Restrict kstats and print real pointers

There are several places where we use zfs_dbgmsg and %p to
print pointers. In the Linux kernel, these values obfuscated
to prevent information leaks which means the pointers aren't
very useful for debugging crash dumps. We decided to restrict
the permissions of dbgmsg (and some other kstats while we were
at it) and print pointers with %px in zfs_dbgmsg as well as
spl_dumpstack

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Gallagher <john.gallagher@delphix.com>
Signed-off-by: sara hartse <sara.hartse@delphix.com>
Closes #8467 
Closes #8476

module/zfs/arc.c

@@ -2266,7 +2266,7 @@ arc_buf_fill(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
 			 */
 			if (error != 0) {
 				zfs_dbgmsg(
-				    "hdr %p, compress %d, psize %d, lsize %d",
+				    "hdr %px, compress %d, psize %d, lsize %d",
 				    hdr, arc_hdr_get_compress(hdr),
 				    HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
 				if (hash_lock != NULL)

module/zfs/metaslab.c

@@ -2643,7 +2643,7 @@ metaslab_condense(metaslab_t *msp, uint64_t txg, dmu_tx_t *tx)
 	ASSERT(msp->ms_loaded);
 
 
-	zfs_dbgmsg("condensing: txg %llu, msp[%llu] %p, vdev id %llu, "
+	zfs_dbgmsg("condensing: txg %llu, msp[%llu] %px, vdev id %llu, "
 	    "spa %s, smp size %llu, segments %lu, forcing condense=%s", txg,
 	    msp->ms_id, msp, msp->ms_group->mg_vd->vdev_id,
 	    msp->ms_group->mg_vd->vdev_spa->spa_name,

module/zfs/range_tree.c

@@ -118,7 +118,7 @@ range_tree_stat_verify(range_tree_t *rt)
 
 	for (i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++) {
 		if (hist[i] != rt->rt_histogram[i]) {
-			zfs_dbgmsg("i=%d, hist=%p, hist=%llu, rt_hist=%llu",
+			zfs_dbgmsg("i=%d, hist=%px, hist=%llu, rt_hist=%llu",
 			    i, hist, hist[i], rt->rt_histogram[i]);
 		}
 		VERIFY3U(hist[i], ==, rt->rt_histogram[i]);

module/zfs/spa_stats.c

@@ -131,6 +131,7 @@ spa_read_history_init(spa_t *spa)
 	shl->procfs_list.pl_private = shl;
 	procfs_list_install(module,
 	    "reads",
+	    0600,
 	    &shl->procfs_list,
 	    spa_read_history_show,
 	    spa_read_history_show_header,
@@ -301,6 +302,7 @@ spa_txg_history_init(spa_t *spa)
 	shl->procfs_list.pl_private = shl;
 	procfs_list_install(module,
 	    "txgs",
+	    0644,
 	    &shl->procfs_list,
 	    spa_txg_history_show,
 	    spa_txg_history_show_header,
@@ -706,6 +708,7 @@ spa_mmp_history_init(spa_t *spa)
 	shl->procfs_list.pl_private = shl;
 	procfs_list_install(module,
 	    "multihost",
+	    0644,
 	    &shl->procfs_list,
 	    spa_mmp_history_show,
 	    spa_mmp_history_show_header,

module/zfs/space_map.c

@@ -848,7 +848,7 @@ space_map_truncate(space_map_t *sm, int blocksize, dmu_tx_t *tx)
 	    doi.doi_bonus_size != sizeof (space_map_phys_t)) ||
 	    doi.doi_data_block_size != blocksize ||
 	    doi.doi_metadata_block_size != 1 << space_map_ibs) {
-		zfs_dbgmsg("txg %llu, spa %s, sm %p, reallocating "
+		zfs_dbgmsg("txg %llu, spa %s, sm %px, reallocating "
 		    "object[%llu]: old bonus %u, old blocksz %u",
 		    dmu_tx_get_txg(tx), spa_name(spa), sm, sm->sm_object,
 		    doi.doi_bonus_size, doi.doi_data_block_size);

module/zfs/vdev_removal.c

@@ -340,7 +340,7 @@ vdev_remove_initiate_sync(void *arg, dmu_tx_t *tx)
 	 */
 	vdev_config_dirty(vd);
 
-	zfs_dbgmsg("starting removal thread for vdev %llu (%p) in txg %llu "
+	zfs_dbgmsg("starting removal thread for vdev %llu (%px) in txg %llu "
 	    "im_obj=%llu", vd->vdev_id, vd, dmu_tx_get_txg(tx),
 	    vic->vic_mapping_object);
 

module/zfs/zfs_debug.c

@@ -94,6 +94,7 @@ zfs_dbgmsg_init(void)
 {
 	procfs_list_install("zfs",
 	    "dbgmsg",
+	    0600,
 	    &zfs_dbgmsgs,
 	    zfs_dbgmsg_show,
 	    zfs_dbgmsg_show_header,

module/zfs/zil.c

@@ -3232,7 +3232,7 @@ zil_close(zilog_t *zilog)
 		txg_wait_synced(zilog->zl_dmu_pool, txg);
 
 	if (zilog_is_dirty(zilog))
-		zfs_dbgmsg("zil (%p) is dirty, txg %llu", zilog, txg);
+		zfs_dbgmsg("zil (%px) is dirty, txg %llu", zilog, txg);
 	if (txg < spa_freeze_txg(zilog->zl_spa))
 		VERIFY(!zilog_is_dirty(zilog));
 

module/zfs/zio.c

@@ -1893,7 +1893,7 @@ zio_deadman_impl(zio_t *pio, int ziodepth)
 		uint64_t delta = gethrtime() - pio->io_timestamp;
 		uint64_t failmode = spa_get_deadman_failmode(pio->io_spa);
 
-		zfs_dbgmsg("slow zio[%d]: zio=%p timestamp=%llu "
+		zfs_dbgmsg("slow zio[%d]: zio=%px timestamp=%llu "
 		    "delta=%llu queued=%llu io=%llu "
 		    "path=%s last=%llu "
 		    "type=%d priority=%d flags=0x%x "
@@ -3444,7 +3444,7 @@ zio_dva_allocate(zio_t *zio)
 	}
 
 	if (error != 0) {
-		zfs_dbgmsg("%s: metaslab allocation failure: zio %p, "
+		zfs_dbgmsg("%s: metaslab allocation failure: zio %px, "
 		    "size %llu, error %d", spa_name(spa), zio, zio->io_size,
 		    error);
 		if (error == ENOSPC && zio->io_size > SPA_MINBLOCKSIZE)