arch/arm64/kernel/kgdb.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * AArch64 KGDB support
   4  *
   5  * Based on arch/arm/kernel/kgdb.c
   6  *
   7  * Copyright (C) 2013 Cavium Inc.
   8  * Author: Vijaya Kumar K <vijaya.kumar@caviumnetworks.com>
   9  */
  10
  11 #include <linux/bug.h>
  12 #include <linux/irq.h>
  13 #include <linux/kdebug.h>
  14 #include <linux/kgdb.h>
  15 #include <linux/kprobes.h>
  16 #include <linux/sched/task_stack.h>
  17
  18 #include <asm/debug-monitors.h>
  19 #include <asm/insn.h>
  20 #include <asm/traps.h>
  21
  22 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
  23         { "x0", 8, offsetof(struct pt_regs, regs[0])},
  24         { "x1", 8, offsetof(struct pt_regs, regs[1])},
  25         { "x2", 8, offsetof(struct pt_regs, regs[2])},
  26         { "x3", 8, offsetof(struct pt_regs, regs[3])},
  27         { "x4", 8, offsetof(struct pt_regs, regs[4])},
  28         { "x5", 8, offsetof(struct pt_regs, regs[5])},
  29         { "x6", 8, offsetof(struct pt_regs, regs[6])},
  30         { "x7", 8, offsetof(struct pt_regs, regs[7])},
  31         { "x8", 8, offsetof(struct pt_regs, regs[8])},
  32         { "x9", 8, offsetof(struct pt_regs, regs[9])},
  33         { "x10", 8, offsetof(struct pt_regs, regs[10])},
  34         { "x11", 8, offsetof(struct pt_regs, regs[11])},
  35         { "x12", 8, offsetof(struct pt_regs, regs[12])},
  36         { "x13", 8, offsetof(struct pt_regs, regs[13])},
  37         { "x14", 8, offsetof(struct pt_regs, regs[14])},
  38         { "x15", 8, offsetof(struct pt_regs, regs[15])},
  39         { "x16", 8, offsetof(struct pt_regs, regs[16])},
  40         { "x17", 8, offsetof(struct pt_regs, regs[17])},
  41         { "x18", 8, offsetof(struct pt_regs, regs[18])},
  42         { "x19", 8, offsetof(struct pt_regs, regs[19])},
  43         { "x20", 8, offsetof(struct pt_regs, regs[20])},
  44         { "x21", 8, offsetof(struct pt_regs, regs[21])},
  45         { "x22", 8, offsetof(struct pt_regs, regs[22])},
  46         { "x23", 8, offsetof(struct pt_regs, regs[23])},
  47         { "x24", 8, offsetof(struct pt_regs, regs[24])},
  48         { "x25", 8, offsetof(struct pt_regs, regs[25])},
  49         { "x26", 8, offsetof(struct pt_regs, regs[26])},
  50         { "x27", 8, offsetof(struct pt_regs, regs[27])},
  51         { "x28", 8, offsetof(struct pt_regs, regs[28])},
  52         { "x29", 8, offsetof(struct pt_regs, regs[29])},
  53         { "x30", 8, offsetof(struct pt_regs, regs[30])},
  54         { "sp", 8, offsetof(struct pt_regs, sp)},
  55         { "pc", 8, offsetof(struct pt_regs, pc)},
  56         /*
  57          * struct pt_regs thinks PSTATE is 64-bits wide but gdb remote
  58          * protocol disagrees. Therefore we must extract only the lower
  59          * 32-bits. Look for the big comment in asm/kgdb.h for more
  60          * detail.
