gdb/sparc-linux-tdep.c

   1 /* Target-dependent code for GNU/Linux SPARC.
   2
   3    Copyright 2003, 2004 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., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #include "defs.h"
  23 #include "floatformat.h"
  24 #include "frame.h"
  25 #include "frame-unwind.h"
  26 #include "gdbarch.h"
  27 #include "gdbcore.h"
  28 #include "osabi.h"
  29 #include "regcache.h"
  30 #include "solib-svr4.h"
  31 #include "symtab.h"
  32 #include "trad-frame.h"
  33
  34 #include "gdb_assert.h"
  35 #include "gdb_string.h"
  36
  37 #include "sparc-tdep.h"
  38
  39 /* Recognizing signal handler frames.  */
  40
  41 /* GNU/Linux has two flavors of signals.  Normal signal handlers, and
  42    "realtime" (RT) signals.  The RT signals can provide additional
  43    information to the signal handler if the SA_SIGINFO flag is set
  44    when establishing a signal handler using `sigaction'.  It is not
  45    unlikely that future versions of GNU/Linux will support SA_SIGINFO
  46    for normal signals too.  */
  47
  48 /* When the sparc Linux kernel calls a signal handler and the
  49    SA_RESTORER flag isn't set, the return address points to a bit of
  50    code on the stack.  This function returns whether the PC appears to
  51    be within this bit of code.
  52
  53    The instruction sequence for normal signals is
  54         mov __NR_sigreturn, %g1         ! hex: 0x821020d8
  55         ta  0x10                        ! hex: 0x91d02010
  56
  57    Checking for the code sequence should be somewhat reliable, because
  58    the effect is to call the system call sigreturn.  This is unlikely
  59    to occur anywhere other than a signal trampoline.
  60
  61    It kind of sucks that we have to read memory from the process in
  62    order to identify a signal trampoline, but there doesn't seem to be
  63    any other way.  However, sparc32_linux_pc_in_sigtramp arranges to
  64    only call us if no function name could be identified, which should
  65    be the case since the code is on the stack.  */
  66
  67 #define LINUX32_SIGTRAMP_INSN0  0x821020d8      /* mov __NR_sigreturn, %g1 */
  68 #define LINUX32_SIGTRAMP_INSN1  0x91d02010      /* ta  0x10 */
  69
  70 /* The instruction sequence for RT signals is
  71        mov __NR_rt_sigreturn, %g1       ! hex: 0x82102065
  72        ta  {0x10,0x6d}                  ! hex: 0x91d02010 or 0x91d0206d
  73
  74    The effect is to call the system call rt_sigreturn.  The trap number
  75    is variable based upon whether this is a 32-bit or 64-bit sparc binary.
  76    Note that 64-bit binaries only use this RT signal return method.  */
  77
  78 #define LINUX32_RT_SIGTRAMP_INSN0       0x82102065
  79 #define LINUX32_RT_SIGTRAMP_INSN1       0x91d02010
  80
  81 /* If PC is in a sigtramp routine consisting of the instructions INSN0
  82    and INSN1, return the address of the start of the routine.
