7 files changed, 467 insertions, 61 deletions

diff --git a/arch/um/sys-i386/Makefile b/arch/um/sys-i386/Makefile
index f5fd5b0156d0..98b20b7bba4f 100644
--- a/arch/um/sys-i386/Makefile
+++ b/arch/um/sys-i386/Makefile
@@ -1,23 +1,18 @@
-obj-y := bitops.o bugs.o checksum.o delay.o fault.o ksyms.o ldt.o ptrace.o \
-        ptrace_user.o semaphore.o signal.o sigcontext.o syscalls.o sysrq.o \
-        sys_call_table.o
+obj-y = bugs.o checksum.o delay.o fault.o ksyms.o ldt.o ptrace.o \
+        ptrace_user.o signal.o sigcontext.o syscalls.o sysrq.o \
+        sys_call_table.o tls.o
 
 obj-$(CONFIG_MODE_SKAS) += stub.o stub_segv.o
 
-obj-$(CONFIG_HIGHMEM) += highmem.o
-obj-$(CONFIG_MODULES) += module.o
+subarch-obj-y = lib/bitops.o kernel/semaphore.o
+subarch-obj-$(CONFIG_HIGHMEM) += mm/highmem.o
+subarch-obj-$(CONFIG_MODULES) += kernel/module.o
 
 USER_OBJS := bugs.o ptrace_user.o sigcontext.o fault.o stub_segv.o
 
-SYMLINKS = bitops.c semaphore.c highmem.c module.c
-
 include arch/um/scripts/Makefile.rules
 
-bitops.c-dir = lib
-semaphore.c-dir = kernel
-highmem.c-dir = mm
-module.c-dir = kernel
-
-$(obj)/stub_segv.o : _c_flags = $(call unprofile,$(CFLAGS))
+extra-$(CONFIG_MODE_TT) += unmap.o
 
-include arch/um/scripts/Makefile.unmap
+$(obj)/stub_segv.o $(obj)/unmap.o: \
+        _c_flags = $(call unprofile,$(CFLAGS))
diff --git a/arch/um/sys-i386/ptrace.c b/arch/um/sys-i386/ptrace.c
index 8032a105949a..6028bc7cc01b 100644
--- a/arch/um/sys-i386/ptrace.c
+++ b/arch/um/sys-i386/ptrace.c
@@ -15,9 +15,22 @@
 #include "sysdep/sigcontext.h"
 #include "sysdep/sc.h"
 
-void arch_switch(void)
+void arch_switch_to_tt(struct task_struct *from, struct task_struct *to)
 {
-        update_debugregs(current->thread.arch.debugregs_seq);
+        update_debugregs(to->thread.arch.debugregs_seq);
+        arch_switch_tls_tt(from, to);
+}
+
+void arch_switch_to_skas(struct task_struct *from, struct task_struct *to)
+{
+        int err = arch_switch_tls_skas(from, to);
+        if (!err)
+                return;
+
+        if (err != -EINVAL)
+                printk(KERN_WARNING "arch_switch_tls_skas failed, errno %d, not EINVAL\n", -err);
+        else
+                printk(KERN_WARNING "arch_switch_tls_skas failed, errno = EINVAL\n");
 }
 
 int is_syscall(unsigned long addr)
@@ -124,22 +137,22 @@ unsigned long getreg(struct task_struct *child, int regno)
 int peek_user(struct task_struct *child, long addr, long data)
 {
 /* read the word at location addr in the USER area. */
-        unsigned long tmp;
+        unsigned long tmp;
 
-        if ((addr & 3) || addr < 0)
-                return -EIO;
+        if ((addr & 3) || addr < 0)
+                return -EIO;
 
