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 protected:
  42
  43   void low_arch_setup () override;
  44 };
  45
  46 /* The singleton target ops object.  */
  47
  48 static riscv_target the_riscv_target;
  49
  50 /* Implementation of linux target ops method "low_arch_setup".  */
  51
  52 void
  53 riscv_target::low_arch_setup ()
  54 {
  55   static const char *expedite_regs[] = { "sp", "pc", NULL };
  56
  57   const riscv_gdbarch_features features
  58     = riscv_linux_read_features (lwpid_of (current_thread));
  59   target_desc *tdesc = riscv_create_target_description (features);
  60
  61   if (!tdesc->expedite_regs)
  62     init_target_desc (tdesc, expedite_regs);
  63   current_process ()->tdesc = tdesc;
  64 }
  65
  66 /* Collect GPRs from REGCACHE into BUF.  */
  67
  68 static void
  69 riscv_fill_gregset (struct regcache *regcache, void *buf)
  70 {
  71   const struct target_desc *tdesc = regcache->tdesc;
  72   elf_gregset_t *regset = (elf_gregset_t *) buf;
  73   int regno = find_regno (tdesc, "zero");
  74   int i;
  75
  76   collect_register_by_name (regcache, "pc", *regset);
  77   for (i = 1; i < ARRAY_SIZE (*regset); i++)
  78     collect_register (regcache, regno + i, *regset + i);
  79 }
  80
  81 /* Supply GPRs from BUF into REGCACHE.  */
  82
  83 static void
  84 riscv_store_gregset (struct regcache *regcache, const void *buf)
  85 {
  86   const elf_gregset_t *regset = (const elf_gregset_t *) buf;
  87   const struct target_desc *tdesc = regcache->tdesc;
  88   int regno = find_regno (tdesc, "zero");
  89   int i;
  90
  91   supply_register_by_name (regcache, "pc", *regset);
  92   supply_register_zeroed (regcache, regno);
  93   for (i = 1; i < ARRAY_SIZE (*regset); i++)
  94     supply_register (regcache, regno + i, *regset + i);
  95 }
  96
  97 /* Collect FPRs from REGCACHE into BUF.  */
  98
  99 static void
 100 riscv_fill_fpregset (struct regcache *regcache, void *buf)
 101 {
 102   const struct target_desc *tdesc = regcache->tdesc;
 103   int regno = find_regno (tdesc, "ft0");
 104   int flen = register_size (regcache->tdesc, regno);
 105   gdb_byte *regbuf = (gdb_byte *) buf;
 106   int i;
 107
 108   for (i = 0; i < ELF_NFPREG - 1; i++, regbuf += flen)
 109     collect_register (regcache, regno + i, regbuf);
 110   collect_register_by_name (regcache, "fcsr", regbuf);
 111 }
 112
 113 /* Supply FPRs from BUF into REGCACHE.  */
 114
 115 static void
 116 riscv_store_fpregset (struct regcache *regcache, const void *buf)
 117 {
 118   const struct target_desc *tdesc = regcache->tdesc;
 119   int regno = find_regno (tdesc, "ft0");
 120   int flen = register_size (regcache->tdesc, regno);
 121   const gdb_byte *regbuf = (const gdb_byte *) buf;
 122   int i;
 123
 124   for (i = 0; i < ELF_NFPREG - 1; i++, regbuf += flen)
 125     supply_register (regcache, regno + i, regbuf);
 126   supply_register_by_name (regcache, "fcsr", regbuf);
 127 }
 128
 129 /* RISC-V/Linux regsets.  FPRs are optional and come in different sizes,
 130    so define multiple regsets for them marking them all as OPTIONAL_REGS
 131    rather than FP_REGS, so that "regsets_fetch_inferior_registers" picks
 132    the right one according to size.  */
 133 static struct regset_info riscv_regsets[] = {
 134   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_PRSTATUS,
 135     sizeof (elf_gregset_t), GENERAL_REGS,
 136     riscv_fill_gregset, riscv_store_gregset },
 137   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 138     sizeof (struct __riscv_mc_q_ext_state), OPTIONAL_REGS,
 139     riscv_fill_fpregset, riscv_store_fpregset },
 140   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 141     sizeof (struct __riscv_mc_d_ext_state), OPTIONAL_REGS,
 142     riscv_fill_fpregset, riscv_store_fpregset },
 143   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_FPREGSET,
 144     sizeof (struct __riscv_mc_f_ext_state), OPTIONAL_REGS,
 145     riscv_fill_fpregset, riscv_store_fpregset },
 146   NULL_REGSET
 147 };
 148
 149 /* RISC-V/Linux regset information.  */
 150 static struct regsets_info riscv_regsets_info =
