gdbserver/linux-nios2-low.cc

   1 /* GNU/Linux/Nios II specific low level interface, for the remote server for
   2    GDB.
   3    Copyright (C) 2008-2021 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   bool low_breakpoint_at (CORE_ADDR pc) override;
  59 };
  60
  61 /* The singleton target ops object.  */
  62
  63 static nios2_target the_nios2_target;
  64
  65 bool
  66 nios2_target::low_supports_breakpoints ()
  67 {
  68   return true;
  69 }
  70
  71 CORE_ADDR
  72 nios2_target::low_get_pc (regcache *regcache)
  73 {
  74   return linux_get_pc_32bit (regcache);
  75 }
  76
  77 void
  78 nios2_target::low_set_pc (regcache *regcache, CORE_ADDR pc)
  79 {
  80   linux_set_pc_32bit (regcache, pc);
  81 }
  82
  83 /* The following definition must agree with the number of registers
  84    defined in "struct user_regs" in GLIBC
  85    (sysdeps/unix/sysv/linux/nios2/sys/user.h), and also with
  86    NIOS2_NUM_REGS in GDB proper.  */
  87
  88 #define nios2_num_regs 49
  89
  90 /* Defined in auto-generated file nios2-linux.c.  */
  91
  92 void init_registers_nios2_linux (void);
  93 extern const struct target_desc *tdesc_nios2_linux;
  94
  95 /* This union is used to convert between int and byte buffer
  96    representations of register contents.  */
  97
  98 union nios2_register
  99 {
 100   unsigned char buf[4];
 101   int reg32;
 102 };
 103
 104 /* Return the ptrace ``address'' of register REGNO. */
 105
 106 static int nios2_regmap[] = {
 107   -1,  1,  2,  3,  4,  5,  6,  7,
 108   8,  9,  10, 11, 12, 13, 14, 15,
 109   16, 17, 18, 19, 20, 21, 22, 23,
 110   24, 25, 26, 27, 28, 29, 30, 31,
 111   32, 33, 34, 35, 36, 37, 38, 39,
 112   40, 41, 42, 43, 44, 45, 46, 47,
 113   48,
 114   0
 115 };
 116
 117 /* Implement the low_arch_setup linux target ops method.  */
 118
 119 void
 120 nios2_target::low_arch_setup ()
 121 {
 122   current_process ()->tdesc = tdesc_nios2_linux;
 123 }
 124
 125 /* Implement the low_cannot_fetch_register linux target ops method.  */
 126
 127 bool
 128 nios2_target::low_cannot_fetch_register (int regno)
 129 {
 130   return (nios2_regmap[regno] == -1);
 131 }
 132
 133 /* Implement the low_cannot_store_register linux target ops method.  */
 134
 135 bool
 136 nios2_target::low_cannot_store_register (int regno)
 137 {
 138   return (nios2_regmap[regno] == -1);
 139 }
 140
 141 /* Breakpoint support.  Also see comments on nios2_breakpoint_from_pc
 142    in nios2-tdep.c.  */
 143
 144 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 145 #define NIOS2_BREAKPOINT 0xb7fd0020
 146 #define CDX_BREAKPOINT 0xd7c9
 147 #else
 148 #define NIOS2_BREAKPOINT 0x003b6ffa
 149 #endif
 150
 151 /* We only register the 4-byte breakpoint, even on R2 targets which also
 152    support 2-byte breakpoints.  Since there is no supports_z_point_type
 153    function provided, gdbserver never inserts software breakpoints itself
 154    and instead relies on GDB to insert the breakpoint of the correct length
 155    via a memory write.  */
 156 static const unsigned int nios2_breakpoint = NIOS2_BREAKPOINT;
 157 #define nios2_breakpoint_len 4
 158
 159 /* Implementation of target ops method "sw_breakpoint_from_kind".  */
 160
 161 const gdb_byte *
 162 nios2_target::sw_breakpoint_from_kind (int kind, int *size)
 163 {
 164   *size = nios2_breakpoint_len;
 165   return (const gdb_byte *) &nios2_breakpoint;
 166 }
 167
 168 /* Implement the low_breakpoint_at linux target ops method.  */
