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authorDave Hansen <dave.hansen@linux.intel.com>2015-06-07 11:37:01 -0700
committerIngo Molnar <mingo@kernel.org>2015-06-09 12:24:30 +0200
commita84eeaa96b36a03188e1423349669c108d3a4bd7 (patch)
tree13f38f8a3859b26458b21cce4cf5ee22851313fb /arch/x86/mm
parent04cd027bcba1ead7bfe39e7f1c6f4d993c4c3323 (diff)
x86/mpx: Use the new get_xsave_field_ptr()API
The MPX registers (bndcsr/bndcfgu/bndstatus) are not directly accessible via normal instructions. They essentially act as if they were floating point registers and are saved/restored along with those registers. There are two main paths in the MPX code where we care about the contents of these registers: 1. #BR (bounds) faults 2. the prctl() code where we are setting MPX up Both of those paths _might_ be called without the FPU having been used. That means that 'tsk->thread.fpu.state' might never be allocated. Also, fpu_save_init() is not preempt-safe. It was a bug to call it without disabling preemption. The new get_xsave_addr() calls unlazy_fpu() instead and properly disables preemption. 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: Andy Lutomirski <luto@amacapital.net> Cc: Dave Hansen <dave@sr71.net> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Suresh Siddha <sbsiddha@gmail.com> Cc: bp@alien8.de Link: http://lkml.kernel.org/r/20150607183701.BC0D37CF@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.c30
1 files changed, 15 insertions, 15 deletions
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 2e0dfd39bd22..9d67e230b4fb 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -272,9 +272,9 @@ bad_opcode:
* The caller is expected to kfree() the returned siginfo_t.
*/
siginfo_t *mpx_generate_siginfo(struct pt_regs *regs,
- struct xregs_state *xsave_buf)
+ struct task_struct *tsk)
{
- struct bndreg *bndregs, *bndreg;
+ const struct bndreg *bndregs, *bndreg;
siginfo_t *info = NULL;
struct insn insn;
uint8_t bndregno;
@@ -294,8 +294,8 @@ siginfo_t *mpx_generate_siginfo(struct pt_regs *regs,
err = -EINVAL;
goto err_out;
}
- /* get the bndregs _area_ of the xsave structure */
- bndregs = get_xsave_addr(xsave_buf, XSTATE_BNDREGS);
+ /* get bndregs field from current task's xsave area */
+ bndregs = get_xsave_field_ptr(XSTATE_BNDREGS);
if (!bndregs) {
err = -EINVAL;
goto err_out;
@@ -342,7 +342,7 @@ err_out:
static __user void *task_get_bounds_dir(struct task_struct *tsk)
{
- struct bndcsr *bndcsr;
+ const struct bndcsr *bndcsr;
if (!cpu_feature_enabled(X86_FEATURE_MPX))
return MPX_INVALID_BOUNDS_DIR;
@@ -357,8 +357,7 @@ static __user void *task_get_bounds_dir(struct task_struct *tsk)
* The bounds directory pointer is stored in a register
* only accessible if we first do an xsave.
*/
- copy_fpregs_to_fpstate(&tsk->thread.fpu);
- bndcsr = get_xsave_addr(&tsk->thread.fpu.state.xsave, XSTATE_BNDCSR);
+ bndcsr = get_xsave_field_ptr(XSTATE_BNDCSR);
if (!bndcsr)
return MPX_INVALID_BOUNDS_DIR;
@@ -389,9 +388,10 @@ int mpx_enable_management(struct task_struct *tsk)
* directory into XSAVE/XRSTOR Save Area and enable MPX through
* XRSTOR instruction.
*
- * copy_xregs_to_kernel() is expected to be very expensive. Storing the bounds
- * directory here means that we do not have to do xsave in the unmap
- * path; we can just use mm->bd_addr instead.
+ * The copy_xregs_to_kernel() beneath get_xsave_field_ptr() is
+ * expected to be relatively expensive. Storing the bounds
+ * directory here means that we do not have to do xsave in the
+ * unmap path; we can just use mm->bd_addr instead.
*/
bd_base = task_get_bounds_dir(tsk);
down_write(&mm->mmap_sem);
@@ -497,12 +497,12 @@ out_unmap:
* bound table is 16KB. With 64-bit mode, the size of BD is 2GB,
* and the size of each bound table is 4MB.
*/
-static int do_mpx_bt_fault(struct xregs_state *xsave_buf)
+static int do_mpx_bt_fault(struct task_struct *tsk)
{
unsigned long bd_entry, bd_base;
- struct bndcsr *bndcsr;
+ const struct bndcsr *bndcsr;
- bndcsr = get_xsave_addr(xsave_buf, XSTATE_BNDCSR);
+ bndcsr = get_xsave_field_ptr(XSTATE_BNDCSR);
if (!bndcsr)
return -EINVAL;
/*
@@ -525,7 +525,7 @@ static int do_mpx_bt_fault(struct xregs_state *xsave_buf)
return allocate_bt((long __user *)bd_entry);
}
-int mpx_handle_bd_fault(struct xregs_state *xsave_buf)
+int mpx_handle_bd_fault(struct task_struct *tsk)
{
/*
* Userspace never asked us to manage the bounds tables,
@@ -534,7 +534,7 @@ int mpx_handle_bd_fault(struct xregs_state *xsave_buf)
if (!kernel_managing_mpx_tables(current->mm))
return -EINVAL;
- if (do_mpx_bt_fault(xsave_buf)) {
+ if (do_mpx_bt_fault(tsk)) {
force_sig(SIGSEGV, current);
/*
* The force_sig() is essentially "handling" this