linux-kernel - static EXPORT_SYMBOL checker causes false positives on ARCH=um

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Date:   Tue, 24 Sep 2019 10:17:40 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     linux-kernel@...r.kernel.org, linux-um@...ts.infradead.org,
        Denis Efremov <efremov@...ux.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Emil Velikov <emil.l.velikov@...il.com>
Cc:     linux-kbuild@...r.kernel.org
Subject: static EXPORT_SYMBOL checker causes false positives on ARCH=um

Hi,

With the new commit 15bfc2348d54 ("modpost: check for static
EXPORT_SYMBOL* functions") we get a lot of warnings on ARCH=um builds:

WARNING: "rename" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "lseek" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "ftruncate64" [vmlinux] is a static EXPORT_SYMBOL
[...]
see https://p.sipsolutions.net/7232995f34907b9d.txt


This hack fixes *most* of them:

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 820eed87fb43..3e443563ebea 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1931,12 +1931,18 @@ static void check_sec_ref(struct module *mod, const char *modname,
 static char *remove_dot(char *s)
 {
 	size_t n = strcspn(s, ".");
+	char *at;
 
 	if (n && s[n]) {
 		size_t m = strspn(s + n + 1, "0123456789");
 		if (m && (s[n + m] == '.' || s[n + m] == 0))
 			s[n] = 0;
 	}
+
+	at = strchr(s, '@');
+	if (at)
+		*at = 0;
+
 	return s;
 }
 

(but obviously just serves to give you an idea of what's going on).


With that, only two remain for me:

WARNING: "__guard" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__stack_smash_handler" [vmlinux] is a static EXPORT_SYMBOL

and I think that's because they don't even exist at all, so arguably the
code shouldn't export them, but I didn't find a way to detect at build
time if -fstack-protector was enabled or not?

Any thoughts?

Thanks,
johannes