gdb/riscv-linux-tdep.c

   1 /* Target-dependent code for GNU/Linux on RISC-V processors.
   2    Copyright (C) 2018-2024 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include "defs.h"
  20 #include "riscv-tdep.h"
  21 #include "osabi.h"
  22 #include "glibc-tdep.h"
  23 #include "linux-tdep.h"
  24 #include "solib-svr4.h"
  25 #include "regset.h"
  26 #include "tramp-frame.h"
  27 #include "trad-frame.h"
  28 #include "gdbarch.h"
  29
  30 /* The following value is derived from __NR_rt_sigreturn in
  31    <include/uapi/asm-generic/unistd.h> from the Linux source tree.  */
  32
  33 #define RISCV_NR_rt_sigreturn 139
  34
  35 /* Define the general register mapping.  The kernel puts the PC at offset 0,
  36    gdb puts it at offset 32.  Register x0 is always 0 and can be ignored.
  37    Registers x1 to x31 are in the same place.  */
  38
  39 static const struct regcache_map_entry riscv_linux_gregmap[] =
  40 {
  41   { 1,  RISCV_PC_REGNUM, 0 },
  42   { 31, RISCV_RA_REGNUM, 0 }, /* x1 to x31 */
  43   { 0 }
  44 };
  45
  46 /* Define the FP register mapping.  The kernel puts the 32 FP regs first, and
  47    then FCSR.  */
  48
  49 static const struct regcache_map_entry riscv_linux_fregmap[] =
  50 {
  51   { 32, RISCV_FIRST_FP_REGNUM, 0 },
  52   { 1, RISCV_CSR_FCSR_REGNUM, 0 },
  53   { 0 }
  54 };
  55
  56 /* Define the general register regset.  */
  57
  58 static const struct regset riscv_linux_gregset =
  59 {
  60   riscv_linux_gregmap, riscv_supply_regset, regcache_collect_regset
  61 };
  62
  63 /* Define the FP register regset.  */
  64
  65 static const struct regset riscv_linux_fregset =
  66 {
  67   riscv_linux_fregmap, riscv_supply_regset, regcache_collect_regset
  68 };
  69
  70 /* Define hook for core file support.  */
  71
  72 static void
  73 riscv_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
  74                                           iterate_over_regset_sections_cb *cb,
  75                                           void *cb_data,
  76                                           const struct regcache *regcache)
  77 {
  78   cb (".reg", (32 * riscv_isa_xlen (gdbarch)), (32 * riscv_isa_xlen (gdbarch)),
  79       &riscv_linux_gregset, NULL, cb_data);
  80   /* The kernel is adding 8 bytes for FCSR.  */
  81   cb (".reg2", (32 * riscv_isa_flen (gdbarch)) + 8,
  82       (32 * riscv_isa_flen (gdbarch)) + 8,
  83       &riscv_linux_fregset, NULL, cb_data);
  84 }
  85
  86 /* Signal trampoline support.  */
  87
  88 static void riscv_linux_sigframe_init (const struct tramp_frame *self,
  89                                        frame_info_ptr this_frame,
  90                                        struct trad_frame_cache *this_cache,
  91                                        CORE_ADDR func);
  92
  93 #define RISCV_INST_LI_A7_SIGRETURN      0x08b00893
  94 #define RISCV_INST_ECALL                0x00000073
  95
  96 static const struct tramp_frame riscv_linux_sigframe = {
  97   SIGTRAMP_FRAME,
  98   4,
  99   {
 100     { RISCV_INST_LI_A7_SIGRETURN, ULONGEST_MAX },
 101     { RISCV_INST_ECALL, ULONGEST_MAX },
 102     { TRAMP_SENTINEL_INSN }
 103   },
 104   riscv_linux_sigframe_init,
 105   NULL
 106 };
 107
 108 /* Runtime signal frames look like this:
 109    struct rt_sigframe {
 110      struct siginfo info;
 111      struct ucontext uc;
 112    };
 113
 114    struct ucontext {
 115      unsigned long __uc_flags;
 116      struct ucontext *uclink;
 117      stack_t uc_stack;
 118      sigset_t uc_sigmask;
 119      char __glibc_reserved[1024 / 8 - sizeof (sigset_t)];
 120      mcontext_t uc_mcontext;
 121    }; */
 122
 123 #define SIGFRAME_SIGINFO_SIZE           128
 124 #define UCONTEXT_MCONTEXT_OFFSET        176
 125
