gdbserver/linux-riscv-low.cc

   1 /* GNU/Linux/RISC-V specific low level interface, for the remote server
   2    for GDB.
   3    Copyright (C) 2020-2024 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
  21 #include "linux-low.h"
  22 #include "tdesc.h"
  23 #include "elf/common.h"
  24 #include "nat/riscv-linux-tdesc.h"
  25 #include "opcode/riscv.h"
  26
  27 /* Work around glibc header breakage causing ELF_NFPREG not to be usable.  */
  28 #ifndef NFPREG
  29 # define NFPREG 33
  30 #endif
  31
  32 /* Linux target op definitions for the RISC-V architecture.  */
  33
  34 class riscv_target : public linux_process_target
  35 {
  36 public:
  37
  38   const regs_info *get_regs_info () override;
  39
  40   int breakpoint_kind_from_pc (CORE_ADDR *pcptr) 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_fetch_register (regcache *regcache, int regno) override;
  53
  54   bool low_supports_breakpoints () override;
  55
  56   CORE_ADDR low_get_pc (regcache *regcache) override;
  57
  58   void low_set_pc (regcache *regcache, CORE_ADDR newpc) override;
  59
  60   bool low_breakpoint_at (CORE_ADDR pc) override;
  61 };
  62
  63 /* The singleton target ops object.  */
  64
  65 static riscv_target the_riscv_target;
  66
  67 bool
  68 riscv_target::low_cannot_fetch_register (int regno)
  69 {
  70   gdb_assert_not_reached ("linux target op low_cannot_fetch_register "
  71                           "is not implemented by the target");
  72 }
  73
  74 bool
  75 riscv_target::low_cannot_store_register (int regno)
  76 {
  77   gdb_assert_not_reached ("linux target op low_cannot_store_register "
  78                           "is not implemented by the target");
  79 }
  80
  81 /* Implementation of linux target ops method "low_arch_setup".  */
  82
  83 void
  84 riscv_target::low_arch_setup ()
  85 {
  86   static const char *expedite_regs[] = { "sp", "pc", NULL };
  87
  88   const riscv_gdbarch_features features
  89     = riscv_linux_read_features (current_thread->id.lwp ());
  90   target_desc_up tdesc = riscv_create_target_description (features);
  91
  92   if (tdesc->expedite_regs.empty ())
  93     {
  94       init_target_desc (tdesc.get (), expedite_regs, GDB_OSABI_LINUX);
  95       gdb_assert (!tdesc->expedite_regs.empty ());
  96     }
  97
  98   current_process ()->tdesc = tdesc.release ();
  99 }
 100
 101 /* Collect GPRs from REGCACHE into BUF.  */
 102
 103 static void
 104 riscv_fill_gregset (struct regcache *regcache, void *buf)
 105 {
 106   const struct target_desc *tdesc = regcache->tdesc;
 107   elf_gregset_t *regset = (elf_gregset_t *) buf;
 108   int regno = find_regno (tdesc, "zero");
 109   int i;
 110
 111   collect_register_by_name (regcache, "pc", *regset);
 112   for (i = 1; i < ARRAY_SIZE (*regset); i++)
 113     collect_register (regcache, regno + i, *regset + i);
 114 }
 115
 116 /* Supply GPRs from BUF into REGCACHE.  */
 117
 118 static void
 119 riscv_store_gregset (struct regcache *regcache, const void *buf)
 120 {
 121   const elf_gregset_t *regset = (const elf_gregset_t *) buf;
 122   const struct target_desc *tdesc = regcache->tdesc;
 123   int regno = find_regno (tdesc, "zero");
 124   int i;
 125
 126   supply_register_by_name (regcache, "pc", *regset);
 127   supply_register_zeroed (regcache, regno);
 128   for (i = 1; i < ARRAY_SIZE (*regset); i++)
 129     supply_register (regcache, regno + i, *regset + i);
 130 }
 131
 132 /* Collect FPRs from REGCACHE into BUF.  */
 133
 134 static void
 135 riscv_fill_fpregset (struct regcache *regcache, void *buf)
 136 {
 137   const struct target_desc *tdesc = regcache->tdesc;
 138   int regno = find_regno (tdesc, "ft0");
 139   int flen = register_size (regcache->tdesc, regno);
 140   gdb_byte *regbuf = (gdb_byte *) buf;
 141   int i;
 142
 143   for (i = 0; i < ELF_NFPREG - 1; i++, regbuf += flen)
 144     collect_register (regcache, regno + i, regbuf);
 145   collect_register_by_name (regcache, "fcsr", regbuf);
 146 }
 147
 148 /* Supply FPRs from BUF into REGCACHE.  */
 149
 150 static void
 151 riscv_store_fpregset (struct regcache *regcache, const void *buf)
 152 {
 153   const struct target_desc *tdesc = regcache->tdesc;
 154   int regno = find_regno (tdesc, "ft0");
 155   int flen = register_size (regcache->tdesc, regno);
 156   const gdb_byte *regbuf = (const gdb_byte *) buf;
 157   int i;
 158
 159   for (i = 0; i < ELF_NFPREG - 1; i++, regbuf += flen)
 160     supply_register (regcache, regno + i, regbuf);
 161   supply_register_by_name (regcache, "fcsr", regbuf);
 162 }
 163
 164 /* RISC-V/Linux regsets.  FPRs are optional and come in different sizes,
 165    so define multiple regsets for them marking them all as OPTIONAL_REGS
 166    rather than FP_REGS, so that "regsets_fetch_inferior_registers" picks
