[dpdk-dev] [PATCH v2] net/mlx: fix rdma-core glue path with EAL plugins

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

Glue object files are looked up in RTE_EAL_PMD_PATH by default when set and
should be installed in this directory.

During startup, EAL attempts to load them automatically like other plug-ins
found there. While normally harmless, dlopen() fails when rdma-core is not
installed, EAL interprets this as a fatal error and terminates the
application.

This patch requests glue objects to be installed in a different directory
to prevent their automatic loading by EAL since they are PMD helpers, not
actual DPDK plug-ins.

Fixes: f6242d0655cd ("net/mlx: make rdma-core glue path configurable")
Cc: stable@dpdk.org

Reported-by: Timothy Redaelli <tredaelli@redhat.com>
Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
---
 doc/guides/nics/mlx4.rst |  7 +++---
 doc/guides/nics/mlx5.rst |  7 +++---
 drivers/net/mlx4/mlx4.c  | 50 ++++++++++++++++++++++++++++++++++++++++++-
 drivers/net/mlx5/mlx5.c  | 50 ++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 106 insertions(+), 8 deletions(-)

diff --git a/doc/guides/nics/mlx4.rst b/doc/guides/nics/mlx4.rst
index 98b971667..afeff276e 100644
--- a/doc/guides/nics/mlx4.rst
+++ b/doc/guides/nics/mlx4.rst
@@ -98,9 +98,10 @@ These options can be modified in the ``.config`` file.
   missing with ``ldd(1)``.
 
   It works by moving these dependencies to a purpose-built rdma-core "glue"
-  plug-in, which must either be installed in ``CONFIG_RTE_EAL_PMD_PATH`` if
-  set, or in a standard location for the dynamic linker (e.g. ``/lib``) if
-  left to the default empty string (``""``).
+  plug-in which must either be installed in a directory whose name is based
+  on ``CONFIG_RTE_EAL_PMD_PATH`` suffixed with ``-glue`` if set, or in a
+  standard location for the dynamic linker (e.g. ``/lib``) if left to the
+  default empty string (``""``).
 
   This option has no performance impact.
 
diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index 0e6e525c9..46d26e4c8 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -171,9 +171,10 @@ These options can be modified in the ``.config`` file.
   missing with ``ldd(1)``.
 
   It works by moving these dependencies to a purpose-built rdma-core "glue"
-  plug-in, which must either be installed in ``CONFIG_RTE_EAL_PMD_PATH`` if
-  set, or in a standard location for the dynamic linker (e.g. ``/lib``) if
-  left to the default empty string (``""``).
+  plug-in which must either be installed in a directory whose name is based
+  on ``CONFIG_RTE_EAL_PMD_PATH`` suffixed with ``-glue`` if set, or in a
+  standard location for the dynamic linker (e.g. ``/lib``) if left to the
+  default empty string (``""``).
 
   This option has no performance impact.
 
diff --git a/drivers/net/mlx4/mlx4.c b/drivers/net/mlx4/mlx4.c
index ee93dafe6..fb8a8b848 100644
--- a/drivers/net/mlx4/mlx4.c
+++ b/drivers/net/mlx4/mlx4.c
@@ -708,11 +708,53 @@ static struct rte_pci_driver mlx4_driver = {
 #ifdef RTE_LIBRTE_MLX4_DLOPEN_DEPS
 
