x86: merge arch/x86/kernel/ldt_32/64.c

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 264 insertions, 0 deletions

diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
new file mode 100644
index 000000000000..a8cdca3615bf
--- /dev/null
+++ b/arch/x86/kernel/ldt.c
@@ -0,0 +1,264 @@
+/*
+ * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
+ * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
+ * Copyright (C) 2002 Andi Kleen
+ *
+ * This handles calls from both 32bit and 64bit mode.
+ */
+
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+
+#include <asm/uaccess.h>
+#include <asm/system.h>
+#include <asm/ldt.h>
+#include <asm/desc.h>
+#include <asm/mmu_context.h>
+
+#ifdef CONFIG_SMP
+static void flush_ldt(void *null)
+{
+        if (current->active_mm)
+                load_LDT(&current->active_mm->context);
+}
+#endif
+
+static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
+{
+        void *oldldt, *newldt;
+        int oldsize;
+
+        if (mincount <= pc->size)
+                return 0;
+        oldsize = pc->size;
+        mincount = (mincount + 511) & (~511);
+        if (mincount * LDT_ENTRY_SIZE > PAGE_SIZE)
+                newldt = vmalloc(mincount * LDT_ENTRY_SIZE);
+        else
+                newldt = kmalloc(mincount * LDT_ENTRY_SIZE, GFP_KERNEL);
+
+        if (!newldt)
+                return -ENOMEM;
+
+        if (oldsize)
+                memcpy(newldt, pc->ldt, oldsize * LDT_ENTRY_SIZE);
+        oldldt = pc->ldt;
+        memset(newldt + oldsize * LDT_ENTRY_SIZE, 0,
+               (mincount - oldsize) * LDT_ENTRY_SIZE);
+
+#ifdef CONFIG_X86_64
+        /* CHECKME: Do we really need this ? */
+        wmb();
+#endif
+        pc->ldt = newldt;
+        wmb();
+        pc->size = mincount;
+        wmb();
+
+        if (reload) {
+#ifdef CONFIG_SMP
+                cpumask_t mask;
+
+                preempt_disable();
+                load_LDT(pc);
+                mask = cpumask_of_cpu(smp_processor_id());
+                if (!cpus_equal(current->mm->cpu_vm_mask, mask))
+                        smp_call_function(flush_ldt, NULL, 1, 1);
+                preempt_enable();
+#else
+                load_LDT(pc);
+#endif
+        }
+        if (oldsize) {
+                if (oldsize * LDT_ENTRY_SIZE > PAGE_SIZE)
+                        vfree(oldldt);
+                else
+                        kfree(oldldt);
+        }
+        return 0;
+}
+
+static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
+{
+        int err = alloc_ldt(new, old->size, 0);
+
+        if (err < 0)
+                return err;
+        memcpy(new->ldt, old->ldt, old->size * LDT_ENTRY_SIZE);
+        return 0;
+}
+
+/*
+ * we do not have to muck with descriptors here, that is
+ * done in switch_mm() as needed.
+ */
+int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+        struct mm_struct *old_mm;
+        int retval = 0;
+
+        mutex_init(&mm->context.lock);
+        mm->context.size = 0;
+        old_mm = current->mm;
+        if (old_mm && old_mm->context.size > 0) {
+                mutex_lock(&old_mm->context.lock);
+                retval = copy_ldt(&mm->context, &old_mm->context);
+                mutex_unlock(&old_mm->context.lock);
+        }
+        return retval;
+}
+
+/*
+ * No need to lock the MM as we are the last user
+ *
+ * 64bit: Don't touch the LDT register - we're already in the next thread.