-        tmp = 0;  /* Default return condition */
-        if(addr < MAX_REG_OFFSET){
-                tmp = getreg(child, addr);
-        }
-        else if((addr >= offsetof(struct user, u_debugreg[0])) &&
-                (addr <= offsetof(struct user, u_debugreg[7]))){
-                addr -= offsetof(struct user, u_debugreg[0]);
-                addr = addr >> 2;
-                tmp = child->thread.arch.debugregs[addr];
-        }
-        return put_user(tmp, (unsigned long *) data);
+        tmp = 0;  /* Default return condition */
+        if(addr < MAX_REG_OFFSET){
+                tmp = getreg(child, addr);
+        }
+        else if((addr >= offsetof(struct user, u_debugreg[0])) &&
+                (addr <= offsetof(struct user, u_debugreg[7]))){
+                addr -= offsetof(struct user, u_debugreg[0]);
+                addr = addr >> 2;
+                tmp = child->thread.arch.debugregs[addr];
+        }
+        return put_user(tmp, (unsigned long __user *) data);
 }
 
 struct i387_fxsave_struct {
diff --git a/arch/um/sys-i386/ptrace_user.c b/arch/um/sys-i386/ptrace_user.c
index 7c376c95de50..9f3bd8ed78f5 100644
--- a/arch/um/sys-i386/ptrace_user.c
+++ b/arch/um/sys-i386/ptrace_user.c
@@ -14,6 +14,7 @@
 #include "sysdep/thread.h"
 #include "user.h"
 #include "os.h"
+#include "uml-config.h"
 
 int ptrace_getregs(long pid, unsigned long *regs_out)
 {
@@ -43,6 +44,7 @@ int ptrace_setfpregs(long pid, unsigned long *regs)
         return 0;
 }
 
+/* All the below stuff is of interest for TT mode only */
 static void write_debugregs(int pid, unsigned long *regs)
 {
         struct user *dummy;
@@ -75,7 +77,6 @@ static void read_debugregs(int pid, unsigned long *regs)
 
 /* Accessed only by the tracing thread */
 static unsigned long kernel_debugregs[8] = { [ 0 ... 7 ] = 0 };
-static int debugregs_seq = 0;
 
 void arch_enter_kernel(void *task, int pid)
 {
@@ -89,6 +90,11 @@ void arch_leave_kernel(void *task, int pid)
         write_debugregs(pid, TASK_DEBUGREGS(task));
 }
 
+#ifdef UML_CONFIG_PT_PROXY
+/* Accessed only by the tracing thread */
+static int debugregs_seq;
+
+/* Only called by the ptrace proxy */
 void ptrace_pokeuser(unsigned long addr, unsigned long data)
 {
         if((addr < offsetof(struct user, u_debugreg[0])) ||
@@ -109,6 +115,7 @@ static void update_debugregs_cb(void *arg)
         write_debugregs(pid, kernel_debugregs);
 }
 
+/* Optimized out in its header when not defined */
 void update_debugregs(int seq)
 {
         int me;
@@ -118,6 +125,7 @@ void update_debugregs(int seq)
         me = os_getpid();
         initial_thread_cb(update_debugregs_cb, &me);
 }
+#endif
 
 /*
  * Overrides for Emacs so that we follow Linus's tabbing style.
diff --git a/arch/um/sys-i386/signal.c b/arch/um/sys-i386/signal.c
index 33a40f5ef0d2..f5d0e1c37ea2 100644
--- a/arch/um/sys-i386/signal.c
+++ b/arch/um/sys-i386/signal.c
@@ -19,7 +19,7 @@
 #include "skas.h"
 
 static int copy_sc_from_user_skas(struct pt_regs *regs,
-                                  struct sigcontext *from)
+                                  struct sigcontext __user *from)
 {
         struct sigcontext sc;
         unsigned long fpregs[HOST_FP_SIZE];
@@ -57,7 +57,7 @@ static int copy_sc_from_user_skas(struct pt_regs *regs,
         return(0);
 }
 