 151   {
 152     riscv_regsets, /* regsets */
 153     0, /* num_regsets */
 154     NULL, /* disabled_regsets */
 155   };
 156
 157 /* Definition of linux_target_ops data member "regs_info".  */
 158 static struct regs_info riscv_regs =
 159   {
 160     NULL, /* regset_bitmap */
 161     NULL, /* usrregs */
 162     &riscv_regsets_info,
 163   };
 164
 165 /* Implementation of linux target ops method "get_regs_info".  */
 166
 167 const regs_info *
 168 riscv_target::get_regs_info ()
 169 {
 170   return &riscv_regs;
 171 }
 172
 173 /* Implementation of linux_target_ops method "fetch_register".  */
 174
 175 static int
 176 riscv_fetch_register (struct regcache *regcache, int regno)
 177 {
 178   const struct target_desc *tdesc = regcache->tdesc;
 179
 180   if (regno != find_regno (tdesc, "zero"))
 181     return 0;
 182   supply_register_zeroed (regcache, regno);
 183   return 1;
 184 }
 185
 186 /* Implementation of linux_target_ops method "get_pc".  */
 187
 188 static CORE_ADDR
 189 riscv_get_pc (struct regcache *regcache)
 190 {
 191   elf_gregset_t regset;
 192
 193   if (sizeof (regset[0]) == 8)
 194     return linux_get_pc_64bit (regcache);
 195   else
 196     return linux_get_pc_32bit (regcache);
 197 }
 198
 199 /* Implementation of linux_target_ops method "set_pc".  */
 200
 201 static void
 202 riscv_set_pc (struct regcache *regcache, CORE_ADDR newpc)
 203 {
 204   elf_gregset_t regset;
 205
 206   if (sizeof (regset[0]) == 8)
 207     linux_set_pc_64bit (regcache, newpc);
 208   else
 209     linux_set_pc_32bit (regcache, newpc);
 210 }
 211
 212 /* Correct in either endianness.  */
 213 static const uint16_t riscv_ibreakpoint[] = { 0x0073, 0x0010 };
 214 static const uint16_t riscv_cbreakpoint = 0x9002;
 215
 216 /* Implementation of linux_target_ops method "breakpoint_kind_from_pc".  */
 217
 218 static int
 219 riscv_breakpoint_kind_from_pc (CORE_ADDR *pcptr)
 220 {
 221   union
 222     {
 223       gdb_byte bytes[2];
 224       uint16_t insn;
 225     }
 226   buf;
 227
 228   if (target_read_memory (*pcptr, buf.bytes, sizeof (buf.insn)) == 0
 229       && riscv_insn_length (buf.insn == sizeof (riscv_ibreakpoint)))
 230     return sizeof (riscv_ibreakpoint);
 231   else
 232     return sizeof (riscv_cbreakpoint);
 233 }
 234
 235 /* Implementation of linux_target_ops method "sw_breakpoint_from_kind".  */
 236
 237 static const gdb_byte *
 238 riscv_sw_breakpoint_from_kind (int kind, int *size)
 239 {
 240   *size = kind;
 241   switch (kind)
 242     {
 243       case sizeof (riscv_ibreakpoint):
 244         return (const gdb_byte *) &riscv_ibreakpoint;
 245       default:
 246         return (const gdb_byte *) &riscv_cbreakpoint;
 247     }
 248 }
 249
 250 /* Implementation of linux_target_ops method "breakpoint_at".  */
 251
 252 static int
 253 riscv_breakpoint_at (CORE_ADDR pc)
 254 {
 255   union
 256     {
 257       gdb_byte bytes[2];
 258       uint16_t insn;
 259     }
 260   buf;
 261
 262   if (target_read_memory (pc, buf.bytes, sizeof (buf.insn)) == 0
 263       && (buf.insn == riscv_cbreakpoint
 264           || (buf.insn == riscv_ibreakpoint[0]
 265               && target_read_memory (pc + sizeof (buf.insn), buf.bytes,
 266                                      sizeof (buf.insn)) == 0
 267               && buf.insn == riscv_ibreakpoint[1])))
 268     return 1;
 269   else
 270     return 0;
 271 }
 272
 273 /* RISC-V/Linux target operations.  */
 274 struct linux_target_ops the_low_target =
 275 {
 276   NULL, /* cannot_fetch_register */
 277   NULL, /* cannot_store_register */
 278   riscv_fetch_register,
 279   riscv_get_pc,
 280   riscv_set_pc,
 281   riscv_breakpoint_kind_from_pc,
 282   riscv_sw_breakpoint_from_kind,
 283   NULL, /* get_next_pcs */
 284   0,    /* decr_pc_after_break */
 285   riscv_breakpoint_at,
 286 };
 287
 288 /* The linux target ops object.  */
 289
 290 linux_process_target *the_linux_target = &the_riscv_target;
 291
 292 /* Initialize the RISC-V/Linux target.  */
 293
 294 void
 295 initialize_low_arch ()
 296 {
 297   initialize_regsets_info (&riscv_regsets_info);
 298 }