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 67f3977f805b ("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

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 174edab..145af02 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -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

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index 39c2502..fdfaae1 100644 (file)
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -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);

diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
index d4c2048..503a6e2 100644 (file)
--- a/arch/powerpc/mm/Makefile
+++ b/arch/powerpc/mm/Makefile
@@ -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 \

diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
deleted file mode 100644 (file)
index d9eae45..0000000
--- a/arch/powerpc/mm/mmap.c
+++ /dev/null
@@ -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;
-       }
-}