Pull asus into test branch

[mv-sheeva.git] / arch / um / sys-i386 / tls.c

diff --git a/arch/um/sys-i386/tls.c b/arch/um/sys-i386/tls.c
index e3c5bc593faea2a7dd85f4f8211acec68ef761fd..643dab58572739d2b1f36f5c4ef32e6e0c1ebcc2 100644 (file)
--- a/arch/um/sys-i386/tls.c
+++ b/arch/um/sys-i386/tls.c
@@ -3,7 +3,6 @@
  * Licensed under the GPL
  */
 
-#include "linux/config.h"
 #include "linux/kernel.h"
 #include "linux/sched.h"
 #include "linux/slab.h"
@@ -24,6 +23,10 @@
 #include "skas.h"
 #endif
 
+/* If needed we can detect when it's uninitialized. */
+static int host_supports_tls = -1;
+int host_gdt_entry_tls_min = -1;
+
 #ifdef CONFIG_MODE_SKAS
 int do_set_thread_area_skas(struct user_desc *info)
 {
@@ -70,8 +73,6 @@ static int get_free_idx(struct task_struct* task)
        return -ESRCH;
 }
 
-#define O_FORCE 1
-
 static inline void clear_user_desc(struct user_desc* info)
 {
        /* Postcondition: LDT_empty(info) returns true. */
@@ -84,6 +85,8 @@ static inline void clear_user_desc(struct user_desc* info)
        info->seg_not_present = 1;
 }
 
+#define O_FORCE 1
+
 static int load_TLS(int flags, struct task_struct *to)
 {
        int ret = 0;
@@ -157,16 +160,34 @@ void clear_flushed_tls(struct task_struct *task)
        }
 }
 
-/* This in SKAS0 does not need to be used, since we have different host
- * processes. Nor will this need to be used when we'll add support to the host
+/* In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
+ * common host process. So this is needed in SKAS0 too.
+ *
+ * However, if each thread had a different host process (and this was discussed
+ * for SMP support) this won't be needed.
+ *
+ * And this will not need be used when (and if) we'll add support to the host
  * SKAS patch. */
+
 int arch_switch_tls_skas(struct task_struct *from, struct task_struct *to)
 {
-       return load_TLS(O_FORCE, to);
+       if (!host_supports_tls)
+               return 0;
+
+       /* We have no need whatsoever to switch TLS for kernel threads; beyond
+        * that, that would also result in us calling os_set_thread_area with
+        * userspace_pid[cpu] == 0, which gives an error. */
+       if (likely(to->mm))
+               return load_TLS(O_FORCE, to);
+
+       return 0;
 }
 
 int arch_switch_tls_tt(struct task_struct *from, struct task_struct *to)
 {
+       if (!host_supports_tls)
+               return 0;
+
        if (needs_TLS_update(to))
                return load_TLS(0, to);
 
@@ -250,6 +271,9 @@ asmlinkage int sys_set_thread_area(struct user_desc __user *user_desc)
        struct user_desc info;
        int idx, ret;
 
+       if (!host_supports_tls)
+               return -ENOSYS;
+
        if (copy_from_user(&info, user_desc, sizeof(info)))
                return -EFAULT;
 
@@ -281,6 +305,9 @@ int ptrace_set_thread_area(struct task_struct *child, int idx,
 {
        struct user_desc info;
 
+       if (!host_supports_tls)
+               return -EIO;
+
        if (copy_from_user(&info, user_desc, sizeof(info)))
                return -EFAULT;
 
@@ -292,6 +319,9 @@ asmlinkage int sys_get_thread_area(struct user_desc __user *user_desc)
        struct user_desc info;
        int idx, ret;
 
+       if (!host_supports_tls)
+               return -ENOSYS;
+
        if (get_user(idx, &user_desc->entry_number))
                return -EFAULT;
 
@@ -315,6 +345,9 @@ int ptrace_get_thread_area(struct task_struct *child, int idx,
        struct user_desc info;
        int ret;
 
+       if (!host_supports_tls)
+               return -EIO;
+
        ret = get_tls_entry(child, &info, idx);
        if (ret < 0)
                goto out;
@@ -324,3 +357,27 @@ int ptrace_get_thread_area(struct task_struct *child, int idx,
 out:
        return ret;
 }
+
+
+/* XXX: This part is probably common to i386 and x86-64. Don't create a common
+ * file for now, do that when implementing x86-64 support.*/
+static int __init __setup_host_supports_tls(void) {
+       check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
+       if (host_supports_tls) {
+               printk(KERN_INFO "Host TLS support detected\n");
+               printk(KERN_INFO "Detected host type: ");
+               switch (host_gdt_entry_tls_min) {
+                       case GDT_ENTRY_TLS_MIN_I386:
+                               printk("i386\n");
+                               break;
+                       case GDT_ENTRY_TLS_MIN_X86_64:
+                               printk("x86_64\n");
+                               break;
+               }
+       } else
+               printk(KERN_ERR "  Host TLS support NOT detected! "
+                               "TLS support inside UML will not work\n");
+       return 0;
+}
+
+__initcall(__setup_host_supports_tls);