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 25 enum 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 34 static 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 */ 49 static 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 */ 67 static inline int decode_signedness(unsigned int insn) 68 { 69 return (insn & 0x400000); 70 } 71 72 static 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 89 static inline int sign_extend_imm13(int imm) 90 { 91 return imm << 19 >> 19; 92 } 93 94 static 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 } 105 106 static 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 } 125 126 static 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 ®s->u_regs[reg]; 132 win = (struct reg_window32 *) regs->u_regs[UREG_FP]; 133 return &win->locals[reg - 16]; 134 } 135 136 static 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 } 151 152 unsigned 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... */ 169 static void unaligned_panic(char *str) 170 { 171 panic("%s", str); 172 } 173 174 /* una_asm.S */ 175 extern int do_int_load(unsigned long *dest_reg, int size, 176 unsigned long *saddr, int is_signed); 177 extern int __do_int_store(unsigned long *dst_addr, int size, 178 unsigned long *src_val); 179 180 static 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 } 195 196 extern void smp_capture(void); 197 extern void smp_release(void); 198 199 static inline void advance(struct pt_regs *regs) 200 { 201 regs->pc = regs->npc; 202 regs->npc += 4; 203 } 204 205 static inline int floating_point_load_or_store_p(unsigned int insn) 206 { 207 return (insn >> 24) & 1; 208 } 209 210 static inline int ok_for_kernel(unsigned int insn) 211 { 212 return !floating_point_load_or_store_p(insn); 213 } 214 215 static 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 } 239 240 asmlinkage 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 } 276 277 asmlinkage 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