1 /* 2 * Copyright (C) 2003 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 3 * Copyright 2003 PathScale, Inc. 4 * 5 * Licensed under the GPL 6 */ 7 8 #include <linux/sched.h> 9 #include <linux/sched/mm.h> 10 #include <linux/syscalls.h> 11 #include <linux/uaccess.h> 12 #include <asm/prctl.h> /* XXX This should get the constants from libc */ 13 #include <os.h> 14 15 long arch_prctl(struct task_struct *task, int option, 16 unsigned long __user *arg2) 17 { 18 unsigned long *ptr = arg2, tmp; 19 long ret; 20 int pid = task->mm->context.id.u.pid; 21 22 /* 23 * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to 24 * be safe), we need to call arch_prctl on the host because 25 * setting %fs may result in something else happening (like a 26 * GDT or thread.fs being set instead). So, we let the host 27 * fiddle the registers and thread struct and restore the 28 * registers afterwards. 29 * 30 * So, the saved registers are stored to the process (this 31 * needed because a stub may have been the last thing to run), 32 * arch_prctl is run on the host, then the registers are read 33 * back. 34 */ 35 switch (option) { 36 case ARCH_SET_FS: 37 case ARCH_SET_GS: 38 ret = restore_registers(pid, ¤t->thread.regs.regs); 39 if (ret) 40 return ret; 41 break; 42 case ARCH_GET_FS: 43 case ARCH_GET_GS: 44 /* 45 * With these two, we read to a local pointer and 46 * put_user it to the userspace pointer that we were 47 * given. If addr isn't valid (because it hasn't been 48 * faulted in or is just bogus), we want put_user to 49 * fault it in (or return -EFAULT) instead of having 50 * the host return -EFAULT. 51 */ 52 ptr = &tmp; 53 } 54 55 ret = os_arch_prctl(pid, option, ptr); 56 if (ret) 57 return ret; 58 59 switch (option) { 60 case ARCH_SET_FS: 61 current->thread.arch.fs = (unsigned long) ptr; 62 ret = save_registers(pid, ¤t->thread.regs.regs); 63 break; 64 case ARCH_SET_GS: 65 ret = save_registers(pid, ¤t->thread.regs.regs); 66 break; 67 case ARCH_GET_FS: 68 ret = put_user(tmp, arg2); 69 break; 70 case ARCH_GET_GS: 71 ret = put_user(tmp, arg2); 72 break; 73 } 74 75 return ret; 76 } 77 78 SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2) 79 { 80 return arch_prctl(current, option, (unsigned long __user *) arg2); 81 } 82 83 void arch_switch_to(struct task_struct *to) 84 { 85 if ((to->thread.arch.fs == 0) || (to->mm == NULL)) 86 return; 87 88 arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs); 89 } 90