1// SPDX-License-Identifier: GPL-2.0
2/*
3 * unaligned.c: Unaligned load/store trap handling with special
4 *              cases for the kernel to do them more quickly.
5 *
6 * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
7 * Copyright (C) 1996 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
8 */
9
10
11#include <linux/kernel.h>
12#include <linux/sched/signal.h>
13#include <linux/mm.h>
14#include <asm/ptrace.h>
15#include <asm/processor.h>
16#include <linux/uaccess.h>
17#include <linux/smp.h>
18#include <linux/perf_event.h>
19#include <linux/extable.h>
20
21#include <asm/setup.h>
22
23#include "kernel.h"
24
25enum direction {
26	load,    /* ld, ldd, ldh, ldsh */
27	store,   /* st, std, sth, stsh */
28	both,    /* Swap, ldstub, etc. */
29	fpload,
30	fpstore,
31	invalid,
32};
33
34static inline enum direction decode_direction(unsigned int insn)
35{
36	unsigned long tmp = (insn >> 21) & 1;
37
38	if(!tmp)
39		return load;
40	else {
41		if(((insn>>19)&0x3f) == 15)
42			return both;
43		else
44			return store;
45	}
46}
47
48/* 8 = double-word, 4 = word, 2 = half-word */
49static inline int decode_access_size(unsigned int insn)
50{
51	insn = (insn >> 19) & 3;
52
53	if(!insn)
54		return 4;
55	else if(insn == 3)
56		return 8;
57	else if(insn == 2)
58		return 2;
59	else {
60		printk("Impossible unaligned trap. insn=%08x\n", insn);
61		die_if_kernel("Byte sized unaligned access?!?!", current->thread.kregs);
62		return 4; /* just to keep gcc happy. */
63	}
64}
65
66/* 0x400000 = signed, 0 = unsigned */
67static inline int decode_signedness(unsigned int insn)
68{
69	return (insn & 0x400000);
70}
71
72static inline void maybe_flush_windows(unsigned int rs1, unsigned int rs2,
73				       unsigned int rd)
74{
75	if(rs2 >= 16 || rs1 >= 16 || rd >= 16) {
76		/* Wheee... */
77		__asm__ __volatile__("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				     "save %sp, -0x40, %sp\n\t"
83				     "save %sp, -0x40, %sp\n\t"
84				     "restore; restore; restore; restore;\n\t"
85				     "restore; restore; restore;\n\t");
86	}
87}
88
89static inline int sign_extend_imm13(int imm)
90{
91	return imm << 19 >> 19;
92}
93
94static inline unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs)
95{
96	struct reg_window32 *win;
97
98	if(reg < 16)
99		return (!reg ? 0 : regs->u_regs[reg]);
100
101	/* Ho hum, the slightly complicated case. */
102	win = (struct reg_window32 *) regs->u_regs[UREG_FP];
103	return win->locals[reg - 16]; /* yes, I know what this does... */
104}
105
106static inline unsigned long safe_fetch_reg(unsigned int reg, struct pt_regs *regs)
107{
108	struct reg_window32 __user *win;
109	unsigned long ret;
110
111	if (reg < 16)
112		return (!reg ? 0 : regs->u_regs[reg]);
113
114	/* Ho hum, the slightly complicated case. */
115	win = (struct reg_window32 __user *) regs->u_regs[UREG_FP];
116
117	if ((unsigned long)win & 3)
118		return -1;
119
120	if (get_user(ret, &win->locals[reg - 16]))
121		return -1;
122
123	return ret;
124}
125
126static inline unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs)
127{
128	struct reg_window32 *win;
129
130	if(reg < 16)
131		return &regs->u_regs[reg];
132	win = (struct reg_window32 *) regs->u_regs[UREG_FP];
133	return &win->locals[reg - 16];
134}
135
136static unsigned long compute_effective_address(struct pt_regs *regs,
137					       unsigned int insn)
138{
139	unsigned int rs1 = (insn >> 14) & 0x1f;
140	unsigned int rs2 = insn & 0x1f;
141	unsigned int rd = (insn >> 25) & 0x1f;
142
143	if(insn & 0x2000) {
144		maybe_flush_windows(rs1, 0, rd);
145		return (fetch_reg(rs1, regs) + sign_extend_imm13(insn));
146	} else {
147		maybe_flush_windows(rs1, rs2, rd);
148		return (fetch_reg(rs1, regs) + fetch_reg(rs2, regs));
149	}
150}
151
152unsigned long safe_compute_effective_address(struct pt_regs *regs,
153					     unsigned int insn)
154{
155	unsigned int rs1 = (insn >> 14) & 0x1f;
