1 // SPDX-License-Identifier: GPL-2.0-or-later
4 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
6 * Derived from "arch/i386/mm/fault.c"
7 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
9 * Modified by Cort Dougan and Paul Mackerras.
11 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
14 #include <linux/signal.h>
15 #include <linux/sched.h>
16 #include <linux/sched/task_stack.h>
17 #include <linux/kernel.h>
18 #include <linux/errno.h>
19 #include <linux/string.h>
20 #include <linux/types.h>
21 #include <linux/pagemap.h>
22 #include <linux/ptrace.h>
23 #include <linux/mman.h>
25 #include <linux/interrupt.h>
26 #include <linux/highmem.h>
27 #include <linux/extable.h>
28 #include <linux/kprobes.h>
29 #include <linux/kdebug.h>
30 #include <linux/perf_event.h>
31 #include <linux/ratelimit.h>
32 #include <linux/context_tracking.h>
33 #include <linux/hugetlb.h>
34 #include <linux/uaccess.h>
35 #include <linux/kfence.h>
36 #include <linux/pkeys.h>
38 #include <asm/asm-prototypes.h>
39 #include <asm/firmware.h>
40 #include <asm/interrupt.h>
43 #include <asm/mmu_context.h>
44 #include <asm/siginfo.h>
45 #include <asm/debug.h>
51 * do_page_fault error handling helpers
55 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code)
58 * If we are in kernel mode, bail out with a SEGV, this will
59 * be caught by the assembly which will restore the non-volatile
60 * registers before calling bad_page_fault()
65 _exception(SIGSEGV, regs, si_code, address);
70 static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)
72 return __bad_area_nosemaphore(regs, address, SEGV_MAPERR);
75 static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
77 struct mm_struct *mm = current->mm;
80 * Something tried to access memory that isn't in our memory map..
81 * Fix it, but check if it's kernel or user first..
85 return __bad_area_nosemaphore(regs, address, si_code);
88 static noinline int bad_area(struct pt_regs *regs, unsigned long address)
90 return __bad_area(regs, address, SEGV_MAPERR);
93 static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address,
94 struct vm_area_struct *vma)
96 struct mm_struct *mm = current->mm;
100 * We don't try to fetch the pkey from page table because reading
101 * page table without locking doesn't guarantee stable pte value.
102 * Hence the pkey value that we return to userspace can be different
103 * from the pkey that actually caused access error.
105 * It does *not* guarantee that the VMA we find here
106 * was the one that we faulted on.
108 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
109 * 2. T1 : set AMR to deny access to pkey=4, touches, page
111 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
112 * 5. T1 : enters fault handler, takes mmap_lock, etc...
113 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
114 * faulted on a pte with its pkey=4.
116 pkey = vma_pkey(vma);
118 mmap_read_unlock(mm);
121 * If we are in kernel mode, bail out with a SEGV, this will
122 * be caught by the assembly which will restore the non-volatile
123 * registers before calling bad_page_fault()
125 if (!user_mode(regs))
128 _exception_pkey(regs, address, pkey);
133 static noinline int bad_access(struct pt_regs *regs, unsigned long address)
135 return __bad_area(regs, address, SEGV_ACCERR);
138 static int do_sigbus(struct pt_regs *regs, unsigned long address,
141 if (!user_mode(regs))
144 current->thread.trap_nr = BUS_ADRERR;
145 #ifdef CONFIG_MEMORY_FAILURE
146 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
147 unsigned int lsb = 0; /* shutup gcc */
149 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
150 current->comm, current->pid, address);
152 if (fault & VM_FAULT_HWPOISON_LARGE)
153 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
154 if (fault & VM_FAULT_HWPOISON)
157 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
162 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
166 static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
170 * Kernel page fault interrupted by SIGKILL. We have no reason to
171 * continue processing.
173 if (fatal_signal_pending(current) && !user_mode(regs))
177 if (fault & VM_FAULT_OOM) {
179 * We ran out of memory, or some other thing happened to us that
180 * made us unable to handle the page fault gracefully.
