[PATCH v3 0/2] syscall_user_dispatch: add build/runtime configs

[Gregory Price]

Syscall User Dispatch is presently compiled in by default for all
architectures enabling CONFIG_GENERIC_ENTRY, and some users may
not wish to have the feature functional at runtime.

Add CONFIG_SYSCALL_USER_DISPATCH and kernel.syscall_user_dispatch
to make it a configurable feature at both build and runtime.

CONFIG_SYSCALL_USER_DISPATCH depends on CONFIG_GENERIC_ENTRY
but is separately configurable.

The runtime control is enabled by default, and disabling the feature
while a task has already armed it does not cause it to become inactive
in that task's context. Instead it remains active until the user
attempts to disable/re-enable via prctl or ptrace.  On the next attempt
to re-enable, the prctl/ptrace call fails gracefully.

Gregory Price (2):
  syscall_user_dispatch: Make it configurable in Kconfig
  syscall_user_dispatch: add kernel.syscall_user_dispatch sysctl

 Documentation/admin-guide/sysctl/kernel.rst   | 17 +++++++++
 arch/Kconfig                                  | 10 +++++
 include/linux/entry-common.h                  | 11 ++----
 include/linux/syscall_user_dispatch.h         | 28 +++++++++++++-
 include/linux/syscall_user_dispatch_types.h   |  2 +-
 kernel/entry/Makefile                         |  3 +-
 kernel/entry/syscall_user_dispatch.c          | 38 +++++++++++++++----
 .../selftests/syscall_user_dispatch/config    |  2 +-
 8 files changed, 92 insertions(+), 19 deletions(-)

---

Changes since v2:
  - CONFIG_SYSCTL -> CONFIG_PROC_SYSCTL
  - selftest fixup for CONFIG_SYSCALL_USER_DISPATCH
  - Reword "IP address range"
  - __always_inline fixup (tglx)
  - include ordering (tglx)
  - proc_dobool (tglx)
  - whitespace (tglx)

-- 
2.54.0