gdbserver/linux-nios2-low.cc

   1 /* GNU/Linux/Nios II specific low level interface, for the remote server for
   2    GDB.
   3    Copyright (C) 2008-2020 Free Software Foundation, Inc.
   4
   5    Contributed by Mentor Graphics, Inc.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22 #include "server.h"
  23 #include "linux-low.h"
  24 #include "elf/common.h"
  25 #include "nat/gdb_ptrace.h"
  26 #include <endian.h>
  27 #include "gdb_proc_service.h"
  28 #include <asm/ptrace.h>
  29
  30 #ifndef PTRACE_GET_THREAD_AREA
  31 #define PTRACE_GET_THREAD_AREA 25
  32 #endif
  33
  34 /* Linux target op definitions for the NIOS II architecture.  */
  35
  36 class nios2_target : public linux_process_target
  37 {
  38 public:
  39
  40   const regs_info *get_regs_info () override;
  41
  42 protected:
  43
  44   void low_arch_setup () override;
  45 };
  46
  47 /* The singleton target ops object.  */
  48
  49 static nios2_target the_nios2_target;
  50
  51 /* The following definition must agree with the number of registers
  52    defined in "struct user_regs" in GLIBC
  53    (sysdeps/unix/sysv/linux/nios2/sys/user.h), and also with
  54    NIOS2_NUM_REGS in GDB proper.  */
  55
  56 #define nios2_num_regs 49
  57
  58 /* Defined in auto-generated file nios2-linux.c.  */
  59
  60 void init_registers_nios2_linux (void);
  61 extern const struct target_desc *tdesc_nios2_linux;
  62
  63 /* This union is used to convert between int and byte buffer
  64    representations of register contents.  */
  65
  66 union nios2_register
  67 {
  68   unsigned char buf[4];
  69   int reg32;
  70 };
  71
  72 /* Return the ptrace ``address'' of register REGNO. */
  73
  74 static int nios2_regmap[] = {
  75   -1,  1,  2,  3,  4,  5,  6,  7,
  76   8,  9,  10, 11, 12, 13, 14, 15,
  77   16, 17, 18, 19, 20, 21, 22, 23,
  78   24, 25, 26, 27, 28, 29, 30, 31,
  79   32, 33, 34, 35, 36, 37, 38, 39,
  80   40, 41, 42, 43, 44, 45, 46, 47,
  81   48,
  82   0
  83 };
  84
  85 /* Implement the low_arch_setup linux target ops method.  */
  86
  87 void
  88 nios2_target::low_arch_setup ()
  89 {
  90   current_process ()->tdesc = tdesc_nios2_linux;
  91 }
  92
  93 /* Implement the cannot_fetch_register linux_target_ops method.  */
  94
  95 static int
  96 nios2_cannot_fetch_register (int regno)
  97 {
  98   if (nios2_regmap[regno] == -1)
  99     return 1;
 100
 101   return 0;
 102 }
 103
 104 /* Implement the cannot_store_register linux_target_ops method.  */
 105
 106 static int
 107 nios2_cannot_store_register (int regno)
 108 {
 109   if (nios2_regmap[regno] == -1)
 110     return 1;
 111
 112   return 0;
 113 }
 114
 115 /* Breakpoint support.  Also see comments on nios2_breakpoint_from_pc
 116    in nios2-tdep.c.  */
 117
 118 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 119 #define NIOS2_BREAKPOINT 0xb7fd0020
 120 #define CDX_BREAKPOINT 0xd7c9
 121 #else
 122 #define NIOS2_BREAKPOINT 0x003b6ffa
 123 #endif
 124
 125 /* We only register the 4-byte breakpoint, even on R2 targets which also
 126    support 2-byte breakpoints.  Since there is no supports_z_point_type
 127    function provided, gdbserver never inserts software breakpoints itself
 128    and instead relies on GDB to insert the breakpoint of the correct length
 129    via a memory write.  */
 130 static const unsigned int nios2_breakpoint = NIOS2_BREAKPOINT;
 131 #define nios2_breakpoint_len 4
 132
 133 /* Implementation of linux_target_ops method "sw_breakpoint_from_kind".  */
 134
 135 static const gdb_byte *
 136 nios2_sw_breakpoint_from_kind (int kind, int *size)
 137 {
 138   *size = nios2_breakpoint_len;
 139   return (const gdb_byte *) &nios2_breakpoint;
 140 }
 141
 142 /* Implement the breakpoint_at linux_target_ops method.  */
 143
 144 static int
