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powerpc/mm: Convert to default topdown mmap layout

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

This change reuses the generic framework added by
commit 67f3977f80 ("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: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/518f9def87d3c889d5958103e7463cf45a2f673d.1649523076.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2022-04-09 19:17:36 +02:00 committed by Michael Ellerman
parent 5cf7f9a0a5
commit 36e5f9ee77
4 changed files with 2 additions and 109 deletions
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2
arch/powerpc/Kconfig
View file

@ -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

2
arch/powerpc/include/asm/processor.h
View file

@ -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);

2
arch/powerpc/mm/Makefile
View file

@ -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 \

105
arch/powerpc/mm/mmap.c
View file

@ -1,105 +0,0 @@
// 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;
}
}