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