-int copy_sc_to_user_skas(struct sigcontext *to, struct _fpstate *to_fp,
+int copy_sc_to_user_skas(struct sigcontext *to, struct _fpstate __user *to_fp,
                          struct pt_regs *regs, unsigned long sp)
 {
         struct sigcontext sc;
@@ -92,7 +92,7 @@ int copy_sc_to_user_skas(struct sigcontext *to, struct _fpstate *to_fp,
                        "errno = %d\n", err);
                 return(1);
         }
-        to_fp = (to_fp ? to_fp : (struct _fpstate *) (to + 1));
+        to_fp = (to_fp ? to_fp : (struct _fpstate __user *) (to + 1));
         sc.fpstate = to_fp;
 
         if(err)
@@ -113,10 +113,11 @@ int copy_sc_to_user_skas(struct sigcontext *to, struct _fpstate *to_fp,
  * saved pointer is in the kernel, but the sigcontext is in userspace, so we
  * copy_to_user it.
  */
-int copy_sc_from_user_tt(struct sigcontext *to, struct sigcontext *from,
+int copy_sc_from_user_tt(struct sigcontext *to, struct sigcontext __user *from,
                          int fpsize)
 {
-        struct _fpstate *to_fp, *from_fp;
+        struct _fpstate *to_fp;
+        struct _fpstate __user *from_fp;
         unsigned long sigs;
         int err;
 
@@ -131,13 +132,14 @@ int copy_sc_from_user_tt(struct sigcontext *to, struct sigcontext *from,
         return(err);
 }
 
-int copy_sc_to_user_tt(struct sigcontext *to, struct _fpstate *fp,
+int copy_sc_to_user_tt(struct sigcontext *to, struct _fpstate __user *fp,
                        struct sigcontext *from, int fpsize, unsigned long sp)
 {
-        struct _fpstate *to_fp, *from_fp;
+        struct _fpstate __user *to_fp;
+        struct _fpstate *from_fp;
         int err;
 
-        to_fp = (fp ? fp : (struct _fpstate *) (to + 1));
+        to_fp = (fp ? fp : (struct _fpstate __user *) (to + 1));
         from_fp = from->fpstate;
         err = copy_to_user(to, from, sizeof(*to));
 
@@ -165,7 +167,7 @@ static int copy_sc_from_user(struct pt_regs *to, void __user *from)
         return(ret);
 }
 
-static int copy_sc_to_user(struct sigcontext *to, struct _fpstate *fp,
+static int copy_sc_to_user(struct sigcontext *to, struct _fpstate __user *fp,
                            struct pt_regs *from, unsigned long sp)
 {
         return(CHOOSE_MODE(copy_sc_to_user_tt(to, fp, UPT_SC(&from->regs),
@@ -173,7 +175,7 @@ static int copy_sc_to_user(struct sigcontext *to, struct _fpstate *fp,
                            copy_sc_to_user_skas(to, fp, from, sp)));
 }
 
-static int copy_ucontext_to_user(struct ucontext *uc, struct _fpstate *fp,
+static int copy_ucontext_to_user(struct ucontext __user *uc, struct _fpstate __user *fp,
                                  sigset_t *set, unsigned long sp)
 {
         int err = 0;
@@ -188,7 +190,7 @@ static int copy_ucontext_to_user(struct ucontext *uc, struct _fpstate *fp,
 
 struct sigframe
 {
-        char *pretcode;
+        char __user *pretcode;
         int sig;
         struct sigcontext sc;
         struct _fpstate fpstate;
@@ -198,10 +200,10 @@ struct sigframe
 
 struct rt_sigframe
 {
-        char *pretcode;
+        char __user *pretcode;
         int sig;
-        struct siginfo *pinfo;
-        void *puc;
+        struct siginfo __user *pinfo;
+        void __user *puc;
         struct siginfo info;
         struct ucontext uc;
         struct _fpstate fpstate;
@@ -213,16 +215,16 @@ int setup_signal_stack_sc(unsigned long stack_top, int sig,
                           sigset_t *mask)
 {
         struct sigframe __user *frame;
-        void *restorer;
+        void __user *restorer;
         unsigned long save_sp = PT_REGS_SP(regs);
         int err = 0;
 
         stack_top &= -8UL;
-        frame = (struct sigframe *) stack_top - 1;
+        frame = (struct sigframe __user *) stack_top - 1;
         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                 return 1;
 
-        restorer = (void *) frame->retcode;
+        restorer = frame->retcode;
         if(ka->sa.sa_flags & SA_RESTORER)
                 restorer = ka->sa.sa_restorer;
 
