linux-kernel - RE: [PATCH V3 07/17] riscv: compat: Re-implement TASK_SIZE for COMPAT

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Date:   Thu, 20 Jan 2022 12:53:11 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Arnd Bergmann' <arnd@...db.de>, Guo Ren <guoren@...nel.org>
CC:     Palmer Dabbelt <palmer@...belt.com>,
        Anup Patel <anup@...infault.org>,
        gregkh <gregkh@...uxfoundation.org>,
        liush <liush@...winnertech.com>, Wei Fu <wefu@...hat.com>,
        Drew Fustini <drew@...gleboard.org>,
        Wang Junqiang <wangjunqiang@...as.ac.cn>,
        Christoph Hellwig <hch@....de>,
        Christoph Hellwig <hch@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-csky@...r.kernel.org" <linux-csky@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        "inux-parisc@...r.kernel.org" <inux-parisc@...r.kernel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: RE: [PATCH V3 07/17] riscv: compat: Re-implement TASK_SIZE for
 COMPAT_32BIT

> > Limit 32-bit compatible process in 0-2GB virtual address range
> > (which is enough for real scenarios), because it could avoid
> > address sign extend problem when 32-bit enter 64-bit and ease
> > software design.

Eh?
I thought nearly all the other 32bit unix ports (of any flavour)
put the user-kernel boundary at 3GB.
(Apart from some very old sparc ones that use 3.5GB.)

2GB is used by Windows.

I think the x86-64 32bit compat code even puts the boundary at 4GB.

	David

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