parisc: add flexible mmap memory layout support

Add support for the flexible mmap memory layout (as described in
http://lwn.net/Articles/91829). This is especially very interesting on
parisc since we currently only support 32bit userspace (even with a
64bit Linux kernel).

Signed-off-by: Helge Deller <deller@gmx.de>

6 files changed, 233 insertions, 43 deletions

diff --git a/arch/parisc/include/asm/elf.h b/arch/parisc/include/asm/elf.h
index ad2b50397894..3391d061eccc 100644
--- a/arch/parisc/include/asm/elf.h
+++ b/arch/parisc/include/asm/elf.h
@@ -348,4 +348,8 @@ struct pt_regs;	/* forward declaration... */
 
 #define ELF_HWCAP       0
 
+struct mm_struct;
+extern unsigned long arch_randomize_brk(struct mm_struct *);
+#define arch_randomize_brk arch_randomize_brk
+
 #endif
diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
index 34899b5d959a..22b89d1edba7 100644
--- a/arch/parisc/include/asm/pgtable.h
+++ b/arch/parisc/include/asm/pgtable.h
@@ -511,6 +511,7 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr,
 /* We provide our own get_unmapped_area to provide cache coherency */
 
 #define HAVE_ARCH_UNMAPPED_AREA
+#define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
 
 #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
 #define __HAVE_ARCH_PTEP_GET_AND_CLEAR
diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h
index cc2290a3cace..198a86feb574 100644
--- a/arch/parisc/include/asm/processor.h
+++ b/arch/parisc/include/asm/processor.h
@@ -30,6 +30,8 @@
 #endif
 #define current_text_addr() ({ void *pc; current_ia(pc); pc; })
 
+#define HAVE_ARCH_PICK_MMAP_LAYOUT
+
 #define TASK_SIZE_OF(tsk)       ((tsk)->thread.task_size)
 #define TASK_SIZE               TASK_SIZE_OF(current)
 #define TASK_UNMAPPED_BASE      (current->thread.map_base)
diff --git a/arch/parisc/include/asm/thread_info.h b/arch/parisc/include/asm/thread_info.h
index d5f97ea3a4e1..4b9b10ce1f9d 100644
--- a/arch/parisc/include/asm/thread_info.h
+++ b/arch/parisc/include/asm/thread_info.h
@@ -76,6 +76,16 @@ struct thread_info {
 #define _TIF_SYSCALL_TRACE_MASK (_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP | \
                                  _TIF_BLOCKSTEP | _TIF_SYSCALL_AUDIT)
 
+#ifdef CONFIG_64BIT
+# ifdef CONFIG_COMPAT
+#  define is_32bit_task()       (test_thread_flag(TIF_32BIT))
+# else
+#  define is_32bit_task()       (0)
+# endif
+#else
+# define is_32bit_task()        (1)
+#endif
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_PARISC_THREAD_INFO_H */
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index 55f92b614182..0bbbf0d3f608 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -13,7 +13,7 @@
  *    Copyright (C) 2000 Grant Grundler <grundler with parisc-linux.org>
  *    Copyright (C) 2001 Alan Modra <amodra at parisc-linux.org>
  *    Copyright (C) 2001-2002 Ryan Bradetich <rbrad at parisc-linux.org>
- *    Copyright (C) 2001-2007 Helge Deller <deller at parisc-linux.org>
+ *    Copyright (C) 2001-2014 Helge Deller <deller@gmx.de>
  *    Copyright (C) 2002 Randolph Chung <tausq with parisc-linux.org>
  *
  *
@@ -49,6 +49,7 @@
 #include <linux/kallsyms.h>
 #include <linux/uaccess.h>
 #include <linux/rcupdate.h>
+#include <linux/random.h>
 
 #include <asm/io.h>
 #include <asm/asm-offsets.h>
@@ -286,3 +287,21 @@ void *dereference_function_descriptor(void *ptr)
         return ptr;
 }
 #endif
+
+static inline unsigned long brk_rnd(void)
+{
+        /* 8MB for 32bit, 1GB for 64bit */
+        if (is_32bit_task())
+                return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
+        else
+                return (get_random_int() & 0x3ffffUL) << PAGE_SHIFT;
+}
+
+unsigned long arch_randomize_brk(struct mm_struct *mm)
+{
+        unsigned long ret = PAGE_ALIGN(mm->brk + brk_rnd());
+
+        if (ret < mm->brk)
+                return mm->brk;
+        return ret;
+}
diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c
index 0d3a9d4927b5..b7cadc4a06cd 100644
--- a/arch/parisc/kernel/sys_parisc.c
+++ b/arch/parisc/kernel/sys_parisc.c
@@ -5,6 +5,7 @@
  *    Copyright (C) 1999-2003 Matthew Wilcox <willy at parisc-linux.org>
  *    Copyright (C) 2000-2003 Paul Bame <bame at parisc-linux.org>
  *    Copyright (C) 2001 Thomas Bogendoerfer <tsbogend at parisc-linux.org>
+ *    Copyright (C) 1999-2014 Helge Deller <deller@gmx.de>
  *
  *
  *    This program is free software; you can redistribute it and/or modify
@@ -23,6 +24,7 @@
  */
 
 #include <asm/uaccess.h>
+#include <asm/elf.h>
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/linkage.h>
@@ -32,78 +34,230 @@
 #include <linux/syscalls.h>
 #include <linux/utsname.h>
 #include <linux/personality.h>
+#include <linux/random.h>
 
-static unsigned long get_unshared_area(unsigned long addr, unsigned long len)
+/* we construct an artificial offset for the mapping based on the physical
+ * address of the kernel mapping variable */
+#define GET_LAST_MMAP(filp)             \
+        (filp ? ((unsigned long) filp->f_mapping) >> 8 : 0UL)
+#define SET_LAST_MMAP(filp, val)        \
+         { /* nothing */ }
+
+static int get_offset(unsigned int last_mmap)
 {
-        struct vm_unmapped_area_info info;
+        return (last_mmap & (SHMLBA-1)) >> PAGE_SHIFT;
+}
 
-        info.flags = 0;
-        info.length = len;
-        info.low_limit = PAGE_ALIGN(addr);
-        info.high_limit = TASK_SIZE;
-        info.align_mask = 0;
-        info.align_offset = 0;
-        return vm_unmapped_area(&info);
+static unsigned long shared_align_offset(unsigned int last_mmap,
+                                         unsigned long pgoff)
+{
+        return (get_offset(last_mmap) + pgoff) << PAGE_SHIFT;
 }
 
-/*
- * We need to know the offset to use.  Old scheme was to look for
- * existing mapping and use the same offset.  New scheme is to use the
- * address of the kernel data structure as the seed for the offset.
- * We'll see how that works...
- *
- * The mapping is cacheline aligned, so there's no information in the bottom
- * few bits of the address.  We're looking for 10 bits (4MB / 4k), so let's
- * drop the bottom 8 bits and use bits 8-17.  
- */
-static int get_offset(struct address_space *mapping)
+static inline unsigned long COLOR_ALIGN(unsigned long addr,
+                         unsigned int last_mmap, unsigned long pgoff)
 {
-        return (unsigned long) mapping >> 8;
+        unsigned long base = (addr+SHMLBA-1) & ~(SHMLBA-1);
+        unsigned long off  = (SHMLBA-1) &
+                (shared_align_offset(last_mmap, pgoff) << PAGE_SHIFT);
+
+        return base + off;