1 files changed, 61 insertions, 43 deletions

diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
index 50dc802a1c46..16ccbd77917f 100644
--- a/arch/x86/mm/kmmio.c
+++ b/arch/x86/mm/kmmio.c
@@ -32,7 +32,7 @@ struct kmmio_fault_page {
         struct list_head list;
         struct kmmio_fault_page *release_next;
         unsigned long page; /* location of the fault page */
-        bool old_presence; /* page presence prior to arming */
+        pteval_t old_presence; /* page presence prior to arming */
         bool armed;
 
         /*
@@ -97,60 +97,62 @@ static struct kmmio_probe *get_kmmio_probe(unsigned long addr)
 static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long page)
 {
         struct list_head *head;
-        struct kmmio_fault_page *p;
+        struct kmmio_fault_page *f;
 
         page &= PAGE_MASK;
         head = kmmio_page_list(page);
-        list_for_each_entry_rcu(p, head, list) {
-                if (p->page == page)
-                        return p;
+        list_for_each_entry_rcu(f, head, list) {
+                if (f->page == page)
+                        return f;
         }
         return NULL;
 }
 
-static void set_pmd_presence(pmd_t *pmd, bool present, bool *old)
+static void clear_pmd_presence(pmd_t *pmd, bool clear, pmdval_t *old)
 {
         pmdval_t v = pmd_val(*pmd);
-        *old = !!(v & _PAGE_PRESENT);
-        v &= ~_PAGE_PRESENT;
-        if (present)
-                v |= _PAGE_PRESENT;
+        if (clear) {
+                *old = v & _PAGE_PRESENT;
+                v &= ~_PAGE_PRESENT;
+        } else  /* presume this has been called with clear==true previously */
+                v |= *old;
         set_pmd(pmd, __pmd(v));
 }
 
-static void set_pte_presence(pte_t *pte, bool present, bool *old)
+static void clear_pte_presence(pte_t *pte, bool clear, pteval_t *old)
 {
         pteval_t v = pte_val(*pte);
-        *old = !!(v & _PAGE_PRESENT);
-        v &= ~_PAGE_PRESENT;
-        if (present)
-                v |= _PAGE_PRESENT;
+        if (clear) {
+                *old = v & _PAGE_PRESENT;
+                v &= ~_PAGE_PRESENT;
+        } else  /* presume this has been called with clear==true previously */
+                v |= *old;
         set_pte_atomic(pte, __pte(v));
 }
 
-static int set_page_presence(unsigned long addr, bool present, bool *old)
+static int clear_page_presence(struct kmmio_fault_page *f, bool clear)
 {
         unsigned int level;
-        pte_t *pte = lookup_address(addr, &level);
+        pte_t *pte = lookup_address(f->page, &level);
 
         if (!pte) {
-                pr_err("kmmio: no pte for page 0x%08lx\n", addr);
+                pr_err("kmmio: no pte for page 0x%08lx\n", f->page);
                 return -1;
         }
 
         switch (level) {
         case PG_LEVEL_2M:
-                set_pmd_presence((pmd_t *)pte, present, old);
+                clear_pmd_presence((pmd_t *)pte, clear, &f->old_presence);
                 break;
         case PG_LEVEL_4K:
-                set_pte_presence(pte, present, old);
+                clear_pte_presence(pte, clear, &f->old_presence);
                 break;
         default:
                 pr_err("kmmio: unexpected page level 0x%x.\n", level);
                 return -1;
         }
 
-        __flush_tlb_one(addr);
+        __flush_tlb_one(f->page);
         return 0;
 }
 
