Stop using realpath to set $IP in WebStart
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	Nikerabbit
	Dec 21 2016, 5:55 PM

Description

I have setup as follows:

/www/domain/docroot/w is a symlink to /srv/mediawiki/targets/production
/srv/mediawiki/targets/production is a symlink to /srv/mediawiki/tags/XXX

If I enable repo authoritative mode and compile bytecode cache for hhvm using:

find -L /www/domain/docroot -name "*.php" > $FL
hhvm --hphp -t hhbc  -v AllVolatile=true --input-list $FL

Then I get errors as follows:

Fatal error: require_once(/srv/mediawiki/tags/XXX/includes/profiler/ProfilerFunctions.php): File not found in /www/domain/docroot/w/includes/WebStart.php on line 64

This is because of the following code:

# Full path to working directory.
# Makes it possible to for example to have effective exclude path in apc.
# __DIR__ breaks symlinked includes, but realpath() returns false
# if we don't have permissions on parent directories.
$IP = getenv( 'MW_INSTALL_PATH' );
if ( $IP === false ) {
        $IP = realpath( '.' ) ?: dirname( __DIR__ );
}

I am not sure whether apc is really concern anymore, as apc itself no longer exists.

It seems it would be possible to override this with an environment variable, but I am not sure how to pass it to HHVM.

Details

	Subject	Repo	Branch	Lines +/-
	WebStart: Remove use of realpath() for $IP	mediawiki/core	master	+2 -5

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Related Objects
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		Status	Subtype	Assigned	Task
		Declined		None	T121913 Enable HHVM Repo Authoritative mode
		Resolved		Krinkle	T153882 Stop using realpath to set $IP in WebStart

Event Timeline

Nikerabbit created this task.Dec 21 2016, 5:55 PM

Restricted Application added a subscriber: Aklapper. · View Herald TranscriptDec 21 2016, 5:55 PM

Nikerabbit added a parent task: T121913: Enable HHVM Repo Authoritative mode.Dec 21 2016, 5:55 PM

Nemo_bis added a project: MediaWiki-General.Dec 21 2016, 5:56 PM

Nemo_bis subscribed.

I believe this is the correct project tag, please correct me if I'm wrong :)

SamanthaNguyen edited projects, added MediaWiki-General; removed MediaWiki-Installer.Dec 22 2016, 8:18 AM

It seems it would be possible to override this with an environment variable, but I am not sure how to pass it to HHVM.

https://serverfault.com/questions/351696/how-do-you-set-server-specific-env-values-in-nginx since I think you're using nginx?

SamanthaNguyen unsubscribed.Jul 14 2017, 3:31 PM

Change 393713 had a related patch set uploaded (by Krinkle; owner: Krinkle):
[mediawiki/core@master] [WIP] WebStart: Remove use of realpath() for $IP

https://gerrit.wikimedia.org/r/393713

gerritbot added a project: Patch-For-Review.Nov 28 2017, 9:40 PM

This use of realpath( '.' ); in assigning $IP also breaks if loading MediaWiki indirectly from a different file.

For example, if MediaWiki is installed in the typical /w/ subdirectory, we recommend using a rewrite rule to make / still respond from /w/index.php. However, that requires configuration specific to Apache. In the mediawiki-docker-dev project, I'm trying to instead take the approach WordPress takes by placing an index.php in the document root that simply includes __DIR__ . '/w/index.php'; instead.

At first this seems to work (document root index.php -> mediawiki index.php -> WebStart). And WebStart includes various other files without problems, but then it starts using $IP to load Setup.php, and that one fails.

In the above case, realpath('.'); resolves to where the PHP script starts:

Fatal error: require_once(): Failed opening required '/var/www/includes/Setup.php' (include_path='.:/usr/local/lib/php') in /var/www/mediawiki/includes/WebStart.php on line 97
Stack trace:

{main}() /var/www/index.php:0

require() /var/www/index.php:3

require() /var/www/mediawiki/index.php:40