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https://github.com/torvalds/linux.git
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eb05df9e7e
Pull x86 cleanups from Peter Anvin: "The biggest textual change is the cleanup to use symbolic constants for x86 trap values. The only *functional* change and the reason for the x86/x32 dependency is the move of is_ia32_task() into <asm/thread_info.h> so that it can be used in other code that needs to understand if a system call comes from the compat entry point (and therefore uses i386 system call numbers) or not. One intended user for that is the BPF system call filter. Moving it out of <asm/compat.h> means we can define it unconditionally, returning always true on i386." * 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86: Move is_ia32_task to asm/thread_info.h from asm/compat.h x86: Rename trap_no to trap_nr in thread_struct x86: Use enum instead of literals for trap values
358 lines
9.1 KiB
C
358 lines
9.1 KiB
C
/*
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* Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
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* Copyright 2003 Andi Kleen, SuSE Labs.
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*
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* [ NOTE: this mechanism is now deprecated in favor of the vDSO. ]
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*
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* Thanks to hpa@transmeta.com for some useful hint.
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* Special thanks to Ingo Molnar for his early experience with
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* a different vsyscall implementation for Linux/IA32 and for the name.
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*
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* vsyscall 1 is located at -10Mbyte, vsyscall 2 is located
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* at virtual address -10Mbyte+1024bytes etc... There are at max 4
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* vsyscalls. One vsyscall can reserve more than 1 slot to avoid
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* jumping out of line if necessary. We cannot add more with this
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* mechanism because older kernels won't return -ENOSYS.
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*
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* Note: the concept clashes with user mode linux. UML users should
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* use the vDSO.
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*/
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#include <linux/time.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/timer.h>
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#include <linux/seqlock.h>
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#include <linux/jiffies.h>
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#include <linux/sysctl.h>
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#include <linux/topology.h>
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#include <linux/clocksource.h>
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#include <linux/getcpu.h>
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#include <linux/cpu.h>
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#include <linux/smp.h>
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#include <linux/notifier.h>
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#include <linux/syscalls.h>
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#include <linux/ratelimit.h>
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#include <asm/vsyscall.h>
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#include <asm/pgtable.h>
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#include <asm/compat.h>
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#include <asm/page.h>
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#include <asm/unistd.h>
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#include <asm/fixmap.h>
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#include <asm/errno.h>
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#include <asm/io.h>
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#include <asm/segment.h>
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#include <asm/desc.h>
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#include <asm/topology.h>
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#include <asm/vgtod.h>
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#include <asm/traps.h>
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#define CREATE_TRACE_POINTS
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#include "vsyscall_trace.h"
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DEFINE_VVAR(int, vgetcpu_mode);
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DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data);
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static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE;
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static int __init vsyscall_setup(char *str)
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{
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if (str) {
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if (!strcmp("emulate", str))
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vsyscall_mode = EMULATE;
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else if (!strcmp("native", str))
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vsyscall_mode = NATIVE;
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else if (!strcmp("none", str))
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vsyscall_mode = NONE;
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else
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return -EINVAL;
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return 0;
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}
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return -EINVAL;
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}
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early_param("vsyscall", vsyscall_setup);
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void update_vsyscall_tz(void)
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{
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vsyscall_gtod_data.sys_tz = sys_tz;
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}
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void update_vsyscall(struct timespec *wall_time, struct timespec *wtm,
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struct clocksource *clock, u32 mult)
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{
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struct timespec monotonic;
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write_seqcount_begin(&vsyscall_gtod_data.seq);
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/* copy vsyscall data */
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vsyscall_gtod_data.clock.vclock_mode = clock->archdata.vclock_mode;
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vsyscall_gtod_data.clock.cycle_last = clock->cycle_last;
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vsyscall_gtod_data.clock.mask = clock->mask;
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vsyscall_gtod_data.clock.mult = mult;
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vsyscall_gtod_data.clock.shift = clock->shift;
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vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec;
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vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
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monotonic = timespec_add(*wall_time, *wtm);
