gdb/nios2-linux-tdep.c

   1 /* Target-dependent code for GNU/Linux on Nios II.
   2    Copyright (C) 2012-2020 Free Software Foundation, Inc.
   3    Contributed by Mentor Graphics, 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 "defs.h"
  21 #include "frame.h"
  22 #include "osabi.h"
  23 #include "solib-svr4.h"
  24 #include "trad-frame.h"
  25 #include "tramp-frame.h"
  26 #include "symtab.h"
  27 #include "regset.h"
  28 #include "regcache.h"
  29 #include "linux-tdep.h"
  30 #include "glibc-tdep.h"
  31 #include "nios2-tdep.h"
  32 #include "gdbarch.h"
  33
  34 /* Core file and register set support.  */
  35
  36 /* Map from the normal register enumeration order to the order that
  37    registers appear in core files, which corresponds to the order
  38    of the register slots in the kernel's struct pt_regs.  */
  39
  40 static const int reg_offsets[NIOS2_NUM_REGS] =
  41 {
  42   -1,  8,  9, 10, 11, 12, 13, 14,       /* r0 - r7 */
  43   0,  1,  2,  3,  4,  5,  6,  7,        /* r8 - r15 */
  44   23, 24, 25, 26, 27, 28, 29, 30,       /* r16 - r23 */
  45   -1, -1, 19, 18, 17, 21, -1, 16,       /* et bt gp sp fp ea sstatus ra */
  46   21,                                   /* pc */
  47   -1, 20, -1, -1, -1, -1, -1, -1,       /* status estatus ...  */
  48   -1, -1, -1, -1, -1, -1, -1, -1
  49 };
  50
  51 /* General register set size.  Should match sizeof (struct pt_regs) +
  52    sizeof (struct switch_stack) from the NIOS2 Linux kernel patch.  */
  53
  54 #define NIOS2_GREGS_SIZE (4 * 34)
  55
  56 /* Implement the supply_regset hook for core files.  */
  57
  58 static void
  59 nios2_supply_gregset (const struct regset *regset,
  60                       struct regcache *regcache,
  61                       int regnum, const void *gregs_buf, size_t len)
  62 {
  63   const gdb_byte *gregs = (const gdb_byte *) gregs_buf;
  64   int regno;
  65   static const gdb_byte zero_buf[4] = {0, 0, 0, 0};
  66
  67   for (regno = NIOS2_Z_REGNUM; regno <= NIOS2_MPUACC_REGNUM; regno++)
  68     if (regnum == -1 || regnum == regno)
  69       {
  70         if (reg_offsets[regno] != -1)
  71           regcache->raw_supply (regno, gregs + 4 * reg_offsets[regno]);
  72         else
  73           regcache->raw_supply (regno, zero_buf);
  74       }
  75 }
  76
  77 /* Implement the collect_regset hook for core files.  */
  78
  79 static void
  80 nios2_collect_gregset (const struct regset *regset,
  81                        const struct regcache *regcache,
  82                        int regnum, void *gregs_buf, size_t len)
  83 {
  84   gdb_byte *gregs = (gdb_byte *) gregs_buf;
  85   int regno;
  86
  87   for (regno = NIOS2_Z_REGNUM; regno <= NIOS2_MPUACC_REGNUM; regno++)
  88     if (regnum == -1 || regnum == regno)
  89       {
  90         if (reg_offsets[regno] != -1)
  91           regcache->raw_collect (regno, gregs + 4 * reg_offsets[regno]);
  92       }
  93 }
  94
  95 static const struct regset nios2_core_regset =
  96 {
  97   NULL,
  98   nios2_supply_gregset,
  99   nios2_collect_gregset
 100 };
 101
 102 /* Iterate over core file register note sections.  */
 103
 104 static void
 105 nios2_iterate_over_regset_sections (struct gdbarch *gdbarch,
 106                                     iterate_over_regset_sections_cb *cb,
 107                                     void *cb_data,
 108                                     const struct regcache *regcache)
 109 {
 110   cb (".reg", NIOS2_GREGS_SIZE, NIOS2_GREGS_SIZE, &nios2_core_regset, NULL,
 111       cb_data);
 112 }
 113
 114 /* Initialize a trad-frame cache corresponding to the tramp-frame.
 115    FUNC is the address of the instruction TRAMP[0] in memory.
 116
 117    This ABI is not documented.  It corresponds to rt_setup_ucontext in
 118    the kernel arch/nios2/kernel/signal.c file.
 119
 120    The key points are:
 121    - The kernel creates a trampoline at the hard-wired address 0x1044.
 122    - The stack pointer points to an object of type struct rt_sigframe.
 123      The definition of this structure is not exported from the kernel.
 124      The register save area is located at offset 152 bytes (as determined
 125      by inspection of the stack contents in the debugger), and the
 126      registers are saved as r1-r23, ra, fp, gp, ea, sp.