 167    the right one according to size.  */
 168 static struct regset_info riscv_regsets[] = {
 169   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_PRSTATUS,
 170     sizeof (elf_gregset_t), GENERAL_REGS,
 171     riscv_fill_gregset, riscv_store_gregset },
 172   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 173     sizeof (struct __riscv_mc_q_ext_state), OPTIONAL_REGS,
 174     riscv_fill_fpregset, riscv_store_fpregset },
 175   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 176     sizeof (struct __riscv_mc_d_ext_state), OPTIONAL_REGS,
 177     riscv_fill_fpregset, riscv_store_fpregset },
 178   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 179     sizeof (struct __riscv_mc_f_ext_state), OPTIONAL_REGS,
 180     riscv_fill_fpregset, riscv_store_fpregset },
 181   NULL_REGSET
 182 };
 183
 184 /* RISC-V/Linux regset information.  */
 185 static struct regsets_info riscv_regsets_info =
 186   {
 187     riscv_regsets, /* regsets */
 188     0, /* num_regsets */
 189     NULL, /* disabled_regsets */
 190   };
 191
 192 /* Definition of linux_target_ops data member "regs_info".  */
 193 static struct regs_info riscv_regs =
 194   {
 195     NULL, /* regset_bitmap */
 196     NULL, /* usrregs */
 197     &riscv_regsets_info,
 198   };
 199
 200 /* Implementation of linux target ops method "get_regs_info".  */
 201
 202 const regs_info *
 203 riscv_target::get_regs_info ()
 204 {
 205   return &riscv_regs;
 206 }
 207
 208 /* Implementation of linux target ops method "low_fetch_register".  */
 209
 210 bool
 211 riscv_target::low_fetch_register (regcache *regcache, int regno)
 212 {
 213   const struct target_desc *tdesc = regcache->tdesc;
 214
 215   if (regno != find_regno (tdesc, "zero"))
 216     return false;
 217   supply_register_zeroed (regcache, regno);
 218   return true;
 219 }
 220
 221 bool
 222 riscv_target::low_supports_breakpoints ()
 223 {
 224   return true;
 225 }
 226
 227 /* Implementation of linux target ops method "low_get_pc".  */
 228
 229 CORE_ADDR
 230 riscv_target::low_get_pc (regcache *regcache)
 231 {
 232   elf_gregset_t regset;
 233
 234   if (sizeof (regset[0]) == 8)
 235     return linux_get_pc_64bit (regcache);
 236   else
 237     return linux_get_pc_32bit (regcache);
 238 }
 239
 240 /* Implementation of linux target ops method "low_set_pc".  */
 241
 242 void
 243 riscv_target::low_set_pc (regcache *regcache, CORE_ADDR newpc)
 244 {
 245   elf_gregset_t regset;
 246
 247   if (sizeof (regset[0]) == 8)
 248     linux_set_pc_64bit (regcache, newpc);
 249   else
 250     linux_set_pc_32bit (regcache, newpc);
 251 }
 252
 253 /* Correct in either endianness.  */
 254 static const uint16_t riscv_ibreakpoint[] = { 0x0073, 0x0010 };
 255 static const uint16_t riscv_cbreakpoint = 0x9002;
 256
 257 /* Implementation of target ops method "breakpoint_kind_from_pc".  */
 258
 259 int
 260 riscv_target::breakpoint_kind_from_pc (CORE_ADDR *pcptr)
 261 {
 262   union
 263     {
 264       gdb_byte bytes[2];
 265       uint16_t insn;
 266     }
 267   buf;
 268
 269   if (target_read_memory (*pcptr, buf.bytes, sizeof (buf.insn)) == 0
 270       && riscv_insn_length (buf.insn == sizeof (riscv_ibreakpoint)))
 271     return sizeof (riscv_ibreakpoint);
 272   else
 273     return sizeof (riscv_cbreakpoint);
 274 }
 275
 276 /* Implementation of target ops method "sw_breakpoint_from_kind".  */
 277
 278 const gdb_byte *
 279 riscv_target::sw_breakpoint_from_kind (int kind, int *size)
 280 {
 281   *size = kind;
 282   switch (kind)
 283     {
 284       case sizeof (riscv_ibreakpoint):
 285         return (const gdb_byte *) &riscv_ibreakpoint;
 286       default:
 287         return (const gdb_byte *) &riscv_cbreakpoint;
 288     }
 289 }
 290
 291 /* Implementation of linux target ops method "low_breakpoint_at".  */
 292
 293 bool
 294 riscv_target::low_breakpoint_at (CORE_ADDR pc)
 295 {
 296   union
 297     {
 298       gdb_byte bytes[2];
 299       uint16_t insn;
 300     }
 301   buf;
 302
 303   if (target_read_memory (pc, buf.bytes, sizeof (buf.insn)) == 0
 304       && (buf.insn == riscv_cbreakpoint
 305           || (buf.insn == riscv_ibreakpoint[0]
 306               && target_read_memory (pc + sizeof (buf.insn), buf.bytes,
 307                                      sizeof (buf.insn)) == 0
 308               && buf.insn == riscv_ibreakpoint[1])))
 309     return true;
 310   else
 311     return false;
 312 }
 313
 314 /* The linux target ops object.  */
 315
 316 linux_process_target *the_linux_target = &the_riscv_target;
 317
 318 /* Initialize the RISC-V/Linux target.  */
 319
 320 void
 321 initialize_low_arch ()
 322 {
 323   initialize_regsets_info (&riscv_regsets_info);
 324 }