1// SPDX-License-Identifier: GPL-2.0
  2// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
  3
  4#include <linux/signal.h>
  5#include <linux/module.h>
  6#include <linux/sched.h>
  7#include <linux/interrupt.h>
  8#include <linux/kernel.h>
  9#include <linux/errno.h>
 10#include <linux/string.h>
 11#include <linux/types.h>
 12#include <linux/ptrace.h>
 13#include <linux/mman.h>
 14#include <linux/mm.h>
 15#include <linux/smp.h>
 16#include <linux/version.h>
 17#include <linux/vt_kern.h>
 18#include <linux/extable.h>
 19#include <linux/uaccess.h>
 20#include <linux/perf_event.h>
 21#include <linux/kprobes.h>
 22
 23#include <asm/hardirq.h>
 24#include <asm/mmu_context.h>
 25#include <asm/traps.h>
 26#include <asm/page.h>
 27
 28int fixup_exception(struct pt_regs *regs)
 29{
 30	const struct exception_table_entry *fixup;
 31
 32	fixup = search_exception_tables(instruction_pointer(regs));
 33	if (fixup) {
 34		regs->pc = fixup->nextinsn;
 35
 36		return 1;
 37	}
 38
 39	return 0;
 40}
 41
 42/*
 43 * This routine handles page faults. It determines the address,
 44 * and the problem, and then passes it off to one of the appropriate
 45 * routines.
 46 */
 47asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
 48			      unsigned long mmu_meh)
 49{
 50	struct vm_area_struct *vma = NULL;
 51	struct task_struct *tsk = current;
 52	struct mm_struct *mm = tsk->mm;
 53	int si_code;
 54	int fault;
 55	unsigned long address = mmu_meh & PAGE_MASK;
 56
 57	if (kprobe_page_fault(regs, tsk->thread.trap_no))
 58		return;
 59
 60	si_code = SEGV_MAPERR;
 61
 62#ifndef CONFIG_CPU_HAS_TLBI
 63	/*
 64	 * We fault-in kernel-space virtual memory on-demand. The
 65	 * 'reference' page table is init_mm.pgd.
 66	 *
 67	 * NOTE! We MUST NOT take any locks for this case. We may
 68	 * be in an interrupt or a critical region, and should
 69	 * only copy the information from the master page table,
 70	 * nothing more.
 71	 */
 72	if (unlikely(address >= VMALLOC_START) &&
 73	    unlikely(address <= VMALLOC_END)) {
 74		/*
 75		 * Synchronize this task's top level page-table
 76		 * with the 'reference' page table.
 77		 *
 78		 * Do _not_ use "tsk" here. We might be inside
 79		 * an interrupt in the middle of a task switch..
 80		 */
 81		int offset = pgd_index(address);
 82		pgd_t *pgd, *pgd_k;
 83		pud_t *pud, *pud_k;
 84		pmd_t *pmd, *pmd_k;
 85		pte_t *pte_k;
 86
 87		unsigned long pgd_base;
 88
 89		pgd_base = (unsigned long)__va(get_pgd());
 90		pgd = (pgd_t *)pgd_base + offset;
 91		pgd_k = init_mm.pgd + offset;
 92
 93		if (!pgd_present(*pgd_k))
 94			goto no_context;
 95		set_pgd(pgd, *pgd_k);
 96
 97		pud = (pud_t *)pgd;
 98		pud_k = (pud_t *)pgd_k;
 99		if (!pud_present(*pud_k))
100			goto no_context;
101
102		pmd = pmd_offset(pud, address);
103		pmd_k = pmd_offset(pud_k, address);
104		if (!pmd_present(*pmd_k))
105			goto no_context;
106		set_pmd(pmd, *pmd_k);
107
108		pte_k = pte_offset_kernel(pmd_k, address);
109		if (!pte_present(*pte_k))
110			goto no_context;
111		return;
112	}
113#endif
114
115	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
116	/*
117	 * If we're in an interrupt or have no user
118	 * context, we must not take the fault..
119	 */
120	if (in_atomic() || !mm)
121		goto bad_area_nosemaphore;
122
123	mmap_read_lock(mm);
124	vma = find_vma(mm, address);
125	if (!vma)
126		goto bad_area;
127	if (vma->vm_start <= address)
128		goto good_area;
129	if (!(vma->vm_flags & VM_GROWSDOWN))
130		goto bad_area;
131	if (expand_stack(vma, address))
132		goto bad_area;
133	/*
134	 * Ok, we have a good vm_area for this memory access, so
135	 * we can handle it..
136	 */
137good_area:
138	si_code = SEGV_ACCERR;
139
140	if (write) {
141		if (!(vma->vm_flags & VM_WRITE))
142			goto bad_area;
143	} else {
144		if (unlikely(!vma_is_accessible(vma)))
145			goto bad_area;
146	}
147
148	/*
149	 * If for any reason at all we couldn't handle the fault,
150	 * make sure we exit gracefully rather than endlessly redo
151	 * the fault.
152	 */
153	fault = handle_mm_fault(vma, address, write ? FAULT_FLAG_WRITE : 0,
154				regs);
155	if (unlikely(fault & VM_FAULT_ERROR)) {
156		if (fault & VM_FAULT_OOM)
157			goto out_of_memory;
158		else if (fault & VM_FAULT_SIGBUS)
159			goto do_sigbus;
160		else if (fault & VM_FAULT_SIGSEGV)
161			goto bad_area;
162		BUG();
163	}
164	mmap_read_unlock(mm);
165	return;
166
167	/*
168	 * Something tried to access memory that isn't in our memory map..
169	 * Fix it, but check if it's kernel or user first..
170	 */
171bad_area:
172	mmap_read_unlock(mm);
173
174bad_area_nosemaphore:
175	/* User mode accesses just cause a SIGSEGV */
176	if (user_mode(regs)) {
177		tsk->thread.trap_no = trap_no(regs);
178		force_sig_fault(SIGSEGV, si_code, (void __user *)address);
179		return;
180	}
181
182no_context:
183	tsk->thread.trap_no = trap_no(regs);
184
185	/* Are we prepared to handle this kernel fault? */
186	if (fixup_exception(regs))
187		return;
188
189	/*
190	 * Oops. The kernel tried to access some bad page. We'll have to
191	 * terminate things with extreme prejudice.
192	 */
193	bust_spinlocks(1);
194	pr_alert("Unable to handle kernel paging request at virtual "
195		 "address 0x%08lx, pc: 0x%08lx\n", address, regs->pc);
196	die(regs, "Oops");
197
198out_of_memory:
199	tsk->thread.trap_no = trap_no(regs);
200
201	/*
202	 * We ran out of memory, call the OOM killer, and return the userspace
203	 * (which will retry the fault, or kill us if we got oom-killed).
204	 */
205	pagefault_out_of_memory();
206	return;
207
208do_sigbus:
209	tsk->thread.trap_no = trap_no(regs);
210
211	mmap_read_unlock(mm);
212
213	/* Kernel mode? Handle exceptions or die */
214	if (!user_mode(regs))
215		goto no_context;
216
217	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
218}