From: Marcos Paulo de Souza <mpdesouza@suse.com>
To: linux-kernel@vger.kernel.org, live-patching@vger.kernel.org
Cc: jpoimboe@redhat.com, joe.lawrence@redhat.com, pmladek@suse.com,
Marcos Paulo de Souza <mpdesouza@suse.com>
Subject: [PATCH v2 1/4] livepatch/shadow: Separate code to get or use pre-allocated shadow variable
Date: Wed, 26 Oct 2022 16:41:19 -0300 [thread overview]
Message-ID: <20221026194122.11761-2-mpdesouza@suse.com> (raw)
In-Reply-To: <20221026194122.11761-1-mpdesouza@suse.com>
From: Petr Mladek <pmladek@suse.com>
Separate code that is used in klp_shadow_get_or_alloc() under klp_mutex.
It splits a long spaghetti function into two. Also it unifies the error
handling. The old used a mix of duplicated code, direct returns,
and goto. The new code has only one unlock, free, and return calls.
It is code refactoring without any functional changes.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
---
Changes from v1:
* Change __klp_shadow_get_or_use to __klp_shadow_get_or_add_locked and add a comment
about it's meaning (Petr)
* Add lockdep_assert_held on __klp_shadow_get_or_add_locked
* Reworked the commit message (Petr)
* Added my SoB (Josh)
kernel/livepatch/shadow.c | 78 ++++++++++++++++++++++-----------------
1 file changed, 45 insertions(+), 33 deletions(-)
diff --git a/kernel/livepatch/shadow.c b/kernel/livepatch/shadow.c
index c2e724d97ddf..81ad7cbbd124 100644
--- a/kernel/livepatch/shadow.c
+++ b/kernel/livepatch/shadow.c
@@ -101,41 +101,22 @@ void *klp_shadow_get(void *obj, unsigned long id)
}
EXPORT_SYMBOL_GPL(klp_shadow_get);
-static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id,
- size_t size, gfp_t gfp_flags,
- klp_shadow_ctor_t ctor, void *ctor_data,
- bool warn_on_exist)
+/* Check if the variable exists. Otherwise, add the pre-allocated one. */
+static void *__klp_shadow_get_or_add_locked(void *obj, unsigned long id,
+ struct klp_shadow *new_shadow,
+ klp_shadow_ctor_t ctor, void *ctor_data,
+ bool *exist)
{
- struct klp_shadow *new_shadow;
void *shadow_data;
- unsigned long flags;
- /* Check if the shadow variable already exists */
- shadow_data = klp_shadow_get(obj, id);
- if (shadow_data)
- goto exists;
-
- /*
- * Allocate a new shadow variable. Fill it with zeroes by default.
- * More complex setting can be done by @ctor function. But it is
- * called only when the buffer is really used (under klp_shadow_lock).
- */
- new_shadow = kzalloc(size + sizeof(*new_shadow), gfp_flags);
- if (!new_shadow)
- return NULL;
+ lockdep_assert_held(&klp_shadow_lock);
- /* Look for <obj, id> again under the lock */
- spin_lock_irqsave(&klp_shadow_lock, flags);
shadow_data = klp_shadow_get(obj, id);
if (unlikely(shadow_data)) {
- /*
- * Shadow variable was found, throw away speculative
- * allocation.
- */
- spin_unlock_irqrestore(&klp_shadow_lock, flags);
- kfree(new_shadow);
- goto exists;
+ *exist = true;
+ return shadow_data;
}
+ *exist = false;
new_shadow->obj = obj;
new_shadow->id = id;
@@ -145,8 +126,6 @@ static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id,
err = ctor(obj, new_shadow->data, ctor_data);
if (err) {
- spin_unlock_irqrestore(&klp_shadow_lock, flags);
- kfree(new_shadow);
pr_err("Failed to construct shadow variable <%p, %lx> (%d)\n",
obj, id, err);
return NULL;
@@ -156,12 +135,45 @@ static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id,
/* No <obj, id> found, so attach the newly allocated one */
hash_add_rcu(klp_shadow_hash, &new_shadow->node,
(unsigned long)new_shadow->obj);
- spin_unlock_irqrestore(&klp_shadow_lock, flags);
return new_shadow->data;
+}
+
+static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id,
+ size_t size, gfp_t gfp_flags,
+ klp_shadow_ctor_t ctor, void *ctor_data,
+ bool warn_on_exist)
+{
+ struct klp_shadow *new_shadow;
+ void *shadow_data;
+ bool exist;
+ unsigned long flags;
+
+ /* Check if the shadow variable already exists */
+ shadow_data = klp_shadow_get(obj, id);
+ if (shadow_data)
+ return shadow_data;
+
+ /*
+ * Allocate a new shadow variable. Fill it with zeroes by default.
