xref: /openbmc/linux/arch/um/kernel/trap.c (revision c21b37f6)
1 /*
2  * Copyright (C) 2000, 2001 Jeff Dike (jdike@karaya.com)
3  * Licensed under the GPL
4  */
5 
6 #include "linux/kernel.h"
7 #include "asm/errno.h"
8 #include "linux/sched.h"
9 #include "linux/mm.h"
10 #include "linux/spinlock.h"
11 #include "linux/init.h"
12 #include "linux/ptrace.h"
13 #include "asm/semaphore.h"
14 #include "asm/pgtable.h"
15 #include "asm/pgalloc.h"
16 #include "asm/tlbflush.h"
17 #include "asm/a.out.h"
18 #include "asm/current.h"
19 #include "asm/irq.h"
20 #include "sysdep/sigcontext.h"
21 #include "kern_util.h"
22 #include "as-layout.h"
23 #include "arch.h"
24 #include "kern.h"
25 #include "chan_kern.h"
26 #include "mconsole_kern.h"
27 #include "mem.h"
28 #include "mem_kern.h"
29 #include "sysdep/sigcontext.h"
30 #include "sysdep/ptrace.h"
31 #include "os.h"
32 #ifdef CONFIG_MODE_SKAS
33 #include "skas.h"
34 #endif
35 #include "os.h"
36 
37 /* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
38 int handle_page_fault(unsigned long address, unsigned long ip,
39 		      int is_write, int is_user, int *code_out)
40 {
41 	struct mm_struct *mm = current->mm;
42 	struct vm_area_struct *vma;
43 	pgd_t *pgd;
44 	pud_t *pud;
45 	pmd_t *pmd;
46 	pte_t *pte;
47 	int err = -EFAULT;
48 
49 	*code_out = SEGV_MAPERR;
50 
51 	/* If the fault was during atomic operation, don't take the fault, just
52 	 * fail. */
53 	if (in_atomic())
54 		goto out_nosemaphore;
55 
56 	down_read(&mm->mmap_sem);
57 	vma = find_vma(mm, address);
58 	if(!vma)
59 		goto out;
60 	else if(vma->vm_start <= address)
61 		goto good_area;
62 	else if(!(vma->vm_flags & VM_GROWSDOWN))
63 		goto out;
64 	else if(is_user && !ARCH_IS_STACKGROW(address))
65 		goto out;
66 	else if(expand_stack(vma, address))
67 		goto out;
68 
69 good_area:
70 	*code_out = SEGV_ACCERR;
71 	if(is_write && !(vma->vm_flags & VM_WRITE))
72 		goto out;
73 
74 	/* Don't require VM_READ|VM_EXEC for write faults! */
75 	if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
76 		goto out;
77 
78 	do {
79 		int fault;
80 survive:
81 		fault = handle_mm_fault(mm, vma, address, is_write);
82 		if (unlikely(fault & VM_FAULT_ERROR)) {
83 			if (fault & VM_FAULT_OOM) {
84 				err = -ENOMEM;
85 				goto out_of_memory;
86 			} else if (fault & VM_FAULT_SIGBUS) {
87 				err = -EACCES;
88 				goto out;
89 			}
90 			BUG();
91 		}
92 		if (fault & VM_FAULT_MAJOR)
93 			current->maj_flt++;
94 		else
95 			current->min_flt++;
96 
97 		pgd = pgd_offset(mm, address);
98 		pud = pud_offset(pgd, address);
99 		pmd = pmd_offset(pud, address);
100 		pte = pte_offset_kernel(pmd, address);
101 	} while(!pte_present(*pte));
102 	err = 0;
103 	/* The below warning was added in place of
104 	 *	pte_mkyoung(); if (is_write) pte_mkdirty();
105 	 * If it's triggered, we'd see normally a hang here (a clean pte is
106 	 * marked read-only to emulate the dirty bit).
107 	 * However, the generic code can mark a PTE writable but clean on a
108 	 * concurrent read fault, triggering this harmlessly. So comment it out.
109 	 */
110 #if 0
111 	WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
112 #endif
113 	flush_tlb_page(vma, address);
114 out:
115 	up_read(&mm->mmap_sem);
116 out_nosemaphore:
117 	return(err);
118 
119 /*
120  * We ran out of memory, or some other thing happened to us that made
121  * us unable to handle the page fault gracefully.
