1// SPDX-License-Identifier: GPL-2.0
2/*
3 * S390 version
4 * Copyright IBM Corp. 1999
5 * Author(s): Hartmut Penner (hp@de.ibm.com)
6 * Ulrich Weigand (uweigand@de.ibm.com)
7 *
8 * Derived from "arch/i386/mm/fault.c"
9 * Copyright (C) 1995 Linus Torvalds
10 */
11
12#include <linux/kernel_stat.h>
13#include <linux/mmu_context.h>
14#include <linux/cpufeature.h>
15#include <linux/perf_event.h>
16#include <linux/signal.h>
17#include <linux/sched.h>
18#include <linux/sched/debug.h>
19#include <linux/kernel.h>
20#include <linux/errno.h>
21#include <linux/string.h>
22#include <linux/types.h>
23#include <linux/ptrace.h>
24#include <linux/mman.h>
25#include <linux/mm.h>
26#include <linux/smp.h>
27#include <linux/kdebug.h>
28#include <linux/init.h>
29#include <linux/console.h>
30#include <linux/extable.h>
31#include <linux/hardirq.h>
32#include <linux/kprobes.h>
33#include <linux/uaccess.h>
34#include <linux/hugetlb.h>
35#include <linux/kfence.h>
36#include <linux/pagewalk.h>
37#include <asm/asm-extable.h>
38#include <asm/asm-offsets.h>
39#include <asm/ptrace.h>
40#include <asm/fault.h>
41#include <asm/diag.h>
42#include <asm/irq.h>
43#include <asm/facility.h>
44#include <asm/uv.h>
45#include "../kernel/entry.h"
46
47/*
48 * Find out which address space caused the exception.
49 */
50static bool is_kernel_fault(struct pt_regs *regs)
51{
52 union teid teid = { .val = regs->int_parm_long };
53
54 if (user_mode(regs))
55 return false;
56 if (teid.as == PSW_BITS_AS_SECONDARY)
57 return false;
58 return true;
59}
60
61static unsigned long get_fault_address(struct pt_regs *regs)
62{
63 union teid teid = { .val = regs->int_parm_long };
64
65 return teid.addr * PAGE_SIZE;
66}
67
68static __always_inline bool fault_is_write(struct pt_regs *regs)
69{
70 union teid teid = { .val = regs->int_parm_long };
71
72 if (test_facility(75))
73 return teid.fsi == TEID_FSI_STORE;
74 return false;
75}
76
77static void dump_pagetable(unsigned long asce, unsigned long address)
78{
79 unsigned long entry, *table = __va(asce & _ASCE_ORIGIN);
80
81 pr_alert("AS:%016lx ", asce);
82 switch (asce & _ASCE_TYPE_MASK) {
83 case _ASCE_TYPE_REGION1:
84 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT;
85 if (get_kernel_nofault(entry, table))
86 goto bad;
87 pr_cont("R1:%016lx ", entry);
88 if (entry & _REGION_ENTRY_INVALID)
89 goto out;
90 table = __va(entry & _REGION_ENTRY_ORIGIN);
91 fallthrough;
92 case _ASCE_TYPE_REGION2:
93 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT;
94 if (get_kernel_nofault(entry, table))
95 goto bad;
96 pr_cont("R2:%016lx ", entry);
97 if (entry & _REGION_ENTRY_INVALID)
98 goto out;
99 table = __va(entry & _REGION_ENTRY_ORIGIN);
100 fallthrough;
101 case _ASCE_TYPE_REGION3:
102 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT;
103 if (get_kernel_nofault(entry, table))
104 goto bad;
105 pr_cont("R3:%016lx ", entry);
106 if (entry & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE))
107 goto out;
108 table = __va(entry & _REGION_ENTRY_ORIGIN);
109 fallthrough;
110 case _ASCE_TYPE_SEGMENT:
111 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
112 if (get_kernel_nofault(entry, table))
113 goto bad;
114 pr_cont("S:%016lx ", entry);
115 if (entry & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE))
116 goto out;
117 table = __va(entry & _SEGMENT_ENTRY_ORIGIN);
118 }
119 table += (address & _PAGE_INDEX) >> PAGE_SHIFT;
120 if (get_kernel_nofault(entry, table))
121 goto bad;
122 pr_cont("P:%016lx ", entry);
123out:
124 pr_cont("\n");
125 return;
126bad:
127 pr_cont("BAD\n");
128}
129
