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. ] |
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 |
18 | * use the vDSO. | |
1da177e4 LT |
19 | */ |
20 | ||
c767a54b JP |
21 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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> |
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> | |
5cec93c2 | 50 | #include <asm/traps.h> |
1da177e4 | 51 | |
c149a665 AL |
52 | #define CREATE_TRACE_POINTS |
53 | #include "vsyscall_trace.h" | |
54 | ||
8c49d9a7 | 55 | DEFINE_VVAR(int, vgetcpu_mode); |
1da177e4 | 56 | |
2e57ae05 | 57 | static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE; |
3ae36655 AL |
58 | |
59 | static int __init vsyscall_setup(char *str) | |
60 | { | |
61 | if (str) { | |
62 | if (!strcmp("emulate", str)) | |
63 | vsyscall_mode = EMULATE; | |
64 | else if (!strcmp("native", str)) | |
65 | vsyscall_mode = NATIVE; | |
66 | else if (!strcmp("none", str)) | |
67 | vsyscall_mode = NONE; | |
68 | else | |
69 | return -EINVAL; | |
70 | ||
71 | return 0; | |
72 | } | |
73 | ||
74 | return -EINVAL; | |
75 | } | |
76 | early_param("vsyscall", vsyscall_setup); | |
77 | ||
5cec93c2 AL |
78 | static void warn_bad_vsyscall(const char *level, struct pt_regs *regs, |
79 | const char *message) | |
1da177e4 | 80 | { |
c767a54b | 81 | if (!show_unhandled_signals) |
5cec93c2 | 82 | return; |
1da177e4 | 83 | |
53b884ac AL |
84 | printk_ratelimited("%s%s[%d] %s ip:%lx cs:%lx sp:%lx ax:%lx si:%lx di:%lx\n", |
85 | level, current->comm, task_pid_nr(current), | |
86 | message, regs->ip, regs->cs, | |
87 | regs->sp, regs->ax, regs->si, regs->di); | |
c9712944 AL |
88 | } |
89 | ||
90 | static int addr_to_vsyscall_nr(unsigned long addr) | |
91 | { | |
92 | int nr; | |
93 | ||
f40c3300 | 94 | if ((addr & ~0xC00UL) != VSYSCALL_ADDR) |
c9712944 AL |
95 | return -EINVAL; |
96 | ||
97 | nr = (addr & 0xC00UL) >> 10; | |
98 | if (nr >= 3) | |
99 | return -EINVAL; | |
100 | ||
101 | return nr; | |
1da177e4 LT |
102 | } |
103 | ||
4fc34901 AL |
104 | static bool write_ok_or_segv(unsigned long ptr, size_t size) |
105 | { | |
106 | /* | |
107 | * XXX: if access_ok, get_user, and put_user handled | |
108 | * sig_on_uaccess_error, this could go away. | |
109 | */ | |
110 | ||
111 | if (!access_ok(VERIFY_WRITE, (void __user *)ptr, size)) { | |
112 | siginfo_t info; | |
113 | struct thread_struct *thread = ¤t->thread; | |
114 | ||
115 | thread->error_code = 6; /* user fault, no page, write */ | |
116 | thread->cr2 = ptr; | |
51e7dc70 | 117 | thread->trap_nr = X86_TRAP_PF; |
4fc34901 AL |
118 | |
119 | memset(&info, 0, sizeof(info)); | |
120 | info.si_signo = SIGSEGV; | |
121 | info.si_errno = 0; | |
122 | info.si_code = SEGV_MAPERR; | |
123 | info.si_addr = (void __user *)ptr; | |
124 | ||
125 | force_sig_info(SIGSEGV, &info, current); | |
126 | return false; | |
127 | } else { | |
128 | return true; | |
129 | } | |
130 | } | |
131 | ||
3ae36655 | 132 | bool emulate_vsyscall(struct pt_regs *regs, unsigned long address) |
1da177e4 | 133 | { |
5cec93c2 AL |
134 | struct task_struct *tsk; |
135 | unsigned long caller; | |
87b526d3 | 136 | int vsyscall_nr, syscall_nr, tmp; |
4fc34901 | 137 | int prev_sig_on_uaccess_error; |
5cec93c2 AL |
138 | long ret; |
139 | ||
3ae36655 AL |
140 | /* |
141 | * No point in checking CS -- the only way to get here is a user mode | |
142 | * trap to a high address, which means that we're in 64-bit user code. | |
143 | */ | |
5cec93c2 | 144 | |
3ae36655 | 145 | WARN_ON_ONCE(address != regs->ip); |
c9712944 | 146 | |
3ae36655 AL |
147 | if (vsyscall_mode == NONE) { |
148 | warn_bad_vsyscall(KERN_INFO, regs, | |
149 | "vsyscall attempted with vsyscall=none"); | |
150 | return false; | |
c9712944 AL |
151 | } |
