gdb/ppc-obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/powerpc.
   2
   3    Copyright (C) 2004-2020 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 "defs.h"
  21 #include "arch-utils.h"
  22 #include "frame.h"
  23 #include "frame-unwind.h"
  24 #include "gdbtypes.h"
  25 #include "osabi.h"
  26 #include "regcache.h"
  27 #include "regset.h"
  28 #include "symtab.h"
  29 #include "trad-frame.h"
  30
  31 #include "ppc-tdep.h"
  32 #include "ppc-obsd-tdep.h"
  33 #include "solib-svr4.h"
  34
  35 /* Register offsets from <machine/reg.h>.  */
  36 struct ppc_reg_offsets ppcobsd_reg_offsets;
  37 struct ppc_reg_offsets ppcobsd_fpreg_offsets;
  38 \f
  39
  40 /* Core file support.  */
  41
  42 /* Supply register REGNUM in the general-purpose register set REGSET
  43    from the buffer specified by GREGS and LEN to register cache
  44    REGCACHE.  If REGNUM is -1, do this for all registers in REGSET.  */
  45
  46 void
  47 ppcobsd_supply_gregset (const struct regset *regset,
  48                         struct regcache *regcache, int regnum,
  49                         const void *gregs, size_t len)
  50 {
  51   ppc_supply_gregset (regset, regcache, regnum, gregs, len);
  52   ppc_supply_fpregset (regset, regcache, regnum, gregs, len);
  53 }
  54
  55 /* Collect register REGNUM in the general-purpose register set
  56    REGSET, from register cache REGCACHE into the buffer specified by
  57    GREGS and LEN.  If REGNUM is -1, do this for all registers in
  58    REGSET.  */
  59
  60 void
  61 ppcobsd_collect_gregset (const struct regset *regset,
  62                          const struct regcache *regcache, int regnum,
  63                          void *gregs, size_t len)
  64 {
  65   ppc_collect_gregset (regset, regcache, regnum, gregs, len);
  66   ppc_collect_fpregset (regset, regcache, regnum, gregs, len);
  67 }
  68
  69 /* OpenBSD/powerpc register set.  */
  70
  71 const struct regset ppcobsd_gregset =
  72 {
  73   &ppcobsd_reg_offsets,
  74   ppcobsd_supply_gregset
  75 };
  76
  77 const struct regset ppcobsd_fpregset =
  78 {
  79   &ppcobsd_fpreg_offsets,
  80   ppc_supply_fpregset
  81 };
  82
  83 /* Iterate over core file register note sections.  */
  84
  85 static void
  86 ppcobsd_iterate_over_regset_sections (struct gdbarch *gdbarch,
  87                                       iterate_over_regset_sections_cb *cb,
  88                                       void *cb_data,
  89                                       const struct regcache *regcache)
  90 {
  91   cb (".reg", 412, 412, &ppcobsd_gregset, NULL, cb_data);
  92 }
  93 \f
  94
  95 /* Signal trampolines.  */
  96
  97 /* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page
  98    in virtual memory.  The randomness makes it somewhat tricky to
  99    detect it, but fortunately we can rely on the fact that the start
 100    of the sigtramp routine is page-aligned.  We recognize the
 101    trampoline by looking for the code that invokes the sigreturn
 102    system call.  The offset where we can find that code varies from
 103    release to release.
