Commit 36e5f9ee authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/mm: Convert to default topdown mmap layout 



Select CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT and
remove arch/powerpc/mm/mmap.c

This change reuses the generic framework added by
commit 67f3977f ("arm64, mm: move generic mmap layout
functions to mm") without any functional change.

Comparison between powerpc implementation and the generic one:
- mmap_is_legacy() is identical.
- arch_mmap_rnd() does exactly the same allthough it's written
slightly differently.
- MIN_GAP and MAX_GAP are identical.
- mmap_base() does the same but uses STACK_RND_MASK which provides
the same values as stack_maxrandom_size().
- arch_pick_mmap_layout() is identical.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/518f9def87d3c889d5958103e7463cf45a2f673d.1649523076.git.christophe.leroy@csgroup.eu
parent 5cf7f9a0

arch/powerpc/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -118,7 +118,6 @@ config PPC 
	select ARCH_HAS_DEBUG_WX		if STRICT_KERNEL_RWX

	select ARCH_HAS_DEVMEM_IS_ALLOWED

	select ARCH_HAS_DMA_MAP_DIRECT 		if PPC_PSERIES

	select ARCH_HAS_ELF_RANDOMIZE

	select ARCH_HAS_FORTIFY_SOURCE

	select ARCH_HAS_GCOV_PROFILE_ALL

	select ARCH_HAS_HUGEPD			if HUGETLB_PAGE
@@ -154,6 +153,7 @@ config PPC 
	select ARCH_USE_MEMTEST

	select ARCH_USE_QUEUED_RWLOCKS		if PPC_QUEUED_SPINLOCKS

	select ARCH_USE_QUEUED_SPINLOCKS	if PPC_QUEUED_SPINLOCKS

	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT

	select ARCH_WANT_IPC_PARSE_VERSION

	select ARCH_WANT_IRQS_OFF_ACTIVATE_MM

	select ARCH_WANT_LD_ORPHAN_WARN

arch/powerpc/include/asm/processor.h

+0 −2
Original line number Diff line number Diff line
@@ -392,8 +392,6 @@ static inline void prefetchw(const void *x) 


#define spin_lock_prefetch(x)	prefetchw(x)



#define HAVE_ARCH_PICK_MMAP_LAYOUT



/* asm stubs */

extern unsigned long isa300_idle_stop_noloss(unsigned long psscr_val);

extern unsigned long isa300_idle_stop_mayloss(unsigned long psscr_val);

arch/powerpc/mm/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 


ccflags-$(CONFIG_PPC64)	:= $(NO_MINIMAL_TOC)



obj-y				:= fault.o mem.o pgtable.o mmap.o maccess.o pageattr.o \

obj-y				:= fault.o mem.o pgtable.o maccess.o pageattr.o \

				   init_$(BITS).o pgtable_$(BITS).o \

				   pgtable-frag.o ioremap.o ioremap_$(BITS).o \

				   init-common.o mmu_context.o drmem.o \

arch/powerpc/mm/mmap.c

deleted100644 → 0
+0 −105
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-or-later

/*

 *  flexible mmap layout support

 *

 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.

 * All Rights Reserved.

 *

 * Started by Ingo Molnar <mingo@elte.hu>

 */



#include <linux/personality.h>

#include <linux/mm.h>

#include <linux/random.h>

#include <linux/sched/signal.h>

#include <linux/sched/mm.h>

#include <linux/elf-randomize.h>

#include <linux/security.h>

#include <linux/mman.h>



/*

 * Top of mmap area (just below the process stack).

 *

 * Leave at least a ~128 MB hole.

 */

#define MIN_GAP (128*1024*1024)

#define MAX_GAP (TASK_SIZE/6*5)



static inline int mmap_is_legacy(struct rlimit *rlim_stack)

{

	if (current->personality & ADDR_COMPAT_LAYOUT)

		return 1;



	if (rlim_stack->rlim_cur == RLIM_INFINITY)

		return 1;



	return sysctl_legacy_va_layout;

}



unsigned long arch_mmap_rnd(void)

{

	unsigned long shift, rnd;



	shift = mmap_rnd_bits;

#ifdef CONFIG_COMPAT

	if (is_32bit_task())

		shift = mmap_rnd_compat_bits;

#endif

	rnd = get_random_long() % (1ul << shift);



	return rnd << PAGE_SHIFT;

}



static inline unsigned long stack_maxrandom_size(void)

{

	if (!(current->flags & PF_RANDOMIZE))

		return 0;



	/* 8MB for 32bit, 1GB for 64bit */

	if (is_32bit_task())

		return (1<<23);

	else

		return (1<<30);

}



static inline unsigned long mmap_base(unsigned long rnd,

				      struct rlimit *rlim_stack)

{

	unsigned long gap = rlim_stack->rlim_cur;

	unsigned long pad = stack_maxrandom_size() + stack_guard_gap;



	/* Values close to RLIM_INFINITY can overflow. */

	if (gap + pad > gap)

		gap += pad;



	if (gap < MIN_GAP)

		gap = MIN_GAP;

	else if (gap > MAX_GAP)

		gap = MAX_GAP;



	return PAGE_ALIGN(DEFAULT_MAP_WINDOW - gap - rnd);

}



/*

 * This function, called very early during the creation of a new

 * process VM image, sets up which VM layout function to use:

 */

void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)

{

	unsigned long random_factor = 0UL;



	if (current->flags & PF_RANDOMIZE)

		random_factor = arch_mmap_rnd();



	/*

	 * Fall back to the standard layout if the personality

	 * bit is set, or if the expected stack growth is unlimited:

	 */

	if (mmap_is_legacy(rlim_stack)) {

		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;

		mm->get_unmapped_area = arch_get_unmapped_area;

	} else {

		mm->mmap_base = mmap_base(random_factor, rlim_stack);

		mm->get_unmapped_area = arch_get_unmapped_area_topdown;

	}

}