[deliverable/linux.git] / arch / x86 / kernel / vsyscall_64.c

/*
 *  Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
 *  Copyright 2003 Andi Kleen, SuSE Labs.
 *
 *  [ NOTE: this mechanism is now deprecated in favor of the vDSO. ]
 *
 *  Thanks to hpa@transmeta.com for some useful hint.
 *  Special thanks to Ingo Molnar for his early experience with
 *  a different vsyscall implementation for Linux/IA32 and for the name.
 *
 *  vsyscall 1 is located at -10Mbyte, vsyscall 2 is located
 *  at virtual address -10Mbyte+1024bytes etc... There are at max 4
 *  vsyscalls. One vsyscall can reserve more than 1 slot to avoid
 *  jumping out of line if necessary. We cannot add more with this
 *  mechanism because older kernels won't return -ENOSYS.
 *
 *  Note: the concept clashes with user mode linux.  UML users should
 *  use the vDSO.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/time.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/seqlock.h>
#include <linux/jiffies.h>
#include <linux/sysctl.h>
#include <linux/topology.h>
#include <linux/timekeeper_internal.h>
#include <linux/getcpu.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/notifier.h>
#include <linux/syscalls.h>
#include <linux/ratelimit.h>

#include <asm/vsyscall.h>
#include <asm/pgtable.h>
#include <asm/compat.h>
#include <asm/page.h>
#include <asm/unistd.h>
#include <asm/fixmap.h>
#include <asm/errno.h>
#include <asm/io.h>
#include <asm/segment.h>
#include <asm/desc.h>
#include <asm/topology.h>
#include <asm/vgtod.h>
#include <asm/traps.h>

#define CREATE_TRACE_POINTS
#include "vsyscall_trace.h"

DEFINE_VVAR(int, vgetcpu_mode);
DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data);

static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE;

static int __init vsyscall_setup(char *str)
{
	if (str) {
		if (!strcmp("emulate", str))
			vsyscall_mode = EMULATE;
		else if (!strcmp("native", str))
			vsyscall_mode = NATIVE;
		else if (!strcmp("none", str))
			vsyscall_mode = NONE;
		else
			return -EINVAL;

		return 0;
	}

	return -EINVAL;
}
early_param("vsyscall", vsyscall_setup);

void update_vsyscall_tz(void)
{
	vsyscall_gtod_data.sys_tz = sys_tz;
}

void update_vsyscall(struct timekeeper *tk)
{
	struct vsyscall_gtod_data *vdata = &vsyscall_gtod_data;

	write_seqcount_begin(&vdata->seq);

	/* copy vsyscall data */
	vdata->clock.vclock_mode	= tk->clock->archdata.vclock_mode;
	vdata->clock.cycle_last		= tk->clock->cycle_last;
	vdata->clock.mask		= tk->clock->mask;
	vdata->clock.mult		= tk->mult;
	vdata->clock.shift		= tk->shift;

	vdata->wall_time_sec		= tk->xtime_sec;
	vdata->wall_time_snsec		= tk->xtime_nsec;

	vdata->monotonic_time_sec	= tk->xtime_sec
					+ tk->wall_to_monotonic.tv_sec;
	vdata->monotonic_time_snsec	= tk->xtime_nsec
					+ (tk->wall_to_monotonic.tv_nsec
						<< tk->shift);
	while (vdata->monotonic_time_snsec >=
					(((u64)NSEC_PER_SEC) << tk->shift)) {
		vdata->monotonic_time_snsec -=
					((u64)NSEC_PER_SEC) << tk->shift;
		vdata->monotonic_time_sec++;
	}

	vdata->wall_time_coarse.tv_sec	= tk->xtime_sec;
	vdata->wall_time_coarse.tv_nsec	= (long)(tk->xtime_nsec >> tk->shift);

	vdata->monotonic_time_coarse	= timespec_add(vdata->wall_time_coarse,
							tk->wall_to_monotonic);

