arch/sparc/kernel/unaligned_32.c

   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
  20 #include <asm/setup.h>
  21
  22 #include "kernel.h"
  23
  24 enum direction {
  25         load,    /* ld, ldd, ldh, ldsh */
  26         store,   /* st, std, sth, stsh */
  27         both,    /* Swap, ldstub, etc. */
  28         fpload,
  29         fpstore,
  30         invalid,
  31 };
  32
  33 static inline enum direction decode_direction(unsigned int insn)
  34 {
  35         unsigned long tmp = (insn >> 21) & 1;
  36
  37         if(!tmp)
  38                 return load;
  39         else {
  40                 if(((insn>>19)&0x3f) == 15)
  41                         return both;
  42                 else
  43                         return store;
  44         }
  45 }
  46
  47 /* 8 = double-word, 4 = word, 2 = half-word */
  48 static inline int decode_access_size(unsigned int insn)
  49 {
  50         insn = (insn >> 19) & 3;
  51
  52         if(!insn)
  53                 return 4;
  54         else if(insn == 3)
  55                 return 8;
  56         else if(insn == 2)
  57                 return 2;
  58         else {
  59                 printk("Impossible unaligned trap. insn=%08x\n", insn);
  60                 die_if_kernel("Byte sized unaligned access?!?!", current->thread.kregs);
  61                 return 4; /* just to keep gcc happy. */
  62         }
  63 }
  64
  65 /* 0x400000 = signed, 0 = unsigned */
  66 static inline int decode_signedness(unsigned int insn)
  67 {
  68         return (insn & 0x400000);
  69 }
  70
  71 static inline void maybe_flush_windows(unsigned int rs1, unsigned int rs2,
  72                                        unsigned int rd)
  73 {
  74         if(rs2 >= 16 || rs1 >= 16 || rd >= 16) {
  75                 /* Wheee... */
  76                 __asm__ __volatile__("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                                      "save %sp, -0x40, %sp\n\t"
  83                                      "restore; restore; restore; restore;\n\t"
  84                                      "restore; restore; restore;\n\t");
  85         }
  86 }
  87
  88 static inline int sign_extend_imm13(int imm)
  89 {
  90         return imm << 19 >> 19;
  91 }
  92
  93 static inline unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs)
  94 {
  95         struct reg_window32 *win;
  96
  97         if(reg < 16)
  98                 return (!reg ? 0 : regs->u_regs[reg]);
  99
 100         /* Ho hum, the slightly complicated case. */
 101         win = (struct reg_window32 *) regs->u_regs[UREG_FP];
 102         return win->locals[reg - 16]; /* yes, I know what this does... */
 103 }
 104
 105 static inline unsigned long safe_fetch_reg(unsigned int reg, struct pt_regs *regs)
 106 {
 107         struct reg_window32 __user *win;
 108         unsigned long ret;
 109
 110         if (reg < 16)
 111                 return (!reg ? 0 : regs->u_regs[reg]);
 112
 113         /* Ho hum, the slightly complicated case. */
 114         win = (struct reg_window32 __user *) regs->u_regs[UREG_FP];
 115
 116         if ((unsigned long)win & 3)
 117                 return -1;
 118
 119         if (get_user(ret, &win->locals[reg - 16]))
 120                 return -1;
 121
 122         return ret;
 123 }
 124
 125 static inline unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs)
 126 {
 127         struct reg_window32 *win;
 128
 129         if(reg < 16)
 130                 return &regs->u_regs[reg];
 131         win = (struct reg_window32 *) regs->u_regs[UREG_FP];
 132         return &win->locals[reg - 16];
 133 }
 134
 135 static unsigned long compute_effective_address(struct pt_regs *regs,
 136                                                unsigned int insn)
 137 {
 138         unsigned int rs1 = (insn >> 14) & 0x1f;
 139         unsigned int rs2 = insn & 0x1f;
 140         unsigned int rd = (insn >> 25) & 0x1f;
 141
 142         if(insn & 0x2000) {
 143                 maybe_flush_windows(rs1, 0, rd);
 144                 return (fetch_reg(rs1, regs) + sign_extend_imm13(insn));
 145         } else {
 146                 maybe_flush_windows(rs1, rs2, rd);
 147                 return (fetch_reg(rs1, regs) + fetch_reg(rs2, regs));
 148         }
 149 }
 150
 151 unsigned long safe_compute_effective_address(struct pt_regs *regs,
 152                                              unsigned int insn)
 153 {
 154         unsigned int rs1 = (insn >> 14) & 0x1f;
 155         unsigned int rs2 = insn & 0x1f;
 156         unsigned int rd = (insn >> 25) & 0x1f;
 157
 158         if(insn & 0x2000) {
 159                 maybe_flush_windows(rs1, 0, rd);
 160                 return (safe_fetch_reg(rs1, regs) + sign_extend_imm13(insn));
 161         } else {
 162                 maybe_flush_windows(rs1, rs2, rd);
 163                 return (safe_fetch_reg(rs1, regs) + safe_fetch_reg(rs2, regs));
 164         }
 165 }
 166
 167 /* This is just to make gcc think panic does return... */
 168 static void unaligned_panic(char *str)
 169 {
 170         panic("%s", str);
 171 }
 172
 173 /* una_asm.S */
 174 extern int do_int_load(unsigned long *dest_reg, int size,
 175                        unsigned long *saddr, int is_signed);
 176 extern int __do_int_store(unsigned long *dst_addr, int size,
 177                           unsigned long *src_val);
 178
 179 static int do_int_store(int reg_num, int size, unsigned long *dst_addr,
 180                         struct pt_regs *regs)
 181 {
 182         unsigned long zero[2] = { 0, 0 };
