1/*
2 * unaligned.c: Unaligned load/store trap handling with special
3 *              cases for the kernel to do them more quickly.
4 *
5 * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
6 * Copyright (C) 1996 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
7 */
8
9
10#include <linux/kernel.h>
11#include <linux/sched.h>
12#include <linux/mm.h>
13#include <asm/ptrace.h>
14#include <asm/processor.h>
15#include <asm/uaccess.h>
16#include <linux/smp.h>
17#include <linux/perf_event.h>
18
19#include <asm/setup.h>
20
21#include "kernel.h"
22
23enum direction {
24	load,    /* ld, ldd, ldh, ldsh */
25	store,   /* st, std, sth, stsh */
26	both,    /* Swap, ldstub, etc. */
27	fpload,
28	fpstore,
29	invalid,
30};
31
32static inline enum direction decode_direction(unsigned int insn)
33{
34	unsigned long tmp = (insn >> 21) & 1;
35
36	if(!tmp)
37		return load;
38	else {
39		if(((insn>>19)&0x3f) == 15)
40			return both;
41		else
42			return store;
43	}
44}
45
46/* 8 = double-word, 4 = word, 2 = half-word */
47static inline int decode_access_size(unsigned int insn)
48{
49	insn = (insn >> 19) & 3;
50
51	if(!insn)
52		return 4;
53	else if(insn == 3)
54		return 8;
55	else if(insn == 2)
56		return 2;
57	else {
58		printk("Impossible unaligned trap. insn=%08x\n", insn);
59		die_if_kernel("Byte sized unaligned access?!?!", current->thread.kregs);
60		return 4; /* just to keep gcc happy. */
61	}
62}
63
64/* 0x400000 = signed, 0 = unsigned */
65static inline int decode_signedness(unsigned int insn)
66{
67	return (insn & 0x400000);
68}
69
70static inline void maybe_flush_windows(unsigned int rs1, unsigned int rs2,
71				       unsigned int rd)
72{
73	if(rs2 >= 16 || rs1 >= 16 || rd >= 16) {
74		/* Wheee... */
75		__asm__ __volatile__("save %sp, -0x40, %sp\n\t"
76				     "save %sp, -0x40, %sp\n\t"
77				     "save %sp, -0x40, %sp\n\t"
78				     "save %sp, -0x40, %sp\n\t"
79				     "save %sp, -0x40, %sp\n\t"
80				     "save %sp, -0x40, %sp\n\t"
81				     "save %sp, -0x40, %sp\n\t"
82				     "restore; restore; restore; restore;\n\t"
83				     "restore; restore; restore;\n\t");
84	}
85}
86
87static inline int sign_extend_imm13(int imm)
88{
89	return imm << 19 >> 19;
90}
91
92static inline unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs)
93{
94	struct reg_window32 *win;
95
96	if(reg < 16)
97		return (!reg ? 0 : regs->u_regs[reg]);
98
99	/* Ho hum, the slightly complicated case. */
100	win = (struct reg_window32 *) regs->u_regs[UREG_FP];
101	return win->locals[reg - 16]; /* yes, I know what this does... */
102}
103
104static inline unsigned long safe_fetch_reg(unsigned int reg, struct pt_regs *regs)
105{
106	struct reg_window32 __user *win;
107	unsigned long ret;
108
109	if (reg < 16)
110		return (!reg ? 0 : regs->u_regs[reg]);
111
112	/* Ho hum, the slightly complicated case. */
113	win = (struct reg_window32 __user *) regs->u_regs[UREG_FP];
114
115	if ((unsigned long)win & 3)
116		return -1;
117
118	if (get_user(ret, &win->locals[reg - 16]))
119		return -1;
120
121	return ret;
122}
123
124static inline unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs)
125{
126	struct reg_window32 *win;
127
128	if(reg < 16)
129		return &regs->u_regs[reg];
130	win = (struct reg_window32 *) regs->u_regs[UREG_FP];
131	return &win->locals[reg - 16];
132}
133
134static unsigned long compute_effective_address(struct pt_regs *regs,
135					       unsigned int insn)
136{
137	unsigned int rs1 = (insn >> 14) & 0x1f;
138	unsigned int rs2 = insn & 0x1f;