  61          */
  62         { "pstate", 4, offsetof(struct pt_regs, pstate)
  63 #ifdef CONFIG_CPU_BIG_ENDIAN
  64                                                         + 4
  65 #endif
  66         },
  67         { "v0", 16, -1 },
  68         { "v1", 16, -1 },
  69         { "v2", 16, -1 },
  70         { "v3", 16, -1 },
  71         { "v4", 16, -1 },
  72         { "v5", 16, -1 },
  73         { "v6", 16, -1 },
  74         { "v7", 16, -1 },
  75         { "v8", 16, -1 },
  76         { "v9", 16, -1 },
  77         { "v10", 16, -1 },
  78         { "v11", 16, -1 },
  79         { "v12", 16, -1 },
  80         { "v13", 16, -1 },
  81         { "v14", 16, -1 },
  82         { "v15", 16, -1 },
  83         { "v16", 16, -1 },
  84         { "v17", 16, -1 },
  85         { "v18", 16, -1 },
  86         { "v19", 16, -1 },
  87         { "v20", 16, -1 },
  88         { "v21", 16, -1 },
  89         { "v22", 16, -1 },
  90         { "v23", 16, -1 },
  91         { "v24", 16, -1 },
  92         { "v25", 16, -1 },
  93         { "v26", 16, -1 },
  94         { "v27", 16, -1 },
  95         { "v28", 16, -1 },
  96         { "v29", 16, -1 },
  97         { "v30", 16, -1 },
  98         { "v31", 16, -1 },
  99         { "fpsr", 4, -1 },
 100         { "fpcr", 4, -1 },
 101 };
 102
 103 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
 104 {
 105         if (regno >= DBG_MAX_REG_NUM || regno < 0)
 106                 return NULL;
 107
 108         if (dbg_reg_def[regno].offset != -1)
 109                 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
 110                        dbg_reg_def[regno].size);
 111         else
 112                 memset(mem, 0, dbg_reg_def[regno].size);
 113         return dbg_reg_def[regno].name;
 114 }
 115
 116 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
 117 {
 118         if (regno >= DBG_MAX_REG_NUM || regno < 0)
 119                 return -EINVAL;
 120
 121         if (dbg_reg_def[regno].offset != -1)
 122                 memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
 123                        dbg_reg_def[regno].size);
 124         return 0;
 125 }
 126
 127 void
 128 sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
 129 {
 130         struct cpu_context *cpu_context = &task->thread.cpu_context;
 131
 132         /* Initialize to zero */
 133         memset((char *)gdb_regs, 0, NUMREGBYTES);
 134
 135         gdb_regs[19] = cpu_context->x19;
 136         gdb_regs[20] = cpu_context->x20;
 137         gdb_regs[21] = cpu_context->x21;
 138         gdb_regs[22] = cpu_context->x22;
 139         gdb_regs[23] = cpu_context->x23;
 140         gdb_regs[24] = cpu_context->x24;
 141         gdb_regs[25] = cpu_context->x25;
 142         gdb_regs[26] = cpu_context->x26;
 143         gdb_regs[27] = cpu_context->x27;
 144         gdb_regs[28] = cpu_context->x28;
 145         gdb_regs[29] = cpu_context->fp;
 146
 147         gdb_regs[31] = cpu_context->sp;
 148         gdb_regs[32] = cpu_context->pc;
 149 }
 150
 151 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
 152 {
 153         regs->pc = pc;
 154 }
 155
 156 static int compiled_break;
 157
 158 static void kgdb_arch_update_addr(struct pt_regs *regs,
 159                                 char *remcom_in_buffer)
 160 {
 161         unsigned long addr;
 162         char *ptr;
 163
 164         ptr = &remcom_in_buffer[1];
 165         if (kgdb_hex2long(&ptr, &addr))
 166                 kgdb_arch_set_pc(regs, addr);
 167         else if (compiled_break == 1)
 168                 kgdb_arch_set_pc(regs, regs->pc + 4);
 169
 170         compiled_break = 0;
 171 }
 172
 173 int kgdb_arch_handle_exception(int exception_vector, int signo,
 174                                int err_code, char *remcom_in_buffer,
 175                                char *remcom_out_buffer,
 176                                struct pt_regs *linux_regs)
 177 {
 178         int err;
 179
 180         switch (remcom_in_buffer[0]) {
 181         case 'D':
 182         case 'k':
 183                 /*
 184                  * Packet D (Detach), k (kill). No special handling
 185                  * is required here. Handle same as c packet.
 186                  */
 187         case 'c':
 188                 /*
 189                  * Packet c (Continue) to continue executing.
 190                  * Set pc to required address.
 191                  * Try to read optional parameter and set pc.
 192                  * If this was a compiled breakpoint, we need to move
 193                  * to the next instruction else we will just breakpoint
 194                  * over and over again.
 195                  */
 196                 kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
 197                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 198                 kgdb_single_step =  0;
 199
 200                 /*
 201                  * Received continue command, disable single step
 202                  */
 203                 if (kernel_active_single_step())
 204                         kernel_disable_single_step();
 205
 206                 err = 0;
 207                 break;
 208         case 's':
 209                 /*
 210                  * Update step address value with address passed
 211                  * with step packet.
 212                  * On debug exception return PC is copied to ELR
 213                  * So just update PC.
