisc/kernel/traps.c              |  5 +-
 arch/openrisc/mm/fault.c                  |  1 +
 arch/parisc/kernel/ptrace.c               |  1 +
 arch/parisc/kernel/traps.c                |  2 +
 arch/parisc/kernel/unaligned.c            |  1 +
 arch/parisc/math-emu/driver.c             |  1 +
 arch/parisc/mm/fault.c                    |  1 +
 arch/powerpc/kernel/process.c             |  1 +
 arch/powerpc/kernel/traps.c               |  3 +-
 arch/powerpc/mm/fault.c                   |  1 +
 arch/powerpc/platforms/cell/spufs/fault.c |  2 +-
 arch/riscv/kernel/traps.c                 |  1 +
 arch/s390/kernel/traps.c                  |  5 +-
 arch/s390/mm/fault.c                      |  2 +
 arch/sh/kernel/hw_breakpoint.c            |  1 +
 arch/sh/kernel/traps_32.c                 |  2 +
 arch/sh/math-emu/math.c                   |  1 +
 arch/sh/mm/fault.c                        |  1 +
 arch/sparc/kernel/process_64.c            |  1 +
 arch/sparc/kernel/sys_sparc_32.c          |  1 +
 arch/sparc/kernel/traps_32.c              | 10 ++++
 arch/sparc/kernel/traps_64.c              | 14 +++++
 arch/sparc/kernel/unaligned_32.c          |  1 +
 arch/sparc/mm/fault_32.c                  |  1 +
 arch/sparc/mm/fault_64.c                  |  1 +
 arch/um/kernel/trap.c                     |  2 +
 arch/unicore32/kernel/fpu-ucf64.c         |  2 +-
 arch/unicore32/mm/fault.c                 |  3 +
 arch/x86/entry/vsyscall/vsyscall_64.c     |  2 +-
 arch/x86/kernel/ptrace.c                  |  2 +-
 arch/x86/kernel/traps.c                   |  3 +
 arch/x86/kernel/umip.c                    |  1 +
 arch/x86/kvm/mmu.c                        |  1 +
 arch/x86/mm/fault.c                       |  1 +
 arch/xtensa/kernel/traps.c                |  1 +
 arch/xtensa/mm/fault.c                    |  1 +
 include/linux/ptrace.h                    |  1 -
 include/linux/tracehook.h                 |  1 +
 kernel/signal.c                           | 93 +------------------------------
 virt/kvm/arm/mmu.c                        |  1 +
 70 files changed, 165 insertions(+), 115 deletions(-)

Eric