	write_seqcount_end(&vdata->seq);
}

static void warn_bad_vsyscall(const char *level, struct pt_regs *regs,
			      const char *message)
{
	if (!show_unhandled_signals)
		return;

	pr_notice_ratelimited("%s%s[%d] %s ip:%lx cs:%lx sp:%lx ax:%lx si:%lx di:%lx\n",
			      level, current->comm, task_pid_nr(current),
			      message, regs->ip, regs->cs,
			      regs->sp, regs->ax, regs->si, regs->di);
}

static int addr_to_vsyscall_nr(unsigned long addr)
{
	int nr;

	if ((addr & ~0xC00UL) != VSYSCALL_START)
		return -EINVAL;

	nr = (addr & 0xC00UL) >> 10;
	if (nr >= 3)
		return -EINVAL;

	return nr;
}

static bool write_ok_or_segv(unsigned long ptr, size_t size)
{
	/*
	 * XXX: if access_ok, get_user, and put_user handled
	 * sig_on_uaccess_error, this could go away.
	 */

	if (!access_ok(VERIFY_WRITE, (void __user *)ptr, size)) {
		siginfo_t info;
		struct thread_struct *thread = &current->thread;

		thread->error_code	= 6;  /* user fault, no page, write */
		thread->cr2		= ptr;
		thread->trap_nr		= X86_TRAP_PF;

		memset(&info, 0, sizeof(info));
		info.si_signo		= SIGSEGV;
		info.si_errno		= 0;
		info.si_code		= SEGV_MAPERR;
		info.si_addr		= (void __user *)ptr;

		force_sig_info(SIGSEGV, &info, current);
		return false;
	} else {
		return true;
	}
}

bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
{
	struct task_struct *tsk;
	unsigned long caller;
	int vsyscall_nr, syscall_nr, tmp;
	int prev_sig_on_uaccess_error;
	long ret;

	/*
	 * No point in checking CS -- the only way to get here is a user mode
	 * trap to a high address, which means that we're in 64-bit user code.
	 */

	WARN_ON_ONCE(address != regs->ip);

	if (vsyscall_mode == NONE) {
		warn_bad_vsyscall(KERN_INFO, regs,
				  "vsyscall attempted with vsyscall=none");
		return false;
	}

	vsyscall_nr = addr_to_vsyscall_nr(address);

	trace_emulate_vsyscall(vsyscall_nr);

	if (vsyscall_nr < 0) {
		warn_bad_vsyscall(KERN_WARNING, regs,
				  "misaligned vsyscall (exploit attempt or buggy program) -- look up the vsyscall kernel parameter if you need a workaround");
		goto sigsegv;
	}

	if (get_user(caller, (unsigned long __user *)regs->sp) != 0) {
		warn_bad_vsyscall(KERN_WARNING, regs,
				  "vsyscall with bad stack (exploit attempt?)");
		goto sigsegv;
	}

	tsk = current;

	/*
	 * Check for access_ok violations and find the syscall nr.
	 *
	 * NULL is a valid user pointer (in the access_ok sense) on 32-bit and
	 * 64-bit, so we don't need to special-case it here.  For all the
	 * vsyscalls, NULL means "don't write anything" not "write it at
	 * address 0".
	 */
	switch (vsyscall_nr) {
	case 0:
		if (!write_ok_or_segv(regs->di, sizeof(struct timeval)) ||
		    !write_ok_or_segv(regs->si, sizeof(struct timezone))) {
			ret = -EFAULT;
			goto check_fault;
		}

		syscall_nr = __NR_gettimeofday;
		break;

	case 1:
		if (!write_ok_or_segv(regs->di, sizeof(time_t))) {
			ret = -EFAULT;
			goto check_fault;
		}

		syscall_nr = __NR_time;
		break;

	case 2:
		if (!write_ok_or_segv(regs->di, sizeof(unsigned)) ||
		    !write_ok_or_segv(regs->si, sizeof(unsigned))) {
			ret = -EFAULT;
			goto check_fault;
		}