 127
 128    This interface was implemented with kernel version 3.19 (the first
 129    official mainline kernel).  Older unofficial kernel versions used
 130    incompatible conventions; we do not support those here.  */
 131
 132 #define NIOS2_SIGRETURN_TRAMP_ADDR 0x1044
 133 #define NIOS2_SIGRETURN_REGSAVE_OFFSET 152
 134
 135 static void
 136 nios2_linux_rt_sigreturn_init (const struct tramp_frame *self,
 137                                struct frame_info *next_frame,
 138                                struct trad_frame_cache *this_cache,
 139                                CORE_ADDR func)
 140 {
 141   CORE_ADDR sp = get_frame_register_unsigned (next_frame, NIOS2_SP_REGNUM);
 142   CORE_ADDR base = sp + NIOS2_SIGRETURN_REGSAVE_OFFSET;
 143   int i;
 144
 145   for (i = 0; i < 23; i++)
 146     trad_frame_set_reg_addr (this_cache, i + 1, base + i * 4);
 147   trad_frame_set_reg_addr (this_cache, NIOS2_RA_REGNUM, base + 23 * 4);
 148   trad_frame_set_reg_addr (this_cache, NIOS2_FP_REGNUM, base + 24 * 4);
 149   trad_frame_set_reg_addr (this_cache, NIOS2_GP_REGNUM, base + 25 * 4);
 150   trad_frame_set_reg_addr (this_cache, NIOS2_PC_REGNUM, base + 27 * 4);
 151   trad_frame_set_reg_addr (this_cache, NIOS2_SP_REGNUM, base + 28 * 4);
 152
 153   /* Save a frame ID.  */
 154   trad_frame_set_id (this_cache, frame_id_build (base, func));
 155 }
 156
 157 /* Trampoline for sigreturn.  This has the form
 158      movi r2, __NR_rt_sigreturn
 159      trap 0
 160    appropriately encoded for R1 or R2.  */
 161
 162 static struct tramp_frame nios2_r1_linux_rt_sigreturn_tramp_frame =
 163 {
 164   SIGTRAMP_FRAME,
 165   4,
 166   {
 167     { MATCH_R1_MOVI | SET_IW_I_B (2) | SET_IW_I_IMM16 (139), ULONGEST_MAX },
 168     { MATCH_R1_TRAP | SET_IW_R_IMM5 (0), ULONGEST_MAX},
 169     { TRAMP_SENTINEL_INSN }
 170   },
 171   nios2_linux_rt_sigreturn_init
 172 };
 173
 174 static struct tramp_frame nios2_r2_linux_rt_sigreturn_tramp_frame =
 175 {
 176   SIGTRAMP_FRAME,
 177   4,
 178   {
 179     { MATCH_R2_MOVI | SET_IW_F2I16_B (2) | SET_IW_F2I16_IMM16 (139), ULONGEST_MAX },
 180     { MATCH_R2_TRAP | SET_IW_X2L5_IMM5 (0), ULONGEST_MAX},
 181     { TRAMP_SENTINEL_INSN }
 182   },
 183   nios2_linux_rt_sigreturn_init
 184 };
 185
 186 /* When FRAME is at a syscall instruction, return the PC of the next
 187    instruction to be executed.  */
 188
 189 static CORE_ADDR
 190 nios2_linux_syscall_next_pc (struct frame_info *frame,
 191                              const struct nios2_opcode *op)
 192 {
 193   CORE_ADDR pc = get_frame_pc (frame);
 194   ULONGEST syscall_nr = get_frame_register_unsigned (frame, NIOS2_R2_REGNUM);
 195
 196   /* If we are about to make a sigreturn syscall, use the unwinder to
 197      decode the signal frame.  */
 198   if (syscall_nr == 139 /* rt_sigreturn */)
 199     return frame_unwind_caller_pc (frame);
 200
 201   return pc + op->size;
 202 }
 203
 204 /* Return true if PC is a kernel helper, a function mapped by the kernel
 205    into user space on an unwritable page.  Currently the only such function
 206    is __kuser_cmpxchg at 0x1004.  See arch/nios2/kernel/entry.S in the Linux
 207    kernel sources and sysdeps/unix/sysv/linux/nios2/atomic-machine.h in
 208    GLIBC.  */
 209 static bool
 210 nios2_linux_is_kernel_helper (CORE_ADDR pc)
 211 {
 212   return pc == 0x1004;
 213 }
 214
 215 /* Hook function for gdbarch_register_osabi.  */
 216
 217 static void
 218 nios2_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 219 {
 220   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 221
 222   linux_init_abi (info, gdbarch);
 223
 224   /* Shared library handling.  */
 225   set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
 226   set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver);
 227
 228   set_solib_svr4_fetch_link_map_offsets (gdbarch,
 229                                          svr4_ilp32_fetch_link_map_offsets);
 230   /* Enable TLS support.  */
 231   set_gdbarch_fetch_tls_load_module_address (gdbarch,
 232                                              svr4_fetch_objfile_link_map);
 233   /* Core file support.  */
 234   set_gdbarch_iterate_over_regset_sections
 235     (gdbarch, nios2_iterate_over_regset_sections);
 236   /* Linux signal frame unwinders.  */
 237   if (gdbarch_bfd_arch_info (gdbarch)->mach == bfd_mach_nios2r2)
 238     tramp_frame_prepend_unwinder (gdbarch,
 239                                   &nios2_r2_linux_rt_sigreturn_tramp_frame);
 240   else
 241     tramp_frame_prepend_unwinder (gdbarch,
 242                                   &nios2_r1_linux_rt_sigreturn_tramp_frame);
 243
 244   tdep->syscall_next_pc = nios2_linux_syscall_next_pc;
 245   tdep->is_kernel_helper = nios2_linux_is_kernel_helper;
 246
 247   /* Index of target address word in glibc jmp_buf.  */
 248   tdep->jb_pc = 10;
 249 }
 250
 251 void _initialize_nios2_linux_tdep ();
 252 void
 253 _initialize_nios2_linux_tdep ()
 254 {
 255
 256   const struct bfd_arch_info *arch_info;
 257
 258   for (arch_info = bfd_lookup_arch (bfd_arch_nios2, 0);
 259        arch_info != NULL;
 260        arch_info = arch_info->next)
 261     gdbarch_register_osabi (bfd_arch_nios2, arch_info->mach,
 262                             GDB_OSABI_LINUX, nios2_linux_init_abi);
 263 }