156	unsigned int rs2 = insn & 0x1f;
157	unsigned int rd = (insn >> 25) & 0x1f;
158
159	if(insn & 0x2000) {
160		maybe_flush_windows(rs1, 0, rd);
161		return (safe_fetch_reg(rs1, regs) + sign_extend_imm13(insn));
162	} else {
163		maybe_flush_windows(rs1, rs2, rd);
164		return (safe_fetch_reg(rs1, regs) + safe_fetch_reg(rs2, regs));
165	}
166}
167
168/* This is just to make gcc think panic does return... */
169static void unaligned_panic(char *str)
170{
171	panic("%s", str);
172}
173
174/* una_asm.S */
175extern int do_int_load(unsigned long *dest_reg, int size,
176		       unsigned long *saddr, int is_signed);
177extern int __do_int_store(unsigned long *dst_addr, int size,
178			  unsigned long *src_val);
179
180static int do_int_store(int reg_num, int size, unsigned long *dst_addr,
181			struct pt_regs *regs)
182{
183	unsigned long zero[2] = { 0, 0 };
184	unsigned long *src_val;
185
186	if (reg_num)
187		src_val = fetch_reg_addr(reg_num, regs);
188	else {
189		src_val = &zero[0];
190		if (size == 8)
191			zero[1] = fetch_reg(1, regs);
192	}
193	return __do_int_store(dst_addr, size, src_val);
194}
195
196extern void smp_capture(void);
197extern void smp_release(void);
198
199static inline void advance(struct pt_regs *regs)
200{
201	regs->pc   = regs->npc;
202	regs->npc += 4;
203}
204
205static inline int floating_point_load_or_store_p(unsigned int insn)
206{
207	return (insn >> 24) & 1;
208}
209
210static inline int ok_for_kernel(unsigned int insn)
211{
212	return !floating_point_load_or_store_p(insn);
213}
214
215static void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
216{
217	const struct exception_table_entry *entry;
218
219	entry = search_exception_tables(regs->pc);
220	if (!entry) {
221		unsigned long address = compute_effective_address(regs, insn);
222        	if(address < PAGE_SIZE) {
223                	printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference in mna handler");
224        	} else
225                	printk(KERN_ALERT "Unable to handle kernel paging request in mna handler");
226	        printk(KERN_ALERT " at virtual address %08lx\n",address);
227		printk(KERN_ALERT "current->{mm,active_mm}->context = %08lx\n",
228			(current->mm ? current->mm->context :
229			current->active_mm->context));
230		printk(KERN_ALERT "current->{mm,active_mm}->pgd = %08lx\n",
231			(current->mm ? (unsigned long) current->mm->pgd :
232			(unsigned long) current->active_mm->pgd));
233	        die_if_kernel("Oops", regs);
234		/* Not reached */
235	}
236	regs->pc = entry->fixup;
237	regs->npc = regs->pc + 4;
238}
239
240asmlinkage void kernel_unaligned_trap(struct pt_regs *regs, unsigned int insn)
241{
242	enum direction dir = decode_direction(insn);
243	int size = decode_access_size(insn);
244
245	if(!ok_for_kernel(insn) || dir == both) {
246		printk("Unsupported unaligned load/store trap for kernel at <%08lx>.\n",
247		       regs->pc);
248		unaligned_panic("Wheee. Kernel does fpu/atomic unaligned load/store.");
249	} else {
250		unsigned long addr = compute_effective_address(regs, insn);
251		int err;
252
253		perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
254		switch (dir) {
255		case load:
256			err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
257							 regs),
258					  size, (unsigned long *) addr,
259					  decode_signedness(insn));
260			break;
261
262		case store:
263			err = do_int_store(((insn>>25)&0x1f), size,
264					   (unsigned long *) addr, regs);
265			break;
266		default:
267			panic("Impossible kernel unaligned trap.");
268			/* Not reached... */
269		}
270		if (err)
271			kernel_mna_trap_fault(regs, insn);
272		else
273			advance(regs);
274	}
275}
276
277asmlinkage void user_unaligned_trap(struct pt_regs *regs, unsigned int insn)
278{
279	send_sig_fault(SIGBUS, BUS_ADRALN,
280		       (void __user *)safe_compute_effective_address(regs, insn),
281		       current);
282}
283