x86/mm: Add task_size parameter to mmap_base()
To correctly handle 32-bit and 64-bit mmap() syscalls in 64bit applications
its required to have separate address bases to place a mapping.
The tasksize can be used as an indicator to select the proper parameters
for mmap_base().
This requires the following changes:
- Add task_size argument to mmap_base() and make the calculation based on it.
- Provide mmap_legacy_base() as a seperate function
- Use the new functions in arch_pick_mmap_layout()
[ tglx: Massaged changelog ]
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: 0x7f454c46@gmail.com
Cc: linux-mm@kvack.org
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Link: http://lkml.kernel.org/r/20170306141721.9188-3-dsafonov@virtuozzo.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index f31ed70..1e9cb94 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -36,25 +36,23 @@ struct va_alignment __read_mostly va_align = {
.flags = -1,
};
-static unsigned long stack_maxrandom_size(void)
+static inline unsigned long tasksize_32bit(void)
+{
+ return IA32_PAGE_OFFSET;
+}
+
+static unsigned long stack_maxrandom_size(unsigned long task_size)
{
unsigned long max = 0;
if ((current->flags & PF_RANDOMIZE) &&
!(current->personality & ADDR_NO_RANDOMIZE)) {
- max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT;
+ max = (-1UL) & __STACK_RND_MASK(task_size == tasksize_32bit());
+ max <<= PAGE_SHIFT;
}
return max;
}
-/*
- * Top of mmap area (just below the process stack).
- *
- * Leave an at least ~128 MB hole with possible stack randomization.
- */
-#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
-#define MAX_GAP (TASK_SIZE/6*5)
-
#ifdef CONFIG_COMPAT
# define mmap32_rnd_bits mmap_rnd_compat_bits
# define mmap64_rnd_bits mmap_rnd_bits
@@ -63,6 +61,8 @@ static unsigned long stack_maxrandom_size(void)
# define mmap64_rnd_bits mmap_rnd_bits
#endif
+#define SIZE_128M (128 * 1024 * 1024UL)
+
static int mmap_is_legacy(void)
{
if (current->personality & ADDR_COMPAT_LAYOUT)
@@ -84,16 +84,30 @@ unsigned long arch_mmap_rnd(void)
return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
}
-static unsigned long mmap_base(unsigned long rnd)
+static unsigned long mmap_base(unsigned long rnd, unsigned long task_size)
{
unsigned long gap = rlimit(RLIMIT_STACK);
+ unsigned long gap_min, gap_max;
- if (gap < MIN_GAP)
- gap = MIN_GAP;
- else if (gap > MAX_GAP)
- gap = MAX_GAP;
+ /*
+ * Top of mmap area (just below the process stack).
+ * Leave an at least ~128 MB hole with possible stack randomization.
+ */
+ gap_min = SIZE_128M + stack_maxrandom_size(task_size);
+ gap_max = (task_size / 6) * 5;
- return PAGE_ALIGN(TASK_SIZE - gap - rnd);
+ if (gap < gap_min)
+ gap = gap_min;
+ else if (gap > gap_max)
+ gap = gap_max;
+
+ return PAGE_ALIGN(task_size - gap - rnd);
+}
+
+static unsigned long mmap_legacy_base(unsigned long rnd,
+ unsigned long task_size)
+{
+ return __TASK_UNMAPPED_BASE(task_size) + rnd;
}
/*
@@ -107,13 +121,13 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
if (current->flags & PF_RANDOMIZE)
random_factor = arch_mmap_rnd();
- mm->mmap_legacy_base = TASK_UNMAPPED_BASE + random_factor;
+ mm->mmap_legacy_base = mmap_legacy_base(random_factor, TASK_SIZE);
if (mmap_is_legacy()) {
mm->mmap_base = mm->mmap_legacy_base;
mm->get_unmapped_area = arch_get_unmapped_area;
} else {
- mm->mmap_base = mmap_base(random_factor);
+ mm->mmap_base = mmap_base(random_factor, TASK_SIZE);
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
}
}