From: Peter Zijlstra <peterz@infradead.org>
To: Dexuan Cui <decui@microsoft.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
jeyu@kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>,
ardb@kernel.org
Subject: [PATCH] jump_label: Fix usage in module __init
Date: Wed, 16 Dec 2020 14:54:35 +0100 [thread overview]
Message-ID: <20201216135435.GV3092@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201216105926.GS3092@hirez.programming.kicks-ass.net>
Final patch looks like this.
---
Subject: jump_label: Fix usage in module __init
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed Dec 16 12:21:36 CET 2020
When the static_key is part of the module, and the module calls
static_key_inc/enable() from it's __init section *AND* has a
static_branch_*() user in that very same __init section, things go
wobbly.
If the static_key lives outside the module, jump_label_add_module()
would append this module's sites to the key and jump_label_update()
would take the static_key_linked() branch and all would be fine.
If all the sites are outside of __init, then everything will be fine
too.
However, when all is aligned just as described above,
jump_label_update() calls __jump_label_update(.init = false) and we'll
not update sites in __init text.
Fixes: 19483677684b ("jump_label: Annotate entries that operate on __init code earlier")
Reported-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Jessica Yu <jeyu@kernel.org>
---
kernel/jump_label.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -793,6 +793,7 @@ int jump_label_text_reserved(void *start
static void jump_label_update(struct static_key *key)
{
struct jump_entry *stop = __stop___jump_table;
+ bool init = system_state < SYSTEM_RUNNING;
struct jump_entry *entry;
#ifdef CONFIG_MODULES
struct module *mod;
@@ -804,15 +805,16 @@ static void jump_label_update(struct sta
preempt_disable();
mod = __module_address((unsigned long)key);
- if (mod)
+ if (mod) {
stop = mod->jump_entries + mod->num_jump_entries;
+ init = mod->state == MODULE_STATE_COMING;
+ }
preempt_enable();
#endif
entry = static_key_entries(key);
/* if there are no users, entry can be NULL */
if (entry)
- __jump_label_update(key, entry, stop,
- system_state < SYSTEM_RUNNING);
+ __jump_label_update(key, entry, stop, init);
}
#ifdef CONFIG_STATIC_KEYS_SELFTEST
next prev parent reply other threads:[~2020-12-16 13:55 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-16 3:54 static_branch_enable() does not work from a __init function? Dexuan Cui
2020-12-16 9:26 ` Peter Zijlstra
2020-12-16 10:59 ` Peter Zijlstra
2020-12-16 13:30 ` [RFC][PATCH] jump_label/static_call: Add MAINTAINERS Peter Zijlstra
2020-12-16 13:42 ` Peter Zijlstra
2020-12-16 14:23 ` Steven Rostedt
2020-12-16 16:19 ` Josh Poimboeuf
2020-12-16 16:19 ` Ard Biesheuvel
2020-12-16 21:16 ` Jason Baron
2020-12-16 13:54 ` Peter Zijlstra [this message]
2020-12-16 16:36 ` [PATCH] jump_label: Fix usage in module __init Josh Poimboeuf
2020-12-16 20:45 ` static_branch_enable() does not work from a __init function? Dexuan Cui
2020-12-16 11:55 ` Jessica Yu
2020-12-16 12:47 ` Peter Zijlstra
2020-12-16 13:10 ` Jessica Yu
2020-12-16 13:23 ` Peter Zijlstra
2020-12-16 13:27 ` Jessica Yu
2020-12-16 12:38 ` Jessica Yu
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