linux-kernel - [PATCH] samples/hw_breakpoint: fix building without module unloading

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Date:   Tue, 25 Jul 2023 10:25:36 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>, Rong Tao <rongtao@...tc.cn>,
        Petr Mladek <pmladek@...e.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Quentin Perret <qperret@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] samples/hw_breakpoint: fix building without module unloading

From: Arnd Bergmann <arnd@...db.de>

__symbol_put() is really meant as an internal helper and is not available
when module unloading is disabled, unlike the previously used symbol_put():

samples/hw_breakpoint/data_breakpoint.c: In function 'hw_break_module_exit':
samples/hw_breakpoint/data_breakpoint.c:73:9: error: implicit declaration of function '__symbol_put'; did you mean '__symbol_get'? [-Werror=implicit-function-declaration]

The hw_break_module_exit() function is not actually used when module
unloading is disabled, but it still causes the build failure for an
undefined identifier. Enclose this one call in an appropriate #ifdef to
clarify what the requirement is. Leaving out the entire exit function
would also work but feels less clar in this case.

Fixes: 910e230d5f1bb ("samples/hw_breakpoint: Fix kernel BUG 'invalid opcode: 0000'")
Fixes: d8a84d33a4954 ("samples/hw_breakpoint: drop use of kallsyms_lookup_name()")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 samples/hw_breakpoint/data_breakpoint.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c
index 9debd128b2ab8..b99322f188e59 100644
--- a/samples/hw_breakpoint/data_breakpoint.c
+++ b/samples/hw_breakpoint/data_breakpoint.c
@@ -70,7 +70,9 @@ static int __init hw_break_module_init(void)
 static void __exit hw_break_module_exit(void)
 {
 	unregister_wide_hw_breakpoint(sample_hbp);
+#ifdef CONFIG_MODULE_UNLOAD
 	__symbol_put(ksym_name);
+#endif
 	printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name);
 }
 
-- 
2.39.2