kernel/api: add runtime verification selftest

Add a selftest for CONFIG_KAPI_RUNTIME_CHECKS that exercises
sys_open/sys_read/sys_write/sys_close through raw syscall() and
verifies KAPI pre-validation catches invalid parameters while
allowing valid operations through.

Test cases (TAP output):
  1-4:   Valid open/read/write/close succeed
  5-8:   Unknown open flag bits and a NULL path are rejected with EINVAL,
         while mode bits above 07777 are accepted (the kernel masks them)
  9-20:  Boundary conditions and error paths (bad and closed fds, zero
         counts, over-long paths, unmapped buffers, wrong access mode)
  21-27: Pipe, file descriptor lifecycle and other error paths
  28-30: A normal open/read/write/close sequence, and read()/write() with
         a NULL buffer and a zero count returning 0
  31:    dmesg contains the expected KAPI warning strings

Tests that depend on CONFIG_KAPI_RUNTIME_CHECKS are skipped when an open()
with an unknown flag bit succeeds, which means the checks are not active.

Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@kernel.org>

0 files changed, 0 insertions, 0 deletions