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vsyscall_gtod_data.monotonic_time_sec = monotonic.tv_sec;
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vsyscall_gtod_data.monotonic_time_nsec = monotonic.tv_nsec;
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vsyscall_gtod_data.wall_time_coarse = __current_kernel_time();
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vsyscall_gtod_data.monotonic_time_coarse =
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timespec_add(vsyscall_gtod_data.wall_time_coarse, *wtm);
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write_seqcount_end(&vsyscall_gtod_data.seq);
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}
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static void warn_bad_vsyscall(const char *level, struct pt_regs *regs,
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const char *message)
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{
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static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
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struct task_struct *tsk;
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if (!show_unhandled_signals || !__ratelimit(&rs))
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return;
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tsk = current;
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printk("%s%s[%d] %s ip:%lx cs:%lx sp:%lx ax:%lx si:%lx di:%lx\n",
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level, tsk->comm, task_pid_nr(tsk),
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message, regs->ip, regs->cs,
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regs->sp, regs->ax, regs->si, regs->di);
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}
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static int addr_to_vsyscall_nr(unsigned long addr)
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{
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int nr;
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if ((addr & ~0xC00UL) != VSYSCALL_START)
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return -EINVAL;
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nr = (addr & 0xC00UL) >> 10;
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if (nr >= 3)
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return -EINVAL;
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return nr;
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}
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static bool write_ok_or_segv(unsigned long ptr, size_t size)
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{
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/*
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* XXX: if access_ok, get_user, and put_user handled
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* sig_on_uaccess_error, this could go away.
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*/
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if (!access_ok(VERIFY_WRITE, (void __user *)ptr, size)) {
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siginfo_t info;
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struct thread_struct *thread = ¤t->thread;
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thread->error_code = 6; /* user fault, no page, write */
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thread->cr2 = ptr;
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thread->trap_nr = X86_TRAP_PF;
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memset(&info, 0, sizeof(info));
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info.si_signo = SIGSEGV;
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info.si_errno = 0;
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info.si_code = SEGV_MAPERR;
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info.si_addr = (void __user *)ptr;
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force_sig_info(SIGSEGV, &info, current);
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return false;
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} else {
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return true;
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}
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}
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bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
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{
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struct task_struct *tsk;
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unsigned long caller;
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int vsyscall_nr;
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int prev_sig_on_uaccess_error;
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long ret;
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/*
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* No point in checking CS -- the only way to get here is a user mode
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* trap to a high address, which means that we're in 64-bit user code.
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*/
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WARN_ON_ONCE(address != regs->ip);
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if (vsyscall_mode == NONE) {
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warn_bad_vsyscall(KERN_INFO, regs,
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"vsyscall attempted with vsyscall=none");
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return false;
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}
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vsyscall_nr = addr_to_vsyscall_nr(address);
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trace_emulate_vsyscall(vsyscall_nr);
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if (vsyscall_nr < 0) {
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warn_bad_vsyscall(KERN_WARNING, regs,
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"misaligned vsyscall (exploit attempt or buggy program) -- look up the vsyscall kernel parameter if you need a workaround");
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goto sigsegv;
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}
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if (get_user(caller, (unsigned long __user *)regs->sp) != 0) {
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warn_bad_vsyscall(KERN_WARNING, regs,
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"vsyscall with bad stack (exploit attempt?)");
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goto sigsegv;
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}
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tsk = current;
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if (seccomp_mode(&tsk->seccomp))
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do_exit(SIGKILL);
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/*
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* With a real vsyscall, page faults cause SIGSEGV. We want to
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* preserve that behavior to make writing exploits harder.
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*/
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prev_sig_on_uaccess_error = current_thread_info()->sig_on_uaccess_error;
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current_thread_info()->sig_on_uaccess_error = 1;
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/*
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* 0 is a valid user pointer (in the access_ok sense) on 32-bit and
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* 64-bit, so we don't need to special-case it here. For all the
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* vsyscalls, 0 means "don't write anything" not "write it at
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* address 0".
