linux-kernel - [PATCH 2/6] kernel/extable: Wrap section comparison in sort_main_extable with COMPARE

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Date:   Tue, 18 Feb 2020 21:54:19 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Arnd Bergmann <arnd@...db.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Jason Baron <jbaron@...mai.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH 2/6] kernel/extable: Wrap section comparison in sort_main_extable with COMPARE_SECTIONS

Clang warns:

../kernel/extable.c:37:52: warning: array comparison always evaluates to
a constant [-Wtautological-compare]
        if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
                                                          ^
1 warning generated.

These are not true arrays, they are linker defined symbols, which are
just addresses so there is not a real issue here. Use the
COMPARE_SECTIONS macro to silence this warning by casting the linker
defined symbols to unsigned long, which keeps the logic the same.

Link: https://github.com/ClangBuiltLinux/linux/issues/765
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
 kernel/extable.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/extable.c b/kernel/extable.c
index a0024f27d3a1..17bf4ccb9de9 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -34,7 +34,8 @@ u32 __initdata __visible main_extable_sort_needed = 1;
 /* Sort the kernel's built-in exception table */
 void __init sort_main_extable(void)
 {
-	if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
+	if (main_extable_sort_needed &&
+	    COMPARE_SECTIONS(__stop___ex_table, >, __start___ex_table)) {
 		pr_notice("Sorting __ex_table...\n");
 		sort_extable(__start___ex_table, __stop___ex_table);
 	}
-- 
2.25.1