Revert "livepatch: Remove reliable stacktrace check in klp_try_switch_task()"

This reverts commit 1d98a69e5cef3aeb68bcefab0e67e342d6bb4dad. Commit
31adf2308f33 ("livepatch: Convert error about unsupported reliable
stacktrace into a warning") weakened the enforcement for architectures
to have reliable stack traces support. The system only warns now about
it.

It only makes sense to reintroduce the compile time checking in
klp_try_switch_task() again and bail out early.

Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>

diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 0a3889c4f617fea572b6485f6f4d10183715b90d..cb85dae09ce571f52389d54a5477c0f7139f6465 100644 (file)
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -305,6 +305,13 @@ static bool klp_try_switch_task(struct task_struct *task)
        if (task->patch_state == klp_target_state)
                return true;
 
+       /*
+        * For arches which don't have reliable stack traces, we have to rely
+        * on other methods (e.g., switching tasks at kernel exit).
+        */
+       if (!klp_have_reliable_stack())
+               return false;
+
        /*
         * Now try to check the stack for any to-be-patched or to-be-unpatched
         * functions.  If all goes well, switch the task to the target patch