130static void dump_fault_info(struct pt_regs *regs)
131{
132 union teid teid = { .val = regs->int_parm_long };
133 unsigned long asce;
134
135 pr_alert("Failing address: %016lx TEID: %016lx",
136 get_fault_address(regs), teid.val);
137 if (test_facility(131))
138 pr_cont(" ESOP-2");
139 else if (machine_has_esop())
140 pr_cont(" ESOP-1");
141 else
142 pr_cont(" SOP");
143 if (test_facility(75))
144 pr_cont(" FSI");
145 pr_cont("\n");
146 pr_alert("Fault in ");
147 switch (teid.as) {
148 case PSW_BITS_AS_HOME:
149 pr_cont("home space ");
150 break;
151 case PSW_BITS_AS_SECONDARY:
152 pr_cont("secondary space ");
153 break;
154 case PSW_BITS_AS_ACCREG:
155 pr_cont("access register ");
156 break;
157 case PSW_BITS_AS_PRIMARY:
158 pr_cont("primary space ");
159 break;
160 }
161 pr_cont("mode while using ");
162 if (is_kernel_fault(regs)) {
163 asce = get_lowcore()->kernel_asce.val;
164 pr_cont("kernel ");
165 } else {
166 asce = get_lowcore()->user_asce.val;
167 pr_cont("user ");
168 }
169 pr_cont("ASCE.\n");
170 dump_pagetable(asce, address: get_fault_address(regs));
171}
172
173int show_unhandled_signals = 1;
174
175static const struct ctl_table s390_fault_sysctl_table[] = {
176 {
177 .procname = "userprocess_debug",
178 .data = &show_unhandled_signals,
179 .maxlen = sizeof(int),
180 .mode = 0644,
181 .proc_handler = proc_dointvec,
182 },
183};
184
185static int __init init_s390_fault_sysctls(void)
186{
187 register_sysctl_init("kernel", s390_fault_sysctl_table);
188 return 0;
189}
190arch_initcall(init_s390_fault_sysctls);
191
192void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault)
193{
194 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
195
196 if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
197 return;
198 if (!unhandled_signal(current, sig: signr))
199 return;
200 if (!__ratelimit(&rs))
201 return;
202 pr_alert("User process fault: interruption code %04x ilc:%d ",
203 regs->int_code & 0xffff, regs->int_code >> 17);
204 print_vma_addr(KERN_CONT "in ", rip: regs->psw.addr);
205 pr_cont("\n");
206 if (is_mm_fault)
207 dump_fault_info(regs);
208 show_regs(regs);
209}
210
211static void do_sigsegv(struct pt_regs *regs, int si_code)
212{
213 report_user_fault(regs, SIGSEGV, is_mm_fault: 1);
214 force_sig_fault(SIGSEGV, code: si_code, addr: (void __user *)get_fault_address(regs));
215}
216
217static void handle_fault_error_nolock(struct pt_regs *regs, int si_code)
218{
219 unsigned long address;
220 bool is_write;
221
222 if (user_mode(regs)) {
223 if (WARN_ON_ONCE(!si_code))
224 si_code = SEGV_MAPERR;
225 return do_sigsegv(regs, si_code);
226 }
227 if (fixup_exception(regs))
228 return;
229 if (is_kernel_fault(regs)) {
230 address = get_fault_address(regs);
231 is_write = fault_is_write(regs);
232 if (kfence_handle_page_fault(addr: address, is_write, regs))
233 return;
234 pr_alert("Unable to handle kernel pointer dereference in virtual kernel address space\n");
235 } else {
236 pr_alert("Unable to handle kernel paging request in virtual user address space\n");
237 }
238 dump_fault_info(regs);
239 die(regs, "Oops");
240}
241
242static void handle_fault_error(struct pt_regs *regs, int si_code)
243{
244 struct mm_struct *mm = current->mm;
245
246 mmap_read_unlock(mm);
247 handle_fault_error_nolock(regs, si_code);
248}
249
250static void do_sigbus(struct pt_regs *regs)
251{
252 force_sig_fault(SIGBUS, BUS_ADRERR, addr: (void __user *)get_fault_address(regs));
253}
254
255/*
256 * This routine handles page faults. It determines the address,
257 * and the problem, and then passes it off to one of the appropriate
258 * routines.