 104
 105    By the way, the mapping mentioned above is read-only, so you cannot
 106    place a breakpoint in the signal trampoline.  */
 107
 108 /* Default page size.  */
 109 static const int ppcobsd_page_size = 4096;
 110
 111 /* Offset for sigreturn(2).  */
 112 static const int ppcobsd_sigreturn_offset[] = {
 113   0x98,                         /* OpenBSD 3.8 */
 114   0x0c,                         /* OpenBSD 3.2 */
 115   -1
 116 };
 117
 118 static int
 119 ppcobsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
 120                                 struct frame_info *this_frame,
 121                                 void **this_cache)
 122 {
 123   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 124   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 125   CORE_ADDR pc = get_frame_pc (this_frame);
 126   CORE_ADDR start_pc = (pc & ~(ppcobsd_page_size - 1));
 127   const int *offset;
 128   const char *name;
 129
 130   find_pc_partial_function (pc, &name, NULL, NULL);
 131   if (name)
 132     return 0;
 133
 134   for (offset = ppcobsd_sigreturn_offset; *offset != -1; offset++)
 135     {
 136       gdb_byte buf[2 * PPC_INSN_SIZE];
 137       unsigned long insn;
 138
 139       if (!safe_frame_unwind_memory (this_frame, start_pc + *offset,
 140                                      buf, sizeof buf))
 141         continue;
 142
 143       /* Check for "li r0,SYS_sigreturn".  */
 144       insn = extract_unsigned_integer (buf, PPC_INSN_SIZE, byte_order);
 145       if (insn != 0x38000067)
 146         continue;
 147
 148       /* Check for "sc".  */
 149       insn = extract_unsigned_integer (buf + PPC_INSN_SIZE,
 150                                        PPC_INSN_SIZE, byte_order);
 151       if (insn != 0x44000002)
 152         continue;
 153
 154       return 1;
 155     }
 156
 157   return 0;
 158 }
 159
 160 static struct trad_frame_cache *
 161 ppcobsd_sigtramp_frame_cache (struct frame_info *this_frame, void **this_cache)
 162 {
 163   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 164   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 165   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 166   struct trad_frame_cache *cache;
 167   CORE_ADDR addr, base, func;
 168   gdb_byte buf[PPC_INSN_SIZE];
 169   unsigned long insn, sigcontext_offset;
 170   int i;
 171
 172   if (*this_cache)
 173     return (struct trad_frame_cache *) *this_cache;
 174
 175   cache = trad_frame_cache_zalloc (this_frame);
 176   *this_cache = cache;
 177
 178   func = get_frame_pc (this_frame);
 179   func &= ~(ppcobsd_page_size - 1);
 180   if (!safe_frame_unwind_memory (this_frame, func, buf, sizeof buf))
 181     return cache;
 182
 183   /* Calculate the offset where we can find `struct sigcontext'.  We
 184      base our calculation on the amount of stack space reserved by the
 185      first instruction of the signal trampoline.  */
 186   insn = extract_unsigned_integer (buf, PPC_INSN_SIZE, byte_order);
 187   sigcontext_offset = (0x10000 - (insn & 0x0000ffff)) + 8;
 188
 189   base = get_frame_register_unsigned (this_frame, gdbarch_sp_regnum (gdbarch));
 190   addr = base + sigcontext_offset + 2 * tdep->wordsize;
 191   for (i = 0; i < ppc_num_gprs; i++, addr += tdep->wordsize)
 192     {
 193       int regnum = i + tdep->ppc_gp0_regnum;
 194       trad_frame_set_reg_addr (cache, regnum, addr);
 195     }
 196   trad_frame_set_reg_addr (cache, tdep->ppc_lr_regnum, addr);
 197   addr += tdep->wordsize;
 198   trad_frame_set_reg_addr (cache, tdep->ppc_cr_regnum, addr);
 199   addr += tdep->wordsize;
 200   trad_frame_set_reg_addr (cache, tdep->ppc_xer_regnum, addr);
