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   const gdb_byte *sw_breakpoint_from_kind (int kind, int *size) override;
  43
  44 protected:
  45
  46   void low_arch_setup () override;
  47
  48   bool low_cannot_fetch_register (int regno) override;
  49
  50   bool low_cannot_store_register (int regno) override;
  51
  52   bool low_supports_breakpoints () override;
  53
  54   CORE_ADDR low_get_pc (regcache *regcache) override;
  55
  56   void low_set_pc (regcache *regcache, CORE_ADDR newpc) override;
  57 };
  58
  59 /* The singleton target ops object.  */
  60
  61 static nios2_target the_nios2_target;
  62
  63 bool
  64 nios2_target::low_supports_breakpoints ()
  65 {
  66   return true;
  67 }
  68
  69 CORE_ADDR
  70 nios2_target::low_get_pc (regcache *regcache)
  71 {
  72   return linux_get_pc_32bit (regcache);
  73 }
  74
  75 void
  76 nios2_target::low_set_pc (regcache *regcache, CORE_ADDR pc)
  77 {
  78   linux_set_pc_32bit (regcache, pc);
  79 }
  80
  81 /* The following definition must agree with the number of registers
  82    defined in "struct user_regs" in GLIBC
  83    (sysdeps/unix/sysv/linux/nios2/sys/user.h), and also with
  84    NIOS2_NUM_REGS in GDB proper.  */
  85
  86 #define nios2_num_regs 49
  87
  88 /* Defined in auto-generated file nios2-linux.c.  */
  89
  90 void init_registers_nios2_linux (void);
  91 extern const struct target_desc *tdesc_nios2_linux;
  92
  93 /* This union is used to convert between int and byte buffer
  94    representations of register contents.  */
  95
  96 union nios2_register
  97 {
  98   unsigned char buf[4];
  99   int reg32;
 100 };
 101
 102 /* Return the ptrace ``address'' of register REGNO. */
 103
 104 static int nios2_regmap[] = {
 105   -1,  1,  2,  3,  4,  5,  6,  7,
 106   8,  9,  10, 11, 12, 13, 14, 15,
 107   16, 17, 18, 19, 20, 21, 22, 23,
 108   24, 25, 26, 27, 28, 29, 30, 31,
 109   32, 33, 34, 35, 36, 37, 38, 39,
 110   40, 41, 42, 43, 44, 45, 46, 47,
 111   48,
 112   0
 113 };
 114
 115 /* Implement the low_arch_setup linux target ops method.  */
 116
 117 void
 118 nios2_target::low_arch_setup ()
 119 {
 120   current_process ()->tdesc = tdesc_nios2_linux;
 121 }
 122
 123 /* Implement the low_cannot_fetch_register linux target ops method.  */
 124
 125 bool
 126 nios2_target::low_cannot_fetch_register (int regno)
 127 {
 128   return (nios2_regmap[regno] == -1);
 129 }
 130
 131 /* Implement the low_cannot_store_register linux target ops method.  */
 132
 133 bool
 134 nios2_target::low_cannot_store_register (int regno)
 135 {
 136   return (nios2_regmap[regno] == -1);
 137 }
 138
 139 /* Breakpoint support.  Also see comments on nios2_breakpoint_from_pc
 140    in nios2-tdep.c.  */
 141
 142 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 143 #define NIOS2_BREAKPOINT 0xb7fd0020
 144 #define CDX_BREAKPOINT 0xd7c9
 145 #else
 146 #define NIOS2_BREAKPOINT 0x003b6ffa
 147 #endif
 148
 149 /* We only register the 4-byte breakpoint, even on R2 targets which also
 150    support 2-byte breakpoints.  Since there is no supports_z_point_type
 151    function provided, gdbserver never inserts software breakpoints itself
 152    and instead relies on GDB to insert the breakpoint of the correct length
 153    via a memory write.  */
 154 static const unsigned int nios2_breakpoint = NIOS2_BREAKPOINT;
 155 #define nios2_breakpoint_len 4
 156
 157 /* Implementation of target ops method "sw_breakpoint_from_kind".  */
 158
 159 const gdb_byte *
 160 nios2_target::sw_breakpoint_from_kind (int kind, int *size)
 161 {
 162   *size = nios2_breakpoint_len;
 163   return (const gdb_byte *) &nios2_breakpoint;
