DPDK patches and discussions
 help / color / mirror / Atom feed
From: Bruce Richardson <bruce.richardson@intel.com>
To: dev@dpdk.org
Cc: Bruce Richardson <bruce.richardson@intel.com>
Subject: [dpdk-dev] [PATCH] eal: don't use default library path for static binaries
Date: Fri, 26 Jun 2020 15:59:57 +0100	[thread overview]
Message-ID: <20200626145957.722089-1-bruce.richardson@intel.com> (raw)

When using statically linked DPDK binaries, the EAL checks the default PMD
path and tries to load any drivers there, despite the fact that all drivers
are normally linked into the binary.  This behaviour can cause issues if
the PMD path and lib dir is configured to a non-standard location which is
not in the ld.so.conf paths, e.g. a build with prefix set to a home
directory location. In a case such as this, EAL will try and
(unnecessarily) load the .so driver files but that load will fail as their
dependent libraries, such as ethdev, for example, will not be found.

Because of this, it is better if statically linked DPDK apps do not load
drivers from the standard paths automatically. The user can always have
this behaviour by explicitly specifying the path using -d flag, if so
desired.

Not loading the libraries automatically can also prevent potential issues
with a user building and running a statically-linked DPDK binary based off
a private copy of DPDK, while there exists on the same machine a
system-wide installation of DPDK in the default locations. Without this
change, the system-installed drivers will be loaded to the binary alongside
the statically-linked drivers, which is not what the user would have
intended.

To detect whether we are in a statically or dynamically linked binary, we
can have EAL try to get a dlopen handle to its own shared library, by
calling dlopen with the RTLD_NOLOAD flag. This will return NULL if there is
no such shared lib loaded i.e. the code is executing from a static library,
or a handle to the lib if it is loaded.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
 lib/librte_eal/common/eal_common_options.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_options.c b/lib/librte_eal/common/eal_common_options.c
index 0901b493c..1d958d11e 100644
--- a/lib/librte_eal/common/eal_common_options.c
+++ b/lib/librte_eal/common/eal_common_options.c
@@ -447,8 +447,15 @@ eal_plugins_init(void)
 	struct shared_driver *solib = NULL;
 	struct stat sb;
 
-	if (*default_solib_dir != '\0' && stat(default_solib_dir, &sb) == 0 &&
-				S_ISDIR(sb.st_mode))
+	/* if we are not statically linked, add default driver loading
+	 * path if it exists as a directory.
+	 * (Using dlopen with NOLOAD flag on eal, will return NULL if the eal
+	 * shared library is not already loaded i.e. it's statically linked.)
+	 */
+	if (dlopen("librte_eal.so", RTLD_LAZY | RTLD_NOLOAD) != NULL &&
+			*default_solib_dir != '\0' &&
+			stat(default_solib_dir, &sb) == 0 &&
+			S_ISDIR(sb.st_mode))
 		eal_plugin_add(default_solib_dir);
 
 	TAILQ_FOREACH(solib, &solib_list, next) {
-- 
2.25.1


             reply	other threads:[~2020-06-26 15:00 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-26 14:59 Bruce Richardson [this message]
2020-06-26 17:05 ` Stephen Hemminger
2020-06-29  9:11   ` Bruce Richardson
2020-06-29  9:19     ` Bruce Richardson
2020-06-29 15:41       ` Stephen Hemminger
2020-06-29 16:15         ` Bruce Richardson
2020-07-05 18:01           ` Thomas Monjalon
2020-06-29 14:53 ` Burakov, Anatoly
2020-06-30 15:39 Pai G, Sunil

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200626145957.722089-1-bruce.richardson@intel.com \
    --to=bruce.richardson@intel.com \
    --cc=dev@dpdk.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).