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