Make ptrace(2) operating on process descriptors

[kib]

Summary

capsicum: add CAP_PTRACE

The capability will allow the ptrace(2) on the procdesc.


pdfork(2): add PD_PTRACE_CAP flag

If the flag is not specified, the process descriptor returned by either
pdfork(2) or pdopenpid(2) has the CAP_PTRACE capability disabled.


ptrace(2): add PT_PROCDESC request modifier


ptrace.2: document PT_PROCDESC

[kib]

This patch adds a capability for ptrace, and allows to do ptrace(req, procdesc, addr, data) instead of ptrace(req, pid, addr, data).

By default, the capability is not enabled, the caller of pdfork(2) or pdopenpid(2) must explicitly prepare process descriptor for debugging.
This way, the existing code that creates process descriptors and passes it somewhere, does not suddenly allow the recipient to debug the process, but it can allow if wanted.