		syscall_nr = __NR_getcpu;
		break;
	}

	/*
	 * Handle seccomp.  regs->ip must be the original value.
	 * See seccomp_send_sigsys and Documentation/prctl/seccomp_filter.txt.
	 *
	 * We could optimize the seccomp disabled case, but performance
	 * here doesn't matter.
	 */
	regs->orig_ax = syscall_nr;
	regs->ax = -ENOSYS;
	tmp = secure_computing(syscall_nr);
	if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
		warn_bad_vsyscall(KERN_DEBUG, regs,
				  "seccomp tried to change syscall nr or ip");
		do_exit(SIGSYS);
	}
	if (tmp)
		goto do_ret;  /* skip requested */

	/*
	 * With a real vsyscall, page faults cause SIGSEGV.  We want to
	 * preserve that behavior to make writing exploits harder.
	 */
	prev_sig_on_uaccess_error = current_thread_info()->sig_on_uaccess_error;
	current_thread_info()->sig_on_uaccess_error = 1;

	ret = -EFAULT;
	switch (vsyscall_nr) {
	case 0:
		ret = sys_gettimeofday(
			(struct timeval __user *)regs->di,
			(struct timezone __user *)regs->si);
		break;

	case 1:
		ret = sys_time((time_t __user *)regs->di);
		break;

	case 2:
		ret = sys_getcpu((unsigned __user *)regs->di,
				 (unsigned __user *)regs->si,
				 NULL);
		break;
	}

	current_thread_info()->sig_on_uaccess_error = prev_sig_on_uaccess_error;

check_fault:
	if (ret == -EFAULT) {
		/* Bad news -- userspace fed a bad pointer to a vsyscall. */
		warn_bad_vsyscall(KERN_INFO, regs,
				  "vsyscall fault (exploit attempt?)");

		/*
		 * If we failed to generate a signal for any reason,
		 * generate one here.  (This should be impossible.)
		 */
		if (WARN_ON_ONCE(!sigismember(&tsk->pending.signal, SIGBUS) &&
				 !sigismember(&tsk->pending.signal, SIGSEGV)))
			goto sigsegv;

		return true;  /* Don't emulate the ret. */
	}

	regs->ax = ret;

do_ret:
	/* Emulate a ret instruction. */
	regs->ip = caller;
	regs->sp += 8;
	return true;

sigsegv:
	force_sig(SIGSEGV, current);
	return true;
}

/*
 * Assume __initcall executes before all user space. Hopefully kmod
 * doesn't violate that. We'll find out if it does.
 */
static void __cpuinit vsyscall_set_cpu(int cpu)
{
	unsigned long d;
	unsigned long node = 0;
#ifdef CONFIG_NUMA
	node = cpu_to_node(cpu);
#endif
	if (cpu_has(&cpu_data(cpu), X86_FEATURE_RDTSCP))
		write_rdtscp_aux((node << 12) | cpu);

	/*
	 * Store cpu number in limit so that it can be loaded quickly
	 * in user space in vgetcpu. (12 bits for the CPU and 8 bits for the node)
	 */
	d = 0x0f40000000000ULL;
	d |= cpu;
	d |= (node & 0xf) << 12;
	d |= (node >> 4) << 48;

	write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
}

static void __cpuinit cpu_vsyscall_init(void *arg)
{
	/* preemption should be already off */
	vsyscall_set_cpu(raw_smp_processor_id());
}

static int __cpuinit
cpu_vsyscall_notifier(struct notifier_block *n, unsigned long action, void *arg)
{
	long cpu = (long)arg;

	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
		smp_call_function_single(cpu, cpu_vsyscall_init, NULL, 1);

	return NOTIFY_DONE;
}

void __init map_vsyscall(void)
{
	extern char __vsyscall_page;
	unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);
	extern char __vvar_page;
	unsigned long physaddr_vvar_page = __pa_symbol(&__vvar_page);

