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 protected:
  44
  45   void low_arch_setup () override;
  46
  47   bool low_cannot_fetch_register (int regno) override;
  48
  49   bool low_cannot_store_register (int regno) override;
  50
  51   bool low_fetch_register (regcache *regcache, int regno) override;
  52
  53   bool low_supports_breakpoints () override;
  54
  55   CORE_ADDR low_get_pc (regcache *regcache) override;
  56
  57   void low_set_pc (regcache *regcache, CORE_ADDR newpc) override;
  58 };
  59
  60 /* The singleton target ops object.  */
  61
  62 static riscv_target the_riscv_target;
  63
  64 bool
  65 riscv_target::low_cannot_fetch_register (int regno)
  66 {
  67   gdb_assert_not_reached ("linux target op low_cannot_fetch_register "
  68                           "is not implemented by the target");
  69 }
  70
  71 bool
  72 riscv_target::low_cannot_store_register (int regno)
  73 {
  74   gdb_assert_not_reached ("linux target op low_cannot_store_register "
  75                           "is not implemented by the target");
  76 }
  77
  78 /* Implementation of linux target ops method "low_arch_setup".  */
  79
  80 void
  81 riscv_target::low_arch_setup ()
  82 {
  83   static const char *expedite_regs[] = { "sp", "pc", NULL };
  84
  85   const riscv_gdbarch_features features
  86     = riscv_linux_read_features (lwpid_of (current_thread));
  87   target_desc *tdesc = riscv_create_target_description (features);
  88
  89   if (!tdesc->expedite_regs)
  90     init_target_desc (tdesc, expedite_regs);
  91   current_process ()->tdesc = tdesc;
  92 }
  93
  94 /* Collect GPRs from REGCACHE into BUF.  */
  95
  96 static void
  97 riscv_fill_gregset (struct regcache *regcache, void *buf)
  98 {
  99   const struct target_desc *tdesc = regcache->tdesc;
 100   elf_gregset_t *regset = (elf_gregset_t *) buf;
 101   int regno = find_regno (tdesc, "zero");
 102   int i;
 103
 104   collect_register_by_name (regcache, "pc", *regset);
 105   for (i = 1; i < ARRAY_SIZE (*regset); i++)
 106     collect_register (regcache, regno + i, *regset + i);
 107 }
 108
 109 /* Supply GPRs from BUF into REGCACHE.  */
 110
 111 static void
 112 riscv_store_gregset (struct regcache *regcache, const void *buf)
 113 {
 114   const elf_gregset_t *regset = (const elf_gregset_t *) buf;
 115   const struct target_desc *tdesc = regcache->tdesc;
 116   int regno = find_regno (tdesc, "zero");
 117   int i;
 118
 119   supply_register_by_name (regcache, "pc", *regset);
 120   supply_register_zeroed (regcache, regno);
 121   for (i = 1; i < ARRAY_SIZE (*regset); i++)
 122     supply_register (regcache, regno + i, *regset + i);
 123 }
 124
 125 /* Collect FPRs from REGCACHE into BUF.  */
 126
 127 static void
 128 riscv_fill_fpregset (struct regcache *regcache, void *buf)
 129 {
 130   const struct target_desc *tdesc = regcache->tdesc;
 131   int regno = find_regno (tdesc, "ft0");
 132   int flen = register_size (regcache->tdesc, regno);
 133   gdb_byte *regbuf = (gdb_byte *) buf;
 134   int i;
 135
 136   for (i = 0; i < ELF_NFPREG - 1; i++, regbuf += flen)
 137     collect_register (regcache, regno + i, regbuf);
 138   collect_register_by_name (regcache, "fcsr", regbuf);
 139 }
 140
 141 /* Supply FPRs from BUF into REGCACHE.  */
 142
 143 static void
 144 riscv_store_fpregset (struct regcache *regcache, const void *buf)
 145 {
 146   const struct target_desc *tdesc = regcache->tdesc;
 147   int regno = find_regno (tdesc, "ft0");
 148   int flen = register_size (regcache->tdesc, regno);
 149   const gdb_byte *regbuf = (const gdb_byte *) buf;
 150   int i;
 151
 152   for (i = 0; i < ELF_NFPREG - 1; i++, regbuf += flen)
 153     supply_register (regcache, regno + i, regbuf);
 154   supply_register_by_name (regcache, "fcsr", regbuf);
 155 }
 156
 157 /* RISC-V/Linux regsets.  FPRs are optional and come in different sizes,
 158    so define multiple regsets for them marking them all as OPTIONAL_REGS
 159    rather than FP_REGS, so that "regsets_fetch_inferior_registers" picks
 160    the right one according to size.  */
 161 static struct regset_info riscv_regsets[] = {
 162   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_PRSTATUS,
 163     sizeof (elf_gregset_t), GENERAL_REGS,
 164     riscv_fill_gregset, riscv_store_gregset },
