1 files changed, 326 insertions, 0 deletions
diff --git a/arch/um/sys-i386/tls.c b/arch/um/sys-i386/tls.c
new file mode 100644
index 00000000000000..e3c5bc593faea2
--- /dev/null
+++ b/arch/um/sys-i386/tls.c
@@ -0,0 +1,326 @@
+/*
+ * 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
+
+#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;
+}
+
+#define O_FORCE 1
+
+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;
+}
+
+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;
+	}
+}
+
+/* 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
+ * SKAS patch. */
+int arch_switch_tls_skas(struct task_struct *from, struct task_struct *to)
+{
+	return load_TLS(O_FORCE, to);
+}
+
+int arch_switch_tls_tt(struct task_struct *from, struct task_struct *to)
+{
+	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 (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 (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 (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;
+
+	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;
+}