@@ -278,16 +280,16 @@ int setup_signal_stack_si(unsigned long stack_top, int sig,
                           siginfo_t *info, sigset_t *mask)
 {
         struct rt_sigframe __user *frame;
-        void *restorer;
+        void __user *restorer;
         unsigned long save_sp = PT_REGS_SP(regs);
         int err = 0;
 
         stack_top &= -8UL;
-        frame = (struct rt_sigframe *) stack_top - 1;
+        frame = (struct rt_sigframe __user *) stack_top - 1;
         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                 return 1;
 
-        restorer = (void *) frame->retcode;
+        restorer = frame->retcode;
         if(ka->sa.sa_flags & SA_RESTORER)
                 restorer = ka->sa.sa_restorer;
 
@@ -333,7 +335,7 @@ err:
 long sys_sigreturn(struct pt_regs regs)
 {
         unsigned long sp = PT_REGS_SP(&current->thread.regs);
-        struct sigframe __user *frame = (struct sigframe *)(sp - 8);
+        struct sigframe __user *frame = (struct sigframe __user *)(sp - 8);
         sigset_t set;
         struct sigcontext __user *sc = &frame->sc;
         unsigned long __user *oldmask = &sc->oldmask;
@@ -365,8 +367,8 @@ long sys_sigreturn(struct pt_regs regs)
 
 long sys_rt_sigreturn(struct pt_regs regs)
 {
-        unsigned long __user sp = PT_REGS_SP(&current->thread.regs);
-        struct rt_sigframe __user *frame = (struct rt_sigframe *) (sp - 4);
+        unsigned long sp = PT_REGS_SP(&current->thread.regs);
+        struct rt_sigframe __user *frame = (struct rt_sigframe __user *) (sp - 4);
         sigset_t set;
         struct ucontext __user *uc = &frame->uc;
         int sig_size = _NSIG_WORDS * sizeof(unsigned long);
diff --git a/arch/um/sys-i386/sys_call_table.S b/arch/um/sys-i386/sys_call_table.S
index ad75c27afe38..1ff61474b25c 100644
--- a/arch/um/sys-i386/sys_call_table.S
+++ b/arch/um/sys-i386/sys_call_table.S
@@ -6,8 +6,6 @@
 
 #define sys_vm86old sys_ni_syscall
 #define sys_vm86 sys_ni_syscall
-#define sys_set_thread_area sys_ni_syscall
-#define sys_get_thread_area sys_ni_syscall
 
 #define sys_stime um_stime
 #define sys_time um_time
diff --git a/arch/um/sys-i386/syscalls.c b/arch/um/sys-i386/syscalls.c
index 83e9be820a86..749dd1bfe60f 100644
--- a/arch/um/sys-i386/syscalls.c
+++ b/arch/um/sys-i386/syscalls.c
@@ -61,21 +61,27 @@ long old_select(struct sel_arg_struct __user *arg)
         return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
 }
 
-/* The i386 version skips reading from %esi, the fourth argument. So we must do
- * this, too.
+/*
+ * The prototype on i386 is:
+ *
+ *     int clone(int flags, void * child_stack, int * parent_tidptr, struct user_desc * newtls, int * child_tidptr)
+ *
+ * and the "newtls" arg. on i386 is read by copy_thread directly from the
+ * register saved on the stack.
  */
 long sys_clone(unsigned long clone_flags, unsigned long newsp,
-               int __user *parent_tid, int unused, int __user *child_tid)
+               int __user *parent_tid, void *newtls, int __user *child_tid)
 {
         long ret;
 
         if (!newsp)
                 newsp = UPT_SP(&current->thread.regs.regs);
+
         current->thread.forking = 1;
         ret = do_fork(clone_flags, newsp, &current->thread.regs, 0, parent_tid,
                       child_tid);
         current->thread.forking = 0;
-        return(ret);
+        return ret;
 }
 
