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printk: avoid -Wsometimes-uninitialized warning 

clang notices that the pi_get_entry() function would use
uninitialized data if it was called with a non-NULL module
pointer on a kernel that does not support modules:

kernel/printk/index.c:32:6: error: variable 'nr_entries' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
        if (!mod) {
            ^~~~
kernel/printk/index.c:38:13: note: uninitialized use occurs here
        if (pos >= nr_entries)
                   ^~~~~~~~~~
kernel/printk/index.c:32:2: note: remove the 'if' if its condition is always true
        if (!mod) {

Rework the condition to make it clear to the compiler that we are always
in the second case. Unfortunately the #ifdef is still required as the
definition of 'struct module' is hidden when modules are disabled.

Fixes: 3370155737 ("printk: Userspace format indexing support")
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210928093456.2438109-1-arnd@kernel.org
This commit is contained in:
Arnd Bergmann 2021-09-28 11:34:33 +02:00 committed by Petr Mladek
parent 9980c4251f
commit 5aa7eea931
1 changed files with 2 additions and 3 deletions
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5
kernel/printk/index.c
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@ -26,10 +26,9 @@ static struct pi_entry *pi_get_entry(const struct module *mod, loff_t pos)
if (mod) {
entries = mod->printk_index_start;
nr_entries = mod->printk_index_size;
}
} else
#endif
if (!mod) {
{
/* vmlinux, comes from linker symbols */
entries = __start_printk_index;
nr_entries = __stop_printk_index - __start_printk_index;