Merge tag 'kbuild-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Use /usr/bin/env for shebang lines in scripts

 - Remove useless -Wnested-externs warning flag

 - Update documents

 - Refactor log handling in modpost

 - Stop building modules without MODULE_LICENSE() tag

 - Make the insane combination of 'static' and EXPORT_SYMBOL an error

 - Improve genksyms to handle _Static_assert()

* tag 'kbuild-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  Documentation/kbuild: Document platform dependency practises
  Documentation/kbuild: Document COMPILE_TEST dependencies
  genksyms: Ignore module scoped _Static_assert()
  modpost: turn static exports into error
  modpost: turn section mismatches to error from fatal()
  modpost: change license incompatibility to error() from fatal()
  modpost: turn missing MODULE_LICENSE() into error
  modpost: refactor error handling and clarify error/fatal difference
  modpost: rename merror() to error()
  kbuild: don't hardcode depmod path
  kbuild: doc: document subdir-y syntax
  kbuild: doc: clarify the difference between extra-y and always-y
  kbuild: doc: split if_changed explanation to a separate section
  kbuild: doc: merge 'Special Rules' and 'Custom kbuild commands' sections
  kbuild: doc: fix 'List directories to visit when descending' section
  kbuild: doc: replace arch/$(ARCH)/ with arch/$(SRCARCH)/
  kbuild: doc: update the description about kbuild Makefiles
  Makefile.extrawarn: remove -Wnested-externs warning
  tweewide: Fix most Shebang lines

14 files changed, 87 insertions, 55 deletions

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 6baee1200615..d53825503874 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -61,7 +61,6 @@ endif
 ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
 
 KBUILD_CFLAGS += -Wdisabled-optimization
-KBUILD_CFLAGS += -Wnested-externs
 KBUILD_CFLAGS += -Wshadow
 KBUILD_CFLAGS += $(call cc-option, -Wlogical-op)
 KBUILD_CFLAGS += -Wmissing-field-initializers
diff --git a/scripts/bloat-o-meter b/scripts/bloat-o-meter
index d7ca46c612b3..652e9542043f 100755
--- a/scripts/bloat-o-meter
+++ b/scripts/bloat-o-meter
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 #
 # Copyright 2004 Matt Mackall <mpm@selenic.com>
 #
diff --git a/scripts/config b/scripts/config
index eee5b7f3a092..8c8d7c3d7acc 100755
--- a/scripts/config
+++ b/scripts/config
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # SPDX-License-Identifier: GPL-2.0
 # Manipulate options in a .config file from the command line
 
diff --git a/scripts/diffconfig b/scripts/diffconfig
index 89abf777f197..627eba5849b5 100755
--- a/scripts/diffconfig
+++ b/scripts/diffconfig
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 # SPDX-License-Identifier: GPL-2.0
 #
 # diffconfig - a tool to compare .config files.
diff --git a/scripts/genksyms/keywords.c b/scripts/genksyms/keywords.c
index 057c6cabad1d..b85e0979a00c 100644
--- a/scripts/genksyms/keywords.c
+++ b/scripts/genksyms/keywords.c
@@ -32,6 +32,9 @@ static struct resword {
 	{ "restrict", RESTRICT_KEYW },
 	{ "asm", ASM_KEYW },
 
+	// c11 keywords that can be used at module scope
+	{ "_Static_assert", STATIC_ASSERT_KEYW },
+
 	// attribute commented out in modutils 2.4.2.  People are using 'attribute' as a
 	// field name which breaks the genksyms parser.  It is not a gcc keyword anyway.
 	// KAO. },
diff --git a/scripts/genksyms/lex.l b/scripts/genksyms/lex.l
index e265c5d96861..ae76472efc43 100644
--- a/scripts/genksyms/lex.l
+++ b/scripts/genksyms/lex.l
@@ -118,7 +118,7 @@ yylex(void)
 {
   static enum {
     ST_NOTSTARTED, ST_NORMAL, ST_ATTRIBUTE, ST_ASM, ST_TYPEOF, ST_TYPEOF_1,
-    ST_BRACKET, ST_BRACE, ST_EXPRESSION,
+    ST_BRACKET, ST_BRACE, ST_EXPRESSION, ST_STATIC_ASSERT,
     ST_TABLE_1, ST_TABLE_2, ST_TABLE_3, ST_TABLE_4,
     ST_TABLE_5, ST_TABLE_6
   } lexstate = ST_NOTSTARTED;
@@ -201,6 +201,11 @@ repeat:
 
 		  case EXPORT_SYMBOL_KEYW:
 		      goto fini;
+
+		  case STATIC_ASSERT_KEYW:
+		    lexstate = ST_STATIC_ASSERT;
+		    count = 0;
+		    goto repeat;
 		  }
 	      }
 	    if (!suppress_type_lookup)
@@ -401,6 +406,26 @@ repeat:
 	}
       break;
 
