kitten/arch/x86_64/kernel/sys_arch_prctl.c

   1 #include <lwk/kernel.h>
   2 #include <lwk/task.h>
   3 #include <arch/prctl.h>
   4 #include <arch/uaccess.h>
   5
   6
   7 long
   8 do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
   9 {
  10         int ret = 0;
  11         int doit = task == current;
  12
  13         switch (code) {
  14         case ARCH_SET_GS:
  15                 if (addr >= task->arch.addr_limit)
  16                         return -EPERM;
  17
  18                 task->arch.thread.gsindex = 0;
  19                 task->arch.thread.gs = addr;
  20                 if (doit) {
  21                         /* The kernel's %gs is currently loaded, so this
  22                            call is needed to set the user version. */
  23                         load_gs_index(0);
  24                         ret = checking_wrmsrl(MSR_KERNEL_GS_BASE, addr);
  25                 }
  26
  27                 break;
  28         case ARCH_SET_FS:
  29                 /* Not strictly needed for fs, but do it for symmetry
  30                    with gs */
  31                 if (addr >= task->arch.addr_limit)
  32                         return -EPERM;
  33
  34                 task->arch.thread.fsindex = 0;
  35                 task->arch.thread.fs = addr;
  36                 if (doit) {
  37                         /* The kernel doesn't use %fs so we can set it
  38                            directly.  set the selector to 0 to not confuse
  39                            __switch_to */
  40                         asm volatile("movl %0,%%fs" :: "r" (0));
  41                         ret = checking_wrmsrl(MSR_FS_BASE, addr);
  42                 }
  43
  44                 break;
  45         case ARCH_GET_FS: {
  46                 unsigned long base;
  47                 if (doit)
  48                         rdmsrl(MSR_FS_BASE, base);
  49                 else
  50                         base = task->arch.thread.fs;
  51                 ret = put_user(base, (unsigned long __user *)addr);
  52                 break;
  53         }
  54         case ARCH_GET_GS: {
  55                 unsigned long base;
  56                 unsigned gsindex;
  57                 if (doit) {
  58                         asm("movl %%gs,%0" : "=r" (gsindex));
  59                         if (gsindex)
  60                                 rdmsrl(MSR_KERNEL_GS_BASE, base);
  61                         else
  62                                 base = task->arch.thread.gs;
  63                 }
  64                 else
  65                         base = task->arch.thread.gs;
  66                 ret = put_user(base, (unsigned long __user *)addr);
  67                 break;
  68         }
  69
  70         default:
  71                 ret = -EINVAL;
  72                 break;
  73         }
  74
  75         return ret;
  76 }
  77
  78
  79 long
  80 sys_arch_prctl(int code, unsigned long addr)
  81 {
  82         return do_arch_prctl(current, code, addr);
  83 }
  84