182 if (!user_mode(regs))
184 pagefault_out_of_memory();
186 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
187 VM_FAULT_HWPOISON_LARGE))
188 return do_sigbus(regs, addr, fault);
189 else if (fault & VM_FAULT_SIGSEGV)
190 return bad_area_nosemaphore(regs, addr);
197 /* Is this a bad kernel fault ? */
198 static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
199 unsigned long address, bool is_write)
201 int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
204 pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n",
205 address >= TASK_SIZE ? "exec-protected" : "user",
207 from_kuid(&init_user_ns, current_uid()));
209 // Kernel exec fault is always bad
213 // Kernel fault on kernel address is bad
214 if (address >= TASK_SIZE)
217 // Read/write fault blocked by KUAP is bad, it can never succeed.
218 if (bad_kuap_fault(regs, address, is_write)) {
219 pr_crit_ratelimited("Kernel attempted to %s user page (%lx) - exploit attempt? (uid: %d)\n",
220 is_write ? "write" : "read", address,
221 from_kuid(&init_user_ns, current_uid()));
223 // Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad
224 if (!search_exception_tables(regs->nip))
227 // Read/write fault in a valid region (the exception table search passed
228 // above), but blocked by KUAP is bad, it can never succeed.
229 return WARN(true, "Bug: %s fault blocked by KUAP!", is_write ? "Write" : "Read");
232 // What's left? Kernel fault on user and allowed by KUAP in the faulting context.
236 static bool access_pkey_error(bool is_write, bool is_exec, bool is_pkey,
237 struct vm_area_struct *vma)
240 * Make sure to check the VMA so that we do not perform
241 * faults just to hit a pkey fault as soon as we fill in a
242 * page. Only called for current mm, hence foreign == 0
244 if (!arch_vma_access_permitted(vma, is_write, is_exec, 0))
250 static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma)
253 * Allow execution from readable areas if the MMU does not
254 * provide separate controls over reading and executing.
256 * Note: That code used to not be enabled for 4xx/BookE.
257 * It is now as I/D cache coherency for these is done at
258 * set_pte_at() time and I see no reason why the test
259 * below wouldn't be valid on those processors. This -may-
260 * break programs compiled with a really old ABI though.
263 return !(vma->vm_flags & VM_EXEC) &&
264 (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
265 !(vma->vm_flags & (VM_READ | VM_WRITE)));
269 if (unlikely(!(vma->vm_flags & VM_WRITE)))
274 if (unlikely(!vma_is_accessible(vma)))
277 * We should ideally do the vma pkey access check here. But in the
278 * fault path, handle_mm_fault() also does the same check. To avoid
279 * these multiple checks, we skip it here and handle access error due
285 #ifdef CONFIG_PPC_SMLPAR
286 static inline void cmo_account_page_fault(void)
288 if (firmware_has_feature(FW_FEATURE_CMO)) {
292 page_ins = be32_to_cpu(get_lppaca()->page_ins);
293 page_ins += 1 << PAGE_FACTOR;
294 get_lppaca()->page_ins = cpu_to_be32(page_ins);
299 static inline void cmo_account_page_fault(void) { }
300 #endif /* CONFIG_PPC_SMLPAR */
302 static void sanity_check_fault(bool is_write, bool is_user,
303 unsigned long error_code, unsigned long address)
306 * Userspace trying to access kernel address, we get PROTFAULT for that.
308 if (is_user && address >= TASK_SIZE) {
309 if ((long)address == -1)
312 pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n",
313 current->comm, current->pid, address,
314 from_kuid(&init_user_ns, current_uid()));
318 if (!IS_ENABLED(CONFIG_PPC_BOOK3S))
322 * For hash translation mode, we should never get a
323 * PROTFAULT. Any update to pte to reduce access will result in us
324 * removing the hash page table entry, thus resulting in a DSISR_NOHPTE
325 * fault instead of DSISR_PROTFAULT.
327 * A pte update to relax the access will not result in a hash page table
328 * entry invalidate and hence can result in DSISR_PROTFAULT.
329 * ptep_set_access_flags() doesn't do a hpte flush. This is why we have
330 * the special !is_write in the below conditional.
332 * For platforms that doesn't supports coherent icache and do support
333 * per page noexec bit, we do setup things such that we do the
334 * sync between D/I cache via fault. But that is handled via low level
335 * hash fault code (hash_page_do_lazy_icache()) and we should not reach
338 * For wrong access that can result in PROTFAULT, the above vma->vm_flags
339 * check should handle those and hence we should fall to the bad_area
340 * handling correctly.
