LU-12678 lnet: prepare to make lnet_lnd const.

Preferred practice is for structs containing function
pointers to be 'const'.  Such structs are generally tempting
attack vectors, and making them const allows linux to place
them in read-only memory, thus reducing the attack surface.

'struct lnet_lnd' is mostly function pointers, but contains
one writable field - a list_head.

Rather than keeping registered lnds in a linked-list, we can place
them in an array indexed by type - type numbers are at most 15 so
this is not a burden.

With these changes, no part of an lnet_lnd is ever modified.

Test-Parameters: trivial
Test-Parameters: testlist=sanity-lnet

Signed-off-by: Mr NeilBrown <neilb@suse.com>
Change-Id: I08c7df551109e05ca4a3cef866e8df737d1a1ad4
Reviewed-on: https://review.whamcloud.com/36830
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/lnet/include/lnet/lib-types.h b/lnet/include/lnet/lib-types.h
index d17929d..703251e 100644 (file)
--- a/lnet/include/lnet/lib-types.h
+++ b/lnet/include/lnet/lib-types.h
@@ -49,6 +49,7 @@
 
 #include <uapi/linux/lnet/lnet-dlc.h>
 #include <uapi/linux/lnet/lnetctl.h>
+#include <uapi/linux/lnet/nidstr.h>
 
 /* Max payload size */
 #define LNET_MAX_PAYLOAD       LNET_MTU
@@ -248,9 +249,6 @@ struct lnet_ni;                                      /* forward ref */
 struct socket;
 
 struct lnet_lnd {
-       /* fields managed by portals */
-       struct list_head        lnd_list;       /* stash in the LND table */
-
        /* fields initialized by the LND */
        __u32                   lnd_type;
 
@@ -1112,7 +1110,7 @@ struct lnet {
        /* uniquely identifies this ni in this epoch */
        __u64                           ln_interface_cookie;
        /* registered LNDs */
-       struct list_head                ln_lnds;
+       struct lnet_lnd                 *ln_lnds[NUM_LNDS];
 
        /* test protocol compatibility flags */
        int                             ln_testprotocompat;

diff --git a/lnet/include/uapi/linux/lnet/nidstr.h b/lnet/include/uapi/linux/lnet/nidstr.h
index 6e3f4ca..c4a297f 100644 (file)
--- a/lnet/include/uapi/linux/lnet/nidstr.h
+++ b/lnet/include/uapi/linux/lnet/nidstr.h
@@ -60,6 +60,8 @@ enum {
        GNILND          = 13,
        GNIIPLND        = 14,
        PTL4LND         = 15,
+
+       NUM_LNDS
 };
 
 struct list_head;

diff --git a/lnet/lnet/api-ni.c b/lnet/lnet/api-ni.c
index d6e5e3d..a593597 100644 (file)
--- a/lnet/lnet/api-ni.c
+++ b/lnet/lnet/api-ni.c
@@ -800,16 +800,14 @@ static void lnet_assert_wire_constants(void)
 static struct lnet_lnd *lnet_find_lnd_by_type(__u32 type)
 {
        struct lnet_lnd *lnd;
-       struct list_head *tmp;
 
        /* holding lnd mutex */
-       list_for_each(tmp, &the_lnet.ln_lnds) {
-               lnd = list_entry(tmp, struct lnet_lnd, lnd_list);
+       if (type >= NUM_LNDS)
+               return NULL;
+       lnd = the_lnet.ln_lnds[type];
+       LASSERT(!lnd || lnd->lnd_type == type);
 
-               if (lnd->lnd_type == type)
-                       return lnd;
-       }
-       return NULL;
+       return lnd;
 }
 
 unsigned int
@@ -827,7 +825,7 @@ lnet_register_lnd(struct lnet_lnd *lnd)
        LASSERT(libcfs_isknown_lnd(lnd->lnd_type));
        LASSERT(lnet_find_lnd_by_type(lnd->lnd_type) == NULL);
 
-       list_add_tail(&lnd->lnd_list, &the_lnet.ln_lnds);
+       the_lnet.ln_lnds[lnd->lnd_type] = lnd;
 
        CDEBUG(D_NET, "%s LND registered\n", libcfs_lnd2str(lnd->lnd_type));
 
@@ -842,7 +840,7 @@ lnet_unregister_lnd(struct lnet_lnd *lnd)
 
        LASSERT(lnet_find_lnd_by_type(lnd->lnd_type) == lnd);
 
-       list_del(&lnd->lnd_list);
+       the_lnet.ln_lnds[lnd->lnd_type] = NULL;
        CDEBUG(D_NET, "%s LND unregistered\n", libcfs_lnd2str(lnd->lnd_type));
 
        mutex_unlock(&the_lnet.ln_lnd_mutex);
@@ -2517,7 +2515,6 @@ int lnet_lib_init(void)
        }
 
        the_lnet.ln_refcount = 0;
-       INIT_LIST_HEAD(&the_lnet.ln_lnds);
        INIT_LIST_HEAD(&the_lnet.ln_net_zombie);
        INIT_LIST_HEAD(&the_lnet.ln_msg_resend);
 
@@ -2543,14 +2540,18 @@ int lnet_lib_init(void)
  *
  * \pre lnet_lib_init() called with success.
  * \pre All LNet users called LNetNIFini() for matching LNetNIInit() calls.
+ *
+ * As this happens at module-unload, all lnds must already be unloaded,
+ * so they must already be unregistered.
  */
 void lnet_lib_exit(void)
 {
-       LASSERT(the_lnet.ln_refcount == 0);
+       int i;
 
-       while (!list_empty(&the_lnet.ln_lnds))
-               lnet_unregister_lnd(list_entry(the_lnet.ln_lnds.next,
-                                              struct lnet_lnd, lnd_list));
+       LASSERT(the_lnet.ln_refcount == 0);
+       lnet_unregister_lnd(&the_lolnd);
+       for (i = 0; i < NUM_LNDS; i++)
+               LASSERT(!the_lnet.ln_lnds[i]);
        lnet_destroy_locks();
 }
 

diff --git a/lnet/lnet/lo.c b/lnet/lnet/lo.c
index a11ecdd..4f0ec8b 100644 (file)
--- a/lnet/lnet/lo.c
+++ b/lnet/lnet/lo.c
@@ -104,10 +104,6 @@ lolnd_startup(struct lnet_ni *ni)
 }
 
 struct lnet_lnd the_lolnd = {
-       .lnd_list       = {
-                               .next = &the_lolnd.lnd_list,
-                               .prev = &the_lolnd.lnd_list
-                       },
        .lnd_type       = LOLND,
        .lnd_startup    = lolnd_startup,
        .lnd_shutdown   = lolnd_shutdown,