259 *
260 * interruption code (int_code):
261 * 04 Protection -> Write-Protection (suppression)
262 * 10 Segment translation -> Not present (nullification)
263 * 11 Page translation -> Not present (nullification)
264 * 3b Region third trans. -> Not present (nullification)
265 */
266static void do_exception(struct pt_regs *regs, int access)
267{
268 struct vm_area_struct *vma;
269 unsigned long address;
270 struct mm_struct *mm;
271 unsigned int flags;
272 vm_fault_t fault;
273 bool is_write;
274
275 /*
276 * The instruction that caused the program check has
277 * been nullified. Don't signal single step via SIGTRAP.
278 */
279 clear_thread_flag(TIF_PER_TRAP);
280 if (kprobe_page_fault(regs, trap: 14))
281 return;
282 mm = current->mm;
283 address = get_fault_address(regs);
284 is_write = fault_is_write(regs);
285 if (is_kernel_fault(regs) || faulthandler_disabled() || !mm)
286 return handle_fault_error_nolock(regs, si_code: 0);
287 perf_sw_event(event_id: PERF_COUNT_SW_PAGE_FAULTS, nr: 1, regs, addr: address);
288 flags = FAULT_FLAG_DEFAULT;
289 if (user_mode(regs))
290 flags |= FAULT_FLAG_USER;
291 if (is_write)
292 access = VM_WRITE;
293 if (access == VM_WRITE)
294 flags |= FAULT_FLAG_WRITE;
295 if (!(flags & FAULT_FLAG_USER))
296 goto lock_mmap;
297 vma = lock_vma_under_rcu(mm, address);
298 if (!vma)
299 goto lock_mmap;
300 if (!(vma->vm_flags & access)) {
301 vma_end_read(vma);
302 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
303 return handle_fault_error_nolock(regs, SEGV_ACCERR);
304 }
305 fault = handle_mm_fault(vma, address, flags: flags | FAULT_FLAG_VMA_LOCK, regs);
306 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
307 vma_end_read(vma);
308 if (!(fault & VM_FAULT_RETRY)) {
309 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
310 goto done;
311 }
312 count_vm_vma_lock_event(VMA_LOCK_RETRY);
313 if (fault & VM_FAULT_MAJOR)
314 flags |= FAULT_FLAG_TRIED;
315 /* Quick path to respond to signals */
316 if (fault_signal_pending(fault_flags: fault, regs)) {
317 if (!user_mode(regs))
318 handle_fault_error_nolock(regs, si_code: 0);
319 return;
320 }
321lock_mmap:
322retry:
323 vma = lock_mm_and_find_vma(mm, address, regs);
324 if (!vma)
325 return handle_fault_error_nolock(regs, SEGV_MAPERR);
326 if (unlikely(!(vma->vm_flags & access)))
327 return handle_fault_error(regs, SEGV_ACCERR);
328 fault = handle_mm_fault(vma, address, flags, regs);
329 if (fault_signal_pending(fault_flags: fault, regs)) {
330 if (!user_mode(regs))
331 handle_fault_error_nolock(regs, si_code: 0);
332 return;
333 }
334 /* The fault is fully completed (including releasing mmap lock) */
335 if (fault & VM_FAULT_COMPLETED)
336 return;
337 if (fault & VM_FAULT_RETRY) {
338 flags |= FAULT_FLAG_TRIED;
339 goto retry;
340 }
341 mmap_read_unlock(mm);
342done:
343 if (!(fault & VM_FAULT_ERROR))
344 return;
345 if (fault & VM_FAULT_OOM) {
346 if (!user_mode(regs))
347 handle_fault_error_nolock(regs, si_code: 0);
348 else
349 pagefault_out_of_memory();
350 } else if (fault & VM_FAULT_SIGSEGV) {
351 if (!user_mode(regs))
352 handle_fault_error_nolock(regs, si_code: 0);
353 else
354 do_sigsegv(regs, SEGV_MAPERR);
355 } else if (fault & (VM_FAULT_SIGBUS | VM_FAULT_HWPOISON |
356 VM_FAULT_HWPOISON_LARGE)) {
357 if (!user_mode(regs))
358 handle_fault_error_nolock(regs, si_code: 0);
359 else
360 do_sigbus(regs);
361 } else {
362 pr_emerg("Unexpected fault flags: %08x\n", fault);
363 BUG();
364 }
365}
366
367void do_protection_exception(struct pt_regs *regs)
368{
369 union teid teid = { .val = regs->int_parm_long };
370
371 /*
372 * Protection exceptions are suppressing, decrement psw address.
