Revert "x86 get_unmapped_area(): use proper mmap base for bottom-up direction"

5ea80f76 · Linus Torvalds <[email protected]> · 2013-08-22 09:13:06 -07:00

This reverts commit df54d6fa54275ce59660453e29d1228c2b45a826.

The commit isn't necessarily wrong, but because it recalculates the
random mmap_base every time, it seems to confuse user memory allocators
that expect contiguous mmap allocations even when the mmap address isn't
specified.

In particular, the MATLAB Java runtime seems to be unhappy. See

  https://bugzilla.kernel.org/show_bug.cgi?id=60774

So we'll want to apply the random offset only once, and Radu has a patch
for that.  Revert this older commit in order to apply the other one.

Reported-by: Jeff Shorey <[email protected]>
Cc: Radu Caragea <[email protected]>
Cc: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: 5ea80f76a56605a190a7ea16846c82aa63dbd0aa
Parents: d936d2d4

Changes

3 files changed · +2 −3

File	Status	Add	Del	Content
arch/x86/kernel/sys_x86_64.c	modified	+1	−1	View file
arch/x86/mm/mmap.c	modified	+1	−1	View file
include/linux/sched.h	modified	+0	−1	View file

arch/x86/kernel/sys_x86_64.c

View file

diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index 48f8375..dbded5a 100644
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -101,7 +101,7 @@ static void find_start_end(unsigned long flags, unsigned long *begin,
 				*begin = new_begin;
 		}
 	} else {
-		*begin = mmap_legacy_base();
+		*begin = TASK_UNMAPPED_BASE;
 		*end = TASK_SIZE;
 	}
 }

arch/x86/mm/mmap.c

View file

diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index f63778c..62c29a5 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -98,7 +98,7 @@ static unsigned long mmap_base(void)
  * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
  * does, but not when emulating X86_32
  */
-unsigned long mmap_legacy_base(void)
+static unsigned long mmap_legacy_base(void)
 {
 	if (mmap_is_ia32())
 		return TASK_UNMAPPED_BASE;

include/linux/sched.h

View file

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e9995eb..078066d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -314,7 +314,6 @@ struct nsproxy;
 struct user_namespace;
 
 #ifdef CONFIG_MMU
-extern unsigned long mmap_legacy_base(void);
 extern void arch_pick_mmap_layout(struct mm_struct *mm);
 extern unsigned long
 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,