@@ -171,9 +173,9 @@ static int arm_kmmio_fault_page(struct kmmio_fault_page *f)
         WARN_ONCE(f->armed, KERN_ERR "kmmio page already armed.\n");
         if (f->armed) {
                 pr_warning("kmmio double-arm: page 0x%08lx, ref %d, old %d\n",
-                                        f->page, f->count, f->old_presence);
+                                        f->page, f->count, !!f->old_presence);
         }
-        ret = set_page_presence(f->page, false, &f->old_presence);
+        ret = clear_page_presence(f, true);
         WARN_ONCE(ret < 0, KERN_ERR "kmmio arming 0x%08lx failed.\n", f->page);
         f->armed = true;
         return ret;
@@ -182,8 +184,7 @@ static int arm_kmmio_fault_page(struct kmmio_fault_page *f)
 /** Restore the given page to saved presence state. */
 static void disarm_kmmio_fault_page(struct kmmio_fault_page *f)
 {
-        bool tmp;
-        int ret = set_page_presence(f->page, f->old_presence, &tmp);
+        int ret = clear_page_presence(f, false);
         WARN_ONCE(ret < 0,
                         KERN_ERR "kmmio disarming 0x%08lx failed.\n", f->page);
         f->armed = false;
@@ -310,7 +311,12 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
         struct kmmio_context *ctx = &get_cpu_var(kmmio_ctx);
 
         if (!ctx->active) {
-                pr_debug("kmmio: spurious debug trap on CPU %d.\n",
+                /*
+                 * debug traps without an active context are due to either
+                 * something external causing them (f.e. using a debugger while
+                 * mmio tracing enabled), or erroneous behaviour
+                 */
+                pr_warning("kmmio: unexpected debug trap on CPU %d.\n",
                                                         smp_processor_id());
                 goto out;
         }
@@ -439,12 +445,12 @@ static void rcu_free_kmmio_fault_pages(struct rcu_head *head)
                                                 head,
                                                 struct kmmio_delayed_release,
                                                 rcu);
-        struct kmmio_fault_page *p = dr->release_list;
-        while (p) {
-                struct kmmio_fault_page *next = p->release_next;
-                BUG_ON(p->count);
-                kfree(p);
-                p = next;
+        struct kmmio_fault_page *f = dr->release_list;
+        while (f) {
+                struct kmmio_fault_page *next = f->release_next;
+                BUG_ON(f->count);
+                kfree(f);
+                f = next;
         }
         kfree(dr);
 }
@@ -453,19 +459,19 @@ static void remove_kmmio_fault_pages(struct rcu_head *head)
 {
         struct kmmio_delayed_release *dr =
                 container_of(head, struct kmmio_delayed_release, rcu);
-        struct kmmio_fault_page *p = dr->release_list;
+        struct kmmio_fault_page *f = dr->release_list;
         struct kmmio_fault_page **prevp = &dr->release_list;
         unsigned long flags;
 
         spin_lock_irqsave(&kmmio_lock, flags);
-        while (p) {
-                if (!p->count) {
-                        list_del_rcu(&p->list);
-                        prevp = &p->release_next;
+        while (f) {
+                if (!f->count) {
+                        list_del_rcu(&f->list);
+                        prevp = &f->release_next;
                 } else {
-                        *prevp = p->release_next;
+                        *prevp = f->release_next;
                 }
-                p = p->release_next;
+                f = f->release_next;
         }
         spin_unlock_irqrestore(&kmmio_lock, flags);
 
@@ -528,8 +534,8 @@ void unregister_kmmio_probe(struct kmmio_probe *p)
 }
 EXPORT_SYMBOL(unregister_kmmio_probe);
 
-static int kmmio_die_notifier(struct notifier_block *nb, unsigned long val,
-                                                                void *args)
+static int
+kmmio_die_notifier(struct notifier_block *nb, unsigned long val, void *args)
 {
         struct die_args *arg = args;
 
@@ -544,11 +550,23 @@ static struct notifier_block nb_die = {
         .notifier_call = kmmio_die_notifier
 };
 
-static int __init init_kmmio(void)
+int kmmio_init(void)
 {
         int i;
+
         for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++)
                 INIT_LIST_HEAD(&kmmio_page_table[i]);
+
         return register_die_notifier(&nb_die);
 }
-fs_initcall(init_kmmio); /* should be before device_initcall() */
+
+void kmmio_cleanup(void)
+{
+        int i;
+
+        unregister_die_notifier(&nb_die);
+        for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++) {
+                WARN_ONCE(!list_empty(&kmmio_page_table[i]),
+                        KERN_ERR "kmmio_page_table not empty at cleanup, any further tracing will leak memory.\n");
+        }
+}