 /**
+ * Suffix RTE_EAL_PMD_PATH with "-glue".
+ *
+ * This function performs a sanity check on RTE_EAL_PMD_PATH before
+ * suffixing its last component.
+ *
+ * @param buf[out]
+ *   Output buffer, should be large enough otherwise NULL is returned.
+ * @param size
+ *   Size of @p out.
+ *
+ * @return
+ *   Pointer to @p buf or @p NULL in case suffix cannot be appended.
+ */
+static char *
+mlx4_glue_path(char *buf, size_t size)
+{
+	static const char *const bad[] = { "/", ".", "..", NULL };
+	const char *path = RTE_EAL_PMD_PATH;
+	size_t len = strlen(path);
+	size_t off;
+	int i;
+
+	while (len && path[len - 1] == '/')
+		--len;
+	for (off = len; off && path[off - 1] != '/'; --off)
+		;
+	for (i = 0; bad[i]; ++i)
+		if (!strncmp(path + off, bad[i], (int)(len - off)))
+			goto error;
+	i = snprintf(buf, size, "%.*s-glue", (int)len, path);
+	if (i == -1 || (size_t)i >= size)
+		goto error;
+	return buf;
+error:
+	ERROR("unable to append \"-glue\" to last component of"
+	      " RTE_EAL_PMD_PATH (\"" RTE_EAL_PMD_PATH "\"),"
+	      " please re-configure DPDK");
+	return NULL;
+}
+
+/**
  * Initialization routine for run-time dependency on rdma-core.
  */
 static int
 mlx4_glue_init(void)
 {
+	char glue_path[sizeof(RTE_EAL_PMD_PATH) - 1 + sizeof("-glue")];
 	const char *path[] = {
 		/*
 		 * A basic security check is necessary before trusting
@@ -720,7 +762,13 @@ mlx4_glue_init(void)
 		 */
 		(geteuid() == getuid() && getegid() == getgid() ?
 		 getenv("MLX4_GLUE_PATH") : NULL),
-		RTE_EAL_PMD_PATH,
+		/*
+		 * When RTE_EAL_PMD_PATH is set, use its glue-suffixed
+		 * variant, otherwise let dlopen() look up libraries on its
+		 * own.
+		 */
+		(*RTE_EAL_PMD_PATH ?
+		 mlx4_glue_path(glue_path, sizeof(glue_path)) : ""),
 	};
 	unsigned int i = 0;
 	void *handle = NULL;
diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
index 61cb93101..0ca16d11d 100644
--- a/drivers/net/mlx5/mlx5.c
+++ b/drivers/net/mlx5/mlx5.c
@@ -1043,11 +1043,53 @@ static struct rte_pci_driver mlx5_driver = {
 #ifdef RTE_LIBRTE_MLX5_DLOPEN_DEPS
 
 /**
+ * Suffix RTE_EAL_PMD_PATH with "-glue".
+ *
+ * This function performs a sanity check on RTE_EAL_PMD_PATH before
+ * suffixing its last component.
+ *
+ * @param buf[out]
+ *   Output buffer, should be large enough otherwise NULL is returned.
+ * @param size
+ *   Size of @p out.
+ *
+ * @return
+ *   Pointer to @p buf or @p NULL in case suffix cannot be appended.
+ */
+static char *
+mlx5_glue_path(char *buf, size_t size)
+{
+	static const char *const bad[] = { "/", ".", "..", NULL };
+	const char *path = RTE_EAL_PMD_PATH;
+	size_t len = strlen(path);
+	size_t off;
+	int i;
+
+	while (len && path[len - 1] == '/')
+		--len;
+	for (off = len; off && path[off - 1] != '/'; --off)
+		;
+	for (i = 0; bad[i]; ++i)
+		if (!strncmp(path + off, bad[i], (int)(len - off)))
+			goto error;
+	i = snprintf(buf, size, "%.*s-glue", (int)len, path);
+	if (i == -1 || (size_t)i >= size)
+		goto error;
+	return buf;
+error:
+	ERROR("unable to append \"-glue\" to last component of"
+	      " RTE_EAL_PMD_PATH (\"" RTE_EAL_PMD_PATH "\"),"
+	      " please re-configure DPDK");
+	return NULL;
+}
+
+/**
  * Initialization routine for run-time dependency on rdma-core.
  */
 static int
 mlx5_glue_init(void)
 {
+	char glue_path[sizeof(RTE_EAL_PMD_PATH) - 1 + sizeof("-glue")];
 	const char *path[] = {
 		/*
 		 * A basic security check is necessary before trusting
@@ -1055,7 +1097,13 @@ mlx5_glue_init(void)
 		 */
 		(geteuid() == getuid() && getegid() == getgid() ?
 		 getenv("MLX5_GLUE_PATH") : NULL),
-		RTE_EAL_PMD_PATH,
+		/*
+		 * When RTE_EAL_PMD_PATH is set, use its glue-suffixed
+		 * variant, otherwise let dlopen() look up libraries on its
+		 * own.
+		 */
+		(*RTE_EAL_PMD_PATH ?
+		 mlx5_glue_path(glue_path, sizeof(glue_path)) : ""),
 	};
 	unsigned int i = 0;
 	void *handle = NULL;
-- 
2.11.0