 214                  * If no step address is passed, resume from the address
 215                  * pointed by PC. Do not update PC
 216                  */
 217                 kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
 218                 atomic_set(&kgdb_cpu_doing_single_step, raw_smp_processor_id());
 219                 kgdb_single_step =  1;
 220
 221                 /*
 222                  * Enable single step handling
 223                  */
 224                 if (!kernel_active_single_step())
 225                         kernel_enable_single_step(linux_regs);
 226                 err = 0;
 227                 break;
 228         default:
 229                 err = -1;
 230         }
 231         return err;
 232 }
 233
 234 static int kgdb_brk_fn(struct pt_regs *regs, unsigned int esr)
 235 {
 236         kgdb_handle_exception(1, SIGTRAP, 0, regs);
 237         return DBG_HOOK_HANDLED;
 238 }
 239 NOKPROBE_SYMBOL(kgdb_brk_fn)
 240
 241 static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int esr)
 242 {
 243         compiled_break = 1;
 244         kgdb_handle_exception(1, SIGTRAP, 0, regs);
 245
 246         return DBG_HOOK_HANDLED;
 247 }
 248 NOKPROBE_SYMBOL(kgdb_compiled_brk_fn);
 249
 250 static int kgdb_step_brk_fn(struct pt_regs *regs, unsigned int esr)
 251 {
 252         if (!kgdb_single_step)
 253                 return DBG_HOOK_ERROR;
 254
 255         kgdb_handle_exception(1, SIGTRAP, 0, regs);
 256         return DBG_HOOK_HANDLED;
 257 }
 258 NOKPROBE_SYMBOL(kgdb_step_brk_fn);
 259
 260 static struct break_hook kgdb_brkpt_hook = {
 261         .fn             = kgdb_brk_fn,
 262         .imm            = KGDB_DYN_DBG_BRK_IMM,
 263 };
 264
 265 static struct break_hook kgdb_compiled_brkpt_hook = {
 266         .fn             = kgdb_compiled_brk_fn,
 267         .imm            = KGDB_COMPILED_DBG_BRK_IMM,
 268 };
 269
 270 static struct step_hook kgdb_step_hook = {
 271         .fn             = kgdb_step_brk_fn
 272 };
 273
 274 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 275 {
 276         struct pt_regs *regs = args->regs;
 277
 278         if (kgdb_handle_exception(1, args->signr, cmd, regs))
 279                 return NOTIFY_DONE;
 280         return NOTIFY_STOP;
 281 }
 282
 283 static int
 284 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 285 {
 286         unsigned long flags;
 287         int ret;
 288
 289         local_irq_save(flags);
 290         ret = __kgdb_notify(ptr, cmd);
 291         local_irq_restore(flags);
 292
 293         return ret;
 294 }
 295
 296 static struct notifier_block kgdb_notifier = {
 297         .notifier_call  = kgdb_notify,
 298         /*
 299          * Want to be lowest priority
 300          */
 301         .priority       = -INT_MAX,
 302 };
 303
 304 /*
 305  * kgdb_arch_init - Perform any architecture specific initialization.
 306  * This function will handle the initialization of any architecture
 307  * specific callbacks.
 308  */
 309 int kgdb_arch_init(void)
 310 {
 311         int ret = register_die_notifier(&kgdb_notifier);
 312
 313         if (ret != 0)
 314                 return ret;
 315
 316         register_kernel_break_hook(&kgdb_brkpt_hook);
 317         register_kernel_break_hook(&kgdb_compiled_brkpt_hook);
 318         register_kernel_step_hook(&kgdb_step_hook);
 319         return 0;
 320 }
 321
 322 /*
 323  * kgdb_arch_exit - Perform any architecture specific uninitalization.
 324  * This function will handle the uninitalization of any architecture
 325  * specific callbacks, for dynamic registration and unregistration.
 326  */
 327 void kgdb_arch_exit(void)
 328 {
 329         unregister_kernel_break_hook(&kgdb_brkpt_hook);
 330         unregister_kernel_break_hook(&kgdb_compiled_brkpt_hook);
 331         unregister_kernel_step_hook(&kgdb_step_hook);
 332         unregister_die_notifier(&kgdb_notifier);
 333 }
 334
 335 const struct kgdb_arch arch_kgdb_ops;
 336
 337 int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
 338 {
 339         int err;
 340
 341         BUILD_BUG_ON(AARCH64_INSN_SIZE != BREAK_INSTR_SIZE);
 342
 343         err = aarch64_insn_read((void *)bpt->bpt_addr, (u32 *)bpt->saved_instr);
 344         if (err)
 345                 return err;
 346
 347         return aarch64_insn_write((void *)bpt->bpt_addr,
 348                         (u32)AARCH64_BREAK_KGDB_DYN_DBG);
 349 }
 350
 351 int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
 352 {
 353         return aarch64_insn_write((void *)bpt->bpt_addr,
 354                         *(u32 *)bpt->saved_instr);
 355 }