152 | ||
3ae36655 | 153 | vsyscall_nr = addr_to_vsyscall_nr(address); |
c149a665 AL |
154 | |
155 | trace_emulate_vsyscall(vsyscall_nr); | |
156 | ||
c9712944 AL |
157 | if (vsyscall_nr < 0) { |
158 | warn_bad_vsyscall(KERN_WARNING, regs, | |
3ae36655 | 159 | "misaligned vsyscall (exploit attempt or buggy program) -- look up the vsyscall kernel parameter if you need a workaround"); |
5cec93c2 AL |
160 | goto sigsegv; |
161 | } | |
d0aff6e6 | 162 | |
5cec93c2 | 163 | if (get_user(caller, (unsigned long __user *)regs->sp) != 0) { |
3ae36655 AL |
164 | warn_bad_vsyscall(KERN_WARNING, regs, |
165 | "vsyscall with bad stack (exploit attempt?)"); | |
5cec93c2 AL |
166 | goto sigsegv; |
167 | } | |
8c73626a | 168 | |
5cec93c2 | 169 | tsk = current; |
4fc34901 AL |
170 | |
171 | /* | |
87b526d3 AL |
172 | * Check for access_ok violations and find the syscall nr. |
173 | * | |
46ed99d1 | 174 | * NULL is a valid user pointer (in the access_ok sense) on 32-bit and |
4fc34901 | 175 | * 64-bit, so we don't need to special-case it here. For all the |
46ed99d1 | 176 | * vsyscalls, NULL means "don't write anything" not "write it at |
4fc34901 AL |
177 | * address 0". |
178 | */ | |
5cec93c2 AL |
179 | switch (vsyscall_nr) { |
180 | case 0: | |
4fc34901 | 181 | if (!write_ok_or_segv(regs->di, sizeof(struct timeval)) || |
87b526d3 AL |
182 | !write_ok_or_segv(regs->si, sizeof(struct timezone))) { |
183 | ret = -EFAULT; | |
184 | goto check_fault; | |
185 | } | |
4fc34901 | 186 | |
87b526d3 AL |
187 | syscall_nr = __NR_gettimeofday; |
188 | break; | |
189 | ||
190 | case 1: | |
191 | if (!write_ok_or_segv(regs->di, sizeof(time_t))) { | |
192 | ret = -EFAULT; | |
193 | goto check_fault; | |
194 | } | |
195 | ||
196 | syscall_nr = __NR_time; | |
197 | break; | |
198 | ||
199 | case 2: | |
200 | if (!write_ok_or_segv(regs->di, sizeof(unsigned)) || | |
201 | !write_ok_or_segv(regs->si, sizeof(unsigned))) { | |
202 | ret = -EFAULT; | |
203 | goto check_fault; | |
204 | } | |
205 | ||
206 | syscall_nr = __NR_getcpu; | |
207 | break; | |
208 | } | |
209 | ||
210 | /* | |
211 | * Handle seccomp. regs->ip must be the original value. | |
212 | * See seccomp_send_sigsys and Documentation/prctl/seccomp_filter.txt. | |
213 | * | |
214 | * We could optimize the seccomp disabled case, but performance | |
215 | * here doesn't matter. | |
216 | */ | |
217 | regs->orig_ax = syscall_nr; | |
218 | regs->ax = -ENOSYS; | |
219 | tmp = secure_computing(syscall_nr); | |
220 | if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) { | |
221 | warn_bad_vsyscall(KERN_DEBUG, regs, | |
222 | "seccomp tried to change syscall nr or ip"); | |
223 | do_exit(SIGSYS); | |
224 | } | |
225 | if (tmp) | |
226 | goto do_ret; /* skip requested */ | |
227 | ||
228 | /* | |
229 | * With a real vsyscall, page faults cause SIGSEGV. We want to | |
230 | * preserve that behavior to make writing exploits harder. | |
231 | */ | |
232 | prev_sig_on_uaccess_error = current_thread_info()->sig_on_uaccess_error; | |
233 | current_thread_info()->sig_on_uaccess_error = 1; | |
234 | ||
235 | ret = -EFAULT; | |
236 | switch (vsyscall_nr) { | |
237 | case 0: | |
5cec93c2 AL |
238 | ret = sys_gettimeofday( |
239 | (struct timeval __user *)regs->di, | |
240 | (struct timezone __user *)regs->si); | |
241 | break; | |
242 | ||
243 | case 1: | |
5cec93c2 AL |
244 | ret = sys_time((time_t __user *)regs->di); |
245 | break; | |
246 | ||
247 | case 2: | |
5cec93c2 AL |
248 | ret = sys_getcpu((unsigned __user *)regs->di, |
249 | (unsigned __user *)regs->si, | |
46ed99d1 | 250 | NULL); |
5cec93c2 | 251 | break; |
5cec93c2 | 252 | } |
8c73626a | 253 | |
4fc34901 AL |
254 | current_thread_info()->sig_on_uaccess_error = prev_sig_on_uaccess_error; |
255 | ||
