selftests: add tests for process_vm_exec

Output:
 $ make run_tests
 TAP version 13
 1..4
 # selftests: process_vm_exec: process_vm_exec
 # 1..1
 # ok 1 275 ns/syscall
 # # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
 ok 1 selftests: process_vm_exec: process_vm_exec
 # selftests: process_vm_exec: process_vm_exec_fault
 # 1..1
 # ok 1 789 ns/signal
 # # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
 ok 2 selftests: process_vm_exec: process_vm_exec_fault
 # selftests: process_vm_exec: ptrace_vm_exec
 # 1..1
 # ok 1 1378 ns/syscall# Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
 ok 3 selftests: process_vm_exec: ptrace_vm_exec
 # selftests: process_vm_exec: process_vm_exec_syscall
 # 1..1
 # ok 1 write works as expectd
 # # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
 ok 4 selftests: process_vm_exec: process_vm_exec_syscall

BUG=183648601
TEST=Compiled and verified locally
SOURCE=FROMLIST(https://lore.kernel.org/linux-api/20210414055217.543246-1-avagin@gmail.com/`)
RELEASE_NOTE=Port process_vm_exec to the COS kernel.

Signed-off-by: Andrei Vagin <avagin@google.com>
Change-Id: I6dcd9069afbeca223ab212dcf6395add63f685f0
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/17936
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>
Tested-by: Oleksandr Tymoshenko <ovt@google.com>
7 files changed