gdbserver/linux-riscv-low.cc

   1 /* GNU/Linux/RISC-V specific low level interface, for the remote server
   2    for GDB.
   3    Copyright (C) 2020 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "server.h"
  21
  22 #include "linux-low.h"
  23 #include "tdesc.h"
  24 #include "elf/common.h"
  25 #include "nat/riscv-linux-tdesc.h"
  26 #include "opcode/riscv.h"
  27
  28 /* Work around glibc header breakage causing ELF_NFPREG not to be usable.  */
  29 #ifndef NFPREG
  30 # define NFPREG 33
  31 #endif
  32
  33 /* Linux target op definitions for the RISC-V architecture.  */
  34
  35 class riscv_target : public linux_process_target
  36 {
  37 public:
  38
  39   const regs_info *get_regs_info () override;
  40
  41   int breakpoint_kind_from_pc (CORE_ADDR *pcptr) override;
  42
  43   const gdb_byte *sw_breakpoint_from_kind (int kind, int *size) override;
  44
  45 protected:
  46
  47   void low_arch_setup () override;
  48
  49   bool low_cannot_fetch_register (int regno) override;
  50
  51   bool low_cannot_store_register (int regno) override;
  52
  53   bool low_fetch_register (regcache *regcache, int regno) override;
  54
  55   bool low_supports_breakpoints () override;
  56
  57   CORE_ADDR low_get_pc (regcache *regcache) override;
  58
  59   void low_set_pc (regcache *regcache, CORE_ADDR newpc) override;
  60 };
  61
  62 /* The singleton target ops object.  */
  63
  64 static riscv_target the_riscv_target;
  65
  66 bool
  67 riscv_target::low_cannot_fetch_register (int regno)
  68 {
  69   gdb_assert_not_reached ("linux target op low_cannot_fetch_register "
  70                           "is not implemented by the target");
  71 }
  72
  73 bool
  74 riscv_target::low_cannot_store_register (int regno)
  75 {
  76   gdb_assert_not_reached ("linux target op low_cannot_store_register "
  77                           "is not implemented by the target");
  78 }
  79
  80 /* Implementation of linux target ops method "low_arch_setup".  */
  81
  82 void
  83 riscv_target::low_arch_setup ()
  84 {
  85   static const char *expedite_regs[] = { "sp", "pc", NULL };
  86
  87   const riscv_gdbarch_features features
  88     = riscv_linux_read_features (lwpid_of (current_thread));
  89   target_desc *tdesc = riscv_create_target_description (features);
  90
  91   if (!tdesc->expedite_regs)
  92     init_target_desc (tdesc, expedite_regs);
  93   current_process ()->tdesc = tdesc;
  94 }
  95
  96 /* Collect GPRs from REGCACHE into BUF.  */
  97
  98 static void
  99 riscv_fill_gregset (struct regcache *regcache, void *buf)
 100 {
 101   const struct target_desc *tdesc = regcache->tdesc;
 102   elf_gregset_t *regset = (elf_gregset_t *) buf;
 103   int regno = find_regno (tdesc, "zero");
 104   int i;
 105
 106   collect_register_by_name (regcache, "pc", *regset);
 107   for (i = 1; i < ARRAY_SIZE (*regset); i++)
 108     collect_register (regcache, regno + i, *regset + i);
 109 }
 110
 111 /* Supply GPRs from BUF into REGCACHE.  */
 112
 113 static void
 114 riscv_store_gregset (struct regcache *regcache, const void *buf)
 115 {
 116   const elf_gregset_t *regset = (const elf_gregset_t *) buf;
 117   const struct target_desc *tdesc = regcache->tdesc;
 118   int regno = find_regno (tdesc, "zero");
 119   int i;
 120
 121   supply_register_by_name (regcache, "pc", *regset);
 122   supply_register_zeroed (regcache, regno);
 123   for (i = 1; i < ARRAY_SIZE (*regset); i++)
 124     supply_register (regcache, regno + i, *regset + i);
 125 }
 126
 127 /* Collect FPRs from REGCACHE into BUF.  */
 128
 129 static void
 130 riscv_fill_fpregset (struct regcache *regcache, void *buf)
 131 {
 132   const struct target_desc *tdesc = regcache->tdesc;
 133   int regno = find_regno (tdesc, "ft0");
 134   int flen = register_size (regcache->tdesc, regno);
 135   gdb_byte *regbuf = (gdb_byte *) buf;
 136   int i;
 137
 138   for (i = 0; i < ELF_NFPREG - 1; i++, regbuf += flen)
 139     collect_register (regcache, regno + i, regbuf);
 140   collect_register_by_name (regcache, "fcsr", regbuf);
 141 }
 142
 143 /* Supply FPRs from BUF into REGCACHE.  */
 144
 145 static void
 146 riscv_store_fpregset (struct regcache *regcache, const void *buf)
 147 {
 148   const struct target_desc *tdesc = regcache->tdesc;
 149   int regno = find_regno (tdesc, "ft0");
 150   int flen = register_size (regcache->tdesc, regno);
 151   const gdb_byte *regbuf = (const gdb_byte *) buf;
 152   int i;
 153
 154   for (i = 0; i < ELF_NFPREG - 1; i++, regbuf += flen)
 155     supply_register (regcache, regno + i, regbuf);
 156   supply_register_by_name (regcache, "fcsr", regbuf);
 157 }
 158
 159 /* RISC-V/Linux regsets.  FPRs are optional and come in different sizes,
 160    so define multiple regsets for them marking them all as OPTIONAL_REGS
 161    rather than FP_REGS, so that "regsets_fetch_inferior_registers" picks