 183         unsigned long *src_val;
 184
 185         if (reg_num)
 186                 src_val = fetch_reg_addr(reg_num, regs);
 187         else {
 188                 src_val = &zero[0];
 189                 if (size == 8)
 190                         zero[1] = fetch_reg(1, regs);
 191         }
 192         return __do_int_store(dst_addr, size, src_val);
 193 }
 194
 195 extern void smp_capture(void);
 196 extern void smp_release(void);
 197
 198 static inline void advance(struct pt_regs *regs)
 199 {
 200         regs->pc   = regs->npc;
 201         regs->npc += 4;
 202 }
 203
 204 static inline int floating_point_load_or_store_p(unsigned int insn)
 205 {
 206         return (insn >> 24) & 1;
 207 }
 208
 209 static inline int ok_for_kernel(unsigned int insn)
 210 {
 211         return !floating_point_load_or_store_p(insn);
 212 }
 213
 214 static void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
 215 {
 216         unsigned long g2 = regs->u_regs [UREG_G2];
 217         unsigned long fixup = search_extables_range(regs->pc, &g2);
 218
 219         if (!fixup) {
 220                 unsigned long address = compute_effective_address(regs, insn);
 221                 if(address < PAGE_SIZE) {
 222                         printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference in mna handler");
 223                 } else
 224                         printk(KERN_ALERT "Unable to handle kernel paging request in mna handler");
 225                 printk(KERN_ALERT " at virtual address %08lx\n",address);
 226                 printk(KERN_ALERT "current->{mm,active_mm}->context = %08lx\n",
 227                         (current->mm ? current->mm->context :
 228                         current->active_mm->context));
 229                 printk(KERN_ALERT "current->{mm,active_mm}->pgd = %08lx\n",
 230                         (current->mm ? (unsigned long) current->mm->pgd :
 231                         (unsigned long) current->active_mm->pgd));
 232                 die_if_kernel("Oops", regs);
 233                 /* Not reached */
 234         }
 235         regs->pc = fixup;
 236         regs->npc = regs->pc + 4;
 237         regs->u_regs [UREG_G2] = g2;
 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 static inline int ok_for_user(struct pt_regs *regs, unsigned int insn,
 278                               enum direction dir)
 279 {
 280         unsigned int reg;
 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(WINREG_ADDR(reg - 16), size))
 293                         return -EFAULT;
 294         }
 295         reg = (insn >> 14) & 0x1f;
 296         if (reg >= 16) {
 297                 if (!access_ok(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(WINREG_ADDR(reg - 16), size))
 304                                 return -EFAULT;
 305                 }
 306         }
 307 #undef WINREG_ADDR
 308         return 0;
 309 }
 310
 311 static void user_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
 312 {
 313         send_sig_fault(SIGBUS, BUS_ADRALN,
 314                        (void __user *)safe_compute_effective_address(regs, insn),
 315                        0, current);
 316 }
 317
 318 asmlinkage void user_unaligned_trap(struct pt_regs *regs, unsigned int insn)
 319 {
 320         enum direction dir;
 321
 322         if(!(current->thread.flags & SPARC_FLAG_UNALIGNED) ||
 323            (((insn >> 30) & 3) != 3))
 324                 goto kill_user;
 325         dir = decode_direction(insn);
 326         if(!ok_for_user(regs, insn, dir)) {
 327                 goto kill_user;
 328         } else {
 329                 int err, size = decode_access_size(insn);
 330                 unsigned long addr;
 331
 332                 if(floating_point_load_or_store_p(insn)) {
 333                         printk("User FPU load/store unaligned unsupported.\n");
 334                         goto kill_user;
 335                 }
 336
 337                 addr = compute_effective_address(regs, insn);
 338                 perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
 339                 switch(dir) {
 340                 case load:
 341                         err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
 342                                                          regs),
 343                                           size, (unsigned long *) addr,
 344                                           decode_signedness(insn));
 345                         break;
 346
 347                 case store:
 348                         err = do_int_store(((insn>>25)&0x1f), size,
 349                                            (unsigned long *) addr, regs);
 350                         break;
 351
 352                 case both:
 353                         /*
 354                          * This was supported in 2.4. However, we question
 355                          * the value of SWAP instruction across word boundaries.
 356                          */
 357                         printk("Unaligned SWAP unsupported.\n");
 358                         err = -EFAULT;
 359                         break;
 360
 361                 default:
 362                         unaligned_panic("Impossible user unaligned trap.");
 363                         goto out;
 364                 }
 365                 if (err)
 366                         goto kill_user;
 367                 else
 368                         advance(regs);
 369                 goto out;
 370         }
 371
 372 kill_user:
 373         user_mna_trap_fault(regs, insn);
 374 out:
 375         ;
 376 }