linux-kernel - [PATCH 04/16] mm: Add generic MAP_BELOW

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Message-Id: <20240827-patches-below_hint_mmap-v1-4-46ff2eb9022d@rivosinc.com>
Date: Tue, 27 Aug 2024 22:49:10 -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 04/16] mm: Add generic MAP_BELOW_HINT

Make the generic implementation of arch_get_mmap_base() and
arch_get_mmap_end() support MAP_BELOW_HINT.

Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
 include/linux/sched/mm.h | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 265b43855d0b..c350bb5ac0a2 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -9,6 +9,7 @@
 #include <linux/gfp.h>
 #include <linux/sync_core.h>
 #include <linux/sched/coredump.h>
+#include <uapi/asm/mman.h>

 /*
  * Routines for handling mm_structs
@@ -170,11 +171,40 @@ static inline void mm_update_next_owner(struct mm_struct *mm)

 #ifdef CONFIG_MMU
 #ifndef arch_get_mmap_end
-#define arch_get_mmap_end(addr, len, flags)	(TASK_SIZE)
+#define arch_get_mmap_end(addr, len, flags)							\
+({												\
+	unsigned long mmap_end;									\
+	typeof(flags) _flags = (flags);								\
+	typeof(addr) _addr = (addr);								\
+	typeof(len) _len = (len);								\
+	mmap_end = TASK_SIZE;									\
+	if (_flags & MAP_BELOW_HINT && _addr != 0)						\
+		mmap_end = MIN(mmap_end, _addr + _len);						\
+	mmap_end;										\
+})
 #endif

 #ifndef arch_get_mmap_base
-#define arch_get_mmap_base(addr, len, base, flags) (base)
+/*
+ * rnd_gap is defined to be (STACK_TOP - _base) due to the definition of
+ * mmap_base in mm/util.c
+ *
+ * Assumes ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT, which all architectures that
+ * implement generic mmap use
+ */
+#define arch_get_mmap_base(addr, len, base, flags)						\
+({												\
+	unsigned long mmap_base;								\
+	typeof(flags) _flags = (flags);								\
+	typeof(addr) _addr = (addr);								\
+	typeof(base) _base = (base);								\
+	typeof(len) _len = (len);								\
+	unsigned long rnd_gap = STACK_TOP - _base;						\
+	mmap_base = _base;									\
+	if (_flags & MAP_BELOW_HINT && _addr != 0)						\
+		mmap_base = MIN(mmap_base, (_addr + _len) - rnd_gap);				\
+	mmap_base;										\
+})
 #endif

 extern void arch_pick_mmap_layout(struct mm_struct *mm,

-- 
2.45.0