Messages in this thread Patch in this message | | | Subject | [PATCH 13/17] x86, mpx: Add temporary variable to reduce masking | From | Dave Hansen <> | Date | Fri, 27 Mar 2015 14:53:12 -0700 |
| |
From: Dave Hansen <dave.hansen@linux.intel.com>
When we allocate a bounds table, we call mmap(), then add a "valid" bit to the value before storing it in to the bounds directory.
If we fail along the way, we go and mask that valid bit _back_ out. That seems a little silly, and this makes it much more clear when we have a plain address versus an actual table _entry_.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> ---
b/arch/x86/mm/mpx.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff -puN arch/x86/mm/mpx.c~mpx-remove-unnecessary-masking arch/x86/mm/mpx.c --- a/arch/x86/mm/mpx.c~mpx-remove-unnecessary-masking 2015-03-27 14:35:08.801943837 -0700 +++ b/arch/x86/mm/mpx.c 2015-03-27 14:35:08.804943972 -0700 @@ -431,6 +431,7 @@ static int allocate_bt(long __user *bd_e unsigned long expected_old_val = 0; unsigned long actual_old_val = 0; unsigned long bt_addr; + unsigned long bd_new_entry; int ret = 0; /* @@ -443,7 +444,7 @@ static int allocate_bt(long __user *bd_e /* * Set the valid flag (kinda like _PAGE_PRESENT in a pte) */ - bt_addr = bt_addr | MPX_BD_ENTRY_VALID_FLAG; + bd_new_entry = bt_addr | MPX_BD_ENTRY_VALID_FLAG; /* * Go poke the address of the new bounds table in to the @@ -457,7 +458,7 @@ static int allocate_bt(long __user *bd_e * of the MPX code that have to pagefault_disable(). */ ret = user_atomic_cmpxchg_inatomic(&actual_old_val, bd_entry, - expected_old_val, bt_addr); + expected_old_val, bd_new_entry); if (ret) goto out_unmap; @@ -488,7 +489,7 @@ static int allocate_bt(long __user *bd_e trace_mpx_new_bounds_table(bt_addr); return 0; out_unmap: - vm_munmap(bt_addr & MPX_BT_ADDR_MASK, MPX_BT_SIZE_BYTES); + vm_munmap(bt_addr, MPX_BT_SIZE_BYTES); return ret; } _
| |