	__set_fixmap(VSYSCALL_FIRST_PAGE, physaddr_vsyscall,
		     vsyscall_mode == NATIVE
		     ? PAGE_KERNEL_VSYSCALL
		     : PAGE_KERNEL_VVAR);
	BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_FIRST_PAGE) !=
		     (unsigned long)VSYSCALL_START);

	__set_fixmap(VVAR_PAGE, physaddr_vvar_page, PAGE_KERNEL_VVAR);
	BUILD_BUG_ON((unsigned long)__fix_to_virt(VVAR_PAGE) !=
		     (unsigned long)VVAR_ADDRESS);
}

static int __init vsyscall_init(void)
{
	BUG_ON(VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE));

	on_each_cpu(cpu_vsyscall_init, NULL, 1);
	/* notifier priority > KVM */
	hotcpu_notifier(cpu_vsyscall_notifier, 30);

	return 0;
}
__initcall(vsyscall_init);
Commit	Line	Data
1da177e4	1	/*
1da177e4 LT	2	* Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
	3	* Copyright 2003 Andi Kleen, SuSE Labs.
	4	*
5cec93c2 AL	5	* [ NOTE: this mechanism is now deprecated in favor of the vDSO. ]
5cec93c2 AL	6	*
1da177e4 LT	7	* Thanks to hpa@transmeta.com for some useful hint.
	8	* Special thanks to Ingo Molnar for his early experience with
	9	* a different vsyscall implementation for Linux/IA32 and for the name.
	10	*
	11	* vsyscall 1 is located at -10Mbyte, vsyscall 2 is located
	12	* at virtual address -10Mbyte+1024bytes etc... There are at max 4
	13	* vsyscalls. One vsyscall can reserve more than 1 slot to avoid
	14	* jumping out of line if necessary. We cannot add more with this
	15	* mechanism because older kernels won't return -ENOSYS.
1da177e4	16	*
5cec93c2 AL	17	* Note: the concept clashes with user mode linux. UML users should
5cec93c2 AL	18	* use the vDSO.
1da177e4 LT	19	*/
1da177e4 LT	20
c767a54b JP	21	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
c767a54b JP	22
1da177e4 LT	23	#include <linux/time.h>
	24	#include <linux/init.h>
	25	#include <linux/kernel.h>
	26	#include <linux/timer.h>
	27	#include <linux/seqlock.h>
	28	#include <linux/jiffies.h>
	29	#include <linux/sysctl.h>
29574022	30	#include <linux/topology.h>
189374ae	31	#include <linux/timekeeper_internal.h>
c08c8205	32	#include <linux/getcpu.h>
8c131af1 AK	33	#include <linux/cpu.h>
	34	#include <linux/smp.h>
	35	#include <linux/notifier.h>
5cec93c2 AL	36	#include <linux/syscalls.h>
5cec93c2 AL	37	#include <linux/ratelimit.h>
1da177e4 LT	38
	39	#include <asm/vsyscall.h>
	40	#include <asm/pgtable.h>
c9712944	41	#include <asm/compat.h>
1da177e4	42	#include <asm/page.h>
7460ed28	43	#include <asm/unistd.h>
1da177e4 LT	44	#include <asm/fixmap.h>
	45	#include <asm/errno.h>
	46	#include <asm/io.h>
c08c8205 VP	47	#include <asm/segment.h>
	48	#include <asm/desc.h>
	49	#include <asm/topology.h>
2aae950b	50	#include <asm/vgtod.h>
5cec93c2	51	#include <asm/traps.h>
1da177e4	52
c149a665 AL	53	#define CREATE_TRACE_POINTS
	54	#include "vsyscall_trace.h"
	55
8c49d9a7	56	DEFINE_VVAR(int, vgetcpu_mode);
