ptrace_test: add test for the PT_ATTACH behavior on sleeping thread

[markj]

tests/sys/kern/ptrace_test.c

4498

The error handling can just be ATF_REQUIRE(shm != MAP_FAILED);

[kib]

Use proper way to check the mmap failure.
Check nanosleep return value and errno.

[kib]

Is there a way to skip the test depending on the sysctl value? Or should I do not bother?

[markj]

In D49887#1137583, @kib wrote:

Is there a way to skip the test depending on the sysctl value? Or should I do not bother?

You can do something like

error = sysctlbyname(..., &val);
ATF_REQUIRE(error == 0);
if (val)
    atf_tc_skip(tc, "test doesn't work with sysctl foo set");

For a chicken switch under the debug MIB, I probably wouldn't bother.

tests/sys/kern/ptrace_test.c

4518

For completeness, also check that WEXITSTATUS(status) == 0?

[kib]

Check exit status of the child.