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authorDave Hansen <dave.hansen@linux.intel.com>2015-06-07 11:37:04 -0700
committerIngo Molnar <mingo@kernel.org>2015-06-09 12:24:33 +0200
commit54587653904c552c56b9dec153d7a89063394b09 (patch)
tree4de02a9b75978d004e1dd800c1d37be6f3d5c499 /arch/x86/mm
parenta1149fc83a1f97612e72ec24a0bdbabff7b85e77 (diff)
x86/mpx: Introduce new 'directory entry' to 'addr' helper function
Currently, to get from a bounds directory entry to the virtual address of a bounds table, we simply mask off a few low bits. However, the set of bits we mask off is different for 32-bit and 64-bit binaries. This breaks the operation out in to a helper function and also adds a temporary variable to store the result until we are sure we are returning one. Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dave Hansen <dave@sr71.net> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20150607183704.007686CE@viggo.jf.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/mpx.c41
1 files changed, 34 insertions, 7 deletions
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 4f7fb7c233cc..8cc793479039 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -576,29 +576,55 @@ static int mpx_resolve_fault(long __user *addr, int write)
return 0;
}
+static unsigned long mpx_bd_entry_to_bt_addr(struct mm_struct *mm,
+ unsigned long bd_entry)
+{
+ unsigned long bt_addr = bd_entry;
+ int align_to_bytes;
+ /*
+ * Bit 0 in a bt_entry is always the valid bit.
+ */
+ bt_addr &= ~MPX_BD_ENTRY_VALID_FLAG;
+ /*
+ * Tables are naturally aligned at 8-byte boundaries
+ * on 64-bit and 4-byte boundaries on 32-bit. The
+ * documentation makes it appear that the low bits
+ * are ignored by the hardware, so we do the same.
+ */
+ if (is_64bit_mm(mm))
+ align_to_bytes = 8;
+ else
+ align_to_bytes = 4;
+ bt_addr &= ~(align_to_bytes-1);
+ return bt_addr;
+}
+
/*
* Get the base of bounds tables pointed by specific bounds
* directory entry.
*/
static int get_bt_addr(struct mm_struct *mm,
- long __user *bd_entry, unsigned long *bt_addr)
+ long __user *bd_entry_ptr,
+ unsigned long *bt_addr_result)
{
int ret;
int valid_bit;
+ unsigned long bd_entry;
+ unsigned long bt_addr;
- if (!access_ok(VERIFY_READ, (bd_entry), sizeof(*bd_entry)))
+ if (!access_ok(VERIFY_READ, (bd_entry_ptr), sizeof(*bd_entry_ptr)))
return -EFAULT;
while (1) {
int need_write = 0;
pagefault_disable();
- ret = get_user(*bt_addr, bd_entry);
+ ret = get_user(bd_entry, bd_entry_ptr);
pagefault_enable();
if (!ret)
break;
if (ret == -EFAULT)
- ret = mpx_resolve_fault(bd_entry, need_write);
+ ret = mpx_resolve_fault(bd_entry_ptr, need_write);
/*
* If we could not resolve the fault, consider it
* userspace's fault and error out.
@@ -607,8 +633,8 @@ static int get_bt_addr(struct mm_struct *mm,
return ret;
}
- valid_bit = *bt_addr & MPX_BD_ENTRY_VALID_FLAG;
- *bt_addr &= MPX_BT_ADDR_MASK;
+ valid_bit = bd_entry & MPX_BD_ENTRY_VALID_FLAG;
+ bt_addr = mpx_bd_entry_to_bt_addr(mm, bd_entry);
/*
* When the kernel is managing bounds tables, a bounds directory
@@ -617,7 +643,7 @@ static int get_bt_addr(struct mm_struct *mm,
* data in the address field, we know something is wrong. This
* -EINVAL return will cause a SIGSEGV.
*/
- if (!valid_bit && *bt_addr)
+ if (!valid_bit && bt_addr)
return -EINVAL;
/*
* Do we have an completely zeroed bt entry? That is OK. It
@@ -628,6 +654,7 @@ static int get_bt_addr(struct mm_struct *mm,
if (!valid_bit)
return -ENOENT;
+ *bt_addr_result = bt_addr;
return 0;
}