linux-kernel - [PATCH 11/16] mips: mm: Support MAP_BELOW

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Message-Id: <20240827-patches-below_hint_mmap-v1-11-46ff2eb9022d@rivosinc.com>
Date: Tue, 27 Aug 2024 22:49:17 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Arnd Bergmann <arnd@...db.de>, Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, 
 Christophe Leroy <christophe.leroy@...roup.eu>, 
 Naveen N Rao <naveen@...nel.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>, 
 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>, 
 Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, 
 Russell King <linux@...linux.org.uk>, 
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
 "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>, 
 Helge Deller <deller@....de>, 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>, Shuah Khan <shuah@...nel.org>, 
 Alexandre Ghiti <alexghiti@...osinc.com>
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Palmer Dabbelt <palmer@...osinc.com>, linux-riscv@...ts.infradead.org, 
 linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org, 
 linux-mm@...ck.org, loongarch@...ts.linux.dev, linux-mips@...r.kernel.org, 
 linux-parisc@...r.kernel.org, linux-s390@...r.kernel.org, 
 linux-sh@...r.kernel.org, sparclinux@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH 11/16] mips: mm: Support MAP_BELOW_HINT

Add support for MAP_BELOW_HINT to mmap by restricting high_limit to addr
when the flag is enabled.

Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
 arch/mips/mm/mmap.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index 7e11d7b58761..1595fda284cd 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -79,6 +79,13 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
 		info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 		info.low_limit = PAGE_SIZE;
 		info.high_limit = mm->mmap_base;
+		if (flags & MAP_BELOW_HINT)
+			/*
+			 * Subtract (STACK_TOP - mm->mmap_base) to get random
+			 * offset defined in mmap_base() in mm/util.c
+			 */
+			info.high_limit = MIN(info.high_limit,
+					      (addr + len) - (STACK_TOP - mm->mmap_base));
 		addr = vm_unmapped_area(&info);

 		if (!(addr & ~PAGE_MASK))
@@ -94,6 +101,8 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,

 	info.low_limit = mm->mmap_base;
 	info.high_limit = TASK_SIZE;
+	if (flags & MAP_BELOW_HINT)
+		info.high_limit = MIN(info.high_limit, addr + len);
 	return vm_unmapped_area(&info);
 }

-- 
2.45.0