arch/riscv/kernel/traps.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2012 Regents of the University of California
   4  */
   5
   6 #include <linux/cpu.h>
   7 #include <linux/kernel.h>
   8 #include <linux/init.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/debug.h>
  11 #include <linux/sched/signal.h>
  12 #include <linux/signal.h>
  13 #include <linux/kdebug.h>
  14 #include <linux/uaccess.h>
  15 #include <linux/kprobes.h>
  16 #include <linux/mm.h>
  17 #include <linux/module.h>
  18 #include <linux/irq.h>
  19 #include <linux/kexec.h>
  20 #include <linux/entry-common.h>
  21
  22 #include <asm/asm-prototypes.h>
  23 #include <asm/bug.h>
  24 #include <asm/cfi.h>
  25 #include <asm/csr.h>
  26 #include <asm/processor.h>
  27 #include <asm/ptrace.h>
  28 #include <asm/syscall.h>
  29 #include <asm/thread_info.h>
  30 #include <asm/vector.h>
  31 #include <asm/irq_stack.h>
  32
  33 int show_unhandled_signals = 1;
  34
  35 static DEFINE_SPINLOCK(die_lock);
  36
  37 static void dump_kernel_instr(const char *loglvl, struct pt_regs *regs)
  38 {
  39         char str[sizeof("0000 ") * 12 + 2 + 1], *p = str;
  40         const u16 *insns = (u16 *)instruction_pointer(regs);
  41         long bad;
  42         u16 val;
  43         int i;
  44
  45         for (i = -10; i < 2; i++) {
  46                 bad = get_kernel_nofault(val, &insns[i]);
  47                 if (!bad) {
  48                         p += sprintf(p, i == 0 ? "(%04hx) " : "%04hx ", val);
  49                 } else {
  50                         printk("%sCode: Unable to access instruction at 0x%px.\n",
  51                                loglvl, &insns[i]);
  52                         return;
  53                 }
  54         }
  55         printk("%sCode: %s\n", loglvl, str);
  56 }
  57
  58 void die(struct pt_regs *regs, const char *str)
  59 {
  60         static int die_counter;
  61         int ret;
  62         long cause;
  63         unsigned long flags;
  64
  65         oops_enter();
  66
  67         spin_lock_irqsave(&die_lock, flags);
  68         console_verbose();
  69         bust_spinlocks(1);
  70
  71         pr_emerg("%s [#%d]\n", str, ++die_counter);
  72         print_modules();
  73         if (regs) {
  74                 show_regs(regs);
  75                 dump_kernel_instr(KERN_EMERG, regs);
  76         }
  77
  78         cause = regs ? regs->cause : -1;
  79         ret = notify_die(DIE_OOPS, str, regs, 0, cause, SIGSEGV);
  80
  81         if (kexec_should_crash(current))
  82                 crash_kexec(regs);
  83
  84         bust_spinlocks(0);
  85         add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
  86         spin_unlock_irqrestore(&die_lock, flags);
  87         oops_exit();
  88
  89         if (in_interrupt())
  90                 panic("Fatal exception in interrupt");
  91         if (panic_on_oops)
  92                 panic("Fatal exception");
  93         if (ret != NOTIFY_STOP)
  94                 make_task_dead(SIGSEGV);
  95 }
  96
  97 void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
  98 {
  99         struct task_struct *tsk = current;
 100
 101         if (show_unhandled_signals && unhandled_signal(tsk, signo)
 102             && printk_ratelimit()) {
 103                 pr_info("%s[%d]: unhandled signal %d code 0x%x at 0x" REG_FMT,
 104                         tsk->comm, task_pid_nr(tsk), signo, code, addr);
 105                 print_vma_addr(KERN_CONT " in ", instruction_pointer(regs));
 106                 pr_cont("\n");
 107                 __show_regs(regs);
 108         }
 109
 110         force_sig_fault(signo, code, (void __user *)addr);
 111 }
 112
 113 static void do_trap_error(struct pt_regs *regs, int signo, int code,
 114         unsigned long addr, const char *str)
 115 {
 116         current->thread.bad_cause = regs->cause;
 117
 118         if (user_mode(regs)) {
 119                 do_trap(regs, signo, code, addr);
 120         } else {
 121                 if (!fixup_exception(regs))
 122                         die(regs, str);
 123         }
 124 }
 125
 126 #if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_RISCV_ALTERNATIVE)
 127 #define __trap_section __noinstr_section(".xip.traps")
 128 #else
 129 #define __trap_section noinstr
 130 #endif
