s390: avoid cache aliasing under z/VM and KVM
commit 1f6b83e5e4d3 ("s390: avoid z13 cache aliasing") checks for the
machine type to optimize address space randomization and zero page
allocation to avoid cache aliases.
This check might fail under a hypervisor with migration support.
z/VMs "Single System Image and Live Guest Relocation" facility will
"fake" the machine type of the oldest system in the group. For example
in a group of zEC12 and Z13 the guest appears to run on a zEC12
(architecture fencing within the relocation domain)
Remove the machine type detection and always use cache aliasing
rules that are known to work for all machines. These are the z13
aliasing rules.
Suggested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 6e552af..ea01477 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -31,9 +31,6 @@
#include <linux/security.h>
#include <asm/pgalloc.h>
-unsigned long mmap_rnd_mask;
-static unsigned long mmap_align_mask;
-
static unsigned long stack_maxrandom_size(void)
{
if (!(current->flags & PF_RANDOMIZE))
@@ -62,10 +59,7 @@
unsigned long arch_mmap_rnd(void)
{
- if (is_32bit_task())
- return (get_random_int() & 0x7ff) << PAGE_SHIFT;
- else
- return (get_random_int() & mmap_rnd_mask) << PAGE_SHIFT;
+ return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
}
static unsigned long mmap_base_legacy(unsigned long rnd)
@@ -92,7 +86,6 @@
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
struct vm_unmapped_area_info info;
- int do_color_align;
if (len > TASK_SIZE - mmap_min_addr)
return -ENOMEM;
@@ -108,15 +101,14 @@
return addr;
}
- do_color_align = 0;
- if (filp || (flags & MAP_SHARED))
- do_color_align = !is_32bit_task();
-
info.flags = 0;
info.length = len;
info.low_limit = mm->mmap_base;
info.high_limit = TASK_SIZE;
- info.align_mask = do_color_align ? (mmap_align_mask << PAGE_SHIFT) : 0;
+ if (filp || (flags & MAP_SHARED))
+ info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
+ else
+ info.align_mask = 0;
info.align_offset = pgoff << PAGE_SHIFT;
return vm_unmapped_area(&info);
}
@@ -130,7 +122,6 @@
struct mm_struct *mm = current->mm;
unsigned long addr = addr0;
struct vm_unmapped_area_info info;
- int do_color_align;
/* requested length too big for entire address space */
if (len > TASK_SIZE - mmap_min_addr)
@@ -148,15 +139,14 @@
return addr;
}
- do_color_align = 0;
- if (filp || (flags & MAP_SHARED))
- do_color_align = !is_32bit_task();
-
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.length = len;
info.low_limit = max(PAGE_SIZE, mmap_min_addr);
info.high_limit = mm->mmap_base;
- info.align_mask = do_color_align ? (mmap_align_mask << PAGE_SHIFT) : 0;
+ if (filp || (flags & MAP_SHARED))
+ info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
+ else
+ info.align_mask = 0;
info.align_offset = pgoff << PAGE_SHIFT;
addr = vm_unmapped_area(&info);
@@ -254,35 +244,3 @@
mm->get_unmapped_area = s390_get_unmapped_area_topdown;
}
}
-
-static int __init setup_mmap_rnd(void)
-{
- struct cpuid cpu_id;
-
- get_cpu_id(&cpu_id);
- switch (cpu_id.machine) {
- case 0x9672:
- case 0x2064:
- case 0x2066:
- case 0x2084:
- case 0x2086:
- case 0x2094:
- case 0x2096:
- case 0x2097:
- case 0x2098:
- case 0x2817:
- case 0x2818:
- case 0x2827:
- case 0x2828:
- mmap_rnd_mask = 0x7ffUL;
- mmap_align_mask = 0UL;
- break;
- case 0x2964: /* z13 */
- default:
- mmap_rnd_mask = 0x3ff80UL;
- mmap_align_mask = 0x7fUL;
- break;
- }
- return 0;
-}
-early_initcall(setup_mmap_rnd);