+    case ST_STATIC_ASSERT:
+      APP;
+      switch (token)
+	{
+	case '(':
+	  ++count;
+	  goto repeat;
+	case ')':
+	  if (--count == 0)
+	    {
+	      lexstate = ST_NORMAL;
+	      token = STATIC_ASSERT_PHRASE;
+	      break;
+	    }
+	  goto repeat;
+	default:
+	  goto repeat;
+	}
+      break;
+
     case ST_TABLE_1:
       goto repeat;
 
diff --git a/scripts/genksyms/parse.y b/scripts/genksyms/parse.y
index e22b42245bcc..8e9b5e69e8f0 100644
--- a/scripts/genksyms/parse.y
+++ b/scripts/genksyms/parse.y
@@ -80,6 +80,7 @@ static void record_compound(struct string_list **keyw,
 %token SHORT_KEYW
 %token SIGNED_KEYW
 %token STATIC_KEYW
+%token STATIC_ASSERT_KEYW
 %token STRUCT_KEYW
 %token TYPEDEF_KEYW
 %token UNION_KEYW
@@ -97,6 +98,7 @@ static void record_compound(struct string_list **keyw,
 %token BRACE_PHRASE
 %token BRACKET_PHRASE
 %token EXPRESSION_PHRASE
+%token STATIC_ASSERT_PHRASE
 
 %token CHAR
 %token DOTS
@@ -130,6 +132,7 @@ declaration1:
 	| function_definition
 	| asm_definition
 	| export_definition
+	| static_assert
 	| error ';'				{ $$ = $2; }
 	| error '}'				{ $$ = $2; }
 	;
@@ -493,6 +496,10 @@ export_definition:
 		{ export_symbol((*$3)->string); $$ = $5; }
 	;
 
+/* Ignore any module scoped _Static_assert(...) */
+static_assert:
+	STATIC_ASSERT_PHRASE ';'			{ $$ = $2; }
+	;
 
 %%
 
diff --git a/scripts/get_abi.pl b/scripts/get_abi.pl
index 68dab828a722..92d9aa6cc4f5 100755
--- a/scripts/get_abi.pl
+++ b/scripts/get_abi.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 # SPDX-License-Identifier: GPL-2.0
 
 use strict;
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f882ce0d9327..d6c81657d695 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -34,12 +34,14 @@ static int external_module = 0;
 static int warn_unresolved = 0;
 /* How a symbol is exported */
 static int sec_mismatch_count = 0;
-static int sec_mismatch_fatal = 0;
+static int sec_mismatch_warn_only = true;
 /* ignore missing files */
 static int ignore_missing_files;
 /* If set to 1, only warn (instead of error) about missing ns imports */
 static int allow_missing_ns_imports;
 
+static bool error_occurred;
+
 enum export {
 	export_plain,      export_unused,     export_gpl,
 	export_unused_gpl, export_gpl_future, export_unknown
@@ -78,6 +80,8 @@ modpost_log(enum loglevel loglevel, const char *fmt, ...)
 
 	if (loglevel == LOG_FATAL)
 		exit(1);
+	if (loglevel == LOG_ERROR)
+		error_occurred = true;
 }
 
 static inline bool strends(const char *str, const char *postfix)
@@ -403,8 +407,8 @@ static void sym_update_namespace(const char *symname, const char *namespace)
 	 * actually an assertion.
 	 */
 	if (!s) {
-		merror("Could not update namespace(%s) for symbol %s\n",
-		       namespace, symname);
+		error("Could not update namespace(%s) for symbol %s\n",
+		      namespace, symname);
 		return;
 	}
 
@@ -2014,7 +2018,7 @@ static void read_symbols(const char *modname)
 	if (!mod->is_vmlinux) {
 		license = get_modinfo(&info, "license");
 		if (!license)
-			warn("missing MODULE_LICENSE() in %s\n", modname);
+			error("missing MODULE_LICENSE() in %s\n", modname);
 		while (license) {
 			if (license_is_gpl_compatible(license))
 				mod->gpl_compatible = 1;
@@ -2141,11 +2145,11 @@ static void check_for_gpl_usage(enum export exp, const char *m, const char *s)
 {
 	switch (exp) {
 	case export_gpl:
-		fatal("GPL-incompatible module %s.ko uses GPL-only symbol '%s'\n",
+		error("GPL-incompatible module %s.ko uses GPL-only symbol '%s'\n",
 		      m, s);
 		break;
 	case export_unused_gpl:
-		fatal("GPL-incompatible module %s.ko uses GPL-only symbol marked UNUSED '%s'\n",
+		error("GPL-incompatible module %s.ko uses GPL-only symbol marked UNUSED '%s'\n",
 		      m, s);
 		break;
 	case export_gpl_future:
@@ -2174,22 +2178,18 @@ static void check_for_unused(enum export exp, const char *m, const char *s)
 	}
 }
 