2ab51657	57	DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data);
1da177e4	58
2e57ae05	59	static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE;
3ae36655 AL	60
	61	static int __init vsyscall_setup(char *str)
	62	{
	63	if (str) {
	64	if (!strcmp("emulate", str))
	65	vsyscall_mode = EMULATE;
	66	else if (!strcmp("native", str))
	67	vsyscall_mode = NATIVE;
	68	else if (!strcmp("none", str))
	69	vsyscall_mode = NONE;
	70	else
	71	return -EINVAL;
	72
	73	return 0;
	74	}
	75
	76	return -EINVAL;
	77	}
	78	early_param("vsyscall", vsyscall_setup);
	79
2c622148 TB	80	void update_vsyscall_tz(void)
2c622148 TB	81	{
2c622148	82	vsyscall_gtod_data.sys_tz = sys_tz;
2c622148 TB	83	}
2c622148 TB	84
650ea024	85	void update_vsyscall(struct timekeeper *tk)
1da177e4	86	{
650ea024	87	struct vsyscall_gtod_data *vdata = &vsyscall_gtod_data;
5cec93c2	88
650ea024	89	write_seqcount_begin(&vdata->seq);
68fe7b23	90
7460ed28	91	/* copy vsyscall data */
650ea024 JS	92	vdata->clock.vclock_mode = tk->clock->archdata.vclock_mode;
	93	vdata->clock.cycle_last = tk->clock->cycle_last;
	94	vdata->clock.mask = tk->clock->mask;
	95	vdata->clock.mult = tk->mult;
	96	vdata->clock.shift = tk->shift;
	97
	98	vdata->wall_time_sec = tk->xtime_sec;
	99	vdata->wall_time_snsec = tk->xtime_nsec;
	100
	101	vdata->monotonic_time_sec = tk->xtime_sec
	102	+ tk->wall_to_monotonic.tv_sec;
	103	vdata->monotonic_time_snsec = tk->xtime_nsec
	104	+ (tk->wall_to_monotonic.tv_nsec
	105	<< tk->shift);
	106	while (vdata->monotonic_time_snsec >=
	107	(((u64)NSEC_PER_SEC) << tk->shift)) {
	108	vdata->monotonic_time_snsec -=
	109	((u64)NSEC_PER_SEC) << tk->shift;
	110	vdata->monotonic_time_sec++;
	111	}
91ec87d5	112
650ea024 JS	113	vdata->wall_time_coarse.tv_sec = tk->xtime_sec;
650ea024 JS	114	vdata->wall_time_coarse.tv_nsec = (long)(tk->xtime_nsec >> tk->shift);
91ec87d5	115
650ea024 JS	116	vdata->monotonic_time_coarse = timespec_add(vdata->wall_time_coarse,
650ea024 JS	117	tk->wall_to_monotonic);
5cec93c2	118
650ea024	119	write_seqcount_end(&vdata->seq);
1da177e4 LT	120	}
1da177e4 LT	121
5cec93c2 AL	122	static void warn_bad_vsyscall(const char level, struct pt_regs regs,
5cec93c2 AL	123	const char *message)
1da177e4	124	{
c767a54b	125	if (!show_unhandled_signals)
5cec93c2	126	return;
1da177e4	127
c767a54b JP	128	pr_notice_ratelimited("%s%s[%d] %s ip:%lx cs:%lx sp:%lx ax:%lx si:%lx di:%lx\n",
	129	level, current->comm, task_pid_nr(current),
	130	message, regs->ip, regs->cs,
	131	regs->sp, regs->ax, regs->si, regs->di);
c9712944 AL	132	}
	133
	134	static int addr_to_vsyscall_nr(unsigned long addr)
	135	{
	136	int nr;
	137
	138	if ((addr & ~0xC00UL) != VSYSCALL_START)
	139	return -EINVAL;
	140
	141	nr = (addr & 0xC00UL) >> 10;
	142	if (nr >= 3)
	143	return -EINVAL;
	144
	145	return nr;
1da177e4 LT	146	}
1da177e4 LT	147
