Date: Sat, 14 May 2022 21:45:26 +0200 From: Paul Floyd <paulf2718@gmail.com> To: freebsd-hackers@freebsd.org Subject: fcntl F_KINFO for Message-ID: <5e7863b6-4c57-16a2-0b54-655defefb347@gmail.com>
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Hi
I'm working on updating Valgrind for FreeBSD 13.1.
I've been trying to rewrite some of the code (used in tracking file
descriptors, --track-fds=yes) to use fcntl and F_KINFO. The old code was
IMO ugly, using KERN_PROC_FILEDESC to get info on all open files and
then do a linear search for the fd.
The new code is a lot shorter, but it doesn't quite work correctly. The
Valgrind regression test system redirects stdout and stderr, which it
then filters and compares to reference files. fcntl / F_KINFO doesn't
seem to work correctly with fd 1 (or at least, that seems to be the
problem the most often).
Here is a small reproducer
#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include
<fcntl.h> #include <sys/mman.h> #include <sys/types.h> #include
<sys/user.h> int main(void) { struct kinfo_file kf; kf.kf_structsize =
KINFO_FILE_SIZE; if (0 == fcntl( 1, F_KINFO, &kf )) { printf("fcntl
succeeded %s\n", kf.kf_path); } else { printf("fcntl failed\n"); } }
Compiled with
clang -g -o fcntl fcntl.c
Then run it.
For the first run
$ ./fcntl > foo $ cat foo fcntl succeeded
There's an empty string for kf_path there.
Now that foo exists
$ ./fcntl > foo $ cat foo fcntl succeeded /usr/home/paulf/foo
Am I doing something wrong here or is this a bug / misfeature in the
implementation of gcntl / K_INFO?
A+
Paul
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