rework test for mounted /proc
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
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@ -65,27 +65,21 @@ mount_svcdir()
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# By default VServer already has /proc mounted, but OpenVZ does not!
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# However, some of our users have an old proc image in /proc
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# NFC how they managed that, but the end result means we have to test if
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# /proc actually works or not. We to this by comparing two reads of
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# /proc/self/stat. They will not match, because at least the minor fault count
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# field (field 10) should have changed.
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#
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# We can use any file here that fills the following requirements:
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# - changes between sequential reads
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# - is world-readable (not blocked in hardened kernel)
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# - Is only a single line (ergo entire check is doable with no forks)
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# /proc actually works or not. We do this by comparing two reads of
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# /proc/self/environ for which we have set the variable VAR to two
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# different values. If the comparison comes back equal, we know that
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# /proc is not working.
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mountproc=true
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f=/proc/self/stat
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f=/proc/self/environ
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if [ -e $f ]; then
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exec 9<$f ; read a <&9 ; exec 9<&-
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exec 9<$f ; read b <&9 ; exec 9<&-
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if [ "$a" = "$b" ]; then
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if [ "$(VAR=a cat $f)" = "$(VAR=b cat $f)" ]; then
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eerror "You have cruft in /proc that should be deleted"
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else
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einfo "/proc is already mounted, skipping"
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mountproc=false
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fi
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fi
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unset a b f
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unset f
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if $mountproc; then
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procfs="proc"
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