summaryrefslogtreecommitdiff
path: root/arch/csky/mm/fault.c
blob: 7215a46b6b8eb8ee4fe81b781decafa75064b4e1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.

#include <linux/extable.h>
#include <linux/kprobes.h>
#include <linux/mmu_context.h>
#include <linux/perf_event.h>

int fixup_exception(struct pt_regs *regs)
{
	const struct exception_table_entry *fixup;

	fixup = search_exception_tables(instruction_pointer(regs));
	if (fixup) {
		regs->pc = fixup->fixup;

		return 1;
	}

	return 0;
}

static inline bool is_write(struct pt_regs *regs)
{
	switch (trap_no(regs)) {
	case VEC_TLBINVALIDS:
		return true;
	case VEC_TLBMODIFIED:
		return true;
	}

	return false;
}

#ifdef CONFIG_CPU_HAS_LDSTEX
static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
{
	return;
}
#else
extern unsigned long csky_cmpxchg_ldw;
extern unsigned long csky_cmpxchg_stw;
static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
{
	if (trap_no(regs) != VEC_TLBMODIFIED)
		return;

	if (instruction_pointer(regs) == csky_cmpxchg_stw)
		instruction_pointer_set(regs, csky_cmpxchg_ldw);
	return;
}
#endif

static inline void no_context(struct pt_regs *regs, unsigned long addr)
{
	current->thread.trap_no = trap_no(regs);

	/* Are we prepared to handle this kernel fault? */
	if (fixup_exception(regs))
		return;

	/*
	 * Oops. The kernel tried to access some bad page. We'll have to
	 * terminate things with extreme prejudice.
	 */
	bust_spinlocks(1);
	pr_alert("Unable to handle kernel paging request at virtual "
		 "addr 0x%08lx, pc: 0x%08lx\n", addr, regs->pc);
	die(regs, "Oops");
	make_task_dead(SIGKILL);
}

static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
{
	current->thread.trap_no = trap_no(regs);

	if (fault & VM_FAULT_OOM) {
		/*
		 * We ran out of memory, call the OOM killer, and return the userspace
		 * (which will retry the fault, or kill us if we got oom-killed).
		 */
		if (!user_mode(regs)) {
			no_context(regs, addr);
			return;
		}
		pagefault_out_of_memory();
		return;
	} else if (fault & VM_FAULT_SIGBUS) {
		/* Kernel mode? Handle exceptions or die */
		if (!user_mode(regs)) {
			no_context(regs, addr);
			return;
		}
		do_trap(regs, SIGBUS, BUS_ADRERR, addr);
		return;
	}
	BUG();
}

static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr)
{
	/*
	 * Something tried to access memory that isn't in our memory map.
	 * Fix it, but check if it's kernel or user first.
	 */
	mmap_read_unlock(mm);
	/* User mode accesses just cause a SIGSEGV */
	if (user_mode(regs)) {
		do_trap(regs, SIGSEGV, code, addr);
		return;
	}

	no_context(regs, addr);
}

static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
{
	pgd_t *pgd, *pgd_k;
	pud_t *pud, *pud_k;
	pmd_t *pmd, *pmd_k;
	pte_t *pte_k;
	int offset;

	/* User mode accesses just cause a SIGSEGV */
	if (user_mode(regs)) {
		do_trap(regs, SIGSEGV, code, addr);
		return;
	}

	/*
	 * Synchronize this task's top level page-table
	 * with the 'reference' page table.
	 *
	 * Do _not_ use "tsk" here. We might be inside
	 * an interrupt in the middle of a task switch..
	 */
	offset = pgd_index(addr);

	pgd = get_pgd() + offset;
	pgd_k = init_mm.pgd + offset;

	if (!pgd_present(*pgd_k)) {
		no_context(regs, addr);
		return;
	}
	set_pgd(pgd, *pgd_k);

	pud = (pud_t *)pgd;
	pud_k = (pud_t *)pgd_k;
	if (!pud_present(*pud_k)) {
		no_context(regs, addr);
		return;
	}