87b526d3 | 256 | check_fault: |
5cec93c2 | 257 | if (ret == -EFAULT) { |
4fc34901 | 258 | /* Bad news -- userspace fed a bad pointer to a vsyscall. */ |
5cec93c2 AL |
259 | warn_bad_vsyscall(KERN_INFO, regs, |
260 | "vsyscall fault (exploit attempt?)"); | |
4fc34901 AL |
261 | |
262 | /* | |
263 | * If we failed to generate a signal for any reason, | |
264 | * generate one here. (This should be impossible.) | |
265 | */ | |
266 | if (WARN_ON_ONCE(!sigismember(&tsk->pending.signal, SIGBUS) && | |
267 | !sigismember(&tsk->pending.signal, SIGSEGV))) | |
268 | goto sigsegv; | |
269 | ||
270 | return true; /* Don't emulate the ret. */ | |
5cec93c2 | 271 | } |
8c73626a | 272 | |
5cec93c2 | 273 | regs->ax = ret; |
1da177e4 | 274 | |
5651721e | 275 | do_ret: |
5cec93c2 AL |
276 | /* Emulate a ret instruction. */ |
277 | regs->ip = caller; | |
278 | regs->sp += 8; | |
3ae36655 | 279 | return true; |
5cec93c2 AL |
280 | |
281 | sigsegv: | |
5cec93c2 | 282 | force_sig(SIGSEGV, current); |
3ae36655 | 283 | return true; |
1da177e4 LT |
284 | } |
285 | ||
5cec93c2 AL |
286 | /* |
287 | * Assume __initcall executes before all user space. Hopefully kmod | |
288 | * doesn't violate that. We'll find out if it does. | |
289 | */ | |
148f9bb8 | 290 | static void vsyscall_set_cpu(int cpu) |
c08c8205 | 291 | { |
fc8b8a60 | 292 | unsigned long d; |
c08c8205 VP |
293 | unsigned long node = 0; |
294 | #ifdef CONFIG_NUMA | |
98c9e27a | 295 | node = cpu_to_node(cpu); |
c08c8205 | 296 | #endif |
92cb7612 | 297 | if (cpu_has(&cpu_data(cpu), X86_FEATURE_RDTSCP)) |
8c131af1 | 298 | write_rdtscp_aux((node << 12) | cpu); |
c08c8205 | 299 | |
5cec93c2 AL |
300 | /* |
301 | * Store cpu number in limit so that it can be loaded quickly | |
302 | * in user space in vgetcpu. (12 bits for the CPU and 8 bits for the node) | |
303 | */ | |
fc8b8a60 JF |
304 | d = 0x0f40000000000ULL; |
305 | d |= cpu; | |
306 | d |= (node & 0xf) << 12; | |
307 | d |= (node >> 4) << 48; | |
5cec93c2 | 308 | |
fc8b8a60 | 309 | write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S); |
c08c8205 VP |
310 | } |
311 | ||
148f9bb8 | 312 | static void cpu_vsyscall_init(void *arg) |
8c131af1 AK |
313 | { |
314 | /* preemption should be already off */ | |
315 | vsyscall_set_cpu(raw_smp_processor_id()); | |
316 | } | |
317 | ||
148f9bb8 | 318 | static int |
8c131af1 AK |
319 | cpu_vsyscall_notifier(struct notifier_block *n, unsigned long action, void *arg) |
320 | { | |
321 | long cpu = (long)arg; | |
5cec93c2 | 322 | |
8bb78442 | 323 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) |
8691e5a8 | 324 | smp_call_function_single(cpu, cpu_vsyscall_init, NULL, 1); |
5cec93c2 | 325 | |
8c131af1 AK |
326 | return NOTIFY_DONE; |
327 | } | |
328 | ||
e4026440 | 329 | void __init map_vsyscall(void) |
1da177e4 | 330 | { |
3ae36655 AL |
331 | extern char __vsyscall_page; |
332 | unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page); | |
1da177e4 | 333 | |
f40c3300 | 334 | __set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall, |
3ae36655 AL |
335 | vsyscall_mode == NATIVE |
336 | ? PAGE_KERNEL_VSYSCALL | |
337 | : PAGE_KERNEL_VVAR); | |
f40c3300 AL |
338 | BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) != |
339 | (unsigned long)VSYSCALL_ADDR); | |
1da177e4 LT |
340 | } |
341 | ||
342 | static int __init vsyscall_init(void) | |
343 | { | |
42112a0f SB |
344 | cpu_notifier_register_begin(); |
345 | ||
15c8b6c1 | 346 | on_each_cpu(cpu_vsyscall_init, NULL, 1); |
be43f83d | 347 | /* notifier priority > KVM */ |
42112a0f SB |
348 | __hotcpu_notifier(cpu_vsyscall_notifier, 30); |
349 | ||
350 | cpu_notifier_register_done(); | |
5cec93c2 | 351 | |
1da177e4 LT |
352 | return 0; |
353 | } | |
1da177e4 | 354 | __initcall(vsyscall_init); |