4fc34901 AL	148	static bool write_ok_or_segv(unsigned long ptr, size_t size)
	149	{
	150	/*
	151	* XXX: if access_ok, get_user, and put_user handled
	152	* sig_on_uaccess_error, this could go away.
	153	*/
	154
	155	if (!access_ok(VERIFY_WRITE, (void __user *)ptr, size)) {
	156	siginfo_t info;
	157	struct thread_struct *thread = &current->thread;
	158
	159	thread->error_code = 6; /* user fault, no page, write */
	160	thread->cr2 = ptr;
51e7dc70	161	thread->trap_nr = X86_TRAP_PF;
4fc34901 AL	162
	163	memset(&info, 0, sizeof(info));
	164	info.si_signo = SIGSEGV;
	165	info.si_errno = 0;
	166	info.si_code = SEGV_MAPERR;
	167	info.si_addr = (void __user *)ptr;
	168
	169	force_sig_info(SIGSEGV, &info, current);
	170	return false;
	171	} else {
	172	return true;
	173	}
	174	}
	175
3ae36655	176	bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
1da177e4	177	{
5cec93c2 AL	178	struct task_struct *tsk;
5cec93c2 AL	179	unsigned long caller;
87b526d3	180	int vsyscall_nr, syscall_nr, tmp;
4fc34901	181	int prev_sig_on_uaccess_error;
5cec93c2 AL	182	long ret;
5cec93c2 AL	183
3ae36655 AL	184	/*
	185	* No point in checking CS -- the only way to get here is a user mode
	186	* trap to a high address, which means that we're in 64-bit user code.
	187	*/
5cec93c2	188
3ae36655	189	WARN_ON_ONCE(address != regs->ip);
c9712944	190
3ae36655 AL	191	if (vsyscall_mode == NONE) {
	192	warn_bad_vsyscall(KERN_INFO, regs,
	193	"vsyscall attempted with vsyscall=none");
	194	return false;
c9712944 AL	195	}
c9712944 AL	196
3ae36655	197	vsyscall_nr = addr_to_vsyscall_nr(address);
c149a665 AL	198
	199	trace_emulate_vsyscall(vsyscall_nr);
	200
c9712944 AL	201	if (vsyscall_nr < 0) {
c9712944 AL	202	warn_bad_vsyscall(KERN_WARNING, regs,
3ae36655	203	"misaligned vsyscall (exploit attempt or buggy program) -- look up the vsyscall kernel parameter if you need a workaround");
5cec93c2 AL	204	goto sigsegv;
5cec93c2 AL	205	}
d0aff6e6	206
5cec93c2	207	if (get_user(caller, (unsigned long __user *)regs->sp) != 0) {
3ae36655 AL	208	warn_bad_vsyscall(KERN_WARNING, regs,
3ae36655 AL	209	"vsyscall with bad stack (exploit attempt?)");
5cec93c2 AL	210	goto sigsegv;
5cec93c2 AL	211	}
8c73626a	212
5cec93c2	213	tsk = current;
4fc34901 AL	214
4fc34901 AL	215	/*
87b526d3 AL	216	* Check for access_ok violations and find the syscall nr.
87b526d3 AL	217	*
46ed99d1	218	* NULL is a valid user pointer (in the access_ok sense) on 32-bit and
4fc34901	219	* 64-bit, so we don't need to special-case it here. For all the
46ed99d1	220	* vsyscalls, NULL means "don't write anything" not "write it at
4fc34901 AL	221	* address 0".
4fc34901 AL	222	*/
5cec93c2 AL	223	switch (vsyscall_nr) {
5cec93c2 AL	224	case 0:
4fc34901	225	if (!write_ok_or_segv(regs->di, sizeof(struct timeval)) \|\|
87b526d3 AL	226	!write_ok_or_segv(regs->si, sizeof(struct timezone))) {
