[PATCH v2 4/5] mips: Use generic mmap top-down layout

[Alexandre Ghiti]

mips uses a top-down layout by default that fits the generic functions.
At the same time, this commit allows to fix problem uncovered
and not fixed for mips here:
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1429066.html

Signed-off-by: Alexandre Ghiti <a...@ghiti.fr>
---
 arch/mips/Kconfig                 |  1 +
 arch/mips/include/asm/processor.h |  5 ---
 arch/mips/mm/mmap.c               | 57 -------------------------------
 3 files changed, 1 insertion(+), 62 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 4a5f5b0ee9a9..c21aa6371eab 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -14,6 +14,7 @@ config MIPS
        select ARCH_USE_CMPXCHG_LOCKREF if 64BIT
        select ARCH_USE_QUEUED_RWLOCKS
        select ARCH_USE_QUEUED_SPINLOCKS
+       select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
        select ARCH_WANT_IPC_PARSE_VERSION
        select BUILDTIME_EXTABLE_SORT
        select CLONE_BACKWARDS
diff --git a/arch/mips/include/asm/processor.h 
b/arch/mips/include/asm/processor.h
index aca909bd7841..fba18d4a9190 100644
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -29,11 +29,6 @@
 
 extern unsigned int vced_count, vcei_count;
 
-/*
- * MIPS does have an arch_pick_mmap_layout()
- */
-#define HAVE_ARCH_PICK_MMAP_LAYOUT 1
-
 #ifdef CONFIG_32BIT
 #ifdef CONFIG_KVM_GUEST
 /* User space process size is limited to 1GB in KVM Guest Mode */
diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index 2f616ebeb7e0..61e65a69bb09 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -20,33 +20,6 @@
 unsigned long shm_align_mask = PAGE_SIZE - 1;  /* Sane caches */
 EXPORT_SYMBOL(shm_align_mask);
 
-/* gap between mmap and stack */
-#define MIN_GAP (128*1024*1024UL)
-#define MAX_GAP ((TASK_SIZE)/6*5)
-
-static 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;
-}
-
-static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
-{
-       unsigned long gap = rlim_stack->rlim_cur;
-
-       if (gap < MIN_GAP)
-               gap = MIN_GAP;
-       else if (gap > MAX_GAP)
-               gap = MAX_GAP;
-
-       return PAGE_ALIGN(TASK_SIZE - gap - rnd);
-}
-
 #define COLOUR_ALIGN(addr, pgoff)                              \
        ((((addr) + shm_align_mask) & ~shm_align_mask) +        \
         (((pgoff) << PAGE_SHIFT) & shm_align_mask))
@@ -144,36 +117,6 @@ unsigned long arch_get_unmapped_area_topdown(struct file 
*filp,
                        addr0, len, pgoff, flags, DOWN);
 }
 
-unsigned long arch_mmap_rnd(void)
-{
-       unsigned long rnd;
-
-#ifdef CONFIG_COMPAT
-       if (TASK_IS_32BIT_ADDR)
-               rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
-       else
-#endif /* CONFIG_COMPAT */
-               rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
-
-       return rnd << PAGE_SHIFT;
-}
-
-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();
-
-       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;
-       }
-}
-
 static inline unsigned long brk_rnd(void)
 {
        unsigned long rnd = get_random_long();
-- 
2.20.1