linux-kernel - Re: [PATCH v1] futex: Add compat_sys_futex

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Message-ID: <189e733e-7056-45c4-a5c6-3371f8219b7e@igalia.com>
Date:   Thu, 23 Nov 2023 13:09:55 -0300
From:   André Almeida <andrealmeid@...lia.com>
To:     Wei Gao <wegao@...e.com>
Cc:     tglx@...utronix.de, dvhart@...radead.org,
        linux-kernel@...r.kernel.org, dave@...olabs.net, mingo@...hat.com,
        peterz@...radead.org, Arnd Bergmann <arnd@...nel.org>
Subject: Re: [PATCH v1] futex: Add compat_sys_futex_waitv for 32bit
 compatibility

[+CC Arnd]

Hi Wei,

Em 23/11/2023 02:31, Wei Gao escreveu:
> From: wei gao <wegao@...e.com>
> 
> Current implementation lead LTP test case futex_waitv failed when compiled with
> -m32. This patch add new compat_sys_futex_waitv to handle m32 mode syscall.
> 
> The failure reason is futex_waitv in m32 mode will deliver kernel with struct
> old_timespec32 timeout, but this struct type can not directly used by current
> sys_futex_waitv implementation.
> 
> The new function copy main logic of current sys_futex_waitv, just update parameter
> type from "struct __kernel_timespec __user *" to "struct old_timespec32 __user *,"
> and use get_old_timespec32 within the new function to get timeout value.
> 

From, what I recall, we don't want to add new syscalls with 
old_timespec32, giving that they will have a limited lifetime. Instead, 
userspace should be able to come up with a 64-bit timespec 
implementation for -m32.

Thanks,
	André