Commit e4e28fd6 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20251027083745.736737934@linutronix.de
parent b2cfc0cd

kernel/futex/core.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

	}

kernel/futex/futex.h

+3 −55
Original line number Diff line number Diff line
@@ -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);