1 files changed, 354 insertions, 0 deletions
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
new file mode 100644
index 00000000000..ea5b5709aa7
--- /dev/null
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -0,0 +1,354 @@
+/*
+ *  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/traps.h>
+
+#define CREATE_TRACE_POINTS
+#include "vsyscall_trace.h"
+
+DEFINE_VVAR(int, vgetcpu_mode);
+
+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);
+
+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_ADDR)
+		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 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 cpu_vsyscall_init(void *arg)
+{
+	/* preemption should be already off */
+	vsyscall_set_cpu(raw_smp_processor_id());
+}
+
+static int
+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);
+
+	__set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall,
+		     vsyscall_mode == NATIVE
+		     ? PAGE_KERNEL_VSYSCALL
+		     : PAGE_KERNEL_VVAR);
+	BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) !=
+		     (unsigned long)VSYSCALL_ADDR);
+}
+
+static int __init vsyscall_init(void)
+{
+	cpu_notifier_register_begin();
+
+	on_each_cpu(cpu_vsyscall_init, NULL, 1);
+	/* notifier priority > KVM */
+	__hotcpu_notifier(cpu_vsyscall_notifier, 30);
+
+	cpu_notifier_register_done();
+
+	return 0;
+}
+__initcall(vsyscall_init);