139	unsigned int rd = (insn >> 25) & 0x1f;
140
141	if(insn & 0x2000) {
142		maybe_flush_windows(rs1, 0, rd);
143		return (fetch_reg(rs1, regs) + sign_extend_imm13(insn));
144	} else {
145		maybe_flush_windows(rs1, rs2, rd);
146		return (fetch_reg(rs1, regs) + fetch_reg(rs2, regs));
147	}
148}
149
150unsigned long safe_compute_effective_address(struct pt_regs *regs,
151					     unsigned int insn)
152{
153	unsigned int rs1 = (insn >> 14) & 0x1f;
154	unsigned int rs2 = insn & 0x1f;
155	unsigned int rd = (insn >> 25) & 0x1f;
156
157	if(insn & 0x2000) {
158		maybe_flush_windows(rs1, 0, rd);
159		return (safe_fetch_reg(rs1, regs) + sign_extend_imm13(insn));
160	} else {
161		maybe_flush_windows(rs1, rs2, rd);
162		return (safe_fetch_reg(rs1, regs) + safe_fetch_reg(rs2, regs));
163	}
164}
165
166/* This is just to make gcc think panic does return... */
167static void unaligned_panic(char *str)
168{
169	panic("%s", str);
170}
171
172/* una_asm.S */
173extern int do_int_load(unsigned long *dest_reg, int size,
174		       unsigned long *saddr, int is_signed);
175extern int __do_int_store(unsigned long *dst_addr, int size,
176			  unsigned long *src_val);
177
178static int do_int_store(int reg_num, int size, unsigned long *dst_addr,
179			struct pt_regs *regs)
180{
181	unsigned long zero[2] = { 0, 0 };
182	unsigned long *src_val;
183
184	if (reg_num)
185		src_val = fetch_reg_addr(reg_num, regs);
186	else {
187		src_val = &zero[0];
188		if (size == 8)
189			zero[1] = fetch_reg(1, regs);
190	}
191	return __do_int_store(dst_addr, size, src_val);
192}
193
194extern void smp_capture(void);
195extern void smp_release(void);
196
197static inline void advance(struct pt_regs *regs)
198{
199	regs->pc   = regs->npc;
200	regs->npc += 4;
201}
202
203static inline int floating_point_load_or_store_p(unsigned int insn)
204{
205	return (insn >> 24) & 1;
206}
207
208static inline int ok_for_kernel(unsigned int insn)
209{
210	return !floating_point_load_or_store_p(insn);
211}
212
213static void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
214{
215	unsigned long g2 = regs->u_regs [UREG_G2];
216	unsigned long fixup = search_extables_range(regs->pc, &g2);
217
218	if (!fixup) {
219		unsigned long address = compute_effective_address(regs, insn);
220        	if(address < PAGE_SIZE) {
221                	printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference in mna handler");
222        	} else
223                	printk(KERN_ALERT "Unable to handle kernel paging request in mna handler");
224	        printk(KERN_ALERT " at virtual address %08lx\n",address);
225		printk(KERN_ALERT "current->{mm,active_mm}->context = %08lx\n",
226			(current->mm ? current->mm->context :
227			current->active_mm->context));
228		printk(KERN_ALERT "current->{mm,active_mm}->pgd = %08lx\n",
229			(current->mm ? (unsigned long) current->mm->pgd :
230			(unsigned long) current->active_mm->pgd));
231	        die_if_kernel("Oops", regs);
232		/* Not reached */
233	}
234	regs->pc = fixup;
235	regs->npc = regs->pc + 4;
236	regs->u_regs [UREG_G2] = g2;
237}
238
239asmlinkage void kernel_unaligned_trap(struct pt_regs *regs, unsigned int insn)
240{
241	enum direction dir = decode_direction(insn);
242	int size = decode_access_size(insn);
243
244	if(!ok_for_kernel(insn) || dir == both) {
245		printk("Unsupported unaligned load/store trap for kernel at <%08lx>.\n",
246		       regs->pc);
247		unaligned_panic("Wheee. Kernel does fpu/atomic unaligned load/store.");
