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Diffstat (limited to 'arch/um/sys-i386/tls.c')
-rw-r--r--arch/um/sys-i386/tls.c384
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 00000000000..a3188e861cc
--- /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);