 169
 170 bool
 171 nios2_target::low_breakpoint_at (CORE_ADDR where)
 172 {
 173   unsigned int insn;
 174
 175   /* For R2, first check for the 2-byte CDX trap.n breakpoint encoding.  */
 176 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 177   read_memory (where, (unsigned char *) &insn, 2);
 178   if (insn == CDX_BREAKPOINT)
 179     return true;
 180 #endif
 181
 182   read_memory (where, (unsigned char *) &insn, 4);
 183   if (insn == nios2_breakpoint)
 184     return true;
 185   return false;
 186 }
 187
 188 /* Fetch the thread-local storage pointer for libthread_db.  */
 189
 190 ps_err_e
 191 ps_get_thread_area (struct ps_prochandle *ph,
 192                     lwpid_t lwpid, int idx, void **base)
 193 {
 194   if (ptrace (PTRACE_GET_THREAD_AREA, lwpid, NULL, base) != 0)
 195     return PS_ERR;
 196
 197   /* IDX is the bias from the thread pointer to the beginning of the
 198      thread descriptor.  It has to be subtracted due to implementation
 199      quirks in libthread_db.  */
 200   *base = (void *) ((char *) *base - idx);
 201
 202   return PS_OK;
 203 }
 204
 205 /* Helper functions to collect/supply a single register REGNO.  */
 206
 207 static void
 208 nios2_collect_register (struct regcache *regcache, int regno,
 209                         union nios2_register *reg)
 210 {
 211   union nios2_register tmp_reg;
 212
 213   collect_register (regcache, regno, &tmp_reg.reg32);
 214   reg->reg32 = tmp_reg.reg32;
 215 }
 216
 217 static void
 218 nios2_supply_register (struct regcache *regcache, int regno,
 219                        const union nios2_register *reg)
 220 {
 221   supply_register (regcache, regno, reg->buf);
 222 }
 223
 224 /* We have only a single register set on Nios II.  */
 225
 226 static void
 227 nios2_fill_gregset (struct regcache *regcache, void *buf)
 228 {
 229   union nios2_register *regset = (union nios2_register *) buf;
 230   int i;
 231
 232   for (i = 1; i < nios2_num_regs; i++)
 233     nios2_collect_register (regcache, i, regset + i);
 234 }
 235
 236 static void
 237 nios2_store_gregset (struct regcache *regcache, const void *buf)
 238 {
 239   const union nios2_register *regset = (union nios2_register *) buf;
 240   int i;
 241
 242   for (i = 0; i < nios2_num_regs; i++)
 243     nios2_supply_register (regcache, i, regset + i);
 244 }
 245
 246 static struct regset_info nios2_regsets[] =
 247 {
 248   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_PRSTATUS,
 249     nios2_num_regs * 4, GENERAL_REGS,
 250     nios2_fill_gregset, nios2_store_gregset },
 251   NULL_REGSET
 252 };
 253
 254 static struct regsets_info nios2_regsets_info =
 255   {
 256     nios2_regsets, /* regsets */
 257     0, /* num_regsets */
 258     NULL, /* disabled_regsets */
 259   };
 260
 261 static struct usrregs_info nios2_usrregs_info =
 262   {
 263     nios2_num_regs,
 264     nios2_regmap,
 265   };
 266
 267 static struct regs_info myregs_info =
 268   {
 269     NULL, /* regset_bitmap */
 270     &nios2_usrregs_info,
 271     &nios2_regsets_info
 272   };
 273
 274 const regs_info *
 275 nios2_target::get_regs_info ()
 276 {
 277   return &myregs_info;
 278 }
 279
 280 /* The linux target ops object.  */
 281
 282 linux_process_target *the_linux_target = &the_nios2_target;
 283
 284 void
 285 initialize_low_arch (void)
 286 {
 287   init_registers_nios2_linux ();
 288
 289   initialize_regsets_info (&nios2_regsets_info);
 290 }