1// SPDX-License-Identifier: GPL-2.0-only
  2/* Page Fault Handling for ARC (TLB Miss / ProtV)
  3 *
  4 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
  5 */
  6
  7#include <linux/signal.h>
  8#include <linux/interrupt.h>
  9#include <linux/sched/signal.h>
 10#include <linux/errno.h>
 11#include <linux/ptrace.h>
 12#include <linux/uaccess.h>
 13#include <linux/kdebug.h>
 14#include <linux/perf_event.h>
 15#include <linux/mm_types.h>
 16#include <asm/pgalloc.h>
 17#include <asm/mmu.h>
 18
 19/*
 20 * kernel virtual address is required to implement vmalloc/pkmap/fixmap
 21 * Refer to asm/processor.h for System Memory Map
 22 *
 23 * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
 24 * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
 25 */
 26noinline static int handle_kernel_vaddr_fault(unsigned long address)
 27{
 28	/*
 29	 * Synchronize this task's top level page-table
 30	 * with the 'reference' page table.
 31	 */
 32	pgd_t *pgd, *pgd_k;
 33	pud_t *pud, *pud_k;
 34	pmd_t *pmd, *pmd_k;
 35
 36	pgd = pgd_offset_fast(current->active_mm, address);
 37	pgd_k = pgd_offset_k(address);
 38
 39	if (!pgd_present(*pgd_k))
 40		goto bad_area;
 41
 42	pud = pud_offset(pgd, address);
 43	pud_k = pud_offset(pgd_k, address);
 44	if (!pud_present(*pud_k))
 45		goto bad_area;
 46
 47	pmd = pmd_offset(pud, address);
 48	pmd_k = pmd_offset(pud_k, address);
 49	if (!pmd_present(*pmd_k))
 50		goto bad_area;
 51
 52	set_pmd(pmd, *pmd_k);
 53
 54	/* XXX: create the TLB entry here */
 55	return 0;
 56
 57bad_area:
 58	return 1;
 59}
 60
 61void do_page_fault(unsigned long address, struct pt_regs *regs)
 62{
 63	struct vm_area_struct *vma = NULL;
 64	struct task_struct *tsk = current;
 65	struct mm_struct *mm = tsk->mm;
 66	int sig, si_code = SEGV_MAPERR;
 67	unsigned int write = 0, exec = 0, mask;
 68	vm_fault_t fault = VM_FAULT_SIGSEGV;	/* handle_mm_fault() output */
 69	unsigned int flags;			/* handle_mm_fault() input */
 70
 71	/*
 72	 * NOTE! We MUST NOT take any locks for this case. We may
 73	 * be in an interrupt or a critical region, and should
 74	 * only copy the information from the master page table,
 75	 * nothing more.
 76	 */
 77	if (address >= VMALLOC_START && !user_mode(regs)) {
 78		if (unlikely(handle_kernel_vaddr_fault(address)))
 79			goto no_context;
 80		else
 81			return;
 82	}
 83
 84	/*
 85	 * If we're in an interrupt or have no user
 86	 * context, we must not take the fault..
 87	 */
 88	if (faulthandler_disabled() || !mm)
 89		goto no_context;
 90
 91	if (regs->ecr_cause & ECR_C_PROTV_STORE)	/* ST/EX */
 92		write = 1;
 93	else if ((regs->ecr_vec == ECR_V_PROTV) &&
 94	         (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
 95		exec = 1;
 96
 97	flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 98	if (user_mode(regs))
 99		flags |= FAULT_FLAG_USER;
100	if (write)
101		flags |= FAULT_FLAG_WRITE;
102
103retry:
104	down_read(&mm->mmap_sem);
105
106	vma = find_vma(mm, address);
107	if (!vma)
108		goto bad_area;
109	if (unlikely(address < vma->vm_start)) {
110		if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address))
111			goto bad_area;
112	}
113
114	/*
115	 * vm_area is good, now check permissions for this memory access
116	 */
117	mask = VM_READ;
118	if (write)
119		mask = VM_WRITE;
120	if (exec)
121		mask = VM_EXEC;
122
123	if (!(vma->vm_flags & mask)) {
124		si_code = SEGV_ACCERR;
125		goto bad_area;
126	}
127
128	fault = handle_mm_fault(vma, address, flags);
129
130	/*
131	 * Fault retry nuances
132	 */
133	if (unlikely(fault & VM_FAULT_RETRY)) {
134
135		/*
136		 * If fault needs to be retried, handle any pending signals
137		 * first (by returning to user mode).
138		 * mmap_sem already relinquished by core mm for RETRY case
139		 */
140		if (fatal_signal_pending(current)) {
141			if (!user_mode(regs))
142				goto no_context;
143			return;
144		}
145		/*
146		 * retry state machine
147		 */
148		if (flags & FAULT_FLAG_ALLOW_RETRY) {
149			flags &= ~FAULT_FLAG_ALLOW_RETRY;
150			flags |= FAULT_FLAG_TRIED;
151			goto retry;
152		}
153	}
154
155bad_area:
156	up_read(&mm->mmap_sem);
157
158	/*
159	 * Major/minor page fault accounting
160	 * (in case of retry we only land here once)
161	 */
162	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
163
164	if (likely(!(fault & VM_FAULT_ERROR))) {
165		if (fault & VM_FAULT_MAJOR) {
166			tsk->maj_flt++;
167			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
168				      regs, address);
169		} else {
170			tsk->min_flt++;
171			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
172				      regs, address);
173		}
174
175		/* Normal return path: fault Handled Gracefully */
176		return;
177	}
178
179	if (!user_mode(regs))
180		goto no_context;
181
182	if (fault & VM_FAULT_OOM) {
183		pagefault_out_of_memory();
184		return;
185	}
186
187	if (fault & VM_FAULT_SIGBUS) {
188		sig = SIGBUS;
189		si_code = BUS_ADRERR;
190	}
191	else {
192		sig = SIGSEGV;
193	}
194
195	tsk->thread.fault_address = address;
196	force_sig_fault(sig, si_code, (void __user *)address);
197	return;
198
199no_context:
200	if (fixup_exception(regs))
201		return;
202
203	die("Oops", regs, address);
204}