1 files changed, 384 insertions, 0 deletions

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);