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rework test for mounted /proc

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The previous test assumed that we could always rely on the minor fault
counter to change between reads of /proc/self/stat, but we found that
this is not the case.

The new test compares two reads of /proc/self/environ for which we have
set the same environment variable to two different values.
If the comparison shows the two reads have the same contents, we know
that /proc is not working.

I would like to thank Robin Johnson and Mike Frysinger for their input
for this patch.

X-Gentoo-Bug: 348416
X-Gentoo-Bug-URL: http://bugs.gentoo.org/show_bug.cgi?id=348416
This commit is contained in:
William Hubbs 2011-03-24 18:27:35 -05:00
parent 25049d3e80
commit 1d63e85794
1 changed files with 7 additions and 13 deletions
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20
sh/init.sh.Linux.in
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@ -65,27 +65,21 @@ mount_svcdir()
# By default VServer already has /proc mounted, but OpenVZ does not!
# However, some of our users have an old proc image in /proc
# NFC how they managed that, but the end result means we have to test if
# /proc actually works or not. We to this by comparing two reads of
# /proc/self/stat. They will not match, because at least the minor fault count
# field (field 10) should have changed.
#
# We can use any file here that fills the following requirements:
# - changes between sequential reads
# - is world-readable (not blocked in hardened kernel)
# - Is only a single line (ergo entire check is doable with no forks)
# /proc actually works or not. We do this by comparing two reads of
# /proc/self/environ for which we have set the variable VAR to two
# different values. If the comparison comes back equal, we know that
# /proc is not working.
mountproc=true
f=/proc/self/stat
f=/proc/self/environ
if [ -e $f ]; then
exec 9<$f ; read a <&9 ; exec 9<&-
exec 9<$f ; read b <&9 ; exec 9<&-
if [ "$a" = "$b" ]; then
if [ "$(VAR=a cat $f)" = "$(VAR=b cat $f)" ]; then
eerror "You have cruft in /proc that should be deleted"
else
einfo "/proc is already mounted, skipping"
mountproc=false
fi
fi
unset a b f
unset f
if $mountproc; then
procfs="proc"