linux-kernel - Re: [PATCH RFC v3 1/2] mm: Add personality flag to limit address to 47 bits

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJF2gTTVX9CFM3oRZZP3hGExwVwA_=n1Lrq_0DQKWA+-ZbOekg@mail.gmail.com>
Date: Fri, 6 Sep 2024 17:14:31 +0800
From: Guo Ren <guoren@...nel.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: Charlie Jenkins <charlie@...osinc.com>, Richard Henderson <richard.henderson@...aro.org>, 
	Ivan Kokshaysky <ink@...assic.park.msu.ru>, Matt Turner <mattst88@...il.com>, 
	Vineet Gupta <vgupta@...nel.org>, Russell King <linux@...linux.org.uk>, 
	Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, 
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
	"James E . J . Bottomley" <James.Bottomley@...senpartnership.com>, Helge Deller <deller@....de>, 
	Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, Naveen N Rao <naveen@...nel.org>, 
	Alexander Gordeev <agordeev@...ux.ibm.com>, Gerald Schaefer <gerald.schaefer@...ux.ibm.com>, 
	Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Sven Schnelle <svens@...ux.ibm.com>, 
	Yoshinori Sato <ysato@...rs.sourceforge.jp>, Rich Felker <dalias@...c.org>, 
	John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>, "David S . Miller" <davem@...emloft.net>, 
	Andreas Larsson <andreas@...sler.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Muchun Song <muchun.song@...ux.dev>, Andrew Morton <akpm@...ux-foundation.org>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, shuah <shuah@...nel.org>, 
	Christoph Hellwig <hch@...radead.org>, Michal Hocko <mhocko@...e.com>, 
	"Kirill A. Shutemov" <kirill@...temov.name>, Chris Torek <chris.torek@...il.com>, 
	Linux-Arch <linux-arch@...r.kernel.org>, linux-kernel@...r.kernel.org, 
	linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org, 
	linux-arm-kernel@...ts.infradead.org, 
	"linux-csky@...r.kernel.org" <linux-csky@...r.kernel.org>, loongarch@...ts.linux.dev, 
	linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org, 
	linux-sh@...r.kernel.org, sparclinux@...r.kernel.org, linux-mm@...ck.org, 
	linux-kselftest@...r.kernel.org, linux-abi-devel@...ts.sourceforge.net
Subject: Re: [PATCH RFC v3 1/2] mm: Add personality flag to limit address to
 47 bits

On Fri, Sep 6, 2024 at 3:18 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Thu, Sep 5, 2024, at 21:15, Charlie Jenkins wrote:
> > Create a personality flag ADDR_LIMIT_47BIT to support applications
> > that wish to transition from running in environments that support at
> > most 47-bit VAs to environments that support larger VAs. This
> > personality can be set to cause all allocations to be below the 47-bit
> > boundary. Using MAP_FIXED with mmap() will bypass this restriction.
> >
> > Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
>
> I think having an architecture-independent mechanism to limit the size
> of the 64-bit address space is useful in general, and we've discussed
> the same thing for arm64 in the past, though we have not actually
> reached an agreement on the ABI previously.
>
> > @@ -22,6 +22,7 @@ enum {
> >       WHOLE_SECONDS =         0x2000000,
> >       STICKY_TIMEOUTS =       0x4000000,
> >       ADDR_LIMIT_3GB =        0x8000000,
> > +     ADDR_LIMIT_47BIT =      0x10000000,
> > };
>
> I'm a bit worried about having this done specifically in the
> personality flag bits, as they are rather limited. We obviously
> don't want to add many more such flags when there could be
> a way to just set the default limit.
>
> It's also unclear to me how we want this flag to interact with
> the existing logic in arch_get_mmap_end(), which attempts to
> limit the default mapping to a 47-bit address space already.

To optimize RISC-V progress, I recommend:

Step 1: Approve the patch.
Step 2: Update Go and OpenJDK's RISC-V backend to utilize it.
Step 3: Wait approximately several iterations for Go & OpenJDK
Step 4: Remove the 47-bit constraint in arch_get_mmap_end()


>
> For some reason, it appears that the arch_get_mmap_end()
> logic on RISC-V defaults to the maximum address
> space for the 'addr==0' case which is inconsistentn with
> the other architectures, so we should probably fix that
> part first, possibly moving more of that logic into a
> shared implementation.
>
>       Arnd
>


-- 
Best Regards
 Guo Ren