 131 #define DO_ERROR_INFO(name, signo, code, str)                                   \
 132 asmlinkage __visible __trap_section void name(struct pt_regs *regs)             \
 133 {                                                                               \
 134         if (user_mode(regs)) {                                                  \
 135                 irqentry_enter_from_user_mode(regs);                            \
 136                 do_trap_error(regs, signo, code, regs->epc, "Oops - " str);     \
 137                 irqentry_exit_to_user_mode(regs);                               \
 138         } else {                                                                \
 139                 irqentry_state_t state = irqentry_nmi_enter(regs);              \
 140                 do_trap_error(regs, signo, code, regs->epc, "Oops - " str);     \
 141                 irqentry_nmi_exit(regs, state);                                 \
 142         }                                                                       \
 143 }
 144
 145 DO_ERROR_INFO(do_trap_unknown,
 146         SIGILL, ILL_ILLTRP, "unknown exception");
 147 DO_ERROR_INFO(do_trap_insn_misaligned,
 148         SIGBUS, BUS_ADRALN, "instruction address misaligned");
 149 DO_ERROR_INFO(do_trap_insn_fault,
 150         SIGSEGV, SEGV_ACCERR, "instruction access fault");
 151
 152 asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *regs)
 153 {
 154         bool handled;
 155
 156         if (user_mode(regs)) {
 157                 irqentry_enter_from_user_mode(regs);
 158
 159                 local_irq_enable();
 160
 161                 handled = riscv_v_first_use_handler(regs);
 162
 163                 local_irq_disable();
 164
 165                 if (!handled)
 166                         do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->epc,
 167                                       "Oops - illegal instruction");
 168
 169                 irqentry_exit_to_user_mode(regs);
 170         } else {
 171                 irqentry_state_t state = irqentry_nmi_enter(regs);
 172
 173                 do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->epc,
 174                               "Oops - illegal instruction");
 175
 176                 irqentry_nmi_exit(regs, state);
 177         }
 178 }
 179
 180 DO_ERROR_INFO(do_trap_load_fault,
 181         SIGSEGV, SEGV_ACCERR, "load access fault");
 182 #ifndef CONFIG_RISCV_M_MODE
 183 DO_ERROR_INFO(do_trap_load_misaligned,
 184         SIGBUS, BUS_ADRALN, "Oops - load address misaligned");
 185 DO_ERROR_INFO(do_trap_store_misaligned,
 186         SIGBUS, BUS_ADRALN, "Oops - store (or AMO) address misaligned");
 187 #else
 188 int handle_misaligned_load(struct pt_regs *regs);
 189 int handle_misaligned_store(struct pt_regs *regs);
 190
 191 asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs *regs)
 192 {
 193         if (user_mode(regs)) {
 194                 irqentry_enter_from_user_mode(regs);
 195
 196                 if (handle_misaligned_load(regs))
 197                         do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
 198                               "Oops - load address misaligned");
 199
 200                 irqentry_exit_to_user_mode(regs);
 201         } else {
 202                 irqentry_state_t state = irqentry_nmi_enter(regs);
 203
 204                 if (handle_misaligned_load(regs))
 205                         do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
 206                               "Oops - load address misaligned");
 207
 208                 irqentry_nmi_exit(regs, state);
 209         }
 210 }
 211
 212 asmlinkage __visible __trap_section void do_trap_store_misaligned(struct pt_regs *regs)
 213 {
 214         if (user_mode(regs)) {
 215                 irqentry_enter_from_user_mode(regs);
 216
 217                 if (handle_misaligned_store(regs))
 218                         do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
 219                                 "Oops - store (or AMO) address misaligned");
 220
 221                 irqentry_exit_to_user_mode(regs);
 222         } else {
 223                 irqentry_state_t state = irqentry_nmi_enter(regs);
 224
 225                 if (handle_misaligned_store(regs))
 226                         do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
