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charset=us-ascii Content-Disposition: inline In-Reply-To: <87y1ivln1v.ffs@tglx> X-Rspamd-Queue-Id: BDA8E140023 X-Rspam-User: X-Stat-Signature: tj87fxp7qqtbfiuqpi4383wixaj5s1x6 X-Rspamd-Server: rspam01 X-HE-Tag: 1690844422-998714 X-HE-Meta: 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 rEeAwXEx Q5WztqOS2Nsh5J2J0+jG8k2y6Y8aOxXIjKgsGpGJQh/+UX0vLsnc1A1fm6xraM6mIennnvpLxk6CFpHGALC0NTUzuUcQ8tIdR7JTHhjqU8FIqc5+nBP3W+a3sEXovrf3Q3X54oE4g08sTPcQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Aug 01, 2023 at 12:43:24AM +0200, Thomas Gleixner wrote: > > Also, sys_futex_{wake,wait}() have this thing as a syscall argument, > > surely you don't want to put this union there as well? > > Why not? The anon union does not break the ABI unless I'm missing > something. Existing user space can still use 'flags' and people who care > about readability can use the bitfield, no? > > Its inside struct futex_waitv and not an explicit syscall argument, right? Nope, see patches 5 and 6, they introduce: sys_futex_wake(void __user *uaddr, unsigned long mask, int nr, unsigned int flags); sys_futex_wait(void __user *uaddr, unsigned long val, unsigned long mask, unsigned int flags, struct __kernel_timespec __user *timeout, clockid_t clockid); Using a union, would turn that into: sys_futex_wake(void __user *uaddr, unsigned long mask, int nr, union futex_flags flags); sys_futex_wait(void __user *uaddr, unsigned long val, unsigned long mask, union futex_flags flags, struct __kernel_timespec __user *timeout, clockid_t clockid); Which then gets people to write garbage like: futex_wake(add, 0xFFFF, 1, (union futex_flags){ .flags = FUTEX2_SIZE_U16 | FUTEX2_PRIVATE)); or futex_wake(add, 0xFFFF, 1, (union futex_flags){ .size = FUTEX2_SIZE_U16, private = true, )); You really want that ?