payloads/libpayload/arch/arm64/gdb.c

   1 /*
   2  * Copyright 2014 Google Inc.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of
   7  * the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but without any warranty; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  */
  14
  15 #include <exception.h>
  16 #include <gdb.h>
  17 #include <libpayload.h>
  18
  19 struct gdb_regs
  20 {
  21         u64 x[31];
  22         u64 sp;         /* shares encoding 0b11111 with XZR in insns */
  23         u64 pc;         /* no longer encoded as a GPR in AArch64! */
  24         u32 spsr;
  25         struct fp_reg
  26         {
  27                 u64 low;
  28                 u64 high;
  29         } __packed v[32];
  30         u32 fpsr;
  31         u32 fpcr;
  32 } __packed;
  33
  34 /* Scratch value to write reentrant exception states to. We never read it. */
  35 static struct exception_state sentinel_exception_state;
  36
  37 static int gdb_exception_hook(u32 type)
  38 {
  39         if (!gdb_handle_reentrant_exception()) {
  40                 u8 signal;
  41
  42                 if (type >= EXC_SYNC_SPX) {
  43                         printf("Impossible exception type: %d!\n", type);
  44                         return 0;
  45                 }
  46
  47                 if (type == EXC_IRQ_SP0 || type == EXC_FIQ_SP0)
  48                         signal = GDB_SIGINT;
  49                 else switch (exception_state.ec) {
  50                 case ESR_EC_UNKNOWN:
  51                         signal = GDB_SIGILL;
  52                         break;
  53                 case ESR_EC_SVC_64:     /* gdb_arch_enter() uses SVC */
  54                 case ESR_EC_SS_SAME:    /* single-step causes this one */
  55                 case ESR_EC_BKPT_64:    /* GDB itself likes to insert BRKs */
  56                         signal = GDB_SIGTRAP;
  57                         break;
  58                 default:
  59                         /* We mostly expect INSN_ABT, DATA_ABT and SERROR here,
  60                            but it makes for a good catchall signal anyway. */
  61                         signal = GDB_SIGSEGV;
  62                         /* GDB itself doesn't read out the ESR, so print it to
  63                            help people understand unexpected exceptions. But we
  64                            can't print anything if GDB is not connected yet. */
  65                         if (gdb_state.connected)
  66                                 printf("Remote-GDB Exception %d, ESR: %#08x\n",
  67                                        type, (uint32_t)exception_state.esr);
  68                 }
  69
  70                 exception_set_state_ptr(&sentinel_exception_state);
  71                 gdb_command_loop(signal);
  72         }
  73
  74         exception_set_state_ptr(&exception_state);
  75
  76         return 1;
  77 }
  78
  79 void gdb_arch_init(void)
  80 {
  81         exception_install_hook(&gdb_exception_hook);
  82         raw_write_oslar_el1(0);         /* Disable OS lock (whatever that is) */
  83         raw_write_mdcr_el2(MDCR_TDE);   /* Route debug exceptions to EL2 */
  84         raw_write_mdscr_el1(MDSCR_KDE); /* Enable debugging of current EL */
  85 }
  86
  87 void gdb_arch_enter(void)
  88 {
  89         u64 *sp;
  90
  91         asm volatile ("mov %0, sp" : "=r"(sp) );
  92
  93         /* Avoid reentrant exceptions, just call the hook if in one already.
  94            This is mostly important when gdb_enter() is called as result of an
  95            exception (as part of the halt() at the end). */
  96         if (sp >= exception_stack && sp <= exception_stack_end)
  97                 gdb_exception_hook(EXC_SYNC_SP0);
  98         else    /* BRK doesn't adjust ELR, so using SVC makes things easier. */
  99                 asm volatile ("svc #0");
 100 }
 101
 102 int gdb_arch_set_single_step(int on)
 103 {
 104         raw_write_mdscr_el1(MDSCR_KDE | (on ? MDSCR_SS : 0));
 105         exception_state.pstate.ss = !!on;
 106         return 0;
 107 }
 108
 109 void gdb_arch_encode_regs(struct gdb_message *message)
 110 {
 111         gdb_message_encode_bytes(message, &exception_state.regs,
 112                                  sizeof(exception_state.regs));
 113         gdb_message_encode_bytes(message, &exception_state.sp,
 114                                  sizeof(exception_state.sp));
 115         gdb_message_encode_bytes(message, &exception_state.elr,
 116                                  sizeof(exception_state.elr));
 117         gdb_message_encode_bytes(message, &exception_state.spsr,
 118                                  sizeof(exception_state.spsr));
 119         gdb_message_encode_zero_bytes(message,
 120                 sizeof(struct gdb_regs) - offsetof(struct gdb_regs, v));
 121 }
 122
 123 void gdb_arch_decode_regs(int offset, struct gdb_message *message)
 124 {
 125         gdb_message_decode_bytes(message, offset,
 126                         &exception_state.regs, sizeof(exception_state.regs));
 127         offset += sizeof(exception_state.regs) * 2;
 128         gdb_message_decode_bytes(message, offset,
 129                         &exception_state.sp, sizeof(exception_state.sp));
 130         offset += sizeof(exception_state.sp) * 2;
 131         gdb_message_decode_bytes(message, offset,
 132                         &exception_state.elr, sizeof(exception_state.elr));
 133         offset += sizeof(exception_state.elr) * 2;
 134         gdb_message_decode_bytes(message, offset,
 135                         &exception_state.spsr, sizeof(exception_state.spsr));
 136         offset += sizeof(exception_state.spsr) * 2;
 137 }