procfdcat(1)

[kib]

Summary

sys: un-staticise finit_open()


tmpfs: VOP_OPEN() should be allowed on unlinked files

There is no reason for such restriction, and other file systems do not
impose it.


pddupfd(2): add a designator for the current process


pddupfd(2): allow to open the executable

One of the common uses for sysctl kern.proc.<pid>.pathname is to
immediately open(2) the returned path to parse the image, e.g. to read
the symbols.  This operation was made more reliable since introduction
of p_textdvp, but still rename or unlink of the binary cause unnecessary
failures for that.

Introduce pddupfd(pfd, PD_DUPFD_EXECUTABLE) special case that returns
read-only file descriptor to the process executable image.


pdfork.2: document PD_DUPFD_ME and PD_DUPFD_EXECUTABLE


tests/sys/kern/procdesc: test pddupfd(PD_DUPFD_ME)

Check that the descriptor of the calling process is duplicated with
O_CLOEXEC set and the file shared, and that a closed descriptor
gives EBADF.


tests/sys/kern/procdesc: test pddupfd(PD_DUPFD_EXECUTABLE)

Check that the returned file descriptor references the process binary,
both for the calling process and for a child whose binary was unlinked
after exec, and that it is close-on-exec, readable and lacks the write
capability right.


procfdcat(1): utility to read content of a file opened by process

It reads the content of a regular file opened by another process, or of
its executable, using pddupfd(2) and pread(2).