Date: Wed, 21 Feb 2024 07:38:32 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Christoph Hellwig <hch@...radead.org>, Maxwell Bland <mbland@...orola.com>
CC: "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "gregkh@...uxfoundation.org"
	<gregkh@...uxfoundation.org>, "agordeev@...ux.ibm.com"
	<agordeev@...ux.ibm.com>, "akpm@...ux-foundation.org"
	<akpm@...ux-foundation.org>, "andreyknvl@...il.com" <andreyknvl@...il.com>,
	"andrii@...nel.org" <andrii@...nel.org>, "aneesh.kumar@...nel.org"
	<aneesh.kumar@...nel.org>, "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
	"ardb@...nel.org" <ardb@...nel.org>, "arnd@...db.de" <arnd@...db.de>,
	"ast@...nel.org" <ast@...nel.org>, "borntraeger@...ux.ibm.com"
	<borntraeger@...ux.ibm.com>, "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
	"brauner@...nel.org" <brauner@...nel.org>, "catalin.marinas@....com"
	<catalin.marinas@....com>, "cl@...ux.com" <cl@...ux.com>,
	"daniel@...earbox.net" <daniel@...earbox.net>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>, "david@...hat.com" <david@...hat.com>,
	"dennis@...nel.org" <dennis@...nel.org>, "dvyukov@...gle.com"
	<dvyukov@...gle.com>, "glider@...gle.com" <glider@...gle.com>,
	"gor@...ux.ibm.com" <gor@...ux.ibm.com>, "guoren@...nel.org"
	<guoren@...nel.org>, "haoluo@...gle.com" <haoluo@...gle.com>,
	"hca@...ux.ibm.com" <hca@...ux.ibm.com>, "john.fastabend@...il.com"
	<john.fastabend@...il.com>, "jolsa@...nel.org" <jolsa@...nel.org>,
	"kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
	"kpsingh@...nel.org" <kpsingh@...nel.org>, "linux-arch@...r.kernel.org"
	<linux-arch@...r.kernel.org>, "linux@...linux.org.uk"
	<linux@...linux.org.uk>, "linux-efi@...r.kernel.org"
	<linux-efi@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
	"linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
	"lstoakes@...il.com" <lstoakes@...il.com>, "mark.rutland@....com"
	<mark.rutland@....com>, "martin.lau@...ux.dev" <martin.lau@...ux.dev>,
	"meted@...ux.ibm.com" <meted@...ux.ibm.com>, "michael.christie@...cle.com"
	<michael.christie@...cle.com>, "mjguzik@...il.com" <mjguzik@...il.com>,
	"mpe@...erman.id.au" <mpe@...erman.id.au>, "mst@...hat.com" <mst@...hat.com>,
	"muchun.song@...ux.dev" <muchun.song@...ux.dev>, "naveen.n.rao@...ux.ibm.com"
	<naveen.n.rao@...ux.ibm.com>, "npiggin@...il.com" <npiggin@...il.com>,
	"palmer@...belt.com" <palmer@...belt.com>, "paul.walmsley@...ive.com"
	<paul.walmsley@...ive.com>, "quic_nprakash@...cinc.com"
	<quic_nprakash@...cinc.com>, "quic_pkondeti@...cinc.com"
	<quic_pkondeti@...cinc.com>, "rick.p.edgecombe@...el.com"
	<rick.p.edgecombe@...el.com>, "ryabinin.a.a@...il.com"
	<ryabinin.a.a@...il.com>, "ryan.roberts@....com" <ryan.roberts@....com>,
	"samitolvanen@...gle.com" <samitolvanen@...gle.com>, "sdf@...gle.com"
	<sdf@...gle.com>, "song@...nel.org" <song@...nel.org>, "surenb@...gle.com"
	<surenb@...gle.com>, "svens@...ux.ibm.com" <svens@...ux.ibm.com>,
	"tj@...nel.org" <tj@...nel.org>, "urezki@...il.com" <urezki@...il.com>,
	"vincenzo.frascino@....com" <vincenzo.frascino@....com>, "will@...nel.org"
	<will@...nel.org>, "wuqiang.matt@...edance.com" <wuqiang.matt@...edance.com>,
	"yonghong.song@...ux.dev" <yonghong.song@...ux.dev>, "zlim.lnx@...il.com"
	<zlim.lnx@...il.com>, "awheeler@...orola.com" <awheeler@...orola.com>
Subject: Re: [PATCH 1/4] mm/vmalloc: allow arch-specific vmalloc_node
 overrides



Le 21/02/2024 à 06:43, Christoph Hellwig a écrit :
> On Tue, Feb 20, 2024 at 02:32:53PM -0600, Maxwell Bland wrote:
>> Present non-uniform use of __vmalloc_node and __vmalloc_node_range makes
>> enforcing appropriate code and data seperation untenable on certain
>> microarchitectures, as VMALLOC_START and VMALLOC_END are monolithic
>> while the use of the vmalloc interface is non-monolithic: in particular,
>> appropriate randomness in ASLR makes it such that code regions must fall
>> in some region between VMALLOC_START and VMALLOC_end, but this
>> necessitates that code pages are intermingled with data pages, meaning
>> code-specific protections, such as arm64's PXNTable, cannot be
>> performantly runtime enforced.
> 
> That's not actually true.  We have MODULE_START/END to separate them,
> which is used by mips only for now.

We have MODULES_VADDR and MODULES_END that are used by arm, arm64, 
loongarcg, powerpc, riscv, s390, sparc, x86_64

is_vmalloc_or_module_addr() is using MODULES_VADDR so I guess this 
function fails on mips ?

> 
>>
>> The solution to this problem allows architectures to override the
>> vmalloc wrapper functions by enforcing that the rest of the kernel does
>> not reimplement __vmalloc_node by using __vmalloc_node_range with the
>> same parameters as __vmalloc_node or provides a __weak tag to those
>> functions using __vmalloc_node_range with parameters repeating those of
>> __vmalloc_node.
> 
> I'm really not too happy about overriding the functions.  Especially
> as the separation is a generally good idea and it would be good to
> move everyone (or at least all modern architectures) over to a scheme
> like this.

Powered by blists - more mailing lists