gdb/x86-64-linux-tdep.c

   1 /* Target-dependent code for GNU/Linux running on x86-64, for GDB.
   2
   3    Copyright 2001, 2003 Free Software Foundation, Inc.
   4
   5    Contributed by Jiri Smid, SuSE Labs.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 59 Temple Place - Suite 330,
  22    Boston, MA 02111-1307, USA.  */
  23
  24 #include "defs.h"
  25 #include "inferior.h"
  26 #include "gdbcore.h"
  27 #include "regcache.h"
  28 #include "osabi.h"
  29
  30 #include "gdb_string.h"
  31
  32 #include "x86-64-tdep.h"
  33
  34 #define LINUX_SIGTRAMP_INSN0    0x48    /* mov $NNNNNNNN, %rax */
  35 #define LINUX_SIGTRAMP_OFFSET0  0
  36 #define LINUX_SIGTRAMP_INSN1    0x0f    /* syscall */
  37 #define LINUX_SIGTRAMP_OFFSET1  7
  38
  39 static const unsigned char linux_sigtramp_code[] =
  40 {
  41   /* mov $__NR_rt_sigreturn, %rax */
  42   LINUX_SIGTRAMP_INSN0, 0xc7, 0xc0, 0x0f, 0x00, 0x00, 0x00,
  43   /* syscall */
  44   LINUX_SIGTRAMP_INSN1, 0x05
  45 };
  46
  47 #define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code)
  48
  49 /* If PC is in a sigtramp routine, return the address of the start of
  50    the routine.  Otherwise, return 0.  */
  51
  52 static CORE_ADDR
  53 x86_64_linux_sigtramp_start (CORE_ADDR pc)
  54 {
  55   unsigned char buf[LINUX_SIGTRAMP_LEN];
  56
  57   /* We only recognize a signal trampoline if PC is at the start of
  58      one of the two instructions.  We optimize for finding the PC at
  59      the start, as will be the case when the trampoline is not the
  60      first frame on the stack.  We assume that in the case where the
  61      PC is not at the start of the instruction sequence, there will be
  62      a few trailing readable bytes on the stack.  */
  63
  64   if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
  65     return 0;
  66
  67   if (buf[0] != LINUX_SIGTRAMP_INSN0)
  68     {
  69       if (buf[0] != LINUX_SIGTRAMP_INSN1)
  70         return 0;
  71
  72       pc -= LINUX_SIGTRAMP_OFFSET1;
  73
  74       if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
  75         return 0;
  76     }
  77
  78   if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0)
  79     return 0;
  80
  81   return pc;
  82 }
  83
  84 /* Return whether PC is in a GNU/Linux sigtramp routine.  */
  85
  86 static int
  87 x86_64_linux_pc_in_sigtramp (CORE_ADDR pc, char *name)
  88 {
  89   /* If we have NAME, we can optimize the search.  The trampoline is
  90      named __restore_rt.  However, it isn't dynamically exported from
  91      the shared C library, so the trampoline may appear to be part of
  92      the preceding function.  This should always be sigaction,
  93      __sigaction, or __libc_sigaction (all aliases to the same
  94      function).  */
  95   if (name == NULL || strstr (name, "sigaction") != NULL)
  96     return (x86_64_linux_sigtramp_start (pc) != 0);
  97
  98   return (strcmp ("__restore_rt", name) == 0);
  99 }
 100
 101 /* Offset to struct sigcontext in ucontext, from <asm/ucontext.h>.  */
 102 #define X86_64_LINUX_UCONTEXT_SIGCONTEXT_OFFSET 40
 103
 104 /* Assuming NEXT_FRAME is a frame following a GNU/Linux sigtramp
 105    routine, return the address of the associated sigcontext structure.  */
 106
 107 static CORE_ADDR
 108 x86_64_linux_sigcontext_addr (struct frame_info *next_frame)
 109 {
 110   CORE_ADDR sp;
 111   char buf[8];
 112
 113   frame_unwind_register (next_frame, SP_REGNUM, buf);
 114   sp = extract_unsigned_integer (buf, 8);
 115
 116   /* The sigcontext structure is part of the user context.  A pointer
 117      to the user context is passed as the third argument to the signal
 118      handler, i.e. in %rdx.  Unfortunately %rdx isn't preserved across
 119      function calls so we can't use it.  Fortunately the user context
 120      is part of the signal frame and the unwound %rsp directly points
 121      at it.  */
 122   return sp + X86_64_LINUX_UCONTEXT_SIGCONTEXT_OFFSET;
 123 }
 124 \f
 125
 126 /* From <asm/sigcontext.h>.  */
 127 static int x86_64_linux_sc_reg_offset[X86_64_NUM_GREGS] =
 128 {
 129   13 * 8,                       /* %rax */
 130   11 * 8,                       /* %rbx */
 131   14 * 8,                       /* %rcx */
 132   12 * 8,                       /* %rdx */
 133   9 * 8,                        /* %rsi */
 134   8 * 8,                        /* %rdi */
 135   10 * 8,                       /* %rbp */
 136   15 * 8,                       /* %rsp */
 137   0 * 8,                        /* %r8 */
 138   1 * 8,                        /* %r9 */
 139   2 * 8,                        /* %r10 */
 140   3 * 8,                        /* %r11 */
 141   4 * 8,                        /* %r12 */
 142   5 * 8,                        /* %r13 */
 143   6 * 8,                        /* %r14 */
 144   7 * 8,                        /* %r15 */
 145   16 * 8,                       /* %rip */
 146   17 * 8,                       /* %eflags */
 147   -1,                           /* %ds */
 148   -1,                           /* %es */
 149
 150   /* FIXME: kettenis/2002030531: The registers %fs and %gs are
 151      available in `struct sigcontext'.  However, they only occupy two
 152      bytes instead of four, which makes using them here rather
 153      difficult.  Leave them out for now.  */
 154   -1,                           /* %fs */
 155   -1                            /* %gs */
 156 };
 157
 158 static void
 159 x86_64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 160 {
 161   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 162   x86_64_init_abi (info, gdbarch);
 163
 164   set_gdbarch_pc_in_sigtramp (gdbarch, x86_64_linux_pc_in_sigtramp);
 165
 166   tdep->sigcontext_addr = x86_64_linux_sigcontext_addr;
 167   tdep->sc_reg_offset = x86_64_linux_sc_reg_offset;
 168   tdep->sc_num_regs = X86_64_NUM_GREGS;
 169 }
 170 \f
 171
 172 /* Provide a prototype to silence -Wmissing-prototypes.  */
 173 extern void _initialize_x86_64_linux_tdep (void);
 174
 175 void
 176 _initialize_x86_64_linux_tdep (void)
 177 {
 178   gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64, GDB_OSABI_LINUX,
 179                           x86_64_linux_init_abi);
 180 }