gdb/nios2-linux-tdep.c

   1 /* Target-dependent code for GNU/Linux on Nios II.
   2    Copyright (C) 2012-2019 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
  33 /* Core file and register set support.  */
  34
  35 /* Map from the normal register enumeration order to the order that
  36    registers appear in core files, which corresponds to the order
  37    of the register slots in the kernel's struct pt_regs.  */
  38
  39 static const int reg_offsets[NIOS2_NUM_REGS] =
  40 {
  41   -1,  8,  9, 10, 11, 12, 13, 14,       /* r0 - r7 */
  42   0,  1,  2,  3,  4,  5,  6,  7,        /* r8 - r15 */
  43   23, 24, 25, 26, 27, 28, 29, 30,       /* r16 - r23 */
  44   -1, -1, 19, 18, 17, 21, -1, 16,       /* et bt gp sp fp ea sstatus ra */
  45   21,                                   /* pc */
  46   -1, 20, -1, -1, -1, -1, -1, -1,       /* status estatus ...  */
  47   -1, -1, -1, -1, -1, -1, -1, -1
  48 };
  49
  50 /* General register set size.  Should match sizeof (struct pt_regs) +
  51    sizeof (struct switch_stack) from the NIOS2 Linux kernel patch.  */
  52
  53 #define NIOS2_GREGS_SIZE (4 * 34)
  54
  55 /* Implement the supply_regset hook for core files.  */
  56
  57 static void
  58 nios2_supply_gregset (const struct regset *regset,
  59                       struct regcache *regcache,
  60                       int regnum, const void *gregs_buf, size_t len)
  61 {
  62   const gdb_byte *gregs = (const gdb_byte *) gregs_buf;
  63   int regno;
  64   static const gdb_byte zero_buf[4] = {0, 0, 0, 0};
  65
  66   for (regno = NIOS2_Z_REGNUM; regno <= NIOS2_MPUACC_REGNUM; regno++)
  67     if (regnum == -1 || regnum == regno)
  68       {
  69         if (reg_offsets[regno] != -1)
  70           regcache->raw_supply (regno, gregs + 4 * reg_offsets[regno]);
  71         else
  72           regcache->raw_supply (regno, zero_buf);
  73       }
  74 }
  75
  76 /* Implement the collect_regset hook for core files.  */
  77
  78 static void
  79 nios2_collect_gregset (const struct regset *regset,
  80                        const struct regcache *regcache,
  81                        int regnum, void *gregs_buf, size_t len)
  82 {
  83   gdb_byte *gregs = (gdb_byte *) gregs_buf;
  84   int regno;
  85
  86   for (regno = NIOS2_Z_REGNUM; regno <= NIOS2_MPUACC_REGNUM; regno++)
  87     if (regnum == -1 || regnum == regno)
  88       {
  89         if (reg_offsets[regno] != -1)
  90           regcache->raw_collect (regno, gregs + 4 * reg_offsets[regno]);
  91       }
  92 }
  93
  94 static const struct regset nios2_core_regset =
  95 {
  96   NULL,
  97   nios2_supply_gregset,
  98   nios2_collect_gregset
  99 };
 100
 101 /* Iterate over core file register note sections.  */
 102
 103 static void
 104 nios2_iterate_over_regset_sections (struct gdbarch *gdbarch,
 105                                     iterate_over_regset_sections_cb *cb,
 106                                     void *cb_data,
 107                                     const struct regcache *regcache)
 108 {
 109   cb (".reg", NIOS2_GREGS_SIZE, NIOS2_GREGS_SIZE, &nios2_core_regset, NULL,
 110       cb_data);
 111 }
 112
 113 /* Initialize a trad-frame cache corresponding to the tramp-frame.
 114    FUNC is the address of the instruction TRAMP[0] in memory.
 115
 116    This ABI is not documented.  It corresponds to rt_setup_ucontext in
 117    the kernel arch/nios2/kernel/signal.c file.
 118
 119    The key points are:
 120    - The kernel creates a trampoline at the hard-wired address 0x1044.
 121    - The stack pointer points to an object of type struct rt_sigframe.
 122      The definition of this structure is not exported from the kernel.
 123      The register save area is located at offset 152 bytes (as determined
 124      by inspection of the stack contents in the debugger), and the
 125      registers are saved as r1-r23, ra, fp, gp, ea, sp.
