gdb/sparc-linux-tdep.c

   1 /* Target-dependent code for GNU/Linux SPARC.
   2
   3    Copyright (C) 2003, 2004, 2005 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 2 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, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street, Fifth Floor,
  20    Boston, MA 02110-1301, USA.  */
  21
  22 #include "defs.h"
  23 #include "dwarf2-frame.h"
  24 #include "floatformat.h"
  25 #include "frame.h"
  26 #include "frame-unwind.h"
  27 #include "gdbarch.h"
  28 #include "gdbcore.h"
  29 #include "osabi.h"
  30 #include "regcache.h"
  31 #include "solib-svr4.h"
  32 #include "symtab.h"
  33 #include "trad-frame.h"
  34 #include "tramp-frame.h"
  35
  36 #include "sparc-tdep.h"
  37
  38 /* Signal trampoline support.  */
  39
  40 static void sparc32_linux_sigframe_init (const struct tramp_frame *self,
  41                                          struct frame_info *next_frame,
  42                                          struct trad_frame_cache *this_cache,
  43                                          CORE_ADDR func);
  44
  45 /* GNU/Linux has two flavors of signals.  Normal signal handlers, and
  46    "realtime" (RT) signals.  The RT signals can provide additional
  47    information to the signal handler if the SA_SIGINFO flag is set
  48    when establishing a signal handler using `sigaction'.  It is not
  49    unlikely that future versions of GNU/Linux will support SA_SIGINFO
  50    for normal signals too.  */
  51
  52 /* When the sparc Linux kernel calls a signal handler and the
  53    SA_RESTORER flag isn't set, the return address points to a bit of
  54    code on the stack.  This code checks whether the PC appears to be
  55    within this bit of code.
  56
  57    The instruction sequence for normal signals is encoded below.
  58    Checking for the code sequence should be somewhat reliable, because
  59    the effect is to call the system call sigreturn.  This is unlikely
  60    to occur anywhere other than a signal trampoline.  */
  61
  62 static const struct tramp_frame sparc32_linux_sigframe =
  63 {
  64   SIGTRAMP_FRAME,
  65   4,
  66   {
  67     { 0x821020d8, -1 },         /* mov __NR_sugreturn, %g1 */
  68     { 0x91d02010, -1 },         /* ta  0x10 */
  69     { TRAMP_SENTINEL_INSN, -1 }
  70   },
  71   sparc32_linux_sigframe_init
  72 };
  73
  74 /* The instruction sequence for RT signals is slightly different.  The
  75    effect is to call the system call rt_sigreturn.  */
  76
  77 static const struct tramp_frame sparc32_linux_rt_sigframe =
  78 {
  79   SIGTRAMP_FRAME,
  80   4,
  81   {
  82     { 0x82102065, -1 },         /* mov __NR_rt_sigreturn, %g1 */
  83     { 0x91d02010, -1 },         /* ta  0x10 */
  84     { TRAMP_SENTINEL_INSN, -1 }
  85   },
  86   sparc32_linux_sigframe_init
  87 };
  88
  89 static void
  90 sparc32_linux_sigframe_init (const struct tramp_frame *self,
  91                              struct frame_info *next_frame,
  92                              struct trad_frame_cache *this_cache,
  93                              CORE_ADDR func)
  94 {
  95   CORE_ADDR base, addr, sp_addr;
  96   int regnum;
  97
  98   base = frame_unwind_register_unsigned (next_frame, SPARC_O1_REGNUM);
  99   if (self == &sparc32_linux_rt_sigframe)
 100     base += 128;
 101
 102   /* Offsets from <bits/sigcontext.h>.  */
 103
 104   trad_frame_set_reg_addr (this_cache, SPARC32_PSR_REGNUM, base + 0);
 105   trad_frame_set_reg_addr (this_cache, SPARC32_PC_REGNUM, base + 4);
 106   trad_frame_set_reg_addr (this_cache, SPARC32_NPC_REGNUM, base + 8);
 107   trad_frame_set_reg_addr (this_cache, SPARC32_Y_REGNUM, base + 12);
 108
 109   /* Since %g0 is always zero, keep the identity encoding.  */
 110   addr = base + 20;
