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Message-Id: <20240905-patches-below_hint_mmap-v3-1-3cd5564efbbb@rivosinc.com>
Date: Thu, 05 Sep 2024 14:15:51 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Arnd Bergmann <arnd@...db.de>, 
 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>, Guo Ren <guoren@...nel.org>, 
 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 Khan <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>
Cc: 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, 
 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, 
 Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH RFC v3 1/2] mm: Add personality flag to limit address to 47
 bits

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>
---
 include/uapi/linux/personality.h | 1 +
 mm/mmap.c                        | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/include/uapi/linux/personality.h b/include/uapi/linux/personality.h
index 49796b7756af..cd3b8c154d9b 100644
--- a/include/uapi/linux/personality.h
+++ b/include/uapi/linux/personality.h
@@ -22,6 +22,7 @@ enum {
 	WHOLE_SECONDS =		0x2000000,
 	STICKY_TIMEOUTS	=	0x4000000,
 	ADDR_LIMIT_3GB = 	0x8000000,
+	ADDR_LIMIT_47BIT = 	0x10000000,
 };
 
 /*
diff --git a/mm/mmap.c b/mm/mmap.c
index d0dfc85b209b..a5c7544853e5 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1766,6 +1766,9 @@ unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
 {
 	unsigned long addr;
 
+	if (current->personality & ADDR_LIMIT_47BIT)
+		info->high_limit = MIN(info->high_limit, BIT(47) - 1);
+
 	if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
 		addr = unmapped_area_topdown(info);
 	else

-- 
2.45.0


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