+ * More complex setting can be done by @ctor function. But it is
+ * called only when the buffer is really used (under klp_shadow_lock).
+ */
+ new_shadow = kzalloc(size + sizeof(*new_shadow), gfp_flags);
+ if (!new_shadow)
+ return NULL;
+
+ /* Look for <obj, id> again under the lock */
+ spin_lock_irqsave(&klp_shadow_lock, flags);
+ shadow_data = __klp_shadow_get_or_add_locked(obj, id, new_shadow,
+ ctor, ctor_data, &exist);
+ spin_unlock_irqrestore(&klp_shadow_lock, flags);
+
+ /* Throw away unused speculative allocation. */
+ if (!shadow_data || exist)
+ kfree(new_shadow);
-exists:
- if (warn_on_exist) {
+ if (exist && warn_on_exist) {
WARN(1, "Duplicate shadow variable <%p, %lx>\n", obj, id);
return NULL;
}
--
2.37.3
next prev parent reply other threads:[~2022-10-26 19:41 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-26 19:41 [PATCH v2 0/4] livepatch: Add garbage collection for shadow variables Marcos Paulo de Souza
2022-10-26 19:41 ` Marcos Paulo de Souza [this message]
2022-10-31 15:44 ` [PATCH v2 1/4] livepatch/shadow: Separate code to get or use pre-allocated shadow variable Petr Mladek
2022-10-26 19:41 ` [PATCH v2 2/4] livepatch/shadow: Separate code removing all shadow variables for a given id Marcos Paulo de Souza
2022-10-26 19:41 ` [PATCH v2 3/4] livepatch/shadow: Introduce klp_shadow_type structure Marcos Paulo de Souza
2022-10-31 16:02 ` Petr Mladek
2023-01-31 4:36 ` Josh Poimboeuf
2022-10-26 19:41 ` [PATCH v2 4/4] livepatch/shadow: Add garbage collection of shadow variables Marcos Paulo de Souza
2022-11-04 1:03 ` Josh Poimboeuf
2022-11-04 10:25 ` Petr Mladek
2022-11-08 1:32 ` Josh Poimboeuf
2022-11-08 9:14 ` Petr Mladek
2022-11-08 18:44 ` Josh Poimboeuf
2022-11-09 14:36 ` Petr Mladek
2023-02-04 23:59 ` Josh Poimboeuf
2023-02-17 16:22 ` Petr Mladek
2022-11-11 9:20 ` Nicolai Stange
2022-11-11 9:55 ` Petr Mladek
2022-11-13 18:51 ` Josh Poimboeuf
2023-01-17 15:01 ` Petr Mladek
2023-01-25 23:22 ` Josh Poimboeuf
2023-01-26 9:36 ` Petr Mladek
2023-02-04 19:34 ` Josh Poimboeuf
2023-01-31 4:40 ` Josh Poimboeuf
2023-01-31 14:23 ` Petr Mladek
2023-01-31 21:17 ` Josh Poimboeuf
2023-02-02 13:58 ` Petr Mladek
2023-02-01 0:18 ` Josh Poimboeuf
2023-02-02 10:14 ` Petr Mladek
2023-02-04 17:37 ` Josh Poimboeuf
2022-11-01 10:43 ` [PATCH v2 0/4] livepatch: Add garbage collection for " Petr Mladek
2023-01-23 17:33 ` Marcos Paulo de Souza
2023-01-24 15:51 ` Petr Mladek
2023-01-26 16:35 ` Petr Mladek
2023-01-26 17:05 ` Joe Lawrence
2023-01-26 18:30 ` Josh Poimboeuf
2023-01-27 10:51 ` Petr Mladek
2023-01-27 11:08 ` Marcos Paulo de Souza
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20221026194122.11761-2-mpdesouza@suse.com \
--to=mpdesouza@suse.com \
--cc=joe.lawrence@redhat.com \
--cc=jpoimboe@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=live-patching@vger.kernel.org \
--cc=pmladek@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).