Merge branch 'reorganize-the-code-of-the-enum-skb_drop_reason'

Menglong Dong says:

====================
reorganize the code of the enum skb_drop_reason

The code of skb_drop_reason is a little wild, let's reorganize them.
Three things and three patches:

1) Move the enum 'skb_drop_reason' and related function to the standalone
   header 'dropreason.h', as Jakub Kicinski suggested, as the skb drop
   reasons are getting more and more.

2) use auto-generation to generate the source file that convert enum
   skb_drop_reason to string.

3) make the comment of skb drop reasons kernel-doc style.

Changes since v3:
3/3: remove some useless comment (Jakub Kicinski)

Changes since v2:
2/3: - add new line in the end of .gitignore
     - fix awk warning by make '\;' to ';', as ';' is not need to be
       escaped
     - export 'drop_reasons' in skbuff.c

Changes since v1:
1/3: move dropreason.h from include/linux/ to include/net/ (Jakub Kicinski)
2/3: generate source file instead of header file for drop reasons string
     array (Jakub Kicinski)
3/3: use inline comment (Jakub Kicinski)
====================

Link: https://lore.kernel.org/r/20220606022436.331005-1-imagedong@tencent.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

4 files changed, 26 insertions, 14 deletions

diff --git a/net/core/.gitignore b/net/core/.gitignore
new file mode 100644
index 000000000000..df1e74372cce
--- /dev/null
+++ b/net/core/.gitignore
@@ -0,0 +1 @@
+dropreason_str.c
diff --git a/net/core/Makefile b/net/core/Makefile
index a8e4f737692b..e8ce3bd283a6 100644
--- a/net/core/Makefile
+++ b/net/core/Makefile
@@ -4,7 +4,8 @@
 #
 
 obj-y := sock.o request_sock.o skbuff.o datagram.o stream.o scm.o \
-	 gen_stats.o gen_estimator.o net_namespace.o secure_seq.o flow_dissector.o
+	 gen_stats.o gen_estimator.o net_namespace.o secure_seq.o \
+	 flow_dissector.o dropreason_str.o
 
 obj-$(CONFIG_SYSCTL) += sysctl_net_core.o
 
@@ -39,3 +40,23 @@ obj-$(CONFIG_NET_SOCK_MSG) += skmsg.o
 obj-$(CONFIG_BPF_SYSCALL) += sock_map.o
 obj-$(CONFIG_BPF_SYSCALL) += bpf_sk_storage.o
 obj-$(CONFIG_OF)	+= of_net.o
+
+clean-files := dropreason_str.c
+
+quiet_cmd_dropreason_str = GEN     $@
+cmd_dropreason_str = awk -F ',' 'BEGIN{ print "\#include <net/dropreason.h>\n"; \
+	print "const char * const drop_reasons[] = {" }\
+	/^enum skb_drop/ { dr=1; }\
+	/^\};/ { dr=0; }\
+	/^\tSKB_DROP_REASON_/ {\
+		if (dr) {\
+			sub(/\tSKB_DROP_REASON_/, "", $$1);\
+			printf "\t[SKB_DROP_REASON_%s] = \"%s\",\n", $$1, $$1;\
+		}\
+	}\
+	END{ print "};" }' $< > $@
+
+$(obj)/dropreason_str.c: $(srctree)/include/net/dropreason.h
+	$(call cmd,dropreason_str)
+
+$(obj)/dropreason_str.o: $(obj)/dropreason_str.c
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 41cac0e4834e..4ad1decce724 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -48,19 +48,6 @@
 static int trace_state = TRACE_OFF;
 static bool monitor_hw;
 
-#undef EM
-#undef EMe
-
-#define EM(a, b)	[a] = #b,
-#define EMe(a, b)	[a] = #b
-
-/* drop_reasons is used to translate 'enum skb_drop_reason' to string,
- * which is reported to user space.
- */
-static const char * const drop_reasons[] = {
-	TRACE_SKB_DROP_REASON
-};
-
 /* net_dm_mutex
  *
  * An overall lock guarding every operation coming from userspace.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 5b3559cb1d82..b661040c100e 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -91,6 +91,9 @@ static struct kmem_cache *skbuff_ext_cache __ro_after_init;
 int sysctl_max_skb_frags __read_mostly = MAX_SKB_FRAGS;
 EXPORT_SYMBOL(sysctl_max_skb_frags);
 
+/* The array 'drop_reasons' is auto-generated in dropreason_str.c */
+EXPORT_SYMBOL(drop_reasons);
+
 /**
  *	skb_panic - private function for out-of-line support
  *	@skb:	buffer