  83    Otherwise, return 0.  */
  84
  85 CORE_ADDR
  86 sparc_linux_sigtramp_start (struct frame_info *next_frame,
  87                             ULONGEST insn0, ULONGEST insn1)
  88 {
  89   CORE_ADDR pc = frame_pc_unwind (next_frame);
  90   ULONGEST word0, word1;
  91   unsigned char buf[8];         /* Two instructions.  */
  92
  93   /* We only recognize a signal trampoline if PC is at the start of
  94      one of the instructions.  We optimize for finding the PC at the
  95      start of the instruction sequence, as will be the case when the
  96      trampoline is not the first frame on the stack.  We assume that
  97      in the case where the PC is not at the start of the instruction
  98      sequence, there will be a few trailing readable bytes on the
  99      stack.  */
 100
 101   if (!safe_frame_unwind_memory (next_frame, pc, buf, sizeof buf))
 102     return 0;
 103
 104   word0 = extract_unsigned_integer (buf, 4);
 105   if (word0 != insn0)
 106     {
 107       if (word0 != insn1)
 108         return 0;
 109
 110       pc -= 4;
 111       if (!safe_frame_unwind_memory (next_frame, pc, buf, sizeof buf))
 112         return 0;
 113
 114       word0 = extract_unsigned_integer (buf, 4);
 115     }
 116
 117   word1 = extract_unsigned_integer (buf + 4, 4);
 118   if (word0 != insn0 || word1 != insn1)
 119     return 0;
 120
 121   return pc;
 122 }
 123
 124 static CORE_ADDR
 125 sparc32_linux_sigtramp_start (struct frame_info *next_frame)
 126 {
 127   return sparc_linux_sigtramp_start (next_frame, LINUX32_SIGTRAMP_INSN0,
 128                                      LINUX32_SIGTRAMP_INSN1);
 129 }
 130
 131 static CORE_ADDR
 132 sparc32_linux_rt_sigtramp_start (struct frame_info *next_frame)
 133 {
 134   return sparc_linux_sigtramp_start (next_frame, LINUX32_RT_SIGTRAMP_INSN0,
 135                                      LINUX32_RT_SIGTRAMP_INSN1);
 136 }
 137
 138 static int
 139 sparc32_linux_sigtramp_p (struct frame_info *next_frame)
 140 {
 141   CORE_ADDR pc = frame_pc_unwind (next_frame);
 142   char *name;
 143
 144   find_pc_partial_function (pc, &name, NULL, NULL);
 145
 146   /* If we have NAME, we can optimize the search.  The trampolines are
 147      named __restore and __restore_rt.  However, they aren't dynamically
 148      exported from the shared C library, so the trampoline may appear to
 149      be part of the preceding function.  This should always be sigaction,
 150      __sigaction, or __libc_sigaction (all aliases to the same function).  */
 151   if (name == NULL || strstr (name, "sigaction") != NULL)
 152     return (sparc32_linux_sigtramp_start (next_frame) != 0
 153             || sparc32_linux_rt_sigtramp_start (next_frame) != 0);
 154
 155   return (strcmp ("__restore", name) == 0
 156           || strcmp ("__restore_rt", name) == 0);
 157 }
 158
 159 static struct sparc_frame_cache *
 160 sparc32_linux_sigtramp_frame_cache (struct frame_info *next_frame,
 161                                     void **this_cache)
 162 {
 163   struct sparc_frame_cache *cache;
 164   CORE_ADDR sigcontext_addr, addr;
 165   int regnum;
 166
 167   if (*this_cache)
 168     return *this_cache;
 169
 170   cache = sparc32_frame_cache (next_frame, this_cache);
 171   gdb_assert (cache == *this_cache);
 172
 173   /* ??? What about signal trampolines that aren't frameless?  */
 174   regnum = SPARC_SP_REGNUM;
 175   cache->base = frame_unwind_register_unsigned (next_frame, regnum);
 176
 177   regnum = SPARC_O1_REGNUM;
 178   sigcontext_addr = frame_unwind_register_unsigned (next_frame, regnum);
 179
 180   addr = sparc32_linux_sigtramp_start (next_frame);
 181   if (addr == 0)
 182     {
 183       /* If this is a RT signal trampoline, adjust SIGCONTEXT_ADDR
 184          accordingly.  */
 185       addr = sparc32_linux_rt_sigtramp_start (next_frame);