 126 static void
 127 riscv_linux_sigframe_init (const struct tramp_frame *self,
 128                            frame_info_ptr this_frame,
 129                            struct trad_frame_cache *this_cache,
 130                            CORE_ADDR func)
 131 {
 132   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 133   int xlen = riscv_isa_xlen (gdbarch);
 134   int flen = riscv_isa_flen (gdbarch);
 135   CORE_ADDR frame_sp = get_frame_sp (this_frame);
 136   CORE_ADDR mcontext_base;
 137   CORE_ADDR regs_base;
 138
 139   mcontext_base = frame_sp + SIGFRAME_SIGINFO_SIZE + UCONTEXT_MCONTEXT_OFFSET;
 140
 141   /* Handle the integer registers.  The first one is PC, followed by x1
 142      through x31.  */
 143   regs_base = mcontext_base;
 144   trad_frame_set_reg_addr (this_cache, RISCV_PC_REGNUM, regs_base);
 145   for (int i = 1; i < 32; i++)
 146     trad_frame_set_reg_addr (this_cache, RISCV_ZERO_REGNUM + i,
 147                              regs_base + (i * xlen));
 148
 149   /* Handle the FP registers.  First comes the 32 FP registers, followed by
 150      fcsr.  */
 151   regs_base += 32 * xlen;
 152   for (int i = 0; i < 32; i++)
 153     trad_frame_set_reg_addr (this_cache, RISCV_FIRST_FP_REGNUM + i,
 154                              regs_base + (i * flen));
 155   regs_base += 32 * flen;
 156   trad_frame_set_reg_addr (this_cache, RISCV_CSR_FCSR_REGNUM, regs_base);
 157
 158   /* Choice of the bottom of the sigframe is somewhat arbitrary.  */
 159   trad_frame_set_id (this_cache, frame_id_build (frame_sp, func));
 160 }
 161
 162 /* When FRAME is at a syscall instruction (ECALL), return the PC of the next
 163    instruction to be executed.  */
 164
 165 static CORE_ADDR
 166 riscv_linux_syscall_next_pc (frame_info_ptr frame)
 167 {
 168   const CORE_ADDR pc = get_frame_pc (frame);
 169   const ULONGEST a7 = get_frame_register_unsigned (frame, RISCV_A7_REGNUM);
 170
 171   if (a7 == RISCV_NR_rt_sigreturn)
 172     return frame_unwind_caller_pc (frame);
 173
 174   return pc + 4 /* Length of the ECALL insn.  */;
 175 }
 176
 177 /* Initialize RISC-V Linux ABI info.  */
 178
 179 static void
 180 riscv_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 181 {
 182   riscv_gdbarch_tdep *tdep = gdbarch_tdep<riscv_gdbarch_tdep> (gdbarch);
 183
 184   linux_init_abi (info, gdbarch, 0);
 185
 186   set_gdbarch_software_single_step (gdbarch, riscv_software_single_step);
 187
 188   set_solib_svr4_fetch_link_map_offsets (gdbarch,
 189                                          (riscv_isa_xlen (gdbarch) == 4
 190                                           ? linux_ilp32_fetch_link_map_offsets
 191                                           : linux_lp64_fetch_link_map_offsets));
 192
 193   /* GNU/Linux uses SVR4-style shared libraries.  */
 194   set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
 195
 196   /* GNU/Linux uses the dynamic linker included in the GNU C Library.  */
 197   set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver);
 198
 199   /* Enable TLS support.  */
 200   set_gdbarch_fetch_tls_load_module_address (gdbarch,
 201                                              svr4_fetch_objfile_link_map);
 202
 203   set_gdbarch_iterate_over_regset_sections
 204     (gdbarch, riscv_linux_iterate_over_regset_sections);
 205
 206   tramp_frame_prepend_unwinder (gdbarch, &riscv_linux_sigframe);
 207
 208   tdep->syscall_next_pc = riscv_linux_syscall_next_pc;
 209 }
 210
 211 /* Initialize RISC-V Linux target support.  */
 212
 213 void _initialize_riscv_linux_tdep ();
 214 void
 215 _initialize_riscv_linux_tdep ()
 216 {
 217   gdbarch_register_osabi (bfd_arch_riscv, 0, GDB_OSABI_LINUX,
 218                           riscv_linux_init_abi);
 219 }