[dpdk-stable] patch 'eal: fix automatic loading of drivers as shared libs' has been queued to stable release 20.11.1

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 20.11.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 02/14/21. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/bluca/dpdk-stable

This queued commit can be viewed at:
https://github.com/bluca/dpdk-stable/commit/dfc264c256874bfe56fb79403a24e0f1fe4c0383

Thanks.

Luca Boccassi

---
>From dfc264c256874bfe56fb79403a24e0f1fe4c0383 Mon Sep 17 00:00:00 2001
From: Bruce Richardson <bruce.richardson at intel.com>
Date: Mon, 8 Feb 2021 16:33:19 +0000
Subject: [PATCH] eal: fix automatic loading of drivers as shared libs

[ upstream commit 9ff791eff609138a69edd89bf4abde71511eef6d ]

When checking the loading of EAL shared lib to see if we have a shared
DPDK build, we only want to include part of the ABI version in the check
rather than the whole thing. For example, with ABI version 21.1 for DPDK
release 21.02, the linker links the binary against librte_eal.so.21,
without the ".1".

To avoid any further brittleness in this area, we can check for multiple
versions when doing the check, since just about any version of EAL implies
a shared build. Therefore we check for presence of librte_eal.so with full
ABI_VERSION extension, and then repeatedly remove the end part of the
filename after the last dot, checking each time. For example (debug log
output for static build):

  EAL: Checking presence of .so 'librte_eal.so.21.1'
  EAL: Checking presence of .so 'librte_eal.so.21'
  EAL: Checking presence of .so 'librte_eal.so'
  EAL: Detected static linkage of DPDK

Fixes: 7781950f4d38 ("eal: fix shared lib mode detection")

Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
Tested-by: Sunil Pai G <sunil.pai.g at intel.com>
---
 lib/librte_eal/common/eal_common_options.c | 35 +++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/lib/librte_eal/common/eal_common_options.c b/lib/librte_eal/common/eal_common_options.c
index 424e8bcf87..622c7bc429 100644
--- a/lib/librte_eal/common/eal_common_options.c
+++ b/lib/librte_eal/common/eal_common_options.c
@@ -494,6 +494,39 @@ out:
 	return retval;
 }
 
+static int
+is_shared_build(void)
+{
+#define EAL_SO "librte_eal.so"
+	char soname[32];
+	size_t len, minlen = strlen(EAL_SO);
+
+	len = strlcpy(soname, EAL_SO"."ABI_VERSION, sizeof(soname));
+	if (len > sizeof(soname)) {
+		RTE_LOG(ERR, EAL, "Shared lib name too long in shared build check\n");
+		len = sizeof(soname) - 1;
+	}
+
+	while (len >= minlen) {
+		/* check if we have this .so loaded, if so - shared build */
+		RTE_LOG(DEBUG, EAL, "Checking presence of .so '%s'\n", soname);
+		if (dlopen(soname, RTLD_LAZY | RTLD_NOLOAD) != NULL) {
+			RTE_LOG(INFO, EAL, "Detected shared linkage of DPDK\n");
+			return 1;
+		}
+
+		/* remove any version numbers off the end to retry */
+		while (len-- > 0)
+			if (soname[len] == '.') {
+				soname[len] = '\0';
+				break;
+			}
+	}
+
+	RTE_LOG(INFO, EAL, "Detected static linkage of DPDK\n");
+	return 0;
+}
+
 int
 eal_plugins_init(void)
 {
@@ -505,7 +538,7 @@ eal_plugins_init(void)
 	 * (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."ABI_VERSION, RTLD_LAZY | RTLD_NOLOAD) != NULL &&
+	if (is_shared_build() &&
 			*default_solib_dir != '\0' &&
 			stat(default_solib_dir, &sb) == 0 &&
 			S_ISDIR(sb.st_mode))
-- 
2.29.2

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-02-12 23:40:09.908777582 +0000
+++ 0001-eal-fix-automatic-loading-of-drivers-as-shared-libs.patch	2021-02-12 23:40:09.855090191 +0000
@@ -1 +1 @@
-From 9ff791eff609138a69edd89bf4abde71511eef6d Mon Sep 17 00:00:00 2001
+From dfc264c256874bfe56fb79403a24e0f1fe4c0383 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 9ff791eff609138a69edd89bf4abde71511eef6d ]
+
@@ -25 +26,0 @@
-Cc: stable at dpdk.org