 164 }
 165
 166 /* Implement the breakpoint_at linux_target_ops method.  */
 167
 168 static int
 169 nios2_breakpoint_at (CORE_ADDR where)
 170 {
 171   unsigned int insn;
 172
 173   /* For R2, first check for the 2-byte CDX trap.n breakpoint encoding.  */
 174 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 175   the_target->read_memory (where, (unsigned char *) &insn, 2);
 176   if (insn == CDX_BREAKPOINT)
 177     return 1;
 178 #endif
 179
 180   the_target->read_memory (where, (unsigned char *) &insn, 4);
 181   if (insn == nios2_breakpoint)
 182     return 1;
 183   return 0;
 184 }
 185
 186 /* Fetch the thread-local storage pointer for libthread_db.  */
 187
 188 ps_err_e
 189 ps_get_thread_area (struct ps_prochandle *ph,
 190                     lwpid_t lwpid, int idx, void **base)
 191 {
 192   if (ptrace (PTRACE_GET_THREAD_AREA, lwpid, NULL, base) != 0)
 193     return PS_ERR;
 194
 195   /* IDX is the bias from the thread pointer to the beginning of the
 196      thread descriptor.  It has to be subtracted due to implementation
 197      quirks in libthread_db.  */
 198   *base = (void *) ((char *) *base - idx);
 199
 200   return PS_OK;
 201 }
 202
 203 /* Helper functions to collect/supply a single register REGNO.  */
 204
 205 static void
 206 nios2_collect_register (struct regcache *regcache, int regno,
 207                         union nios2_register *reg)
 208 {
 209   union nios2_register tmp_reg;
 210
 211   collect_register (regcache, regno, &tmp_reg.reg32);
 212   reg->reg32 = tmp_reg.reg32;
 213 }
 214
 215 static void
 216 nios2_supply_register (struct regcache *regcache, int regno,
 217                        const union nios2_register *reg)
 218 {
 219   supply_register (regcache, regno, reg->buf);
 220 }
 221
 222 /* We have only a single register set on Nios II.  */
 223
 224 static void
 225 nios2_fill_gregset (struct regcache *regcache, void *buf)
 226 {
 227   union nios2_register *regset = (union nios2_register *) buf;
 228   int i;
 229
 230   for (i = 1; i < nios2_num_regs; i++)
 231     nios2_collect_register (regcache, i, regset + i);
 232 }
 233
 234 static void
 235 nios2_store_gregset (struct regcache *regcache, const void *buf)
 236 {
 237   const union nios2_register *regset = (union nios2_register *) buf;
 238   int i;
 239
 240   for (i = 0; i < nios2_num_regs; i++)
 241     nios2_supply_register (regcache, i, regset + i);
 242 }
 243
 244 static struct regset_info nios2_regsets[] =
 245 {
 246   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_PRSTATUS,
 247     nios2_num_regs * 4, GENERAL_REGS,
 248     nios2_fill_gregset, nios2_store_gregset },
 249   NULL_REGSET
 250 };
 251
 252 static struct regsets_info nios2_regsets_info =
 253   {
 254     nios2_regsets, /* regsets */
 255     0, /* num_regsets */
 256     NULL, /* disabled_regsets */
 257   };
 258
 259 static struct usrregs_info nios2_usrregs_info =
 260   {
 261     nios2_num_regs,
 262     nios2_regmap,
 263   };
 264
 265 static struct regs_info myregs_info =
 266   {
 267     NULL, /* regset_bitmap */
 268     &nios2_usrregs_info,
 269     &nios2_regsets_info
 270   };
 271
 272 const regs_info *
 273 nios2_target::get_regs_info ()
 274 {
 275   return &myregs_info;
 276 }
 277
 278 struct linux_target_ops the_low_target =
 279 {
 280   NULL, /* get_next_pcs */
 281   0,
 282   nios2_breakpoint_at,
 283 };
 284
 285 /* The linux target ops object.  */
 286
 287 linux_process_target *the_linux_target = &the_nios2_target;
 288
 289 void
 290 initialize_low_arch (void)
 291 {
 292   init_registers_nios2_linux ();
 293
 294   initialize_regsets_info (&nios2_regsets_info);
 295 }