 162    the right one according to size.  */
 163 static struct regset_info riscv_regsets[] = {
 164   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_PRSTATUS,
 165     sizeof (elf_gregset_t), GENERAL_REGS,
 166     riscv_fill_gregset, riscv_store_gregset },
 167   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 168     sizeof (struct __riscv_mc_q_ext_state), OPTIONAL_REGS,
 169     riscv_fill_fpregset, riscv_store_fpregset },
 170   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 171     sizeof (struct __riscv_mc_d_ext_state), OPTIONAL_REGS,
 172     riscv_fill_fpregset, riscv_store_fpregset },
 173   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 174     sizeof (struct __riscv_mc_f_ext_state), OPTIONAL_REGS,
 175     riscv_fill_fpregset, riscv_store_fpregset },
 176   NULL_REGSET
 177 };
 178
 179 /* RISC-V/Linux regset information.  */
 180 static struct regsets_info riscv_regsets_info =
 181   {
 182     riscv_regsets, /* regsets */
 183     0, /* num_regsets */
 184     NULL, /* disabled_regsets */
 185   };
 186
 187 /* Definition of linux_target_ops data member "regs_info".  */
 188 static struct regs_info riscv_regs =
 189   {
 190     NULL, /* regset_bitmap */
 191     NULL, /* usrregs */
 192     &riscv_regsets_info,
 193   };
 194
 195 /* Implementation of linux target ops method "get_regs_info".  */
 196
 197 const regs_info *
 198 riscv_target::get_regs_info ()
 199 {
 200   return &riscv_regs;
 201 }
 202
 203 /* Implementation of linux target ops method "low_fetch_register".  */
 204
 205 bool
 206 riscv_target::low_fetch_register (regcache *regcache, int regno)
 207 {
 208   const struct target_desc *tdesc = regcache->tdesc;
 209
 210   if (regno != find_regno (tdesc, "zero"))
 211     return false;
 212   supply_register_zeroed (regcache, regno);
 213   return true;
 214 }
 215
 216 bool
 217 riscv_target::low_supports_breakpoints ()
 218 {
 219   return true;
 220 }
 221
 222 /* Implementation of linux target ops method "low_get_pc".  */
 223
 224 CORE_ADDR
 225 riscv_target::low_get_pc (regcache *regcache)
 226 {
 227   elf_gregset_t regset;
 228
 229   if (sizeof (regset[0]) == 8)
 230     return linux_get_pc_64bit (regcache);
 231   else
 232     return linux_get_pc_32bit (regcache);
 233 }
 234
 235 /* Implementation of linux target ops method "low_set_pc".  */
 236
 237 void
 238 riscv_target::low_set_pc (regcache *regcache, CORE_ADDR newpc)
 239 {
 240   elf_gregset_t regset;
 241
 242   if (sizeof (regset[0]) == 8)
 243     linux_set_pc_64bit (regcache, newpc);
 244   else
 245     linux_set_pc_32bit (regcache, newpc);
 246 }
 247
 248 /* Correct in either endianness.  */
 249 static const uint16_t riscv_ibreakpoint[] = { 0x0073, 0x0010 };
 250 static const uint16_t riscv_cbreakpoint = 0x9002;
 251
 252 /* Implementation of target ops method "breakpoint_kind_from_pc".  */
 253
 254 int
 255 riscv_target::breakpoint_kind_from_pc (CORE_ADDR *pcptr)
 256 {
 257   union
 258     {
 259       gdb_byte bytes[2];
 260       uint16_t insn;
 261     }
 262   buf;
 263
 264   if (target_read_memory (*pcptr, buf.bytes, sizeof (buf.insn)) == 0
 265       && riscv_insn_length (buf.insn == sizeof (riscv_ibreakpoint)))
 266     return sizeof (riscv_ibreakpoint);
 267   else
 268     return sizeof (riscv_cbreakpoint);
 269 }
 270
 271 /* Implementation of target ops method "sw_breakpoint_from_kind".  */
 272
 273 const gdb_byte *
 274 riscv_target::sw_breakpoint_from_kind (int kind, int *size)
 275 {
 276   *size = kind;
 277   switch (kind)
 278     {
 279       case sizeof (riscv_ibreakpoint):
 280         return (const gdb_byte *) &riscv_ibreakpoint;
 281       default:
 282         return (const gdb_byte *) &riscv_cbreakpoint;
 283     }
 284 }
 285
 286 /* Implementation of linux_target_ops method "breakpoint_at".  */
 287
 288 static int
 289 riscv_breakpoint_at (CORE_ADDR pc)
 290 {
 291   union
 292     {
 293       gdb_byte bytes[2];
 294       uint16_t insn;
 295     }
 296   buf;
 297
 298   if (target_read_memory (pc, buf.bytes, sizeof (buf.insn)) == 0
 299       && (buf.insn == riscv_cbreakpoint
 300           || (buf.insn == riscv_ibreakpoint[0]
 301               && target_read_memory (pc + sizeof (buf.insn), buf.bytes,
 302                                      sizeof (buf.insn)) == 0
 303               && buf.insn == riscv_ibreakpoint[1])))
 304     return 1;
 305   else
 306     return 0;
 307 }
 308
 309 /* RISC-V/Linux target operations.  */
 310 struct linux_target_ops the_low_target =
 311 {
 312   0,    /* decr_pc_after_break */
 313   riscv_breakpoint_at,
 314 };
 315
 316 /* The linux target ops object.  */
 317
 318 linux_process_target *the_linux_target = &the_riscv_target;
 319
 320 /* Initialize the RISC-V/Linux target.  */
 321
 322 void
 323 initialize_low_arch ()
 324 {
 325   initialize_regsets_info (&riscv_regsets_info);
 326 }