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 #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 &regs->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 }