342 * For embedded with per page exec support that doesn't support coherent
343 * icache we do get PROTFAULT and we handle that D/I cache sync in
344 * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON
345 * is conditional for server MMU.
347 * For radix, we can get prot fault for autonuma case, because radix
348 * page table will have them marked noaccess for user.
350 if (radix_enabled() || is_write)
353 WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
357 * Define the correct "is_write" bit in error_code based
358 * on the processor family
360 #if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
361 #define page_fault_is_write(__err) ((__err) & ESR_DST)
363 #define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE)
366 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
367 #define page_fault_is_bad(__err) (0)
368 #elif defined(CONFIG_PPC_8xx)
369 #define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G)
370 #elif defined(CONFIG_PPC64)
371 #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S)
373 #define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S)
377 * For 600- and 800-family processors, the error_code parameter is DSISR
378 * for a data fault, SRR1 for an instruction fault.
379 * For 400-family processors the error_code parameter is ESR for a data fault,
380 * 0 for an instruction fault.
381 * For 64-bit processors, the error_code parameter is DSISR for a data access
382 * fault, SRR1 & 0x08000000 for an instruction access fault.
384 * The return value is 0 if the fault was handled, or the signal
385 * number if this is a kernel fault that can't be handled here.
387 static int ___do_page_fault(struct pt_regs *regs, unsigned long address,
388 unsigned long error_code)
390 struct vm_area_struct * vma;
391 struct mm_struct *mm = current->mm;
392 unsigned int flags = FAULT_FLAG_DEFAULT;
393 int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
394 int is_user = user_mode(regs);
395 int is_write = page_fault_is_write(error_code);
396 vm_fault_t fault, major = 0;
397 bool kprobe_fault = kprobe_page_fault(regs, 11);
399 if (unlikely(debugger_fault_handler(regs) || kprobe_fault))
402 if (unlikely(page_fault_is_bad(error_code))) {
404 _exception(SIGBUS, regs, BUS_OBJERR, address);
410 /* Additional sanity check(s) */
411 sanity_check_fault(is_write, is_user, error_code, address);
414 * The kernel should never take an execute fault nor should it
415 * take a page fault to a kernel address or a page fault to a user
416 * address outside of dedicated places
418 if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write))) {
419 if (kfence_handle_page_fault(address, is_write, regs))
426 * If we're in an interrupt, have no user context or are running
427 * in a region with pagefaults disabled then we must not take the fault
429 if (unlikely(faulthandler_disabled() || !mm)) {
431 printk_ratelimited(KERN_ERR "Page fault in user mode"
432 " with faulthandler_disabled()=%d"
434 faulthandler_disabled(), mm);
435 return bad_area_nosemaphore(regs, address);
438 interrupt_cond_local_irq_enable(regs);
440 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
443 * We want to do this outside mmap_lock, because reading code around nip
444 * can result in fault, which will cause a deadlock when called with
448 flags |= FAULT_FLAG_USER;
450 flags |= FAULT_FLAG_WRITE;
452 flags |= FAULT_FLAG_INSTRUCTION;
454 /* When running in the kernel we expect faults to occur only to
455 * addresses in user space. All other faults represent errors in the
456 * kernel and should generate an OOPS. Unfortunately, in the case of an
457 * erroneous fault occurring in a code path which already holds mmap_lock
458 * we will deadlock attempting to validate the fault against the
459 * address space. Luckily the kernel only validly references user
460 * space from well defined areas of code, which are listed in the
463 * As the vast majority of faults will be valid we will only perform
464 * the source reference check when there is a possibility of a deadlock.
465 * Attempt to lock the address space, if we cannot we then validate the
466 * source. If this is invalid we can skip the address space check,
467 * thus avoiding the deadlock.
