linux-kernel - [tip: locking/urgent] static_call: Align static_call_is

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Date:   Fri, 19 Mar 2021 12:25:08 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Sumit Garg <sumit.garg@...aro.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/urgent] static_call: Align static_call_is_init()
 patching condition

The following commit has been merged into the locking/urgent branch of tip:

Commit-ID:     698bacefe993ad2922c9d3b1380591ad489355e9
Gitweb:        https://git.kernel.org/tip/698bacefe993ad2922c9d3b1380591ad489355e9
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 18 Mar 2021 11:29:56 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 19 Mar 2021 13:16:44 +01:00

static_call: Align static_call_is_init() patching condition

The intent is to avoid writing init code after init (because the text
might have been freed). The code is needlessly different between
jump_label and static_call and not obviously correct.

The existing code relies on the fact that the module loader clears the
init layout, such that within_module_init() always fails, while
jump_label relies on the module state which is more obvious and
matches the kernel logic.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Jarkko Sakkinen <jarkko@...nel.org>
Tested-by: Sumit Garg <sumit.garg@...aro.org>
Link: https://lkml.kernel.org/r/20210318113610.636651340@infradead.org
---
 kernel/static_call.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/kernel/static_call.c b/kernel/static_call.c
index 080c8a9..fc22590 100644
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -149,6 +149,7 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
 	};
 
 	for (site_mod = &first; site_mod; site_mod = site_mod->next) {
+		bool init = system_state < SYSTEM_RUNNING;
 		struct module *mod = site_mod->mod;
 
 		if (!site_mod->sites) {
@@ -168,6 +169,7 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
 		if (mod) {
 			stop = mod->static_call_sites +
 			       mod->num_static_call_sites;
+			init = mod->state == MODULE_STATE_COMING;
 		}
 #endif
 
@@ -175,16 +177,8 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
 		     site < stop && static_call_key(site) == key; site++) {
 			void *site_addr = static_call_addr(site);
 
-			if (static_call_is_init(site)) {
-				/*
-				 * Don't write to call sites which were in
-				 * initmem and have since been freed.
-				 */
-				if (!mod && system_state >= SYSTEM_RUNNING)
-					continue;
-				if (mod && !within_module_init((unsigned long)site_addr, mod))
-					continue;
-			}
+			if (!init && static_call_is_init(site))
+				continue;
 
 			if (!kernel_text_address((unsigned long)site_addr)) {
 				WARN_ONCE(1, "can't patch static call site at %pS",