linux-kernel - RE: [PATCH V2 2/4] riscv: mm: Fixup compat arch_get_mmap

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Date: Fri, 22 Dec 2023 08:59:47 +0000
From: David Laight <David.Laight@...LAB.COM>
To: "'guoren@...nel.org'" <guoren@...nel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "paul.walmsley@...ive.com"
	<paul.walmsley@...ive.com>, "palmer@...belt.com" <palmer@...belt.com>,
	"alexghiti@...osinc.com" <alexghiti@...osinc.com>, "charlie@...osinc.com"
	<charlie@...osinc.com>, "xiao.w.wang@...el.com" <xiao.w.wang@...el.com>,
	"david@...hat.com" <david@...hat.com>, "panqinglin2020@...as.ac.cn"
	<panqinglin2020@...as.ac.cn>, "rick.p.edgecombe@...el.com"
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	<conor.dooley@...rochip.com>, "cleger@...osinc.com" <cleger@...osinc.com>,
	"leobras@...hat.com" <leobras@...hat.com>
CC: "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>, "Guo
 Ren" <guoren@...ux.alibaba.com>, "stable@...r.kernel.org"
	<stable@...r.kernel.org>
Subject: RE: [PATCH V2 2/4] riscv: mm: Fixup compat arch_get_mmap_end

From: guoren@...nel.org <guoren@...nel.org>
> Sent: 21 December 2023 15:47
> 
> From: Guo Ren <guoren@...ux.alibaba.com>
> 
> When the task is in COMPAT mode, the arch_get_mmap_end should be 2GB,
> not TASK_SIZE_64. The TASK_SIZE has contained is_compat_mode()
> detection, so change the definition of STACK_TOP_MAX to TASK_SIZE
> directly.

Why 2G ?

IIRC for 32-bit native x86 the limit is 3G, but in compat mode
it is (just under) 4G.

There is a special mmap option (for programs like wine) to
limit mmap() to 2G.

	David

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