gdb/gdbserver/linux-nios2-low.c

   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 /* The following definition must agree with the number of registers
  35    defined in "struct user_regs" in GLIBC
  36    (sysdeps/unix/sysv/linux/nios2/sys/user.h), and also with
  37    NIOS2_NUM_REGS in GDB proper.  */
  38
  39 #define nios2_num_regs 49
  40
  41 /* Defined in auto-generated file nios2-linux.c.  */
  42
  43 void init_registers_nios2_linux (void);
  44 extern const struct target_desc *tdesc_nios2_linux;
  45
  46 /* This union is used to convert between int and byte buffer
  47    representations of register contents.  */
  48
  49 union nios2_register
  50 {
  51   unsigned char buf[4];
  52   int reg32;
  53 };
  54
  55 /* Return the ptrace ``address'' of register REGNO. */
  56
  57 static int nios2_regmap[] = {
  58   -1,  1,  2,  3,  4,  5,  6,  7,
  59   8,  9,  10, 11, 12, 13, 14, 15,
  60   16, 17, 18, 19, 20, 21, 22, 23,
  61   24, 25, 26, 27, 28, 29, 30, 31,
  62   32, 33, 34, 35, 36, 37, 38, 39,
  63   40, 41, 42, 43, 44, 45, 46, 47,
  64   48,
  65   0
  66 };
  67
  68 /* Implement the arch_setup linux_target_ops method.  */
  69
  70 static void
  71 nios2_arch_setup (void)
  72 {
  73   current_process ()->tdesc = tdesc_nios2_linux;
  74 }
  75
  76 /* Implement the cannot_fetch_register linux_target_ops method.  */
  77
  78 static int
  79 nios2_cannot_fetch_register (int regno)
  80 {
  81   if (nios2_regmap[regno] == -1)
  82     return 1;
  83
  84   return 0;
  85 }
  86
  87 /* Implement the cannot_store_register linux_target_ops method.  */
  88
  89 static int
  90 nios2_cannot_store_register (int regno)
  91 {
  92   if (nios2_regmap[regno] == -1)
  93     return 1;
  94
  95   return 0;
  96 }
  97
  98 /* Breakpoint support.  Also see comments on nios2_breakpoint_from_pc
  99    in nios2-tdep.c.  */
 100
 101 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 102 #define NIOS2_BREAKPOINT 0xb7fd0020
 103 #define CDX_BREAKPOINT 0xd7c9
 104 #else
 105 #define NIOS2_BREAKPOINT 0x003b6ffa
 106 #endif
 107
 108 /* We only register the 4-byte breakpoint, even on R2 targets which also
 109    support 2-byte breakpoints.  Since there is no supports_z_point_type
 110    function provided, gdbserver never inserts software breakpoints itself
 111    and instead relies on GDB to insert the breakpoint of the correct length
 112    via a memory write.  */
 113 static const unsigned int nios2_breakpoint = NIOS2_BREAKPOINT;
 114 #define nios2_breakpoint_len 4
 115
 116 /* Implementation of linux_target_ops method "sw_breakpoint_from_kind".  */
 117
 118 static const gdb_byte *
 119 nios2_sw_breakpoint_from_kind (int kind, int *size)
 120 {
 121   *size = nios2_breakpoint_len;
 122   return (const gdb_byte *) &nios2_breakpoint;
 123 }
 124
 125 /* Implement the breakpoint_at linux_target_ops method.  */
 126
 127 static int
 128 nios2_breakpoint_at (CORE_ADDR where)
 129 {
 130   unsigned int insn;
 131
 132   /* For R2, first check for the 2-byte CDX trap.n breakpoint encoding.  */
 133 #if defined(__nios2_arch__) && __nios2_arch__ == 2
 134   (*the_target->read_memory) (where, (unsigned char *) &insn, 2);
 135   if (insn == CDX_BREAKPOINT)
 136     return 1;
 137 #endif
 138
 139   (*the_target->read_memory) (where, (unsigned char *) &insn, 4);
