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 protected:
  41
  42   void low_arch_setup () override;
  43 };
  44
  45 /* The singleton target ops object.  */
  46
  47 static nios2_target the_nios2_target;
  48
  49 /* The following definition must agree with the number of registers
  50    defined in "struct user_regs" in GLIBC
  51    (sysdeps/unix/sysv/linux/nios2/sys/user.h), and also with
  52    NIOS2_NUM_REGS in GDB proper.  */
  53
  54 #define nios2_num_regs 49
  55
  56 /* Defined in auto-generated file nios2-linux.c.  */
  57
  58 void init_registers_nios2_linux (void);
  59 extern const struct target_desc *tdesc_nios2_linux;
  60
  61 /* This union is used to convert between int and byte buffer
  62    representations of register contents.  */
  63
  64 union nios2_register
  65 {
  66   unsigned char buf[4];
  67   int reg32;
  68 };
  69
  70 /* Return the ptrace ``address'' of register REGNO. */
  71
  72 static int nios2_regmap[] = {
  73   -1,  1,  2,  3,  4,  5,  6,  7,
  74   8,  9,  10, 11, 12, 13, 14, 15,
  75   16, 17, 18, 19, 20, 21, 22, 23,
  76   24, 25, 26, 27, 28, 29, 30, 31,
  77   32, 33, 34, 35, 36, 37, 38, 39,
  78   40, 41, 42, 43, 44, 45, 46, 47,
  79   48,
  80   0
  81 };
  82
  83 /* Implement the low_arch_setup linux target ops method.  */
  84
  85 void
  86 nios2_target::low_arch_setup ()
  87 {
  88   current_process ()->tdesc = tdesc_nios2_linux;
  89 }
  90
  91 /* Implement the cannot_fetch_register linux_target_ops method.  */
  92
  93 static int
  94 nios2_cannot_fetch_register (int regno)
  95 {
  96   if (nios2_regmap[regno] == -1)
  97     return 1;
  98
  99   return 0;
 100 }
 101
 102 /* Implement the cannot_store_register linux_target_ops method.  */
 103
 104 static int
 105 nios2_cannot_store_register (int regno)
 106 {
 107   if (nios2_regmap[regno] == -1)
 108     return 1;
 109
 110   return 0;
 111 }
 112
 113 /* Breakpoint support.  Also see comments on nios2_breakpoint_from_pc
 114    in nios2-tdep.c.  */
 115
 116 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 117 #define NIOS2_BREAKPOINT 0xb7fd0020
 118 #define CDX_BREAKPOINT 0xd7c9
 119 #else
 120 #define NIOS2_BREAKPOINT 0x003b6ffa
 121 #endif
 122
 123 /* We only register the 4-byte breakpoint, even on R2 targets which also
 124    support 2-byte breakpoints.  Since there is no supports_z_point_type
 125    function provided, gdbserver never inserts software breakpoints itself
 126    and instead relies on GDB to insert the breakpoint of the correct length
 127    via a memory write.  */
 128 static const unsigned int nios2_breakpoint = NIOS2_BREAKPOINT;
 129 #define nios2_breakpoint_len 4
 130
 131 /* Implementation of linux_target_ops method "sw_breakpoint_from_kind".  */
 132
 133 static const gdb_byte *
 134 nios2_sw_breakpoint_from_kind (int kind, int *size)
 135 {
 136   *size = nios2_breakpoint_len;
 137   return (const gdb_byte *) &nios2_breakpoint;
 138 }
 139
 140 /* Implement the breakpoint_at linux_target_ops method.  */
 141
 142 static int
 143 nios2_breakpoint_at (CORE_ADDR where)
 144 {
 145   unsigned int insn;
 146
 147   /* For R2, first check for the 2-byte CDX trap.n breakpoint encoding.  */
 148 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 149   the_target->read_memory (where, (unsigned char *) &insn, 2);
 150   if (insn == CDX_BREAKPOINT)
 151     return 1;
 152 #endif
 153