	227	ret = -EFAULT;
	228	goto check_fault;
	229	}
4fc34901	230
87b526d3 AL	231	syscall_nr = __NR_gettimeofday;
	232	break;
	233
	234	case 1:
	235	if (!write_ok_or_segv(regs->di, sizeof(time_t))) {
	236	ret = -EFAULT;
	237	goto check_fault;
	238	}
	239
	240	syscall_nr = __NR_time;
	241	break;
	242
	243	case 2:
	244	if (!write_ok_or_segv(regs->di, sizeof(unsigned)) \|\|
	245	!write_ok_or_segv(regs->si, sizeof(unsigned))) {
	246	ret = -EFAULT;
	247	goto check_fault;
	248	}
	249
	250	syscall_nr = __NR_getcpu;
	251	break;
	252	}
	253
	254	/*
	255	* Handle seccomp. regs->ip must be the original value.
	256	* See seccomp_send_sigsys and Documentation/prctl/seccomp_filter.txt.
	257	*
	258	* We could optimize the seccomp disabled case, but performance
	259	* here doesn't matter.
	260	*/
	261	regs->orig_ax = syscall_nr;
	262	regs->ax = -ENOSYS;
	263	tmp = secure_computing(syscall_nr);
	264	if ((!tmp && regs->orig_ax != syscall_nr) \|\| regs->ip != address) {
	265	warn_bad_vsyscall(KERN_DEBUG, regs,
	266	"seccomp tried to change syscall nr or ip");
	267	do_exit(SIGSYS);
	268	}
	269	if (tmp)
	270	goto do_ret; /* skip requested */
	271
	272	/*
	273	* With a real vsyscall, page faults cause SIGSEGV. We want to
	274	* preserve that behavior to make writing exploits harder.
	275	*/
	276	prev_sig_on_uaccess_error = current_thread_info()->sig_on_uaccess_error;
	277	current_thread_info()->sig_on_uaccess_error = 1;
	278
	279	ret = -EFAULT;
	280	switch (vsyscall_nr) {
	281	case 0:
5cec93c2 AL	282	ret = sys_gettimeofday(
	283	(struct timeval __user *)regs->di,
	284	(struct timezone __user *)regs->si);
	285	break;
	286
	287	case 1:
5cec93c2 AL	288	ret = sys_time((time_t __user *)regs->di);
	289	break;
	290
	291	case 2:
5cec93c2 AL	292	ret = sys_getcpu((unsigned __user *)regs->di,
5cec93c2 AL	293	(unsigned __user *)regs->si,
46ed99d1	294	NULL);
5cec93c2	295	break;
5cec93c2	296	}
8c73626a	297
4fc34901 AL	298	current_thread_info()->sig_on_uaccess_error = prev_sig_on_uaccess_error;
4fc34901 AL	299
87b526d3	300	check_fault:
5cec93c2	301	if (ret == -EFAULT) {
4fc34901	302	/* Bad news -- userspace fed a bad pointer to a vsyscall. */
5cec93c2 AL	303	warn_bad_vsyscall(KERN_INFO, regs,
5cec93c2 AL	304	"vsyscall fault (exploit attempt?)");
4fc34901 AL	305
	306	/*
	307	* If we failed to generate a signal for any reason,
	308	* generate one here. (This should be impossible.)
	309	*/
	310	if (WARN_ON_ONCE(!sigismember(&tsk->pending.signal, SIGBUS) &&
	311	!sigismember(&tsk->pending.signal, SIGSEGV)))
	312	goto sigsegv;
	313
	314	return true; /* Don't emulate the ret. */
5cec93c2	315	}
8c73626a	316
5cec93c2	317	regs->ax = ret;
1da177e4	318
5651721e	319	do_ret:
5cec93c2 AL	320	/* Emulate a ret instruction. */
	321	regs->ip = caller;
	322	regs->sp += 8;
3ae36655	323	return true;
