DPDK patches and discussions
 help / color / mirror / Atom feed
* Re: [dpdk-dev] [PATCH] eal: don't use default library path for static binaries
@ 2020-06-30 15:39 Pai G, Sunil
  0 siblings, 0 replies; 9+ messages in thread
From: Pai G, Sunil @ 2020-06-30 15:39 UTC (permalink / raw)
  To: Richardson, Bruce, dev; +Cc: Richardson, Bruce, Stokes, Ian

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Bruce Richardson
> Sent: Friday, June 26, 2020 8:30 PM
> To: dev@dpdk.org
> Cc: Richardson, Bruce <bruce.richardson@intel.com>
> Subject: [dpdk-dev] [PATCH] eal: don't use default library path for static
> binaries
> 
> 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

While trying to enable DPDK meson build for OVS , this patch turned out to be quite beneficial when DPDK was installed using a prefix.
This fixes the "Cannot open shared object file: No such file or directory" seen when OVS is built with static DPDK libraries.
Tested following scenarios with the patch and all of them function as expected:
1. system installed - OVS with DPDK static libs 
2. system installed - OVS with DPDK shared libs
3. directory installed using the prefix - OVS with DPDK static libs 
4. directory installed using the prefix - OVS with DPDK shared libs

OVS community would be grateful if this could be back ported to 19.11 

Acked-by: Sunil Pai G <sunil.pai.g@intel.com


^ permalink raw reply	[flat|nested] 9+ messages in thread
* [dpdk-dev] [PATCH] eal: don't use default library path for static binaries
@ 2020-06-26 14:59 Bruce Richardson
  2020-06-26 17:05 ` Stephen Hemminger
  2020-06-29 14:53 ` Burakov, Anatoly
  0 siblings, 2 replies; 9+ messages in thread
From: Bruce Richardson @ 2020-06-26 14:59 UTC (permalink / raw)
  To: dev; +Cc: Bruce Richardson

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


^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2020-07-05 18:01 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-06-30 15:39 [dpdk-dev] [PATCH] eal: don't use default library path for static binaries Pai G, Sunil
  -- strict thread matches above, loose matches on Subject: below --
2020-06-26 14:59 Bruce Richardson
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

DPDK patches and discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/dev/0 dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dev dev/ https://inbox.dpdk.org/dev \
		dev@dpdk.org
	public-inbox-index dev

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git