linux-kernel - [tip: core/rseq] futex: Convert to get/put_user

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Message-ID: <176173344660.2601451.5718059126503367083.tip-bot2@tip-bot2>
Date: Wed, 29 Oct 2025 10:24:06 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: core/rseq] futex: Convert to get/put_user_inline()

The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     536e6a70108b609e36866efe8c401d1ed32759ea
Gitweb:        https://git.kernel.org/tip/536e6a70108b609e36866efe8c401d1ed32759ea
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:44:00 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 29 Oct 2025 11:07:10 +01:00

futex: Convert to get/put_user_inline()

Replace the open coded implementation with the new get/put_user_inline()
helpers. This might be replaced by a regular get/put_user(), but that needs
a proper performance evaluation.

No functional change intended

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://patch.msgid.link/20251027083745.736737934@linutronix.de
---
 kernel/futex/core.c  |  4 +--
 kernel/futex/futex.h | 58 ++-----------------------------------------
 2 files changed, 5 insertions(+), 57 deletions(-)

diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index 125804f..ebcccb1 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -581,7 +581,7 @@ int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key,
 	if (flags & FLAGS_NUMA) {
 		u32 __user *naddr = (void *)uaddr + size / 2;
 
-		if (futex_get_value(&node, naddr))
+		if (get_user_inline(node, naddr))
 			return -EFAULT;
 
 		if ((node != FUTEX_NO_NODE) &&
@@ -601,7 +601,7 @@ int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key,
 			node = numa_node_id();
 			node_updated = true;
 		}
-		if (node_updated && futex_put_value(node, naddr))
+		if (node_updated && put_user_inline(node, naddr))
 			return -EFAULT;
 	}
 
diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index 2cd5709..30c2afa 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -281,63 +281,11 @@ static inline int futex_cmpxchg_value_locked(u32 *curval, u32 __user *uaddr, u32
 	return ret;
 }
 
-/*
- * This does a plain atomic user space read, and the user pointer has
- * already been verified earlier by get_futex_key() to be both aligned
- * and actually in user space, just like futex_atomic_cmpxchg_inatomic().
- *
- * We still want to avoid any speculation, and while __get_user() is
- * the traditional model for this, it's actually slower than doing
- * this manually these days.
- *
- * We could just have a per-architecture special function for it,
- * the same way we do futex_atomic_cmpxchg_inatomic(), but rather
- * than force everybody to do that, write it out long-hand using
- * the low-level user-access infrastructure.
- *
- * This looks a bit overkill, but generally just results in a couple
- * of instructions.
- */
-static __always_inline int futex_get_value(u32 *dest, u32 __user *from)
-{
-	u32 val;
-
-	if (can_do_masked_user_access())
-		from = masked_user_access_begin(from);
-	else if (!user_read_access_begin(from, sizeof(*from)))
-		return -EFAULT;
-	unsafe_get_user(val, from, Efault);
-	user_read_access_end();
-	*dest = val;
-	return 0;
-Efault:
-	user_read_access_end();
-	return -EFAULT;
-}
-
-static __always_inline int futex_put_value(u32 val, u32 __user *to)
-{
-	if (can_do_masked_user_access())
-		to = masked_user_access_begin(to);
-	else if (!user_write_access_begin(to, sizeof(*to)))
-		return -EFAULT;
-	unsafe_put_user(val, to, Efault);
-	user_write_access_end();
-	return 0;
-Efault:
-	user_write_access_end();
-	return -EFAULT;
-}
-
+/* Read from user memory with pagefaults disabled */
 static inline int futex_get_value_locked(u32 *dest, u32 __user *from)
 {
-	int ret;
-
-	pagefault_disable();
-	ret = futex_get_value(dest, from);
-	pagefault_enable();
-
-	return ret;
+	guard(pagefault)();
+	return get_user_inline(*dest, from);
 }
 
 extern void __futex_unqueue(struct futex_q *q);