Initialize "ar_errno" and "ar_retval" fields of struct audit_record to 0

[aniketp]

Summary

execve(2) & fexecve(2) don't have any return value/status
on succesful invocation. au_errno_to_bsm() then places the
default BSM_ERRNO_UNKNOWN's local errno mapping for
"ar->ar_errno". If the errno is not found in bsm_errnos[] in
bsm_errno.c, then we set it as 0 for successful execution.

Also, a minor grammatical correction in bsm_arg.c

Test Plan

Set the audit mask corresponding to ex audit class and try to
audit a successful execution of execve(2), where the forked
process successfully overlays the calling process, then in the
audit record's return token, you'll get something like this:

return,failure: Unknown error: 201,4294967295

[asomers]

This seems insufficiently deterministic. You're mapping a wide range of possible errnos to 0. I think you should look for a more direct way to determine whether execve succeeded or not.

[aniketp]

Place the initialisation of ar_errno and ar_retval in audit.c instead of audit_bsm.c
Also, move the typo corrections to D15702

[asomers]

What do you expect an execve audit record to look like after this change? Could you update D15669 to include the correct expectations (after this fix), with an atf_expect_tc_fail statement?