469 if (unlikely(!mmap_read_trylock(mm))) {
470 if (!is_user && !search_exception_tables(regs->nip))
471 return bad_area_nosemaphore(regs, address);
477 * The above down_read_trylock() might have succeeded in
478 * which case we'll have missed the might_sleep() from
484 vma = find_vma(mm, address);
486 return bad_area(regs, address);
488 if (unlikely(vma->vm_start > address)) {
489 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
490 return bad_area(regs, address);
492 if (unlikely(expand_stack(vma, address)))
493 return bad_area(regs, address);
496 if (unlikely(access_pkey_error(is_write, is_exec,
497 (error_code & DSISR_KEYFAULT), vma)))
498 return bad_access_pkey(regs, address, vma);
500 if (unlikely(access_error(is_write, is_exec, vma)))
501 return bad_access(regs, address);
504 * If for any reason at all we couldn't handle the fault,
505 * make sure we exit gracefully rather than endlessly redo
508 fault = handle_mm_fault(vma, address, flags, regs);
510 major |= fault & VM_FAULT_MAJOR;
512 if (fault_signal_pending(fault, regs))
513 return user_mode(regs) ? 0 : SIGBUS;
516 * Handle the retry right now, the mmap_lock has been released in that
519 if (unlikely(fault & VM_FAULT_RETRY)) {
520 flags |= FAULT_FLAG_TRIED;
524 mmap_read_unlock(current->mm);
526 if (unlikely(fault & VM_FAULT_ERROR))
527 return mm_fault_error(regs, address, fault);
530 * Major/minor page fault accounting.
533 cmo_account_page_fault();
537 NOKPROBE_SYMBOL(___do_page_fault);
539 static __always_inline void __do_page_fault(struct pt_regs *regs)
543 err = ___do_page_fault(regs, regs->dar, regs->dsisr);
545 bad_page_fault(regs, err);
548 DEFINE_INTERRUPT_HANDLER(do_page_fault)
550 __do_page_fault(regs);
553 #ifdef CONFIG_PPC_BOOK3S_64
554 /* Same as do_page_fault but interrupt entry has already run in do_hash_fault */
555 void hash__do_page_fault(struct pt_regs *regs)
557 __do_page_fault(regs);
559 NOKPROBE_SYMBOL(hash__do_page_fault);
563 * bad_page_fault is called when we have a bad access from the kernel.
564 * It is called from the DSI and ISI handlers in head.S and from some
565 * of the procedures in traps.c.
567 static void __bad_page_fault(struct pt_regs *regs, int sig)
569 int is_write = page_fault_is_write(regs->dsisr);
571 /* kernel has accessed a bad area */
573 switch (TRAP(regs)) {
574 case INTERRUPT_DATA_STORAGE:
575 case INTERRUPT_DATA_SEGMENT:
576 case INTERRUPT_H_DATA_STORAGE:
577 pr_alert("BUG: %s on %s at 0x%08lx\n",
578 regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
579 "Unable to handle kernel data access",
580 is_write ? "write" : "read", regs->dar);
582 case INTERRUPT_INST_STORAGE:
583 case INTERRUPT_INST_SEGMENT:
584 pr_alert("BUG: Unable to handle kernel instruction fetch%s",
585 regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
587 case INTERRUPT_ALIGNMENT:
588 pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
592 pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
596 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
599 if (task_stack_end_corrupted(current))
600 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
602 die("Kernel access of bad area", regs, sig);
605 void bad_page_fault(struct pt_regs *regs, int sig)
607 const struct exception_table_entry *entry;
609 /* Are we prepared to handle this fault? */
610 entry = search_exception_tables(instruction_pointer(regs));
612 instruction_pointer_set(regs, extable_fixup(entry));
614 __bad_page_fault(regs, sig);
617 #ifdef CONFIG_PPC_BOOK3S_64
618 DEFINE_INTERRUPT_HANDLER(do_bad_page_fault_segv)
620 bad_page_fault(regs, SIGSEGV);
624 * In radix, segment interrupts indicate the EA is not addressable by the
625 * page table geometry, so they are always sent here.
627 * In hash, this is called if do_slb_fault returns error. Typically it is
628 * because the EA was outside the region allowed by software.
630 DEFINE_INTERRUPT_HANDLER(do_bad_segment_interrupt)
632 int err = regs->result;
634 if (err == -EFAULT) {
636 _exception(SIGSEGV, regs, SEGV_BNDERR, regs->dar);
638 bad_page_fault(regs, SIGSEGV);
639 } else if (err == -EINVAL) {
640 unrecoverable_exception(regs);