xref: /kernel/linux/linux-6.6/arch/x86/um/syscalls_64.c (revision 62306a36) 
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 <registers.h>
14#include <os.h>
15
16long arch_prctl(struct task_struct *task, int option,
17		unsigned long __user *arg2)
18{
19	unsigned long *ptr = arg2, tmp;
20	long ret;
21	int pid = task->mm->context.id.u.pid;
22
23	/*
24	 * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to
25	 * be safe), we need to call arch_prctl on the host because
26	 * setting %fs may result in something else happening (like a
27	 * GDT or thread.fs being set instead).  So, we let the host
28	 * fiddle the registers and thread struct and restore the
29	 * registers afterwards.
30	 *
31	 * So, the saved registers are stored to the process (this
32	 * needed because a stub may have been the last thing to run),
33	 * arch_prctl is run on the host, then the registers are read
34	 * back.
35	 */
36	switch (option) {
37	case ARCH_SET_FS:
38	case ARCH_SET_GS:
39		ret = restore_pid_registers(pid, &current->thread.regs.regs);
40		if (ret)
41			return ret;
42		break;
43	case ARCH_GET_FS:
44	case ARCH_GET_GS:
45		/*
46		 * With these two, we read to a local pointer and
47		 * put_user it to the userspace pointer that we were
48		 * given.  If addr isn't valid (because it hasn't been
49		 * faulted in or is just bogus), we want put_user to
50		 * fault it in (or return -EFAULT) instead of having
51		 * the host return -EFAULT.
52		 */
53		ptr = &tmp;
54	}
55
56	ret = os_arch_prctl(pid, option, ptr);
57	if (ret)
58		return ret;
59
60	switch (option) {
61	case ARCH_SET_FS:
62		current->thread.arch.fs = (unsigned long) ptr;
63		ret = save_registers(pid, &current->thread.regs.regs);
64		break;
65	case ARCH_SET_GS:
66		ret = save_registers(pid, &current->thread.regs.regs);
67		break;
68	case ARCH_GET_FS:
69		ret = put_user(tmp, arg2);
70		break;
71	case ARCH_GET_GS:
72		ret = put_user(tmp, arg2);
73		break;
74	}
75
76	return ret;
77}
78
79SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
80{
81	return arch_prctl(current, option, (unsigned long __user *) arg2);
82}
83
84void arch_switch_to(struct task_struct *to)
85{
86	if ((to->thread.arch.fs == 0) || (to->mm == NULL))
87		return;
88
89	arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs);
90}
91
92SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
93		unsigned long, prot, unsigned long, flags,
94		unsigned long, fd, unsigned long, off)
95{
96	if (off & ~PAGE_MASK)
97		return -EINVAL;
98
99	return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
100}
101