122  */
123 out_of_memory:
124 	if (is_init(current)) {
125 		up_read(&mm->mmap_sem);
126 		yield();
127 		down_read(&mm->mmap_sem);
128 		goto survive;
129 	}
130 	goto out;
131 }
132 
133 static void bad_segv(struct faultinfo fi, unsigned long ip)
134 {
135 	struct siginfo si;
136 
137 	si.si_signo = SIGSEGV;
138 	si.si_code = SEGV_ACCERR;
139 	si.si_addr = (void __user *) FAULT_ADDRESS(fi);
140 	current->thread.arch.faultinfo = fi;
141 	force_sig_info(SIGSEGV, &si, current);
142 }
143 
144 static void segv_handler(int sig, union uml_pt_regs *regs)
145 {
146 	struct faultinfo * fi = UPT_FAULTINFO(regs);
147 
148 	if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){
149 		bad_segv(*fi, UPT_IP(regs));
150 		return;
151 	}
152 	segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
153 }
154 
155 /*
156  * We give a *copy* of the faultinfo in the regs to segv.
157  * This must be done, since nesting SEGVs could overwrite
158  * the info in the regs. A pointer to the info then would
159  * give us bad data!
160  */
161 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
162 		   union uml_pt_regs *regs)
163 {
164 	struct siginfo si;
165 	void *catcher;
166 	int err;
167 	int is_write = FAULT_WRITE(fi);
168 	unsigned long address = FAULT_ADDRESS(fi);
169 
170 	if(!is_user && (address >= start_vm) && (address < end_vm)){
171 		flush_tlb_kernel_vm();
172 		return 0;
173 	}
174 	else if(current->mm == NULL) {
175 		show_regs(container_of(regs, struct pt_regs, regs));
176   		panic("Segfault with no mm");
177 	}
178 
179 	if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
180 		err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
181 	else {
182 		err = -EFAULT;
183 		/* A thread accessed NULL, we get a fault, but CR2 is invalid.
184 		 * This code is used in __do_copy_from_user() of TT mode. */
185 		address = 0;
186 	}
187 
188 	catcher = current->thread.fault_catcher;
189 	if(!err)
190 		return 0;
191 	else if(catcher != NULL){
192 		current->thread.fault_addr = (void *) address;
193 		do_longjmp(catcher, 1);
194 	}
195 	else if(current->thread.fault_addr != NULL)
196 		panic("fault_addr set but no fault catcher");
197 	else if(!is_user && arch_fixup(ip, regs))
198 		return 0;
199 
200 	if(!is_user) {
201 		show_regs(container_of(regs, struct pt_regs, regs));
202 		panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
203 		      address, ip);
204 	}
205 
206 	if (err == -EACCES) {
207 		si.si_signo = SIGBUS;
208 		si.si_errno = 0;
209 		si.si_code = BUS_ADRERR;
210 		si.si_addr = (void __user *)address;
211 		current->thread.arch.faultinfo = fi;
212 		force_sig_info(SIGBUS, &si, current);
213 	} else if (err == -ENOMEM) {
214 		printk("VM: killing process %s\n", current->comm);
215 		do_exit(SIGKILL);
216 	} else {
217 		BUG_ON(err != -EFAULT);
218 		si.si_signo = SIGSEGV;
219 		si.si_addr = (void __user *) address;
220 		current->thread.arch.faultinfo = fi;
221 		force_sig_info(SIGSEGV, &si, current);
222 	}
223 	return 0;
224 }
225 
226 void relay_signal(int sig, union uml_pt_regs *regs)
227 {
228 	if(arch_handle_signal(sig, regs))
229 		return;
230 
231 	if(!UPT_IS_USER(regs)){
232 		if(sig == SIGBUS)
233 			printk("Bus error - the host /dev/shm or /tmp mount "
234 			       "likely just ran out of space\n");
235 		panic("Kernel mode signal %d", sig);
236 	}
237 
238 	current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
239 	force_sig(sig, current);
240 }
241 
242 static void bus_handler(int sig, union uml_pt_regs *regs)
243 {
244 	if(current->thread.fault_catcher != NULL)
245 		do_longjmp(current->thread.fault_catcher, 1);
246 	else relay_signal(sig, regs);
247 }
248 
249 static void winch(int sig, union uml_pt_regs *regs)
250 {
251 	do_IRQ(WINCH_IRQ, regs);
252 }
253 
254 const struct kern_handlers handlinfo_kern = {
255 	.relay_signal = relay_signal,
256 	.winch = winch,
257 	.bus_handler = bus_handler,
258 	.page_fault = segv_handler,
259 	.sigio_handler = sigio_handler,
260 	.timer_handler = timer_handler
261 };
262 
263 void trap_init(void)
264 {
265 }
266