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