linux-kernel - Re: [PATCH V4 2/9] jump_label: Add the jump_label_can_update

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Date:   Thu, 7 Feb 2019 14:21:09 +0100
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Chris von Recklinghausen <crecklin@...hat.com>,
        Jason Baron <jbaron@...mai.com>, Scott Wood <swood@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Clark Williams <williams@...hat.com>, x86@...nel.org
Subject: Re: [PATCH V4 2/9] jump_label: Add the jump_label_can_update_check()
 helper

On 2/5/19 10:13 PM, Borislav Petkov wrote:
> On Tue, Feb 05, 2019 at 02:50:39PM +0100, Daniel Bristot de Oliveira wrote:
>>>> +		if (jump_label_can_update_check(entry, init)) {
>>>> +			arch_jump_label_transform(entry,
>>>> +						  jump_label_type(entry));
>>>
>>> Yeah, let that one stick out.
>>
>> I did not get this part...
> 
> Just let the line stick outside of the 80 cols rule which is not a hard
> one:
> 
> +          if (jump_label_can_update_check(entry, init)) {
> +                  arch_jump_label_transform(entry, jump_label_type(entry));
> 
> 
> :-)
> 

How about this?

----------------- %< ----------------------------
Subject: jump_label: Add a jump_label_can_update() helper

Move the check if a jump_entry is valid to a function.

Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc: Chris von Recklinghausen <crecklin@...hat.com>
Cc: Jason Baron <jbaron@...mai.com>
Cc: Scott Wood <swood@...hat.com>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Clark Williams <williams@...hat.com>
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
---
 kernel/jump_label.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 288d630da22d..1e6f4d27e28d 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -374,22 +374,29 @@ static enum jump_label_type jump_label_type(struct jump_entry *entry)
 	return enabled ^ branch;
 }
 
+static bool jump_label_can_update(struct jump_entry *entry, bool init)
+{
+	/*
+	 * Cannot update code that was in an init text area.
+	 */
+	if (!init || jump_entry_is_init(entry))
+		return false;
+
+	if (WARN_ONCE(!kernel_text_address(jump_entry_code(entry)),
+			 "can't patch jump_label at %pS", (void *)jump_entry_code(entry)))
+		return false;
+
+	return true;
+}
+
 static void __jump_label_update(struct static_key *key,
 				struct jump_entry *entry,
 				struct jump_entry *stop,
 				bool init)
 {
 	for_each_label_entry(key, entry, stop) {
-		/*
-		 * An entry->code of 0 indicates an entry which has been
-		 * disabled because it was in an init text area.
-		 */
-		if (init || !jump_entry_is_init(entry)) {
-			if (kernel_text_address(jump_entry_code(entry)))
-				arch_jump_label_transform(entry, jump_label_type(entry));
-			else
-				WARN_ONCE(1, "can't patch jump_label at %pS",
-					  (void *)jump_entry_code(entry));
+		if (jump_label_can_update(entry, init)) {
+			arch_jump_label_transform(entry, jump_label_type(entry));
 		}
 	}
 }
---------------- >% --------------------

Thanks!

-- Daniel