 /*
@@ -104,7 +110,7 @@ long sys_ipc (uint call, int first, int second,
                 union semun fourth;
                 if (!ptr)
                         return -EINVAL;
-                if (get_user(fourth.__pad, (void **) ptr))
+                if (get_user(fourth.__pad, (void __user * __user *) ptr))
                         return -EFAULT;
                 return sys_semctl (first, second, third, fourth);
         }
diff --git a/arch/um/sys-i386/tls.c b/arch/um/sys-i386/tls.c
new file mode 100644
index 000000000000..a3188e861cc7
--- /dev/null
+++ b/arch/um/sys-i386/tls.c
@@ -0,0 +1,384 @@
+/*
+ * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
+ * Licensed under the GPL
+ */
+
+#include "linux/config.h"
+#include "linux/kernel.h"
+#include "linux/sched.h"
+#include "linux/slab.h"
+#include "linux/types.h"
+#include "asm/uaccess.h"
+#include "asm/ptrace.h"
+#include "asm/segment.h"
+#include "asm/smp.h"
+#include "asm/desc.h"
+#include "choose-mode.h"
+#include "kern.h"
+#include "kern_util.h"
+#include "mode_kern.h"
+#include "os.h"
+#include "mode.h"
+
+#ifdef CONFIG_MODE_SKAS
+#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)
+{
+        int ret;
+        u32 cpu;
+
+        cpu = get_cpu();
+        ret = os_set_thread_area(info, userspace_pid[cpu]);
+        put_cpu();
+        return ret;
+}
+
+int do_get_thread_area_skas(struct user_desc *info)
+{
+        int ret;
+        u32 cpu;
+
+        cpu = get_cpu();
+        ret = os_get_thread_area(info, userspace_pid[cpu]);
+        put_cpu();
+        return ret;
+}
+#endif
+
+/*
+ * sys_get_thread_area: get a yet unused TLS descriptor index.
+ * XXX: Consider leaving one free slot for glibc usage at first place. This must
+ * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
+ *
+ * Also, this must be tested when compiling in SKAS mode with dinamic linking
+ * and running against NPTL.
+ */
+static int get_free_idx(struct task_struct* task)
+{
+        struct thread_struct *t = &task->thread;
+        int idx;
+
+        if (!t->arch.tls_array)
+                return GDT_ENTRY_TLS_MIN;
+
+        for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
+                if (!t->arch.tls_array[idx].present)
+                        return idx + GDT_ENTRY_TLS_MIN;
+        return -ESRCH;
+}
+
+static inline void clear_user_desc(struct user_desc* info)
+{
+        /* Postcondition: LDT_empty(info) returns true. */
+        memset(info, 0, sizeof(*info));
+
+        /* Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
+         * indeed an empty user_desc.
+         */
+        info->read_exec_only = 1;
+        info->seg_not_present = 1;
+}
+
+#define O_FORCE 1
+
+static int load_TLS(int flags, struct task_struct *to)
+{
+        int ret = 0;
+        int idx;
+
+        for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
+                struct uml_tls_struct* curr = &to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];
+
+                /* Actually, now if it wasn't flushed it gets cleared and
+                 * flushed to the host, which will clear it.*/
+                if (!curr->present) {
+                        if (!curr->flushed) {
+                                clear_user_desc(&curr->tls);
+                                curr->tls.entry_number = idx;
+                        } else {
+                                WARN_ON(!LDT_empty(&curr->tls));
+                                continue;
+                        }
+                }
+
+                if (!(flags & O_FORCE) && curr->flushed)
+                        continue;
+
+                ret = do_set_thread_area(&curr->tls);
+                if (ret)
+                        goto out;
+
+                curr->flushed = 1;
+        }
+out:
+        return ret;
+}
+
+/* Verify if we need to do a flush for the new process, i.e. if there are any
+ * present desc's, only if they haven't been flushed.
+ */
+static inline int needs_TLS_update(struct task_struct *task)
+{
+        int i;
+        int ret = 0;
+
+        for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
+                struct uml_tls_struct* curr = &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
+
+                /* Can't test curr->present, we may need to clear a descriptor
+                 * which had a value. */
+                if (curr->flushed)
+                        continue;
+                ret = 1;
+                break;
+        }
+        return ret;
+}
+
+/* On a newly forked process, the TLS descriptors haven't yet been flushed. So
+ * we mark them as such and the first switch_to will do the job.
+ */
+void clear_flushed_tls(struct task_struct *task)
+{
+        int i;
+
+        for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
+                struct uml_tls_struct* curr = &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
