LXR linux/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
  22struct 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
 103char *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
 116int 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
 127void
 128sleeping_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
 151void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
 152{
 153        regs->pc = pc;
 154}
 155
 156static int compiled_break;
 157
 158static 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
 173int 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
 234static 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}
 239NOKPROBE_SYMBOL(kgdb_brk_fn)
 240
 241static 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}
 248NOKPROBE_SYMBOL(kgdb_compiled_brk_fn);
 249
 250static 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}
 258NOKPROBE_SYMBOL(kgdb_step_brk_fn);
 259
 260static struct break_hook kgdb_brkpt_hook = {
 261        .fn             = kgdb_brk_fn,
 262        .imm            = KGDB_DYN_DBG_BRK_IMM,
 263};
 264
 265static struct break_hook kgdb_compiled_brkpt_hook = {
 266        .fn             = kgdb_compiled_brk_fn,
 267        .imm            = KGDB_COMPILED_DBG_BRK_IMM,
 268};
 269
 270static struct step_hook kgdb_step_hook = {
 271        .fn             = kgdb_step_brk_fn
 272};
 273
 274static 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
 283static int
 284kgdb_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
 296static 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 */
 309int 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 */
 327void 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
 335const struct kgdb_arch arch_kgdb_ops;
 336
 337int 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
 351int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
 352{
 353        return aarch64_insn_write((void *)bpt->bpt_addr,
 354                        *(u32 *)bpt->saved_instr);
 355}
 356