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Date:   Wed, 17 Apr 2019 01:22:46 -0400
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Christoph Hellwig <hch@....de>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mips@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Alexandre Ghiti <alex@...ti.fr>
Subject: [PATCH v3 10/11] mips: Use generic mmap top-down layout

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 <alex@...ti.fr>
---
 arch/mips/Kconfig                 |  1 +
 arch/mips/include/asm/processor.h |  5 ---
 arch/mips/mm/mmap.c               | 67 -------------------------------
 3 files changed, 1 insertion(+), 72 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 4a5f5b0ee9a9..ec2f07561e4d 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 if MMU
 	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 ffbe69f3a7d9..61e65a69bb09 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -20,43 +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		((STACK_TOP)/6*5)
-#define STACK_RND_MASK	(0x7ff >> (PAGE_SHIFT - 12))
-
-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;
-	unsigned long pad = stack_guard_gap;
-
-	/* Account for stack randomization if necessary */
-	if (current->flags & PF_RANDOMIZE)
-		pad += (STACK_RND_MASK << PAGE_SHIFT);
-
-	/* 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(STACK_TOP - gap - rnd);
-}
-
 #define COLOUR_ALIGN(addr, pgoff)				\
 	((((addr) + shm_align_mask) & ~shm_align_mask) +	\
 	 (((pgoff) << PAGE_SHIFT) & shm_align_mask))
@@ -154,36 +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

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