	pmd = pmd_offset(pud, addr);
	pmd_k = pmd_offset(pud_k, addr);
	if (!pmd_present(*pmd_k)) {
		no_context(regs, addr);
		return;
	}
	set_pmd(pmd, *pmd_k);

	pte_k = pte_offset_kernel(pmd_k, addr);
	if (!pte_present(*pte_k)) {
		no_context(regs, addr);
		return;
	}

	flush_tlb_one(addr);
}

static inline bool access_error(struct pt_regs *regs, struct vm_area_struct *vma)
{
	if (is_write(regs)) {
		if (!(vma->vm_flags & VM_WRITE))
			return true;
	} else {
		if (unlikely(!vma_is_accessible(vma)))
			return true;
	}
	return false;
}

/*
 * This routine handles page faults.  It determines the address and the
 * problem, and then passes it off to one of the appropriate routines.
 */
asmlinkage void do_page_fault(struct pt_regs *regs)
{
	struct task_struct *tsk;
	struct vm_area_struct *vma;
	struct mm_struct *mm;
	unsigned long addr = read_mmu_entryhi() & PAGE_MASK;
	unsigned int flags = FAULT_FLAG_DEFAULT;
	int code = SEGV_MAPERR;
	vm_fault_t fault;

	tsk = current;
	mm = tsk->mm;

	csky_cmpxchg_fixup(regs);

	if (kprobe_page_fault(regs, tsk->thread.trap_no))
		return;

	/*
	 * Fault-in kernel-space virtual memory on-demand.
	 * The 'reference' page table is init_mm.pgd.
	 *
	 * NOTE! We MUST NOT take any locks for this case. We may
	 * be in an interrupt or a critical region, and should
	 * only copy the information from the master page table,
	 * nothing more.
	 */
	if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) {
		vmalloc_fault(regs, code, addr);
		return;
	}

	/* Enable interrupts if they were enabled in the parent context. */
	if (likely(regs->sr & BIT(6)))
		local_irq_enable();

	/*
	 * If we're in an interrupt, have no user context, or are running
	 * in an atomic region, then we must not take the fault.
	 */
	if (unlikely(faulthandler_disabled() || !mm)) {
		no_context(regs, addr);
		return;
	}

	if (user_mode(regs))
		flags |= FAULT_FLAG_USER;

	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

	if (is_write(regs))
		flags |= FAULT_FLAG_WRITE;
retry:
	mmap_read_lock(mm);
	vma = find_vma(mm, addr);
	if (unlikely(!vma)) {
		bad_area(regs, mm, code, addr);
		return;
	}
	if (likely(vma->vm_start <= addr))
		goto good_area;
	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
		bad_area(regs, mm, code, addr);
		return;
	}
	if (unlikely(expand_stack(vma, addr))) {
		bad_area(regs, mm, code, addr);
		return;
	}

	/*
	 * Ok, we have a good vm_area for this memory access, so
	 * we can handle it.
	 */
good_area:
	code = SEGV_ACCERR;

	if (unlikely(access_error(regs, vma))) {
		bad_area(regs, mm, code, addr);
		return;
	}

	/*
	 * If for any reason at all we could not handle the fault,
	 * make sure we exit gracefully rather than endlessly redo
	 * the fault.
	 */
	fault = handle_mm_fault(vma, addr, flags, regs);

	/*
	 * If we need to retry but a fatal signal is pending, handle the
	 * signal first. We do not need to release the mmap_lock because it
	 * would already be released in __lock_page_or_retry in mm/filemap.c.
	 */
	if (fault_signal_pending(fault, regs)) {
		if (!user_mode(regs))
			no_context(regs, addr);
		return;
	}

	if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_RETRY))) {
		flags |= FAULT_FLAG_TRIED;

		/*
		 * No need to mmap_read_unlock(mm) as we would
		 * have already released it in __lock_page_or_retry
		 * in mm/filemap.c.
		 */
		goto retry;
	}

	mmap_read_unlock(mm);

	if (unlikely(fault & VM_FAULT_ERROR)) {
		mm_fault_error(regs, addr, fault);
		return;
	}
	return;
}