-static int check_exports(struct module *mod)
+static void check_exports(struct module *mod)
 {
 	struct symbol *s, *exp;
-	int err = 0;
 
 	for (s = mod->unres; s; s = s->next) {
 		const char *basename;
 		exp = find_symbol(s->name);
 		if (!exp || exp->module == mod) {
-			if (have_vmlinux && !s->weak) {
+			if (have_vmlinux && !s->weak)
 				modpost_log(warn_unresolved ? LOG_WARN : LOG_ERROR,
 					    "\"%s\" [%s.ko] undefined!\n",
 					    s->name, mod->name);
-				if (!warn_unresolved)
-					err = 1;
-			}
 			continue;
 		}
 		basename = strrchr(mod->name, '/');
@@ -2203,8 +2203,6 @@ static int check_exports(struct module *mod)
 			modpost_log(allow_missing_ns_imports ? LOG_WARN : LOG_ERROR,
 				    "module %s uses symbol %s from namespace %s, but does not import it.\n",
 				    basename, exp->name, exp->namespace);
-			if (!allow_missing_ns_imports)
-				err = 1;
 			add_namespace(&mod->missing_namespaces, exp->namespace);
 		}
 
@@ -2212,11 +2210,9 @@ static int check_exports(struct module *mod)
 			check_for_gpl_usage(exp->export, basename, exp->name);
 		check_for_unused(exp->export, basename, exp->name);
 	}
-
-	return err;
 }
 
-static int check_modname_len(struct module *mod)
+static void check_modname_len(struct module *mod)
 {
 	const char *mod_name;
 
@@ -2225,12 +2221,8 @@ static int check_modname_len(struct module *mod)
 		mod_name = mod->name;
 	else
 		mod_name++;
-	if (strlen(mod_name) >= MODULE_NAME_LEN) {
-		merror("module name is too long [%s.ko]\n", mod->name);
-		return 1;
-	}
-
-	return 0;
+	if (strlen(mod_name) >= MODULE_NAME_LEN)
+		error("module name is too long [%s.ko]\n", mod->name);
 }
 
 /**
@@ -2289,10 +2281,9 @@ static void add_staging_flag(struct buffer *b, const char *name)
 /**
  * Record CRCs for unresolved symbols
  **/
-static int add_versions(struct buffer *b, struct module *mod)
+static void add_versions(struct buffer *b, struct module *mod)
 {
 	struct symbol *s, *exp;
-	int err = 0;
 
 	for (s = mod->unres; s; s = s->next) {
 		exp = find_symbol(s->name);
@@ -2304,7 +2295,7 @@ static int add_versions(struct buffer *b, struct module *mod)
 	}
 
 	if (!modversions)
-		return err;
+		return;
 
 	buf_printf(b, "\n");
 	buf_printf(b, "static const struct modversion_info ____versions[]\n");
@@ -2319,9 +2310,8 @@ static int add_versions(struct buffer *b, struct module *mod)
 			continue;
 		}
 		if (strlen(s->name) >= MODULE_NAME_LEN) {
-			merror("too long symbol \"%s\" [%s.ko]\n",
-			       s->name, mod->name);
-			err = 1;
+			error("too long symbol \"%s\" [%s.ko]\n",
+			      s->name, mod->name);
 			break;
 		}
 		buf_printf(b, "\t{ %#8x, \"%s\" },\n",
@@ -2329,8 +2319,6 @@ static int add_versions(struct buffer *b, struct module *mod)
 	}
 
 	buf_printf(b, "};\n");
-
-	return err;
 }
 
 static void add_depends(struct buffer *b, struct module *mod)
@@ -2554,7 +2542,6 @@ int main(int argc, char **argv)
 	char *missing_namespace_deps = NULL;
 	char *dump_write = NULL, *files_source = NULL;
 	int opt;
-	int err;
 	int n;
 	struct dump_list *dump_read_start = NULL;
 	struct dump_list **dump_read_iter = &dump_read_start;
@@ -2589,7 +2576,7 @@ int main(int argc, char **argv)
 			warn_unresolved = 1;
 			break;
 		case 'E':
-			sec_mismatch_fatal = 1;
+			sec_mismatch_warn_only = false;
 			break;
 		case 'N':
 			allow_missing_ns_imports = 1;
@@ -2624,8 +2611,6 @@ int main(int argc, char **argv)
 	if (!have_vmlinux)
 		warn("Symbol info of vmlinux is missing. Unresolved symbol check will be entirely skipped.\n");
 