+
+                /* Still correct to do this, if it wasn't present on the host it
+                 * will remain as flushed as it was. */
+                if (!curr->present)
+                        continue;
+
+                curr->flushed = 0;
+        }
+}
+
+/* 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)
+{
+        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);
+
+        return 0;
+}
+
+static int set_tls_entry(struct task_struct* task, struct user_desc *info,
+                         int idx, int flushed)
+{
+        struct thread_struct *t = &task->thread;
+
+        if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
+                return -EINVAL;
+
+        t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
+        t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
+        t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
+
+        return 0;
+}
+
+int arch_copy_tls(struct task_struct *new)
+{
+        struct user_desc info;
+        int idx, ret = -EFAULT;
+
+        if (copy_from_user(&info,
+                           (void __user *) UPT_ESI(&new->thread.regs.regs),
+                           sizeof(info)))
+                goto out;
+
+        ret = -EINVAL;
+        if (LDT_empty(&info))
+                goto out;
+
+        idx = info.entry_number;
+
+        ret = set_tls_entry(new, &info, idx, 0);
+out:
+        return ret;
+}
+
+/* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */
+static int get_tls_entry(struct task_struct* task, struct user_desc *info, int idx)
+{
+        struct thread_struct *t = &task->thread;
+
+        if (!t->arch.tls_array)
+                goto clear;
+
+        if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
+                return -EINVAL;
+
+        if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
+                goto clear;
+
+        *info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;
+
+out:
+        /* Temporary debugging check, to make sure that things have been
+         * flushed. This could be triggered if load_TLS() failed.
+         */
+        if (unlikely(task == current && !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
+                printk(KERN_ERR "get_tls_entry: task with pid %d got here "
+                                "without flushed TLS.", current->pid);
+        }
+
+        return 0;
+clear:
+        /* When the TLS entry has not been set, the values read to user in the
+         * tls_array are 0 (because it's cleared at boot, see
+         * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
+         */
+        clear_user_desc(info);
+        info->entry_number = idx;
+        goto out;
+}
+
+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;
+
+        idx = info.entry_number;
+
+        if (idx == -1) {
+                idx = get_free_idx(current);
+                if (idx < 0)
+                        return idx;
+                info.entry_number = idx;
+                /* Tell the user which slot we chose for him.*/
+                if (put_user(idx, &user_desc->entry_number))
+                        return -EFAULT;
+        }
+
+        ret = CHOOSE_MODE_PROC(do_set_thread_area_tt, do_set_thread_area_skas, &info);
+        if (ret)
+                return ret;
+        return set_tls_entry(current, &info, idx, 1);
+}
+
+/*
+ * Perform set_thread_area on behalf of the traced child.
+ * Note: error handling is not done on the deferred load, and this differ from
+ * i386. However the only possible error are caused by bugs.
+ */
+int ptrace_set_thread_area(struct task_struct *child, int idx,
+                struct user_desc __user *user_desc)
+{
+        struct user_desc info;
+
+        if (!host_supports_tls)
+                return -EIO;
+
+        if (copy_from_user(&info, user_desc, sizeof(info)))
+                return -EFAULT;
+
+        return set_tls_entry(child, &info, idx, 0);
+}
+
+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;
+
+        ret = get_tls_entry(current, &info, idx);
+        if (ret < 0)
+                goto out;
+
+        if (copy_to_user(user_desc, &info, sizeof(info)))
+                ret = -EFAULT;
+
+out:
+        return ret;
+}
+
+/*
+ * Perform get_thread_area on behalf of the traced child.
+ */
+int ptrace_get_thread_area(struct task_struct *child, int idx,
+                struct user_desc __user *user_desc)
+{
+        struct user_desc info;
+        int ret;
+
+        if (!host_supports_tls)
+                return -EIO;
+
+        ret = get_tls_entry(child, &info, idx);
+        if (ret < 0)
+                goto out;
+
+        if (copy_to_user(user_desc, &info, sizeof(info)))
+                ret = -EFAULT;
+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 1;
+}
+
+__initcall(__setup_host_supports_tls);