From 4e7f92ffbfc0300fee239a0a518367dfaba6eac4 Mon Sep 17 00:00:00 2001
From: Vladimir Oltean <vladimir.oltean@nxp.com>
Date: Fri, 26 Nov 2021 19:28:42 +0200
Subject: [PATCH 5/8] net: mscc: ocelot: create a function that replaces an
 existing VCAP filter
Git-commit: 95706be13b9f755d93b5b82bdc782af439f1ec22
Patch-mainline: v5.16-rc3
References: git-fixes

VCAP (Versatile Content Aware Processor) is the TCAM-based engine behind
tc flower offload on ocelot, among other things. The ingress port mask
on which VCAP rules match is present as a bit field in the actual key of
the rule. This means that it is possible for a rule to be shared among
multiple source ports. When the rule is added one by one on each desired
port, that the ingress port mask of the key must be edited and rewritten
to hardware.

But the API in ocelot_vcap.c does not allow for this. For one thing,
ocelot_vcap_filter_add() and ocelot_vcap_filter_del() are not symmetric,
because ocelot_vcap_filter_add() works with a preallocated and
prepopulated filter and programs it to hardware, and
ocelot_vcap_filter_del() does both the job of removing the specified
filter from hardware, as well as kfreeing it. That is to say, the only
option of editing a filter in place, which is to delete it, modify the
structure and add it back, does not work because it results in
use-after-free.

This patch introduces ocelot_vcap_filter_replace, which trivially
reprograms a VCAP entry to hardware, at the exact same index at which it
existed before, without modifying any list or allocating any memory.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
 drivers/net/ethernet/mscc/ocelot_vcap.c | 16 ++++++++++++++++
 include/soc/mscc/ocelot_vcap.h          |  2 ++
 2 files changed, 18 insertions(+)

diff --git a/drivers/net/ethernet/mscc/ocelot_vcap.c b/drivers/net/ethernet/mscc/ocelot_vcap.c
index 99d7376a70a7..337cd08b1a54 100644
--- a/drivers/net/ethernet/mscc/ocelot_vcap.c
+++ b/drivers/net/ethernet/mscc/ocelot_vcap.c
@@ -1217,6 +1217,22 @@ int ocelot_vcap_filter_del(struct ocelot *ocelot,
 }
 EXPORT_SYMBOL(ocelot_vcap_filter_del);
 
+int ocelot_vcap_filter_replace(struct ocelot *ocelot,
+			       struct ocelot_vcap_filter *filter)
+{
+	struct ocelot_vcap_block *block = &ocelot->block[filter->block_id];
+	int index;
+
+	index = ocelot_vcap_block_get_filter_index(block, filter);
+	if (index < 0)
+		return index;
+
+	vcap_entry_set(ocelot, index, filter);
+
+	return 0;
+}
+EXPORT_SYMBOL(ocelot_vcap_filter_replace);
+
 int ocelot_vcap_filter_stats_update(struct ocelot *ocelot,
 				    struct ocelot_vcap_filter *filter)
 {
diff --git a/include/soc/mscc/ocelot_vcap.h b/include/soc/mscc/ocelot_vcap.h
index 4869ebbd438d..56c19068d991 100644
--- a/include/soc/mscc/ocelot_vcap.h
+++ b/include/soc/mscc/ocelot_vcap.h
@@ -693,6 +693,8 @@ int ocelot_vcap_filter_add(struct ocelot *ocelot,
 			   struct netlink_ext_ack *extack);
 int ocelot_vcap_filter_del(struct ocelot *ocelot,
 			   struct ocelot_vcap_filter *rule);
+int ocelot_vcap_filter_replace(struct ocelot *ocelot,
+			       struct ocelot_vcap_filter *filter);
 struct ocelot_vcap_filter *
 ocelot_vcap_block_find_filter_by_id(struct ocelot_vcap_block *block,
 				    unsigned long cookie, bool tc_offload);
-- 
2.16.4