 154   the_target->read_memory (where, (unsigned char *) &insn, 4);
 155   if (insn == nios2_breakpoint)
 156     return 1;
 157   return 0;
 158 }
 159
 160 /* Fetch the thread-local storage pointer for libthread_db.  */
 161
 162 ps_err_e
 163 ps_get_thread_area (struct ps_prochandle *ph,
 164                     lwpid_t lwpid, int idx, void **base)
 165 {
 166   if (ptrace (PTRACE_GET_THREAD_AREA, lwpid, NULL, base) != 0)
 167     return PS_ERR;
 168
 169   /* IDX is the bias from the thread pointer to the beginning of the
 170      thread descriptor.  It has to be subtracted due to implementation
 171      quirks in libthread_db.  */
 172   *base = (void *) ((char *) *base - idx);
 173
 174   return PS_OK;
 175 }
 176
 177 /* Helper functions to collect/supply a single register REGNO.  */
 178
 179 static void
 180 nios2_collect_register (struct regcache *regcache, int regno,
 181                         union nios2_register *reg)
 182 {
 183   union nios2_register tmp_reg;
 184
 185   collect_register (regcache, regno, &tmp_reg.reg32);
 186   reg->reg32 = tmp_reg.reg32;
 187 }
 188
 189 static void
 190 nios2_supply_register (struct regcache *regcache, int regno,
 191                        const union nios2_register *reg)
 192 {
 193   supply_register (regcache, regno, reg->buf);
 194 }
 195
 196 /* We have only a single register set on Nios II.  */
 197
 198 static void
 199 nios2_fill_gregset (struct regcache *regcache, void *buf)
 200 {
 201   union nios2_register *regset = (union nios2_register *) buf;
 202   int i;
 203
 204   for (i = 1; i < nios2_num_regs; i++)
 205     nios2_collect_register (regcache, i, regset + i);
 206 }
 207
 208 static void
 209 nios2_store_gregset (struct regcache *regcache, const void *buf)
 210 {
 211   const union nios2_register *regset = (union nios2_register *) buf;
 212   int i;
 213
 214   for (i = 0; i < nios2_num_regs; i++)
 215     nios2_supply_register (regcache, i, regset + i);
 216 }
 217
 218 static struct regset_info nios2_regsets[] =
 219 {
 220   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_PRSTATUS,
 221     nios2_num_regs * 4, GENERAL_REGS,
 222     nios2_fill_gregset, nios2_store_gregset },
 223   NULL_REGSET
 224 };
 225
 226 static struct regsets_info nios2_regsets_info =
 227   {
 228     nios2_regsets, /* regsets */
 229     0, /* num_regsets */
 230     NULL, /* disabled_regsets */
 231   };
 232
 233 static struct usrregs_info nios2_usrregs_info =
 234   {
 235     nios2_num_regs,
 236     nios2_regmap,
 237   };
 238
 239 static struct regs_info regs_info =
 240   {
 241     NULL, /* regset_bitmap */
 242     &nios2_usrregs_info,
 243     &nios2_regsets_info
 244   };
 245
 246 static const struct regs_info *
 247 nios2_regs_info (void)
 248 {
 249   return &regs_info;
 250 }
 251
 252 struct linux_target_ops the_low_target =
 253 {
 254   nios2_regs_info,
 255   nios2_cannot_fetch_register,
 256   nios2_cannot_store_register,
 257   NULL,
 258   linux_get_pc_32bit,
 259   linux_set_pc_32bit,
 260   NULL, /* breakpoint_kind_from_pc */
 261   nios2_sw_breakpoint_from_kind,
 262   NULL, /* get_next_pcs */
 263   0,
 264   nios2_breakpoint_at,
 265 };
 266
 267 /* The linux target ops object.  */
 268
 269 linux_process_target *the_linux_target = &the_nios2_target;
 270
 271 void
 272 initialize_low_arch (void)
 273 {
 274   init_registers_nios2_linux ();
 275
 276   initialize_regsets_info (&nios2_regsets_info);
 277 }