 227                                 "Oops - store (or AMO) address misaligned");
 228
 229                 irqentry_nmi_exit(regs, state);
 230         }
 231 }
 232 #endif
 233 DO_ERROR_INFO(do_trap_store_fault,
 234         SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault");
 235 DO_ERROR_INFO(do_trap_ecall_s,
 236         SIGILL, ILL_ILLTRP, "environment call from S-mode");
 237 DO_ERROR_INFO(do_trap_ecall_m,
 238         SIGILL, ILL_ILLTRP, "environment call from M-mode");
 239
 240 static inline unsigned long get_break_insn_length(unsigned long pc)
 241 {
 242         bug_insn_t insn;
 243
 244         if (get_kernel_nofault(insn, (bug_insn_t *)pc))
 245                 return 0;
 246
 247         return GET_INSN_LENGTH(insn);
 248 }
 249
 250 void handle_break(struct pt_regs *regs)
 251 {
 252 #ifdef CONFIG_KPROBES
 253         if (kprobe_single_step_handler(regs))
 254                 return;
 255
 256         if (kprobe_breakpoint_handler(regs))
 257                 return;
 258 #endif
 259 #ifdef CONFIG_UPROBES
 260         if (uprobe_single_step_handler(regs))
 261                 return;
 262
 263         if (uprobe_breakpoint_handler(regs))
 264                 return;
 265 #endif
 266         current->thread.bad_cause = regs->cause;
 267
 268         if (user_mode(regs))
 269                 force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->epc);
 270 #ifdef CONFIG_KGDB
 271         else if (notify_die(DIE_TRAP, "EBREAK", regs, 0, regs->cause, SIGTRAP)
 272                                                                 == NOTIFY_STOP)
 273                 return;
 274 #endif
 275         else if (report_bug(regs->epc, regs) == BUG_TRAP_TYPE_WARN ||
 276                  handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN)
 277                 regs->epc += get_break_insn_length(regs->epc);
 278         else
 279                 die(regs, "Kernel BUG");
 280 }
 281
 282 asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
 283 {
 284         if (user_mode(regs)) {
 285                 irqentry_enter_from_user_mode(regs);
 286
 287                 handle_break(regs);
 288
 289                 irqentry_exit_to_user_mode(regs);
 290         } else {
 291                 irqentry_state_t state = irqentry_nmi_enter(regs);
 292
 293                 handle_break(regs);
 294
 295                 irqentry_nmi_exit(regs, state);
 296         }
 297 }
 298
 299 asmlinkage __visible __trap_section void do_trap_ecall_u(struct pt_regs *regs)
 300 {
 301         if (user_mode(regs)) {
 302                 long syscall = regs->a7;
 303
 304                 regs->epc += 4;
 305                 regs->orig_a0 = regs->a0;
 306
 307                 riscv_v_vstate_discard(regs);
 308
 309                 syscall = syscall_enter_from_user_mode(regs, syscall);
 310
 311                 if (syscall >= 0 && syscall < NR_syscalls)
 312                         syscall_handler(regs, syscall);
 313                 else if (syscall != -1)
 314                         regs->a0 = -ENOSYS;
 315
 316                 syscall_exit_to_user_mode(regs);
 317         } else {
 318                 irqentry_state_t state = irqentry_nmi_enter(regs);
 319
 320                 do_trap_error(regs, SIGILL, ILL_ILLTRP, regs->epc,
 321                         "Oops - environment call from U-mode");
 322
 323                 irqentry_nmi_exit(regs, state);
 324         }
 325
 326 }
 327
 328 #ifdef CONFIG_MMU
 329 asmlinkage __visible noinstr void do_page_fault(struct pt_regs *regs)
 330 {
 331         irqentry_state_t state = irqentry_enter(regs);
 332
 333         handle_page_fault(regs);
 334
 335         local_irq_disable();
 336
 337         irqentry_exit(regs, state);
 338 }
 339 #endif
 340
 341 static void noinstr handle_riscv_irq(struct pt_regs *regs)
 342 {
 343         struct pt_regs *old_regs;
 344
 345         irq_enter_rcu();
 346         old_regs = set_irq_regs(regs);
 347         handle_arch_irq(regs);
 348         set_irq_regs(old_regs);
 349         irq_exit_rcu();
 350 }
 351
 352 asmlinkage void noinstr do_irq(struct pt_regs *regs)
 353 {
 354         irqentry_state_t state = irqentry_enter(regs);
 355 #ifdef CONFIG_IRQ_STACKS
 356         if (on_thread_stack()) {
