linux-kernel - Re: [PATCH v11 RESEND 5/9] arm64: futex: refactor futex atomic operation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aW5UXFz-TykfkGpV@willie-the-truck>
Date: Mon, 19 Jan 2026 15:57:16 +0000
From: Will Deacon <will@...nel.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: catalin.marinas@....com, maz@...nel.org, broonie@...nel.org,
	oliver.upton@...ux.dev, miko.lenczewski@....com,
	kevin.brodsky@....com, ardb@...nel.org, suzuki.poulose@....com,
	lpieralisi@...nel.org, yangyicong@...ilicon.com,
	scott@...amperecomputing.com, joey.gouly@....com,
	yuzenghui@...wei.com, pbonzini@...hat.com, shuah@...nel.org,
	mark.rutland@....com, arnd@...db.de,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev, kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v11 RESEND 5/9] arm64: futex: refactor futex atomic
 operation

On Sun, Dec 14, 2025 at 11:22:44AM +0000, Yeoreum Yun wrote:
> Refactor futex atomic operations using ll/sc method with
> clearing PSTATE.PAN to prepare to apply FEAT_LSUI on them.
> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
> Reviewed-by: Catalin Marinas <catalin.marinas@....com>
> ---
>  arch/arm64/include/asm/futex.h | 128 +++++++++++++++++++++------------
>  1 file changed, 82 insertions(+), 46 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
> index bc06691d2062..f8cb674bdb3f 100644
> --- a/arch/arm64/include/asm/futex.h
> +++ b/arch/arm64/include/asm/futex.h
> @@ -7,17 +7,21 @@
> 
>  #include <linux/futex.h>
>  #include <linux/uaccess.h>
> +#include <linux/stringify.h>
> 
>  #include <asm/errno.h>
> 
>  #define FUTEX_MAX_LOOPS	128 /* What's the largest number you can think of? */
> 
> -#define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg)		\
> -do {									\
> +#define LLSC_FUTEX_ATOMIC_OP(op, insn)					\
> +static __always_inline int						\
> +__llsc_futex_atomic_##op(int oparg, u32 __user *uaddr, int *oval)	\
> +{									\
>  	unsigned int loops = FUTEX_MAX_LOOPS;				\
> +	int ret, oldval, tmp;						\
>  									\
>  	uaccess_enable_privileged();					\
> -	asm volatile(							\
> +	asm volatile("// __llsc_futex_atomic_" #op "\n"			\
>  "	prfm	pstl1strm, %2\n"					\
>  "1:	ldxr	%w1, %2\n"						\
>  	insn "\n"							\
> @@ -35,45 +39,103 @@ do {									\
>  	: "r" (oparg), "Ir" (-EAGAIN)					\
>  	: "memory");							\
>  	uaccess_disable_privileged();					\
> -} while (0)
> +									\
> +	if (!ret)							\
> +		*oval = oldval;						\
> +									\
> +	return ret;							\
> +}
> +
> +LLSC_FUTEX_ATOMIC_OP(add, "add	%w3, %w1, %w5")
> +LLSC_FUTEX_ATOMIC_OP(or,  "orr	%w3, %w1, %w5")
> +LLSC_FUTEX_ATOMIC_OP(and, "and	%w3, %w1, %w5")
> +LLSC_FUTEX_ATOMIC_OP(eor, "eor	%w3, %w1, %w5")
> +LLSC_FUTEX_ATOMIC_OP(set, "mov	%w3, %w5")

Since you're reworking this code, how about we take the opportunity to
use named arguments instead of the numbers?

Will