 140   if (insn == nios2_breakpoint)
 141     return 1;
 142   return 0;
 143 }
 144
 145 /* Fetch the thread-local storage pointer for libthread_db.  */
 146
 147 ps_err_e
 148 ps_get_thread_area (struct ps_prochandle *ph,
 149                     lwpid_t lwpid, int idx, void **base)
 150 {
 151   if (ptrace (PTRACE_GET_THREAD_AREA, lwpid, NULL, base) != 0)
 152     return PS_ERR;
 153
 154   /* IDX is the bias from the thread pointer to the beginning of the
 155      thread descriptor.  It has to be subtracted due to implementation
 156      quirks in libthread_db.  */
 157   *base = (void *) ((char *) *base - idx);
 158
 159   return PS_OK;
 160 }
 161
 162 /* Helper functions to collect/supply a single register REGNO.  */
 163
 164 static void
 165 nios2_collect_register (struct regcache *regcache, int regno,
 166                         union nios2_register *reg)
 167 {
 168   union nios2_register tmp_reg;
 169
 170   collect_register (regcache, regno, &tmp_reg.reg32);
 171   reg->reg32 = tmp_reg.reg32;
 172 }
 173
 174 static void
 175 nios2_supply_register (struct regcache *regcache, int regno,
 176                        const union nios2_register *reg)
 177 {
 178   supply_register (regcache, regno, reg->buf);
 179 }
 180
 181 /* We have only a single register set on Nios II.  */
 182
 183 static void
 184 nios2_fill_gregset (struct regcache *regcache, void *buf)
 185 {
 186   union nios2_register *regset = (union nios2_register *) buf;
 187   int i;
 188
 189   for (i = 1; i < nios2_num_regs; i++)
 190     nios2_collect_register (regcache, i, regset + i);
 191 }
 192
 193 static void
 194 nios2_store_gregset (struct regcache *regcache, const void *buf)
 195 {
 196   const union nios2_register *regset = (union nios2_register *) buf;
 197   int i;
 198
 199   for (i = 0; i < nios2_num_regs; i++)
 200     nios2_supply_register (regcache, i, regset + i);
 201 }
 202
 203 static struct regset_info nios2_regsets[] =
 204 {
 205   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_PRSTATUS,
 206     nios2_num_regs * 4, GENERAL_REGS,
 207     nios2_fill_gregset, nios2_store_gregset },
 208   NULL_REGSET
 209 };
 210
 211 static struct regsets_info nios2_regsets_info =
 212   {
 213     nios2_regsets, /* regsets */
 214     0, /* num_regsets */
 215     NULL, /* disabled_regsets */
 216   };
 217
 218 static struct usrregs_info nios2_usrregs_info =
 219   {
 220     nios2_num_regs,
 221     nios2_regmap,
 222   };
 223
 224 static struct regs_info regs_info =
 225   {
 226     NULL, /* regset_bitmap */
 227     &nios2_usrregs_info,
 228     &nios2_regsets_info
 229   };
 230
 231 static const struct regs_info *
 232 nios2_regs_info (void)
 233 {
 234   return &regs_info;
 235 }
 236
 237 struct linux_target_ops the_low_target =
 238 {
 239   nios2_arch_setup,
 240   nios2_regs_info,
 241   nios2_cannot_fetch_register,
 242   nios2_cannot_store_register,
 243   NULL,
 244   linux_get_pc_32bit,
 245   linux_set_pc_32bit,
 246   NULL, /* breakpoint_kind_from_pc */
 247   nios2_sw_breakpoint_from_kind,
 248   NULL, /* get_next_pcs */
 249   0,
 250   nios2_breakpoint_at,
 251 };
 252
 253 void
 254 initialize_low_arch (void)
 255 {
 256   init_registers_nios2_linux ();
 257
 258   initialize_regsets_info (&nios2_regsets_info);
 259 }