Subject: [PATCH v9 3/7] powerpc/code-patching: Use WARN_ON and fix check in poking_init

From: Benjamin Gray <[email-masked]>
Date: Tue, 25 Oct 2022 15:44:05 +1100

BUG_ON() when failing to initialise the code patching window is
excessive, as most critical patching happens during boot before strict
RWX control is enabled. Failure to patch after boot is not inherently
fatal, so aborting the kernel is better determined by the caller.

The return value of cpuhp_setup_state() is also >= 0 on success,
so check for < 0.

Signed-off-by: Benjamin Gray <[email-masked]>
Reviewed-by: Russell Currey <[email-masked]>
---
v9:	* Reword commit message to explain why init failure is not fatal
---
 arch/powerpc/lib/code-patching.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 54e145247643..3b3b09d5d2e1 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -82,16 +82,13 @@ static int text_area_cpu_down(unsigned int cpu)
 
 static __ro_after_init DEFINE_STATIC_KEY_FALSE(poking_init_done);
 
-/*
- * Although BUG_ON() is rude, in this case it should only happen if ENOMEM, and
- * we judge it as being preferable to a kernel that will crash later when
- * someone tries to use patch_instruction().
- */
 void __init poking_init(void)
 {
-	BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
-		"powerpc/text_poke:online", text_area_cpu_up,
-		text_area_cpu_down));
+	WARN_ON(cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+				  "powerpc/text_poke:online",
+				  text_area_cpu_up,
+				  text_area_cpu_down) < 0);
+
 	static_branch_enable(&poking_init_done);
 }
 
-- 
2.37.3