-	err = 0;
-
 	for (mod = modules; mod; mod = mod->next) {
 		char fname[PATH_MAX];
 
@@ -2634,14 +2619,14 @@ int main(int argc, char **argv)
 
 		buf.pos = 0;
 
-		err |= check_modname_len(mod);
-		err |= check_exports(mod);
+		check_modname_len(mod);
+		check_exports(mod);
 
 		add_header(&buf, mod);
 		add_intree_flag(&buf, !external_module);
 		add_retpoline(&buf);
 		add_staging_flag(&buf, mod->name);
-		err |= add_versions(&buf, mod);
+		add_versions(&buf, mod);
 		add_depends(&buf, mod);
 		add_moddevtable(&buf, mod);
 		add_srcversion(&buf, mod);
@@ -2655,21 +2640,21 @@ int main(int argc, char **argv)
 
 	if (dump_write)
 		write_dump(dump_write);
-	if (sec_mismatch_count && sec_mismatch_fatal)
-		fatal("Section mismatches detected.\n"
+	if (sec_mismatch_count && !sec_mismatch_warn_only)
+		error("Section mismatches detected.\n"
 		      "Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
 	for (n = 0; n < SYMBOL_HASH_SIZE; n++) {
 		struct symbol *s;
 
 		for (s = symbolhash[n]; s; s = s->next) {
 			if (s->is_static)
-				warn("\"%s\" [%s] is a static %s\n",
-				     s->name, s->module->name,
-				     export_str(s->export));
+				error("\"%s\" [%s] is a static %s\n",
+				      s->name, s->module->name,
+				      export_str(s->export));
 		}
 	}
 
 	free(buf.p);
 
-	return err;
+	return error_occurred ? 1 : 0;
 }
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 3aa052722233..e6f46eee0af0 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -201,6 +201,19 @@ enum loglevel {
 
 void modpost_log(enum loglevel loglevel, const char *fmt, ...);
 
+/*
+ * warn - show the given message, then let modpost continue running, still
+ *        allowing modpost to exit successfully. This should be used when
+ *        we still allow to generate vmlinux and modules.
+ *
+ * error - show the given message, then let modpost continue running, but fail
+ *         in the end. This should be used when we should stop building vmlinux
+ *         or modules, but we can continue running modpost to catch as many
+ *         issues as possible.
+ *
+ * fatal - show the given message, and bail out immediately. This should be
+ *         used when there is no point to continue running modpost.
+ */
 #define warn(fmt, args...)	modpost_log(LOG_WARN, fmt, ##args)
-#define merror(fmt, args...)	modpost_log(LOG_ERROR, fmt, ##args)
+#define error(fmt, args...)	modpost_log(LOG_ERROR, fmt, ##args)
 #define fatal(fmt, args...)	modpost_log(LOG_FATAL, fmt, ##args)
diff --git a/scripts/show_delta b/scripts/show_delta
index 264399307c4f..28e67e178194 100755
--- a/scripts/show_delta
+++ b/scripts/show_delta
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 # SPDX-License-Identifier: GPL-2.0-only
 #
 # show_deltas: Read list of printk messages instrumented with
diff --git a/scripts/sphinx-pre-install b/scripts/sphinx-pre-install
index 40fa6923e80a..828a8615a918 100755
--- a/scripts/sphinx-pre-install
+++ b/scripts/sphinx-pre-install
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 # SPDX-License-Identifier: GPL-2.0-or-later
 use strict;
 
diff --git a/scripts/split-man.pl b/scripts/split-man.pl
index c3db607ee9ec..96bd99dc977a 100755
--- a/scripts/split-man.pl
+++ b/scripts/split-man.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 # SPDX-License-Identifier: GPL-2.0
 #
 # Author: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
diff --git a/scripts/tracing/draw_functrace.py b/scripts/tracing/draw_functrace.py
index b65735758520..74f8aadfd4cb 100755
--- a/scripts/tracing/draw_functrace.py
+++ b/scripts/tracing/draw_functrace.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 # SPDX-License-Identifier: GPL-2.0-only
 
 """