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*/
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ret = -EFAULT;
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switch (vsyscall_nr) {
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case 0:
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if (!write_ok_or_segv(regs->di, sizeof(struct timeval)) ||
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!write_ok_or_segv(regs->si, sizeof(struct timezone)))
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break;
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ret = sys_gettimeofday(
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(struct timeval __user *)regs->di,
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(struct timezone __user *)regs->si);
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break;
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case 1:
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if (!write_ok_or_segv(regs->di, sizeof(time_t)))
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break;
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ret = sys_time((time_t __user *)regs->di);
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break;
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case 2:
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if (!write_ok_or_segv(regs->di, sizeof(unsigned)) ||
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!write_ok_or_segv(regs->si, sizeof(unsigned)))
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break;
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ret = sys_getcpu((unsigned __user *)regs->di,
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(unsigned __user *)regs->si,
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0);
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break;
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}
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current_thread_info()->sig_on_uaccess_error = prev_sig_on_uaccess_error;
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if (ret == -EFAULT) {
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/* Bad news -- userspace fed a bad pointer to a vsyscall. */
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warn_bad_vsyscall(KERN_INFO, regs,
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"vsyscall fault (exploit attempt?)");
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/*
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* If we failed to generate a signal for any reason,
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* generate one here. (This should be impossible.)
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*/
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if (WARN_ON_ONCE(!sigismember(&tsk->pending.signal, SIGBUS) &&
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!sigismember(&tsk->pending.signal, SIGSEGV)))
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goto sigsegv;
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return true; /* Don't emulate the ret. */
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}
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regs->ax = ret;
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/* Emulate a ret instruction. */
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regs->ip = caller;
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regs->sp += 8;
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return true;
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sigsegv:
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force_sig(SIGSEGV, current);
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return true;
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}
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/*
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* Assume __initcall executes before all user space. Hopefully kmod
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* doesn't violate that. We'll find out if it does.
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*/
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static void __cpuinit vsyscall_set_cpu(int cpu)
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{
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unsigned long d;
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unsigned long node = 0;
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#ifdef CONFIG_NUMA
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node = cpu_to_node(cpu);
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#endif
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if (cpu_has(&cpu_data(cpu), X86_FEATURE_RDTSCP))
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write_rdtscp_aux((node << 12) | cpu);
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/*
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* Store cpu number in limit so that it can be loaded quickly
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* in user space in vgetcpu. (12 bits for the CPU and 8 bits for the node)
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*/
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d = 0x0f40000000000ULL;
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d |= cpu;
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d |= (node & 0xf) << 12;
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d |= (node >> 4) << 48;
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write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
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}
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static void __cpuinit cpu_vsyscall_init(void *arg)
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{
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/* preemption should be already off */
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vsyscall_set_cpu(raw_smp_processor_id());
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}
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static int __cpuinit
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cpu_vsyscall_notifier(struct notifier_block *n, unsigned long action, void *arg)
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{
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long cpu = (long)arg;
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if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
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smp_call_function_single(cpu, cpu_vsyscall_init, NULL, 1);
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return NOTIFY_DONE;
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}
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void __init map_vsyscall(void)
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{
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extern char __vsyscall_page;
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unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);
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extern char __vvar_page;
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unsigned long physaddr_vvar_page = __pa_symbol(&__vvar_page);
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__set_fixmap(VSYSCALL_FIRST_PAGE, physaddr_vsyscall,
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vsyscall_mode == NATIVE
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? PAGE_KERNEL_VSYSCALL
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: PAGE_KERNEL_VVAR);
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BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_FIRST_PAGE) !=
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(unsigned long)VSYSCALL_START);
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__set_fixmap(VVAR_PAGE, physaddr_vvar_page, PAGE_KERNEL_VVAR);
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BUILD_BUG_ON((unsigned long)__fix_to_virt(VVAR_PAGE) !=
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(unsigned long)VVAR_ADDRESS);
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}
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static int __init vsyscall_init(void)
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{
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BUG_ON(VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE));
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on_each_cpu(cpu_vsyscall_init, NULL, 1);
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/* notifier priority > KVM */
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hotcpu_notifier(cpu_vsyscall_notifier, 30);
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return 0;
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}
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__initcall(vsyscall_init);
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