bin/182098: [patch] Change kldxref fts_open ordering so it produces a consistent linker.hints between machines of the same architecture.

Derek Schrock dereks at lifeofadishwasher.com
Sat Sep 28 21:10:01 UTC 2013


The following reply was made to PR bin/182098; it has been noted by GNATS.

From: Derek Schrock <dereks at lifeofadishwasher.com>
To: Jilles Tjoelker <jilles at stack.nl>
Cc: bug-followup at FreeBSD.org
Subject: Re: bin/182098: [patch] Change kldxref fts_open ordering so it
 produces a consistent linker.hints between machines of the same
 architecture.
Date: Sat, 28 Sep 2013 17:06:00 -0400

 Looks like I wanted to postpone the last message instead of sending it:
 
 Ok I see what you mean by using FTS_D.  Everything looks good to me, I
 compared the linker.hints generated by the two system from the initial 
 description.  They're the same.
 
 However, I slightly modified the testing script from your last comment
 and found three .ko files that don't seem to generate an entry in the 
 linker.hints files:
 
 Patched kldxref:
 $ /usr/src/usr.sbin/kldxref/kldxref -R /boot/
 
 $ dir="kernel"; strings="$(strings /boot/$dir/linker.hints)"; for f in /boot/"$dir"/*.ko ; do f="${f##*/}"; case "$strings" in *"$f"*) ;; *) echo "what? $f" ;; esac; done
 what? musb.ko
 what? scc.ko
 what? uss820dci.ko
 
 System kldxref:
 $ kldxref -R /boot/
 
 $ dir="kernel"; strings="$(strings /boot/$dir/linker.hints)"; for f in /boot/"$dir"/*.ko ; do f="${f##*/}"; case "$strings" in *"$f"*) ;; *) echo "what? $f" ;; esac; done
 what? musb.ko
 what? scc.ko
 what? uss820dci.ko
 
 Can we assume this isn't a problem with patch since the system kldxref 
 doesn't generate a linker.hints with strings that reference those ko 
 files?
 
 On Sat, Sep 28, 2013 at 04:50:10PM -0400, Derek Schrock wrote:
 > Ok I see what you mean by using FTS_D.  Everything looks good to me, I
 > compared the linker.hints generated by the two system from
 > 
 > On Sat, Sep 28, 2013 at 08:39:53PM +0200, Jilles Tjoelker wrote:
 > > On Tue, Sep 24, 2013 at 09:32:42PM -0400, Derek Schrock wrote:
 > > > On Mon, Sep 16, 2013 at 12:39:58AM +0200, Jilles Tjoelker wrote:
 > > > > In the interest of reproducible builds, your patch seems a good idea. It
 > > > > seems unattractive to run kldxref /boot/kernel on every machine.
 > > > > 
 > > > > The implementation of compare() seems unnecessarily complex though. In
 > > > > find -s, the fts_names are simply passed to strcoll() (here, strcmp()
 > > > > would be better). The trickery with the length may cause inconsistent
 > > > > results if one filename is a prefix of another (rare).
 > > 
 > > > Fair enough after reading more of the fts(3) man fts_name is always
 > > > null terminated.
 > > 
 > > > > This change may also expose a latent bug with kldxref -R: it does not
 > > > > work properly if a directory contains both files that need a mention in
 > > > > a hints file and subdirectories, and at least one such file appears
 > > > > after a subdirectory. Because your change alters the traversal order, it
 > > > > might break a use of kldxref -R that previously happened to work. You
 > > > > can make it work reliably by sorting FTS_D entries after other entries.
 > > 
 > > > Yep, after some additional testing with the patched kldxref it
 > > > produced different linker.hints files. 
 > > 
 > > Hmm, that is unexpected. The sorting happens on entries of each
 > > directory, and find -s does the same.
 > > 
 > > > The new patch uses fts_parent's fts_name (the directory's name).
 > > > First compare the parent's name, if the same compare the passed
 > > > FTSENTs.
 > > 
 > > The comparison on the parent's name seems redundant due to the way
 > > fts(3) does the sorting.
 > > 
 > > I tried my idea using FTS_D.
 > > 
 > > Here is a script to test kldxref on this:
 > > 
 > > #!/bin/sh
 > > 
 > > kldxref=${1:-kldxref}
 > > kldxrefpath=$(command -v "$kldxref" 2>/dev/null) || {
 > > 	printf "%s not found\n" "$kldxref"
 > > 	exit
 > > }
 > > printf "Testing %s\n" "$kldxrefpath"
 > > tmpdir=$(mktemp -d -t kldxreftest) || exit
 > > cd "$tmpdir" || exit
 > > cp /boot/kernel/if_re.ko . || exit
 > > mkdir subdir1 || exit
 > > cp /boot/kernel/if_faith.ko . || exit
 > > cp /boot/kernel/zlib.ko . || exit
 > > cp /boot/kernel/unionfs.ko subdir1 || exit
 > > printf "Directory structure created in %s\n" "$tmpdir"
 > > "$kldxref" -R "$tmpdir"
 > > mainstrings=$(strings linker.hints)
 > > subdir1strings=$(strings subdir1/linker.hints)
 > > bad=
 > > for m in if_re.ko if_faith.ko zlib.ko; do
 > > 	case $mainstrings in
 > > 	*"$m"*) ;;
 > > 	*) printf "%s is missing from main\n" "$m"; bad=1 ;;
 > > 	esac
 > > 	case $subdir1strings in
 > > 	*"$m"*) printf "subdir1 wrongly has %s\n" "$m"; bad=1 ;;
 > > 	esac
 > > done
 > > for m in unionfs.ko; do
 > > 	case $subdir1strings in
 > > 	*"$m"*) ;;
 > > 	*) printf "%s is missing from subdir1\n" "$m"; bad=1 ;;
 > > 	esac
 > > 	case $mainstrings in
 > > 	*"$m"*) printf "main wrongly has %s\n" "$m"; bad=1 ;;
 > > 	esac
 > > done
 > > if [ -z "$bad" ]; then
 > > 	printf "%s appears to be working correctly\n" "$kldxrefpath"
 > > fi
 > > 
 > > My suggested patch:
 > > 
 > > Index: usr.sbin/kldxref/kldxref.c
 > > ===================================================================
 > > --- usr.sbin/kldxref/kldxref.c	(revision 255570)
 > > +++ usr.sbin/kldxref/kldxref.c	(working copy)
 > > @@ -274,6 +274,16 @@
 > >  	exit(1);
 > >  }
 > >  
 > > +int 
 > > +compare(const FTSENT* const* a, const FTSENT* const* b)
 > > +{
 > > +	if ((*a)->fts_info == FTS_D && (*b)->fts_info != FTS_D)
 > > +		return 1;
 > > +	if ((*a)->fts_info != FTS_D && (*b)->fts_info == FTS_D)
 > > +		return -1;
 > > +	return strcmp((*a)->fts_name, (*b)->fts_name);
 > > +}
 > > +
 > >  int
 > >  main(int argc, char *argv[])
 > >  {
 > > @@ -315,7 +325,7 @@
 > >  		err(1, "%s", argv[0]);
 > >  	}
 > >  
 > > -	ftsp = fts_open(argv, fts_options, 0);
 > > +	ftsp = fts_open(argv, fts_options, compare);
 > >  	if (ftsp == NULL)
 > >  		exit(1);
 > >  
 > > 
 > > -- 
 > > Jilles Tjoelker


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