 357                 ulong *sp = per_cpu(irq_stack_ptr, smp_processor_id())
 358                                         + IRQ_STACK_SIZE/sizeof(ulong);
 359                 __asm__ __volatile(
 360                 "addi   sp, sp, -"RISCV_SZPTR  "\n"
 361                 REG_S"  ra, (sp)                \n"
 362                 "addi   sp, sp, -"RISCV_SZPTR  "\n"
 363                 REG_S"  s0, (sp)                \n"
 364                 "addi   s0, sp, 2*"RISCV_SZPTR "\n"
 365                 "move   sp, %[sp]               \n"
 366                 "move   a0, %[regs]             \n"
 367                 "call   handle_riscv_irq        \n"
 368                 "addi   sp, s0, -2*"RISCV_SZPTR"\n"
 369                 REG_L"  s0, (sp)                \n"
 370                 "addi   sp, sp, "RISCV_SZPTR   "\n"
 371                 REG_L"  ra, (sp)                \n"
 372                 "addi   sp, sp, "RISCV_SZPTR   "\n"
 373                 :
 374                 : [sp] "r" (sp), [regs] "r" (regs)
 375                 : "a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7",
 376                   "t0", "t1", "t2", "t3", "t4", "t5", "t6",
 377 #ifndef CONFIG_FRAME_POINTER
 378                   "s0",
 379 #endif
 380                   "memory");
 381         } else
 382 #endif
 383                 handle_riscv_irq(regs);
 384
 385         irqentry_exit(regs, state);
 386 }
 387
 388 #ifdef CONFIG_GENERIC_BUG
 389 int is_valid_bugaddr(unsigned long pc)
 390 {
 391         bug_insn_t insn;
 392
 393         if (pc < VMALLOC_START)
 394                 return 0;
 395         if (get_kernel_nofault(insn, (bug_insn_t *)pc))
 396                 return 0;
 397         if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
 398                 return (insn == __BUG_INSN_32);
 399         else
 400                 return ((insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16);
 401 }
 402 #endif /* CONFIG_GENERIC_BUG */
 403
 404 #ifdef CONFIG_VMAP_STACK
 405 /*
 406  * Extra stack space that allows us to provide panic messages when the kernel
 407  * has overflowed its stack.
 408  */
 409 static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)],
 410                 overflow_stack)__aligned(16);
 411 /*
 412  * A temporary stack for use by handle_kernel_stack_overflow.  This is used so
 413  * we can call into C code to get the per-hart overflow stack.  Usage of this
 414  * stack must be protected by spin_shadow_stack.
 415  */
 416 long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16);
 417
 418 /*
 419  * A pseudo spinlock to protect the shadow stack from being used by multiple
 420  * harts concurrently.  This isn't a real spinlock because the lock side must
 421  * be taken without a valid stack and only a single register, it's only taken
 422  * while in the process of panicing anyway so the performance and error
 423  * checking a proper spinlock gives us doesn't matter.
 424  */
 425 unsigned long spin_shadow_stack;
 426
 427 asmlinkage unsigned long get_overflow_stack(void)
 428 {
 429         return (unsigned long)this_cpu_ptr(overflow_stack) +
 430                 OVERFLOW_STACK_SIZE;
 431 }
 432
 433 asmlinkage void handle_bad_stack(struct pt_regs *regs)
 434 {
 435         unsigned long tsk_stk = (unsigned long)current->stack;
 436         unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack);
 437
 438         /*
 439          * We're done with the shadow stack by this point, as we're on the
 440          * overflow stack.  Tell any other concurrent overflowing harts that
 441          * they can proceed with panicing by releasing the pseudo-spinlock.
 442          *
 443          * This pairs with an amoswap.aq in handle_kernel_stack_overflow.
 444          */
 445         smp_store_release(&spin_shadow_stack, 0);
 446
 447         console_verbose();
 448
 449         pr_emerg("Insufficient stack space to handle exception!\n");
 450         pr_emerg("Task stack:     [0x%016lx..0x%016lx]\n",
 451                         tsk_stk, tsk_stk + THREAD_SIZE);
 452         pr_emerg("Overflow stack: [0x%016lx..0x%016lx]\n",
 453                         ovf_stk, ovf_stk + OVERFLOW_STACK_SIZE);
 454
 455         __show_regs(regs);
 456         panic("Kernel stack overflow");
 457
 458         for (;;)
 459                 wait_for_interrupt();
 460 }
 461 #endif