373 * The exception to this rule are aborted transactions, for these
374 * the PSW already points to the correct location.
375 */
376 if (!(regs->int_code & 0x200)) {
377 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
378 set_pt_regs_flag(regs, PIF_PSW_ADDR_ADJUSTED);
379 }
380 /*
381 * If bit 61 if the TEID is not set, the remainder of the
382 * TEID is unpredictable. Special handling is required.
383 */
384 if (unlikely(!teid.b61)) {
385 if (user_mode(regs)) {
386 dump_fault_info(regs);
387 die(regs, "Unexpected TEID");
388 }
389 /* Assume low-address protection in kernel mode. */
390 return handle_fault_error_nolock(regs, si_code: 0);
391 }
392 if (unlikely(cpu_has_nx() && teid.b56)) {
393 regs->int_parm_long = (teid.addr * PAGE_SIZE) | (regs->psw.addr & PAGE_MASK);
394 return handle_fault_error_nolock(regs, SEGV_ACCERR);
395 }
396 do_exception(regs, VM_WRITE);
397}
398NOKPROBE_SYMBOL(do_protection_exception);
399
400void do_dat_exception(struct pt_regs *regs)
401{
402 do_exception(regs, VM_ACCESS_FLAGS);
403}
404NOKPROBE_SYMBOL(do_dat_exception);
405
406#if IS_ENABLED(CONFIG_PGSTE)
407
408void do_secure_storage_access(struct pt_regs *regs)
409{
410 union teid teid = { .val = regs->int_parm_long };
411 unsigned long addr = get_fault_address(regs);
412 struct vm_area_struct *vma;
413 struct folio_walk fw;
414 struct mm_struct *mm;
415 struct folio *folio;
416 int rc;
417
418 /*
419 * Bit 61 indicates if the address is valid, if it is not the
420 * kernel should be stopped or SIGSEGV should be sent to the
421 * process. Bit 61 is not reliable without the misc UV feature,
422 * therefore this needs to be checked too.
423 */
424 if (uv_has_feature(BIT_UV_FEAT_MISC) && !teid.b61) {
425 /*
426 * When this happens, userspace did something that it
427 * was not supposed to do, e.g. branching into secure
428 * memory. Trigger a segmentation fault.
429 */
430 if (user_mode(regs)) {
431 send_sig(SIGSEGV, current, 0);
432 return;
433 }
434 /*
435 * The kernel should never run into this case and
436 * there is no way out of this situation.
437 */
438 panic("Unexpected PGM 0x3d with TEID bit 61=0");
439 }
440 if (is_kernel_fault(regs)) {
441 folio = phys_to_folio(addr);
442 if (unlikely(!folio_try_get(folio)))
443 return;
444 rc = arch_make_folio_accessible(folio);
445 folio_put(folio);
446 if (rc)
447 BUG();
448 } else {
449 if (faulthandler_disabled())
450 return handle_fault_error_nolock(regs, 0);
451 mm = current->mm;
452 mmap_read_lock(mm);
453 vma = find_vma(mm, addr);
454 if (!vma)
455 return handle_fault_error(regs, SEGV_MAPERR);
456 folio = folio_walk_start(&fw, vma, addr, 0);
457 if (!folio) {
458 mmap_read_unlock(mm);
459 return;
460 }
461 /* arch_make_folio_accessible() needs a raised refcount. */
462 folio_get(folio);
463 rc = arch_make_folio_accessible(folio);
464 folio_put(folio);
465 folio_walk_end(&fw, vma);
466 if (rc)
467 send_sig(SIGSEGV, current, 0);
468 mmap_read_unlock(mm);
469 }
470}
471NOKPROBE_SYMBOL(do_secure_storage_access);
472
473#endif /* CONFIG_PGSTE */
474

source code of linux/arch/s390/mm/fault.c