gdb/i386obsd-nat.c - gdb

Functions defined

Source code

  1. /* Native-dependent code for OpenBSD/i386.

  3.    Copyright (C) 2002-2015 Free Software Foundation, Inc.

  5.    This file is part of GDB.

  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.

  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.

  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/>.  */

  20. #include "defs.h"
  21. #include "gdbcore.h"
  22. #include "regcache.h"
  23. #include "target.h"

  25. #include <sys/sysctl.h>
  26. #include <machine/frame.h>
  27. #include <machine/pcb.h>

  29. #include "i386-tdep.h"
  30. #include "i386bsd-nat.h"
  31. #include "obsd-nat.h"
  32. #include "bsd-kvm.h"

  34. static int
  35. ‌i386obsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  36. {
  37.   struct gdbarch *gdbarch = get_regcache_arch (regcache);
  38.   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  39.   struct switchframe sf;

  41.   /* The following is true for OpenBSD 3.6:

  43.      The pcb contains %esp and %ebp at the point of the context switch
  44.      in cpu_switch().  At that point we have a stack frame as
  45.      described by `struct switchframe', which for OpenBSD 3.6 has the
  46.      following layout:

  48.      interrupt level
  49.      %edi
  50.      %esi
  51.      %ebx
  52.      %eip

  54.      we reconstruct the register state as it would look when we just
  55.      returned from cpu_switch().  */

  57.   /* The stack pointer shouldn't be zero.  */
  58.   if (pcb->pcb_esp == 0)
  59.     return 0;

  61.   /* Read the stack frame, and check its validity.  We do this by
  62.      checking if the saved interrupt priority level in the stack frame
  63.      looks reasonable..  */
  64. #ifdef PCB_SAVECTX
  65.   if ((pcb->pcb_flags & PCB_SAVECTX) == 0)
  66.     {
  67.       /* Yes, we have a frame that matches cpu_switch().  */
  68.       read_memory (pcb->pcb_esp, (gdb_byte *) &sf, sizeof sf);
  69.       pcb->pcb_esp += sizeof (struct switchframe);
  70.       regcache_raw_supply (regcache, I386_EDI_REGNUM, &sf.sf_edi);
  71.       regcache_raw_supply (regcache, I386_ESI_REGNUM, &sf.sf_esi);
  72.       regcache_raw_supply (regcache, I386_EBX_REGNUM, &sf.sf_ebx);
  73.       regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip);
  74.     }
  75.   else
  76. #endif
  77.     {
  78.       /* No, the pcb must have been last updated by savectx().  */
  79.       pcb->pcb_esp = pcb->pcb_ebp;
  80.       pcb->pcb_ebp = read_memory_integer(pcb->pcb_esp, 4, byte_order);
  81.       sf.sf_eip = read_memory_integer(pcb->pcb_esp + 4, 4, byte_order);
  82.       regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip);
  83.     }

  85.   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
  86.   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);

  88.   return 1;
  89. }


  92. /* Prevent warning from -Wmissing-prototypes.  */
  93. void _initialize_i386obsd_nat (void);

  95. void
  96. ‌_initialize_i386obsd_nat (void)
  97. {
  98.   /* Add some extra features to the common *BSD/i386 target.  */
  99.   obsd_add_target (i386bsd_target ());

  101.   /* Support debugging kernel virtual memory images.  */
  102.   bsd_kvm_add_target (i386obsd_supply_pcb);

  104.   /* OpenBSD provides a vm.psstrings sysctl that we can use to locate
  105.      the sigtramp.  That way we can still recognize a sigtramp if its
  106.      location is changed in a new kernel.  This is especially
  107.      important for OpenBSD, since it uses a different memory layout
  108.      than NetBSD, yet we cannot distinguish between the two.

  110.      Of course this is still based on the assumption that the sigtramp
  111.      is placed directly under the location where the program arguments
  112.      and environment can be found.  */
  113. #ifdef VM_PSSTRINGS
  114.   {
  115.     struct _ps_strings _ps;
  116.     int mib[2];
  117.     size_t len;

  119.     mib[0] = CTL_VM;
  120.     mib[1] = VM_PSSTRINGS;
  121.     len = sizeof (_ps);
  122.     if (sysctl (mib, 2, &_ps, &len, NULL, 0) == 0)
  123.       {
  124.         i386obsd_sigtramp_start_addr = (u_long) _ps.val - 128;
  125.         i386obsd_sigtramp_end_addr = (u_long) _ps.val;
  126.       }
  127.   }
  128. #endif
  129. }