 126
 127    This interface was implemented with kernel version 3.19 (the first
 128    official mainline kernel).  Older unofficial kernel versions used
 129    incompatible conventions; we do not support those here.  */
 130
 131 #define NIOS2_SIGRETURN_TRAMP_ADDR 0x1044
 132 #define NIOS2_SIGRETURN_REGSAVE_OFFSET 152
 133
 134 static void
 135 nios2_linux_rt_sigreturn_init (const struct tramp_frame *self,
 136                                struct frame_info *next_frame,
 137                                struct trad_frame_cache *this_cache,
 138                                CORE_ADDR func)
 139 {
 140   CORE_ADDR sp = get_frame_register_unsigned (next_frame, NIOS2_SP_REGNUM);
 141   CORE_ADDR base = sp + NIOS2_SIGRETURN_REGSAVE_OFFSET;
 142   int i;
 143
 144   for (i = 0; i < 23; i++)
 145     trad_frame_set_reg_addr (this_cache, i + 1, base + i * 4);
 146   trad_frame_set_reg_addr (this_cache, NIOS2_RA_REGNUM, base + 23 * 4);
 147   trad_frame_set_reg_addr (this_cache, NIOS2_FP_REGNUM, base + 24 * 4);
 148   trad_frame_set_reg_addr (this_cache, NIOS2_GP_REGNUM, base + 25 * 4);
 149   trad_frame_set_reg_addr (this_cache, NIOS2_PC_REGNUM, base + 27 * 4);
 150   trad_frame_set_reg_addr (this_cache, NIOS2_SP_REGNUM, base + 28 * 4);
 151
 152   /* Save a frame ID.  */
 153   trad_frame_set_id (this_cache, frame_id_build (base, func));
 154 }
 155
 156 /* Trampoline for sigreturn.  This has the form
 157      movi r2, __NR_rt_sigreturn
 158      trap 0
 159    appropriately encoded for R1 or R2.  */
 160
 161 static struct tramp_frame nios2_r1_linux_rt_sigreturn_tramp_frame =
 162 {
 163   SIGTRAMP_FRAME,
 164   4,
 165   {
 166     { MATCH_R1_MOVI | SET_IW_I_B (2) | SET_IW_I_IMM16 (139), ULONGEST_MAX },
 167     { MATCH_R1_TRAP | SET_IW_R_IMM5 (0), ULONGEST_MAX},
 168     { TRAMP_SENTINEL_INSN }
 169   },
 170   nios2_linux_rt_sigreturn_init
 171 };
 172
 173 static struct tramp_frame nios2_r2_linux_rt_sigreturn_tramp_frame =
 174 {
 175   SIGTRAMP_FRAME,
 176   4,
 177   {
 178     { MATCH_R2_MOVI | SET_IW_F2I16_B (2) | SET_IW_F2I16_IMM16 (139), ULONGEST_MAX },
 179     { MATCH_R2_TRAP | SET_IW_X2L5_IMM5 (0), ULONGEST_MAX},
 180     { TRAMP_SENTINEL_INSN }
 181   },
 182   nios2_linux_rt_sigreturn_init
 183 };
 184
 185 /* When FRAME is at a syscall instruction, return the PC of the next
 186    instruction to be executed.  */
 187
 188 static CORE_ADDR
 189 nios2_linux_syscall_next_pc (struct frame_info *frame,
 190                              const struct nios2_opcode *op)
 191 {
 192   CORE_ADDR pc = get_frame_pc (frame);
 193   ULONGEST syscall_nr = get_frame_register_unsigned (frame, NIOS2_R2_REGNUM);
 194
 195   /* If we are about to make a sigreturn syscall, use the unwinder to
 196      decode the signal frame.  */
 197   if (syscall_nr == 139 /* rt_sigreturn */)
 198     return frame_unwind_caller_pc (frame);
 199
 200   return pc + op->size;
 201 }
 202
 203 /* Return true if PC is a kernel helper, a function mapped by the kernel
 204    into user space on an unwritable page.  Currently the only such function
 205    is __kuser_cmpxchg at 0x1004.  See arch/nios2/kernel/entry.S in the Linux
 206    kernel sources and sysdeps/unix/sysv/linux/nios2/atomic-machine.h in
 207    GLIBC.  */
 208 static bool
 209 nios2_linux_is_kernel_helper (CORE_ADDR pc)
 210 {
 211   return pc == 0x1004;
 212 }
 213
 214 /* Hook function for gdbarch_register_osabi.  */
 215
 216 static void
 217 nios2_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 218 {
 219   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 220
 221   linux_init_abi (info, gdbarch);
 222
 223   /* Shared library handling.  */
 224   set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
 225   set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver);
 226
 227   set_solib_svr4_fetch_link_map_offsets (gdbarch,
 228                                          svr4_ilp32_fetch_link_map_offsets);
 229   /* Enable TLS support.  */
 230   set_gdbarch_fetch_tls_load_module_address (gdbarch,
 231                                              svr4_fetch_objfile_link_map);
 232   /* Core file support.  */
 233   set_gdbarch_iterate_over_regset_sections
 234     (gdbarch, nios2_iterate_over_regset_sections);
 235   /* Linux signal frame unwinders.  */
 236   if (gdbarch_bfd_arch_info (gdbarch)->mach == bfd_mach_nios2r2)
 237     tramp_frame_prepend_unwinder (gdbarch,
 238                                   &nios2_r2_linux_rt_sigreturn_tramp_frame);
 239   else
 240     tramp_frame_prepend_unwinder (gdbarch,
 241                                   &nios2_r1_linux_rt_sigreturn_tramp_frame);
 242
 243   tdep->syscall_next_pc = nios2_linux_syscall_next_pc;
 244   tdep->is_kernel_helper = nios2_linux_is_kernel_helper;
 245
 246   /* Index of target address word in glibc jmp_buf.  */
 247   tdep->jb_pc = 10;
 248 }
 249
 250 void
 251 _initialize_nios2_linux_tdep (void)
 252 {
 253
 254   const struct bfd_arch_info *arch_info;
 255
 256   for (arch_info = bfd_lookup_arch (bfd_arch_nios2, 0);
 257        arch_info != NULL;
 258        arch_info = arch_info->next)
 259     gdbarch_register_osabi (bfd_arch_nios2, arch_info->mach,
 260                             GDB_OSABI_LINUX, nios2_linux_init_abi);
 261 }