 145 nios2_breakpoint_at (CORE_ADDR where)
 146 {
 147   unsigned int insn;
 148
 149   /* For R2, first check for the 2-byte CDX trap.n breakpoint encoding.  */
 150 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 151   the_target->read_memory (where, (unsigned char *) &insn, 2);
 152   if (insn == CDX_BREAKPOINT)
 153     return 1;
 154 #endif
 155
 156   the_target->read_memory (where, (unsigned char *) &insn, 4);
 157   if (insn == nios2_breakpoint)
 158     return 1;
 159   return 0;
 160 }
 161
 162 /* Fetch the thread-local storage pointer for libthread_db.  */
 163
 164 ps_err_e
 165 ps_get_thread_area (struct ps_prochandle *ph,
 166                     lwpid_t lwpid, int idx, void **base)
 167 {
 168   if (ptrace (PTRACE_GET_THREAD_AREA, lwpid, NULL, base) != 0)
 169     return PS_ERR;
 170
 171   /* IDX is the bias from the thread pointer to the beginning of the
 172      thread descriptor.  It has to be subtracted due to implementation
 173      quirks in libthread_db.  */
 174   *base = (void *) ((char *) *base - idx);
 175
 176   return PS_OK;
 177 }
 178
 179 /* Helper functions to collect/supply a single register REGNO.  */
 180
 181 static void
 182 nios2_collect_register (struct regcache *regcache, int regno,
 183                         union nios2_register *reg)
 184 {
 185   union nios2_register tmp_reg;
 186
 187   collect_register (regcache, regno, &tmp_reg.reg32);
 188   reg->reg32 = tmp_reg.reg32;
 189 }
 190
 191 static void
 192 nios2_supply_register (struct regcache *regcache, int regno,
 193                        const union nios2_register *reg)
 194 {
 195   supply_register (regcache, regno, reg->buf);
 196 }
 197
 198 /* We have only a single register set on Nios II.  */
 199
 200 static void
 201 nios2_fill_gregset (struct regcache *regcache, void *buf)
 202 {
 203   union nios2_register *regset = (union nios2_register *) buf;
 204   int i;
 205
 206   for (i = 1; i < nios2_num_regs; i++)
 207     nios2_collect_register (regcache, i, regset + i);
 208 }
 209
 210 static void
 211 nios2_store_gregset (struct regcache *regcache, const void *buf)
 212 {
 213   const union nios2_register *regset = (union nios2_register *) buf;
 214   int i;
 215
 216   for (i = 0; i < nios2_num_regs; i++)
 217     nios2_supply_register (regcache, i, regset + i);
 218 }
 219
 220 static struct regset_info nios2_regsets[] =
 221 {
 222   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_PRSTATUS,
 223     nios2_num_regs * 4, GENERAL_REGS,
 224     nios2_fill_gregset, nios2_store_gregset },
 225   NULL_REGSET
 226 };
 227
 228 static struct regsets_info nios2_regsets_info =
 229   {
 230     nios2_regsets, /* regsets */
 231     0, /* num_regsets */
 232     NULL, /* disabled_regsets */
 233   };
 234
 235 static struct usrregs_info nios2_usrregs_info =
 236   {
 237     nios2_num_regs,
 238     nios2_regmap,
 239   };
 240
 241 static struct regs_info myregs_info =
 242   {
 243     NULL, /* regset_bitmap */
 244     &nios2_usrregs_info,
 245     &nios2_regsets_info
 246   };
 247
 248 const regs_info *
 249 nios2_target::get_regs_info ()
 250 {
 251   return &myregs_info;
 252 }
 253
 254 struct linux_target_ops the_low_target =
 255 {
 256   nios2_cannot_fetch_register,
 257   nios2_cannot_store_register,
 258   NULL,
 259   linux_get_pc_32bit,
 260   linux_set_pc_32bit,
 261   NULL, /* breakpoint_kind_from_pc */
 262   nios2_sw_breakpoint_from_kind,
 263   NULL, /* get_next_pcs */
 264   0,
 265   nios2_breakpoint_at,
 266 };
 267
 268 /* The linux target ops object.  */
 269
 270 linux_process_target *the_linux_target = &the_nios2_target;
 271
 272 void
 273 initialize_low_arch (void)
 274 {
 275   init_registers_nios2_linux ();
 276
 277   initialize_regsets_info (&nios2_regsets_info);
 278 }