1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
4 *
5 * Derived from MIPS:
6 * Copyright (C) 1995 - 2000 by Ralf Baechle
7 */
8 #include <linux/context_tracking.h>
9 #include <linux/signal.h>
10 #include <linux/sched.h>
11 #include <linux/interrupt.h>
12 #include <linux/kernel.h>
13 #include <linux/entry-common.h>
14 #include <linux/errno.h>
15 #include <linux/string.h>
16 #include <linux/types.h>
17 #include <linux/ptrace.h>
18 #include <linux/ratelimit.h>
19 #include <linux/mman.h>
20 #include <linux/mm.h>
21 #include <linux/smp.h>
22 #include <linux/kdebug.h>
23 #include <linux/kprobes.h>
24 #include <linux/perf_event.h>
25 #include <linux/uaccess.h>
26
27 #include <asm/branch.h>
28 #include <asm/mmu_context.h>
29 #include <asm/ptrace.h>
30
31 int show_unhandled_signals = 1;
32
no_context(struct pt_regs * regs,unsigned long address)33 static void __kprobes no_context(struct pt_regs *regs, unsigned long address)
34 {
35 const int field = sizeof(unsigned long) * 2;
36
37 /* Are we prepared to handle this kernel fault? */
38 if (fixup_exception(regs))
39 return;
40
41 /*
42 * Oops. The kernel tried to access some bad page. We'll have to
43 * terminate things with extreme prejudice.
44 */
45 bust_spinlocks(1);
46
47 pr_alert("CPU %d Unable to handle kernel paging request at "
48 "virtual address %0*lx, era == %0*lx, ra == %0*lx\n",
49 raw_smp_processor_id(), field, address, field, regs->csr_era,
50 field, regs->regs[1]);
51 die("Oops", regs);
52 }
53
do_out_of_memory(struct pt_regs * regs,unsigned long address)54 static void __kprobes do_out_of_memory(struct pt_regs *regs, unsigned long address)
55 {
56 /*
57 * We ran out of memory, call the OOM killer, and return the userspace
58 * (which will retry the fault, or kill us if we got oom-killed).
59 */
60 if (!user_mode(regs)) {
61 no_context(regs, address);
62 return;
63 }
64 pagefault_out_of_memory();
65 }
66
do_sigbus(struct pt_regs * regs,unsigned long write,unsigned long address,int si_code)67 static void __kprobes do_sigbus(struct pt_regs *regs,
68 unsigned long write, unsigned long address, int si_code)
69 {
70 /* Kernel mode? Handle exceptions or die */
71 if (!user_mode(regs)) {
72 no_context(regs, address);
73 return;
74 }
75
76 /*
77 * Send a sigbus, regardless of whether we were in kernel
78 * or user mode.
79 */
80 current->thread.csr_badvaddr = address;
81 current->thread.trap_nr = read_csr_excode();
82 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
83 }
84
do_sigsegv(struct pt_regs * regs,unsigned long write,unsigned long address,int si_code)85 static void __kprobes do_sigsegv(struct pt_regs *regs,
86 unsigned long write, unsigned long address, int si_code)
87 {
88 const int field = sizeof(unsigned long) * 2;
89 static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
90
91 /* Kernel mode? Handle exceptions or die */
92 if (!user_mode(regs)) {
93 no_context(regs, address);
94 return;
95 }
96
97 /* User mode accesses just cause a SIGSEGV */
98 current->thread.csr_badvaddr = address;
99 if (!write)
100 current->thread.error_code = 1;
101 else
102 current->thread.error_code = 2;
103 current->thread.trap_nr = read_csr_excode();
104
105 if (show_unhandled_signals &&
106 unhandled_signal(current, SIGSEGV) && __ratelimit(&ratelimit_state)) {
107 pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n",
108 current->comm,
109 write ? "write access to" : "read access from",
110 field, address);
111 pr_info("era = %0*lx in", field,
112 (unsigned long) regs->csr_era);
113 print_vma_addr(KERN_CONT " ", regs->csr_era);
114 pr_cont("\n");
115 pr_info("ra = %0*lx in", field,
116 (unsigned long) regs->regs[1]);
117 print_vma_addr(KERN_CONT " ", regs->regs[1]);
118 pr_cont("\n");
119 }
120 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
121 }
122
123 /*
124 * This routine handles page faults. It determines the address,
125 * and the problem, and then passes it off to one of the appropriate
126 * routines.