 186       if (addr)
 187         sigcontext_addr += 128;
 188       else
 189         addr = frame_func_unwind (next_frame);
 190     }
 191   cache->pc = addr;
 192
 193   cache->saved_regs = trad_frame_alloc_saved_regs (next_frame);
 194
 195   cache->saved_regs[SPARC32_PSR_REGNUM].addr = sigcontext_addr + 0;
 196   cache->saved_regs[SPARC32_PC_REGNUM].addr = sigcontext_addr + 4;
 197   cache->saved_regs[SPARC32_NPC_REGNUM].addr = sigcontext_addr + 8;
 198   cache->saved_regs[SPARC32_Y_REGNUM].addr = sigcontext_addr + 12;
 199
 200   /* Since %g0 is always zero, keep the identity encoding.  */
 201   for (regnum = SPARC_G1_REGNUM, addr = sigcontext_addr + 20;
 202        regnum <= SPARC_O7_REGNUM; regnum++, addr += 4)
 203     cache->saved_regs[regnum].addr = addr;
 204
 205   for (regnum = SPARC_L0_REGNUM, addr = cache->base;
 206        regnum <= SPARC_I7_REGNUM; regnum++, addr += 4)
 207     cache->saved_regs[regnum].addr = addr;
 208
 209   return cache;
 210 }
 211
 212 static void
 213 sparc32_linux_sigtramp_frame_this_id (struct frame_info *next_frame,
 214                                       void **this_cache,
 215                                       struct frame_id *this_id)
 216 {
 217   struct sparc_frame_cache *cache =
 218     sparc32_linux_sigtramp_frame_cache (next_frame, this_cache);
 219
 220   (*this_id) = frame_id_build (cache->base, cache->pc);
 221 }
 222
 223 static void
 224 sparc32_linux_sigtramp_frame_prev_register (struct frame_info *next_frame,
 225                                             void **this_cache,
 226                                             int regnum, int *optimizedp,
 227                                             enum lval_type *lvalp,
 228                                             CORE_ADDR *addrp,
 229                                             int *realnump, void *valuep)
 230 {
 231   struct sparc_frame_cache *cache =
 232     sparc32_linux_sigtramp_frame_cache (next_frame, this_cache);
 233
 234   trad_frame_get_prev_register (next_frame, cache->saved_regs, regnum,
 235                                 optimizedp, lvalp, addrp, realnump, valuep);
 236 }
 237
 238 static const struct frame_unwind sparc32_linux_sigtramp_frame_unwind =
 239 {
 240   SIGTRAMP_FRAME,
 241   sparc32_linux_sigtramp_frame_this_id,
 242   sparc32_linux_sigtramp_frame_prev_register
 243 };
 244
 245 static const struct frame_unwind *
 246 sparc32_linux_sigtramp_frame_sniffer (struct frame_info *next_frame)
 247 {
 248   if (sparc32_linux_sigtramp_p (next_frame))
 249     return &sparc32_linux_sigtramp_frame_unwind;
 250
 251   return NULL;
 252 }
 253 \f
 254
 255 static void
 256 sparc32_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 257 {
 258   /* GNU/Linux is very similar to Solaris ...  */
 259   sparc32_sol2_init_abi (info, gdbarch);
 260
 261   /* ... but doesn't have kernel-assisted single-stepping support.  */
 262   set_gdbarch_software_single_step (gdbarch, sparc_software_single_step);
 263
 264   /* GNU/Linux doesn't support the 128-bit `long double' from the psABI.  */
 265   set_gdbarch_long_double_bit (gdbarch, 64);
 266   set_gdbarch_long_double_format (gdbarch, &floatformat_ieee_double_big);
 267
 268   frame_unwind_append_sniffer (gdbarch, sparc32_linux_sigtramp_frame_sniffer);
 269
 270   /* Enable TLS support.  */
 271   set_gdbarch_fetch_tls_load_module_address (gdbarch,
 272                                              svr4_fetch_objfile_link_map);
 273 }
 274
 275 /* Provide a prototype to silence -Wmissing-prototypes.  */
 276 extern void _initialize_sparc_linux_tdep (void);
 277
 278 void
 279 _initialize_sparc_linux_tdep (void)
 280 {
 281   gdbarch_register_osabi (bfd_arch_sparc, 0, GDB_OSABI_LINUX,
 282                           sparc32_linux_init_abi);
 283 }