 111   sp_addr = base + 16 + ((SPARC_SP_REGNUM - SPARC_G0_REGNUM) * 4);
 112   for (regnum = SPARC_G1_REGNUM; regnum <= SPARC_O7_REGNUM; regnum++)
 113     {
 114       trad_frame_set_reg_addr (this_cache, regnum, addr);
 115       addr += 4;
 116     }
 117
 118   base = frame_unwind_register_unsigned (next_frame, SPARC_SP_REGNUM);
 119   addr = get_frame_memory_unsigned (next_frame, sp_addr, 4);
 120
 121   for (regnum = SPARC_L0_REGNUM; regnum <= SPARC_I7_REGNUM; regnum++)
 122     {
 123       trad_frame_set_reg_addr (this_cache, regnum, addr);
 124       addr += 4;
 125     }
 126   trad_frame_set_id (this_cache, frame_id_build (base, func));
 127 }
 128 \f
 129 /* Return the address of a system call's alternative return
 130    address.  */
 131
 132 static CORE_ADDR
 133 sparc32_linux_step_trap (unsigned long insn)
 134 {
 135   if (insn == 0x91d02010)
 136     {
 137       ULONGEST sc_num;
 138
 139       regcache_cooked_read_unsigned (current_regcache,
 140                                      SPARC_G1_REGNUM, &sc_num);
 141
 142       /* __NR_rt_sigreturn is 101 and __NR_sigreturn is 216  */
 143       if (sc_num == 101 || sc_num == 216)
 144         {
 145           ULONGEST sp, pc_offset;
 146
 147           regcache_cooked_read_unsigned (current_regcache,
 148                                          SPARC_SP_REGNUM, &sp);
 149
 150           /* The kernel puts the sigreturn registers on the stack,
 151              and this is where the signal unwinding state is take from
 152              when returning from a signal.
 153
 154              For __NR_sigreturn, this register area sits 96 bytes from
 155              the base of the stack.  The saved PC sits 4 bytes into the
 156              sigreturn register save area.
 157
 158              For __NR_rt_sigreturn a siginfo_t, which is 128 bytes, sits
 159              right before the sigreturn register save area.  */
 160
 161           pc_offset = 96 + 4;
 162           if (sc_num == 101)
 163             pc_offset += 128;
 164
 165           return read_memory_unsigned_integer (sp + pc_offset, 4);
 166         }
 167     }
 168
 169   return 0;
 170 }
 171 \f
 172
 173 static void
 174 sparc32_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 175 {
 176   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 177
 178   tramp_frame_prepend_unwinder (gdbarch, &sparc32_linux_sigframe);
 179   tramp_frame_prepend_unwinder (gdbarch, &sparc32_linux_rt_sigframe);
 180
 181   /* GNU/Linux has SVR4-style shared libraries...  */
 182   set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
 183   set_solib_svr4_fetch_link_map_offsets
 184     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 185
 186   /* ...which means that we need some special handling when doing
 187      prologue analysis.  */
 188   tdep->plt_entry_size = 12;
 189
 190   /* GNU/Linux doesn't support the 128-bit `long double' from the psABI.  */
 191   set_gdbarch_long_double_bit (gdbarch, 64);
 192   set_gdbarch_long_double_format (gdbarch, &floatformat_ieee_double_big);
 193
 194   /* Enable TLS support.  */
 195   set_gdbarch_fetch_tls_load_module_address (gdbarch,
 196                                              svr4_fetch_objfile_link_map);
 197
 198   /* Make sure we can single-step over signal return system calls.  */
 199   tdep->step_trap = sparc32_linux_step_trap;
 200
 201   /* Hook in the DWARF CFI frame unwinder.  */
 202   frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);
 203 }
 204
 205 /* Provide a prototype to silence -Wmissing-prototypes.  */
 206 extern void _initialize_sparc_linux_tdep (void);
 207
 208 void
 209 _initialize_sparc_linux_tdep (void)
 210 {
 211   gdbarch_register_osabi (bfd_arch_sparc, 0, GDB_OSABI_LINUX,
 212                           sparc32_linux_init_abi);
 213 }