127 */
__do_page_fault(struct pt_regs * regs,unsigned long write,unsigned long address)128 static void __kprobes __do_page_fault(struct pt_regs *regs,
129 unsigned long write, unsigned long address)
130 {
131 int si_code = SEGV_MAPERR;
132 unsigned int flags = FAULT_FLAG_DEFAULT;
133 struct task_struct *tsk = current;
134 struct mm_struct *mm = tsk->mm;
135 struct vm_area_struct *vma = NULL;
136 vm_fault_t fault;
137
138 /*
139 * We fault-in kernel-space virtual memory on-demand. The
140 * 'reference' page table is init_mm.pgd.
141 *
142 * NOTE! We MUST NOT take any locks for this case. We may
143 * be in an interrupt or a critical region, and should
144 * only copy the information from the master page table,
145 * nothing more.
146 */
147 if (address & __UA_LIMIT) {
148 if (!user_mode(regs))
149 no_context(regs, address);
150 else
151 do_sigsegv(regs, write, address, si_code);
152 return;
153 }
154
155 /*
156 * If we're in an interrupt or have no user
157 * context, we must not take the fault..
158 */
159 if (faulthandler_disabled() || !mm) {
160 do_sigsegv(regs, write, address, si_code);
161 return;
162 }
163
164 if (user_mode(regs))
165 flags |= FAULT_FLAG_USER;
166
167 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
168 retry:
169 mmap_read_lock(mm);
170 vma = find_vma(mm, address);
171 if (!vma)
172 goto bad_area;
173 if (vma->vm_start <= address)
174 goto good_area;
175 if (!(vma->vm_flags & VM_GROWSDOWN))
176 goto bad_area;
177 if (!expand_stack(vma, address))
178 goto good_area;
179 /*
180 * Something tried to access memory that isn't in our memory map..
181 * Fix it, but check if it's kernel or user first..
182 */
183 bad_area:
184 mmap_read_unlock(mm);
185 do_sigsegv(regs, write, address, si_code);
186 return;
187
188 /*
189 * Ok, we have a good vm_area for this memory access, so
190 * we can handle it..
191 */
192 good_area:
193 si_code = SEGV_ACCERR;
194
195 if (write) {
196 flags |= FAULT_FLAG_WRITE;
197 if (!(vma->vm_flags & VM_WRITE))
198 goto bad_area;
199 } else {
200 if (!(vma->vm_flags & VM_READ) && address != exception_era(regs))
201 goto bad_area;
202 if (!(vma->vm_flags & VM_EXEC) && address == exception_era(regs))
203 goto bad_area;
204 }
205
206 /*
207 * If for any reason at all we couldn't handle the fault,
208 * make sure we exit gracefully rather than endlessly redo
209 * the fault.
210 */
211 fault = handle_mm_fault(vma, address, flags, regs);
212
213 if (fault_signal_pending(fault, regs)) {
214 if (!user_mode(regs))
215 no_context(regs, address);
216 return;
217 }
218
219 /* The fault is fully completed (including releasing mmap lock) */
220 if (fault & VM_FAULT_COMPLETED)
221 return;
222
223 if (unlikely(fault & VM_FAULT_RETRY)) {
224 flags |= FAULT_FLAG_TRIED;
225
226 /*
227 * No need to mmap_read_unlock(mm) as we would
228 * have already released it in __lock_page_or_retry
229 * in mm/filemap.c.
230 */
231 goto retry;
232 }
233 if (unlikely(fault & VM_FAULT_ERROR)) {
234 mmap_read_unlock(mm);
235 if (fault & VM_FAULT_OOM) {
236 do_out_of_memory(regs, address);
237 return;
238 } else if (fault & VM_FAULT_SIGSEGV) {
239 do_sigsegv(regs, write, address, si_code);
240 return;
241 } else if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
242 do_sigbus(regs, write, address, si_code);
243 return;
244 }
245 BUG();
246 }
247
248 mmap_read_unlock(mm);
249 }
250
do_page_fault(struct pt_regs * regs,unsigned long write,unsigned long address)251 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
252 unsigned long write, unsigned long address)
253 {
254 irqentry_state_t state = irqentry_enter(regs);
255
256 /* Enable interrupt if enabled in parent context */
257 if (likely(regs->csr_prmd & CSR_PRMD_PIE))
258 local_irq_enable();
259
260 __do_page_fault(regs, write, address);
261
262 local_irq_disable();
263
264 irqentry_exit(regs, state);
265 }
266