5cec93c2 AL	324
5cec93c2 AL	325	sigsegv:
5cec93c2	326	force_sig(SIGSEGV, current);
3ae36655	327	return true;
1da177e4 LT	328	}
1da177e4 LT	329
5cec93c2 AL	330	/*
	331	* Assume __initcall executes before all user space. Hopefully kmod
	332	* doesn't violate that. We'll find out if it does.
	333	*/
8c131af1	334	static void __cpuinit vsyscall_set_cpu(int cpu)
c08c8205	335	{
fc8b8a60	336	unsigned long d;
c08c8205 VP	337	unsigned long node = 0;
c08c8205 VP	338	#ifdef CONFIG_NUMA
98c9e27a	339	node = cpu_to_node(cpu);
c08c8205	340	#endif
92cb7612	341	if (cpu_has(&cpu_data(cpu), X86_FEATURE_RDTSCP))
8c131af1	342	write_rdtscp_aux((node << 12) \| cpu);
c08c8205	343
5cec93c2 AL	344	/*
	345	* Store cpu number in limit so that it can be loaded quickly
	346	* in user space in vgetcpu. (12 bits for the CPU and 8 bits for the node)
	347	*/
fc8b8a60 JF	348	d = 0x0f40000000000ULL;
	349	d \|= cpu;
	350	d \|= (node & 0xf) << 12;
	351	d \|= (node >> 4) << 48;
5cec93c2	352
fc8b8a60	353	write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
c08c8205 VP	354	}
c08c8205 VP	355
8c131af1 AK	356	static void __cpuinit cpu_vsyscall_init(void *arg)
	357	{
	358	/* preemption should be already off */
	359	vsyscall_set_cpu(raw_smp_processor_id());
	360	}
	361
	362	static int __cpuinit
	363	cpu_vsyscall_notifier(struct notifier_block n, unsigned long action, void arg)
	364	{
	365	long cpu = (long)arg;
5cec93c2	366
8bb78442	367	if (action == CPU_ONLINE \|\| action == CPU_ONLINE_FROZEN)
8691e5a8	368	smp_call_function_single(cpu, cpu_vsyscall_init, NULL, 1);
5cec93c2	369
8c131af1 AK	370	return NOTIFY_DONE;
	371	}
	372
e4026440	373	void __init map_vsyscall(void)
1da177e4	374	{
3ae36655 AL	375	extern char __vsyscall_page;
3ae36655 AL	376	unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);
9fd67b4e AL	377	extern char __vvar_page;
9fd67b4e AL	378	unsigned long physaddr_vvar_page = __pa_symbol(&__vvar_page);
1da177e4	379
3ae36655 AL	380	__set_fixmap(VSYSCALL_FIRST_PAGE, physaddr_vsyscall,
	381	vsyscall_mode == NATIVE
	382	? PAGE_KERNEL_VSYSCALL
	383	: PAGE_KERNEL_VVAR);
	384	BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_FIRST_PAGE) !=
	385	(unsigned long)VSYSCALL_START);
	386
9fd67b4e	387	__set_fixmap(VVAR_PAGE, physaddr_vvar_page, PAGE_KERNEL_VVAR);
3ae36655 AL	388	BUILD_BUG_ON((unsigned long)__fix_to_virt(VVAR_PAGE) !=
3ae36655 AL	389	(unsigned long)VVAR_ADDRESS);
1da177e4 LT	390	}
	391
	392	static int __init vsyscall_init(void)
	393	{
5cec93c2 AL	394	BUG_ON(VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE));
5cec93c2 AL	395
15c8b6c1	396	on_each_cpu(cpu_vsyscall_init, NULL, 1);
be43f83d SY	397	/* notifier priority > KVM */
be43f83d SY	398	hotcpu_notifier(cpu_vsyscall_notifier, 30);
5cec93c2	399
1da177e4 LT	400	return 0;
1da177e4 LT	401	}
1da177e4	402	__initcall(vsyscall_init);