+ */
+void destroy_context(struct mm_struct *mm)
+{
+        if (mm->context.size) {
+#ifdef CONFIG_X86_32
+                /* CHECKME: Can this ever happen ? */
+                if (mm == current->active_mm)
+                        clear_LDT();
+#endif
+                if (mm->context.size * LDT_ENTRY_SIZE > PAGE_SIZE)
+                        vfree(mm->context.ldt);
+                else
+                        kfree(mm->context.ldt);
+                mm->context.size = 0;
+        }
+}
+
+static int read_ldt(void __user *ptr, unsigned long bytecount)
+{
+        int err;
+        unsigned long size;
+        struct mm_struct *mm = current->mm;
+
+        if (!mm->context.size)
+                return 0;
+        if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES)
+                bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES;
+
+        mutex_lock(&mm->context.lock);
+        size = mm->context.size * LDT_ENTRY_SIZE;
+        if (size > bytecount)
+                size = bytecount;
+
+        err = 0;
+        if (copy_to_user(ptr, mm->context.ldt, size))
+                err = -EFAULT;
+        mutex_unlock(&mm->context.lock);
+        if (err < 0)
+                goto error_return;
+        if (size != bytecount) {
+                /* zero-fill the rest */
+                if (clear_user(ptr + size, bytecount - size) != 0) {
+                        err = -EFAULT;
+                        goto error_return;
+                }
+        }
+        return bytecount;
+error_return:
+        return err;
+}
+
+static int read_default_ldt(void __user *ptr, unsigned long bytecount)
+{
+        /* CHECKME: Can we use _one_ random number ? */
+#ifdef CONFIG_X86_32
+        unsigned long size = 5 * sizeof(struct desc_struct);
+#else
+        unsigned long size = 128;
+#endif
+        if (bytecount > size)
+                bytecount = size;
+        if (clear_user(ptr, bytecount))
+                return -EFAULT;
+        return bytecount;
+}
+
+static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
+{
+        struct mm_struct *mm = current->mm;
+        __u32 entry_1, entry_2;
+        int error;
+        struct user_desc ldt_info;
+
+        error = -EINVAL;
+        if (bytecount != sizeof(ldt_info))
+                goto out;
+        error = -EFAULT;
+        if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
+                goto out;
+
+        error = -EINVAL;
+        if (ldt_info.entry_number >= LDT_ENTRIES)
+                goto out;
+        if (ldt_info.contents == 3) {
+                if (oldmode)
+                        goto out;
+                if (ldt_info.seg_not_present == 0)
+                        goto out;
+        }
+
+        mutex_lock(&mm->context.lock);
+        if (ldt_info.entry_number >= mm->context.size) {
+                error = alloc_ldt(&current->mm->context,
+                                  ldt_info.entry_number + 1, 1);
+                if (error < 0)
+                        goto out_unlock;
+        }
+
+        /* Allow LDTs to be cleared by the user. */
+        if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
+                if (oldmode || LDT_empty(&ldt_info)) {
+                        entry_1 = 0;
+                        entry_2 = 0;
+                        goto install;
+                }
+        }
+
+        entry_1 = LDT_entry_a(&ldt_info);
+        entry_2 = LDT_entry_b(&ldt_info);
+        if (oldmode)
+                entry_2 &= ~(1 << 20);
+
+        /* Install the new entry ...  */
+install:
+        write_ldt_entry(mm->context.ldt, ldt_info.entry_number, entry_1,
+                        entry_2);
+        error = 0;
+
+out_unlock:
+        mutex_unlock(&mm->context.lock);
+out:
+        return error;
+}
+
+asmlinkage int sys_modify_ldt(int func, void __user *ptr,
+                              unsigned long bytecount)
+{
+        int ret = -ENOSYS;
+
+        switch (func) {
+        case 0:
+                ret = read_ldt(ptr, bytecount);
+                break;
+        case 1:
+                ret = write_ldt(ptr, bytecount, 1);
+                break;
+        case 2:
+                ret = read_default_ldt(ptr, bytecount);
+                break;
+        case 0x11:
+                ret = write_ldt(ptr, bytecount, 0);
+                break;
+        }
+        return ret;
+}