248	} else {
249		unsigned long addr = compute_effective_address(regs, insn);
250		int err;
251
252		perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
253		switch (dir) {
254		case load:
255			err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
256							 regs),
257					  size, (unsigned long *) addr,
258					  decode_signedness(insn));
259			break;
260
261		case store:
262			err = do_int_store(((insn>>25)&0x1f), size,
263					   (unsigned long *) addr, regs);
264			break;
265		default:
266			panic("Impossible kernel unaligned trap.");
267			/* Not reached... */
268		}
269		if (err)
270			kernel_mna_trap_fault(regs, insn);
271		else
272			advance(regs);
273	}
274}
275
276static inline int ok_for_user(struct pt_regs *regs, unsigned int insn,
277			      enum direction dir)
278{
279	unsigned int reg;
280	int check = (dir == load) ? VERIFY_READ : VERIFY_WRITE;
281	int size = ((insn >> 19) & 3) == 3 ? 8 : 4;
282
283	if ((regs->pc | regs->npc) & 3)
284		return 0;
285
286	/* Must access_ok() in all the necessary places. */
287#define WINREG_ADDR(regnum) \
288	((void __user *)(((unsigned long *)regs->u_regs[UREG_FP])+(regnum)))
289
290	reg = (insn >> 25) & 0x1f;
291	if (reg >= 16) {
292		if (!access_ok(check, WINREG_ADDR(reg - 16), size))
293			return -EFAULT;
294	}
295	reg = (insn >> 14) & 0x1f;
296	if (reg >= 16) {
297		if (!access_ok(check, WINREG_ADDR(reg - 16), size))
298			return -EFAULT;
299	}
300	if (!(insn & 0x2000)) {
301		reg = (insn & 0x1f);
302		if (reg >= 16) {
303			if (!access_ok(check, WINREG_ADDR(reg - 16), size))
304				return -EFAULT;
305		}
306	}
307#undef WINREG_ADDR
308	return 0;
309}
310
311static void user_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
312{
313	siginfo_t info;
314
315	info.si_signo = SIGBUS;
316	info.si_errno = 0;
317	info.si_code = BUS_ADRALN;
318	info.si_addr = (void __user *)safe_compute_effective_address(regs, insn);
319	info.si_trapno = 0;
320	send_sig_info(SIGBUS, &info, current);
321}
322
323asmlinkage void user_unaligned_trap(struct pt_regs *regs, unsigned int insn)
324{
325	enum direction dir;
326
327	if(!(current->thread.flags & SPARC_FLAG_UNALIGNED) ||
328	   (((insn >> 30) & 3) != 3))
329		goto kill_user;
330	dir = decode_direction(insn);
331	if(!ok_for_user(regs, insn, dir)) {
332		goto kill_user;
333	} else {
334		int err, size = decode_access_size(insn);
335		unsigned long addr;
336
337		if(floating_point_load_or_store_p(insn)) {
338			printk("User FPU load/store unaligned unsupported.\n");
339			goto kill_user;
340		}
341
342		addr = compute_effective_address(regs, insn);
343		perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
344		switch(dir) {
345		case load:
346			err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
347							 regs),
348					  size, (unsigned long *) addr,
349					  decode_signedness(insn));
350			break;
351
352		case store:
353			err = do_int_store(((insn>>25)&0x1f), size,
354					   (unsigned long *) addr, regs);
355			break;
356
357		case both:
358			/*
359			 * This was supported in 2.4. However, we question
360			 * the value of SWAP instruction across word boundaries.
361			 */
362			printk("Unaligned SWAP unsupported.\n");
363			err = -EFAULT;
364			break;
365
366		default:
367			unaligned_panic("Impossible user unaligned trap.");
368			goto out;
369		}
370		if (err)
371			goto kill_user;
372		else
373			advance(regs);
374		goto out;
375	}
376
377kill_user:
378	user_mna_trap_fault(regs, insn);
379out:
380	;
381}
382