"ps -e" without procfs(5)

[Mikolaj Golub]

On Mon, 31 Oct 2011 11:49:48 +0200 Kostik Belousov wrote:

 KB> I suspect this is my bug: Reading the GET_PS_STRINGS_CHUNK_SZ may validly
 KB> return EFAULT if the string is shorter than the chunk and aligned at
 KB> the end of the page, assuming the next page is not mapped. There should
 KB> be a fallback to fubyte() read loop. I remember that copyinstr() was
 KB> unsuitable.

Hm, I thought that this issue was only for reading arg and env strings (which
could be shorter than GET_PS_STRINGS_CHUNK_SZ), but investigating the cases
when EFAULT was returned in my tests (running buildworld and procstat in loop)
I saw that it also returned when reading other objects (like struct
ps_strings), and a fallback to fubyte() read loop was successful in those
cases too.

So I updated the patch to do fallback for any type of read (although it does
not contain a good comment explaining why fubyte() read might succeed when
proc_rwmem() failed).

Also there were the cases when EFAULT was returned because arg vector
contained the NULL pointer. I observed this for sh processes. In
lib/libc/gen/setproctitle.c I found this comment:

                        oargc = ps_strings->ps_nargvstr;
                        oargv = ps_strings->ps_argvstr;
                        for (i = len = 0; i < oargc; i++) {
                                /*
                                 * The program may have scribbled into its
                                 * argv array, e.g., to remove some arguments.
                                 * If that has happened, break out before
                                 * trying to call strlen on a NULL pointer.
                                 */
                                if (oargv[i] == NULL) {
                                        oargc = i;
                                        break;
                                }

I have updated my patch to do the same.

Running buildworld test after these changes I have observed EFAULT only once,
for cc process, when argv contained a pointer to 0x40.

Also, for kern.proc.args some times errors like below are observed:

procstat: sysctl: kern.proc.args: 58002: 8: Exec format error

And for kern.proc.env:

procstat: sysctl: kern.proc.env: 81352: 16: Device busy

But I have not investigated these cases yet.

The update version:

http://people.freebsd.org/~trociny/env.sys.2.patch

-- 
Mikolaj Golub