 165   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 166     sizeof (struct __riscv_mc_q_ext_state), OPTIONAL_REGS,
 167     riscv_fill_fpregset, riscv_store_fpregset },
 168   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 169     sizeof (struct __riscv_mc_d_ext_state), OPTIONAL_REGS,
 170     riscv_fill_fpregset, riscv_store_fpregset },
 171   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 172     sizeof (struct __riscv_mc_f_ext_state), OPTIONAL_REGS,
 173     riscv_fill_fpregset, riscv_store_fpregset },
 174   NULL_REGSET
 175 };
 176
 177 /* RISC-V/Linux regset information.  */
 178 static struct regsets_info riscv_regsets_info =
 179   {
 180     riscv_regsets, /* regsets */
 181     0, /* num_regsets */
 182     NULL, /* disabled_regsets */
 183   };
 184
 185 /* Definition of linux_target_ops data member "regs_info".  */
 186 static struct regs_info riscv_regs =
 187   {
 188     NULL, /* regset_bitmap */
 189     NULL, /* usrregs */
 190     &riscv_regsets_info,
 191   };
 192
 193 /* Implementation of linux target ops method "get_regs_info".  */
 194
 195 const regs_info *
 196 riscv_target::get_regs_info ()
 197 {
 198   return &riscv_regs;
 199 }
 200
 201 /* Implementation of linux target ops method "low_fetch_register".  */
 202
 203 bool
 204 riscv_target::low_fetch_register (regcache *regcache, int regno)
 205 {
 206   const struct target_desc *tdesc = regcache->tdesc;
 207
 208   if (regno != find_regno (tdesc, "zero"))
 209     return false;
 210   supply_register_zeroed (regcache, regno);
 211   return true;
 212 }
 213
 214 bool
 215 riscv_target::low_supports_breakpoints ()
 216 {
 217   return true;
 218 }
 219
 220 /* Implementation of linux target ops method "low_get_pc".  */
 221
 222 CORE_ADDR
 223 riscv_target::low_get_pc (regcache *regcache)
 224 {
 225   elf_gregset_t regset;
 226
 227   if (sizeof (regset[0]) == 8)
 228     return linux_get_pc_64bit (regcache);
 229   else
 230     return linux_get_pc_32bit (regcache);
 231 }
 232
 233 /* Implementation of linux target ops method "low_set_pc".  */
 234
 235 void
 236 riscv_target::low_set_pc (regcache *regcache, CORE_ADDR newpc)
 237 {
 238   elf_gregset_t regset;
 239
 240   if (sizeof (regset[0]) == 8)
 241     linux_set_pc_64bit (regcache, newpc);
 242   else
 243     linux_set_pc_32bit (regcache, newpc);
 244 }
 245
 246 /* Correct in either endianness.  */
 247 static const uint16_t riscv_ibreakpoint[] = { 0x0073, 0x0010 };
 248 static const uint16_t riscv_cbreakpoint = 0x9002;
 249
 250 /* Implementation of target ops method "breakpoint_kind_from_pc".  */
 251
 252 int
 253 riscv_target::breakpoint_kind_from_pc (CORE_ADDR *pcptr)
 254 {
 255   union
 256     {
 257       gdb_byte bytes[2];
 258       uint16_t insn;
 259     }
 260   buf;
 261
 262   if (target_read_memory (*pcptr, buf.bytes, sizeof (buf.insn)) == 0
 263       && riscv_insn_length (buf.insn == sizeof (riscv_ibreakpoint)))
 264     return sizeof (riscv_ibreakpoint);
 265   else
 266     return sizeof (riscv_cbreakpoint);
 267 }
 268
 269 /* Implementation of linux_target_ops method "sw_breakpoint_from_kind".  */
 270
 271 static const gdb_byte *
 272 riscv_sw_breakpoint_from_kind (int kind, int *size)
 273 {
 274   *size = kind;
 275   switch (kind)
 276     {
 277       case sizeof (riscv_ibreakpoint):
 278         return (const gdb_byte *) &riscv_ibreakpoint;
 279       default:
 280         return (const gdb_byte *) &riscv_cbreakpoint;
 281     }
 282 }
 283
 284 /* Implementation of linux_target_ops method "breakpoint_at".  */
 285
 286 static int
 287 riscv_breakpoint_at (CORE_ADDR pc)
 288 {
 289   union
 290     {
 291       gdb_byte bytes[2];
 292       uint16_t insn;
 293     }
 294   buf;
 295
 296   if (target_read_memory (pc, buf.bytes, sizeof (buf.insn)) == 0
 297       && (buf.insn == riscv_cbreakpoint
 298           || (buf.insn == riscv_ibreakpoint[0]
 299               && target_read_memory (pc + sizeof (buf.insn), buf.bytes,
 300                                      sizeof (buf.insn)) == 0
 301               && buf.insn == riscv_ibreakpoint[1])))
 302     return 1;
 303   else
 304     return 0;
 305 }
 306
 307 /* RISC-V/Linux target operations.  */
 308 struct linux_target_ops the_low_target =
 309 {
 310   riscv_sw_breakpoint_from_kind,
 311   NULL, /* get_next_pcs */
 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 }