 201   addr += tdep->wordsize;
 202   trad_frame_set_reg_addr (cache, tdep->ppc_ctr_regnum, addr);
 203   addr += tdep->wordsize;
 204   trad_frame_set_reg_addr (cache, gdbarch_pc_regnum (gdbarch), addr);
 205   /* SRR0?  */
 206   addr += tdep->wordsize;
 207
 208   /* Construct the frame ID using the function start.  */
 209   trad_frame_set_id (cache, frame_id_build (base, func));
 210
 211   return cache;
 212 }
 213
 214 static void
 215 ppcobsd_sigtramp_frame_this_id (struct frame_info *this_frame,
 216                                 void **this_cache, struct frame_id *this_id)
 217 {
 218   struct trad_frame_cache *cache =
 219     ppcobsd_sigtramp_frame_cache (this_frame, this_cache);
 220
 221   trad_frame_get_id (cache, this_id);
 222 }
 223
 224 static struct value *
 225 ppcobsd_sigtramp_frame_prev_register (struct frame_info *this_frame,
 226                                       void **this_cache, int regnum)
 227 {
 228   struct trad_frame_cache *cache =
 229     ppcobsd_sigtramp_frame_cache (this_frame, this_cache);
 230
 231   return trad_frame_get_register (cache, this_frame, regnum);
 232 }
 233
 234 static const struct frame_unwind ppcobsd_sigtramp_frame_unwind = {
 235   SIGTRAMP_FRAME,
 236   default_frame_unwind_stop_reason,
 237   ppcobsd_sigtramp_frame_this_id,
 238   ppcobsd_sigtramp_frame_prev_register,
 239   NULL,
 240   ppcobsd_sigtramp_frame_sniffer
 241 };
 242 \f
 243
 244 static void
 245 ppcobsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 246 {
 247   /* OpenBSD doesn't support the 128-bit `long double' from the psABI.  */
 248   set_gdbarch_long_double_bit (gdbarch, 64);
 249   set_gdbarch_long_double_format (gdbarch, floatformats_ieee_double);
 250
 251   /* OpenBSD currently uses a broken GCC.  */
 252   set_gdbarch_return_value (gdbarch, ppc_sysv_abi_broken_return_value);
 253
 254   /* OpenBSD uses SVR4-style shared libraries.  */
 255   set_solib_svr4_fetch_link_map_offsets
 256     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 257
 258   set_gdbarch_iterate_over_regset_sections
 259     (gdbarch, ppcobsd_iterate_over_regset_sections);
 260
 261   frame_unwind_append_unwinder (gdbarch, &ppcobsd_sigtramp_frame_unwind);
 262 }
 263
 264 void
 265 _initialize_ppcobsd_tdep (void)
 266 {
 267   gdbarch_register_osabi (bfd_arch_rs6000, 0, GDB_OSABI_OPENBSD,
 268                           ppcobsd_init_abi);
 269   gdbarch_register_osabi (bfd_arch_powerpc, 0, GDB_OSABI_OPENBSD,
 270                           ppcobsd_init_abi);
 271
 272   /* Avoid initializing the register offsets again if they were
 273      already initialized by ppcobsd-nat.c.  */
 274   if (ppcobsd_reg_offsets.pc_offset == 0)
 275     {
 276       /* General-purpose registers.  */
 277       ppcobsd_reg_offsets.r0_offset = 0;
 278       ppcobsd_reg_offsets.gpr_size = 4;
 279       ppcobsd_reg_offsets.xr_size = 4;
 280       ppcobsd_reg_offsets.pc_offset = 384;
 281       ppcobsd_reg_offsets.ps_offset = 388;
 282       ppcobsd_reg_offsets.cr_offset = 392;
 283       ppcobsd_reg_offsets.lr_offset = 396;
 284       ppcobsd_reg_offsets.ctr_offset = 400;
 285       ppcobsd_reg_offsets.xer_offset = 404;
 286       ppcobsd_reg_offsets.mq_offset = 408;
 287
 288       /* Floating-point registers.  */
 289       ppcobsd_reg_offsets.f0_offset = 128;
 290       ppcobsd_reg_offsets.fpscr_offset = -1;
 291
 292     }
 293
 294   if (ppcobsd_fpreg_offsets.fpscr_offset == 0)
 295     {
 296       /* Floating-point registers.  */
 297       ppcobsd_reg_offsets.f0_offset = 0;
 298       ppcobsd_reg_offsets.fpscr_offset = 256;
 299       ppcobsd_reg_offsets.fpscr_size = 4;
 300     }
 301 }