Merge branch 'x86/jumplabel' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 jumplabel changes from Peter Anvin:
 "One more x86 tree for this merge window.  This tree improves the
  handling of jump labels, so that most of the time we don't have to do
  a massive initial patching run.

  Furthermore, we will error out of the jump label is not what is
  expected, eg if it has been corrupted or tampered with"

* 'x86/jumplabel' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/jump-label: Show where and what was wrong on errors
  x86/jump-label: Add safety checks to jump label conversions
  x86/jump-label: Do not bother updating nops if they are correct
  x86/jump-label: Use best default nops for inital jump label calls

diff --combined arch/x86/kernel/jump_label.c
index 460f5d9,912a528..ee11b7d
--- 1/arch/x86/kernel/jump_label.c
--- 2/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@@ -24,32 -24,59 +24,71 @@@ union jump_code_union 
        } __attribute__((packed));
  };
  
+ static void bug_at(unsigned char *ip, int line)
+ {
+       /*
+        * The location is not an op that we were expecting.
+        * Something went wrong. Crash the box, as something could be
+        * corrupting the kernel.
+        */
+       pr_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n",
+              ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line);
+       BUG();
+ }
+ 
  static void __jump_label_transform(struct jump_entry *entry,
                                   enum jump_label_type type,
-                                  void *(*poker)(void *, const void *, size_t))
+                                  void *(*poker)(void *, const void *, size_t),
+                                  int init)
  {
        union jump_code_union code;
+       const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
  
        if (type == JUMP_LABEL_ENABLE) {
+               /*
+                * We are enabling this jump label. If it is not a nop
+                * then something must have gone wrong.
+                */
+               if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0))
+                       bug_at((void *)entry->code, __LINE__);
+ 
                code.jump = 0xe9;
                code.offset = entry->target -
                                (entry->code + JUMP_LABEL_NOP_SIZE);
-       } else
+       } else {
+               /*
+                * We are disabling this jump label. If it is not what
+                * we think it is, then something must have gone wrong.
+                * If this is the first initialization call, then we
+                * are converting the default nop to the ideal nop.
+                */
+               if (init) {
+                       const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
+                       if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
+                               bug_at((void *)entry->code, __LINE__);
+               } else {
+                       code.jump = 0xe9;
+                       code.offset = entry->target -
+                               (entry->code + JUMP_LABEL_NOP_SIZE);
+                       if (unlikely(memcmp((void *)entry->code, &code, 5) != 0))
+                               bug_at((void *)entry->code, __LINE__);
+               }
                memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
+       }
  
 -      (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
 +      /*
 +       * Make text_poke_bp() a default fallback poker.
 +       *
 +       * At the time the change is being done, just ignore whether we
 +       * are doing nop -> jump or jump -> nop transition, and assume
 +       * always nop being the 'currently valid' instruction
 +       *
 +       */
 +      if (poker)
 +              (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
 +      else
 +              text_poke_bp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE,
 +                           (void *)entry->code + JUMP_LABEL_NOP_SIZE);
  }
  
  void arch_jump_label_transform(struct jump_entry *entry,
@@@ -57,15 -84,38 +96,38 @@@
  {
        get_online_cpus();
        mutex_lock(&text_mutex);
-       __jump_label_transform(entry, type, NULL);
 -      __jump_label_transform(entry, type, text_poke_smp, 0);
++      __jump_label_transform(entry, type, NULL, 0);
        mutex_unlock(&text_mutex);
        put_online_cpus();
  }
  
+ static enum {
+       JL_STATE_START,
+       JL_STATE_NO_UPDATE,
+       JL_STATE_UPDATE,
+ } jlstate __initdata_or_module = JL_STATE_START;
+ 
  __init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
                                      enum jump_label_type type)
  {
-       __jump_label_transform(entry, type, text_poke_early);
+       /*
+        * This function is called at boot up and when modules are
+        * first loaded. Check if the default nop, the one that is
+        * inserted at compile time, is the ideal nop. If it is, then
+        * we do not need to update the nop, and we can leave it as is.
+        * If it is not, then we need to update the nop to the ideal nop.
+        */
+       if (jlstate == JL_STATE_START) {
+               const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
+               const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
+ 
+               if (memcmp(ideal_nop, default_nop, 5) != 0)
+                       jlstate = JL_STATE_UPDATE;
+               else
+                       jlstate = JL_STATE_NO_UPDATE;
+       }
+       if (jlstate == JL_STATE_UPDATE)
+               __jump_label_transform(entry, type, text_poke_early, 1);
  }
  
  #endif