x86/mpx: Remove MPX APIs

MPX is being removed from the kernel due to a lack of support in the
toolchain going forward (gcc).

The first step is to remove the userspace-visible ABIs so that applications
will stop using it.  The most visible one are the enable/disable prctl()s.
Remove them first.

This is the most minimal and least invasive change needed to ensure that
apps stop using MPX with new kernels.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190705175321.DB42F0AD@viggo.jf.intel.com

diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 094bb03..961e0a4 100644 (file)
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -181,7 +181,7 @@ struct prctl_mm_map {
 #define PR_GET_THP_DISABLE     42
 
 /*
- * Tell the kernel to start/stop helping userspace manage bounds tables.
+ * No longer implemented, but left here to ensure the numbers stay reserved:
  */
 #define PR_MPX_ENABLE_MANAGEMENT  43
 #define PR_MPX_DISABLE_MANAGEMENT 44

diff --git a/kernel/sys.c b/kernel/sys.c
index 2969304..384b000 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -103,12 +103,6 @@
 #ifndef SET_TSC_CTL
 # define SET_TSC_CTL(a)                (-EINVAL)
 #endif
-#ifndef MPX_ENABLE_MANAGEMENT
-# define MPX_ENABLE_MANAGEMENT()       (-EINVAL)
-#endif
-#ifndef MPX_DISABLE_MANAGEMENT
-# define MPX_DISABLE_MANAGEMENT()      (-EINVAL)
-#endif
 #ifndef GET_FP_MODE
 # define GET_FP_MODE(a)                (-EINVAL)
 #endif
@@ -2456,15 +2450,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
                up_write(&me->mm->mmap_sem);
                break;
        case PR_MPX_ENABLE_MANAGEMENT:
-               if (arg2 || arg3 || arg4 || arg5)
-                       return -EINVAL;
-               error = MPX_ENABLE_MANAGEMENT();
-               break;
        case PR_MPX_DISABLE_MANAGEMENT:
-               if (arg2 || arg3 || arg4 || arg5)
-                       return -EINVAL;
-               error = MPX_DISABLE_MANAGEMENT();
-               break;
+               /* No longer implemented: */
+               return -EINVAL;
        case PR_SET_FP_MODE:
                error = SET_FP_MODE(me, arg2);
                break;