gdb/amd64-obsd-nat.c

   1 /* Native-dependent code for OpenBSD/amd64.
   2
   3    Copyright (C) 2003-2017 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 "gdbcore.h"
  22 #include "regcache.h"
  23 #include "target.h"
  24
  25 #include "amd64-tdep.h"
  26 #include "amd64-nat.h"
  27 #include "obsd-nat.h"
  28
  29 /* Mapping between the general-purpose registers in OpenBSD/amd64
  30    `struct reg' format and GDB's register cache layout for
  31    OpenBSD/i386.
  32
  33    Note that most (if not all) OpenBSD/amd64 registers are 64-bit,
  34    while the OpenBSD/i386 registers are all 32-bit, but since we're
  35    little-endian we get away with that.  */
  36
  37 /* From <machine/reg.h>.  */
  38 static int amd64obsd32_r_reg_offset[] =
  39 {
  40   14 * 8,                       /* %eax */
  41   3 * 8,                        /* %ecx */
  42   2 * 8,                        /* %edx */
  43   13 * 8,                       /* %ebx */
  44   15 * 8,                       /* %esp */
  45   12 * 8,                       /* %ebp */
  46   1 * 8,                        /* %esi */
  47   0 * 8,                        /* %edi */
  48   16 * 8,                       /* %eip */
  49   17 * 8,                       /* %eflags */
  50   18 * 8,                       /* %cs */
  51   19 * 8,                       /* %ss */
  52   20 * 8,                       /* %ds */
  53   21 * 8,                       /* %es */
  54   22 * 8,                       /* %fs */
  55   23 * 8                        /* %gs */
  56 };
  57 \f
  58
  59 /* Support for debugging kernel virtual memory images.  */
  60
  61 #include <sys/types.h>
  62 #include <machine/frame.h>
  63 #include <machine/pcb.h>
  64
  65 #include "bsd-kvm.h"
  66
  67 static int
  68 amd64obsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  69 {
  70   struct switchframe sf;
  71   int regnum;
  72
  73   /* The following is true for OpenBSD 3.5:
  74
  75      The pcb contains the stack pointer at the point of the context
  76      switch in cpu_switch().  At that point we have a stack frame as
  77      described by `struct switchframe', which for OpenBSD 3.5 has the
  78      following layout:
  79
  80      interrupt level
  81      %r15
  82      %r14
  83      %r13
  84      %r12
  85      %rbp
  86      %rbx
  87      return address
  88
  89      Together with %rsp in the pcb, this accounts for all callee-saved
  90      registers specified by the psABI.  From this information we
  91      reconstruct the register state as it would look when we just
  92      returned from cpu_switch().
  93
  94      For core dumps the pcb is saved by savectx().  In that case the
  95      stack frame only contains the return address, and there is no way
  96      to recover the other registers.  */
  97
  98   /* The stack pointer shouldn't be zero.  */
  99   if (pcb->pcb_rsp == 0)
 100     return 0;
 101
 102   /* Read the stack frame, and check its validity.  */
 103   read_memory (pcb->pcb_rsp, (gdb_byte *) &sf, sizeof sf);
 104   if (sf.sf_rbp == pcb->pcb_rbp)
 105     {
 106       /* Yes, we have a frame that matches cpu_switch().  */
 107       pcb->pcb_rsp += sizeof (struct switchframe);
 108       regcache_raw_supply (regcache, 12, &sf.sf_r12);
 109       regcache_raw_supply (regcache, 13, &sf.sf_r13);
 110       regcache_raw_supply (regcache, 14, &sf.sf_r14);
 111       regcache_raw_supply (regcache, 15, &sf.sf_r15);
 112       regcache_raw_supply (regcache, AMD64_RBX_REGNUM, &sf.sf_rbx);
 113       regcache_raw_supply (regcache, AMD64_RIP_REGNUM, &sf.sf_rip);
 114     }
 115   else
 116     {
 117       /* No, the pcb must have been last updated by savectx().  */
 118       pcb->pcb_rsp += 8;
 119       regcache_raw_supply (regcache, AMD64_RIP_REGNUM, &sf);
 120     }
 121
 122   regcache_raw_supply (regcache, AMD64_RSP_REGNUM, &pcb->pcb_rsp);
 123   regcache_raw_supply (regcache, AMD64_RBP_REGNUM, &pcb->pcb_rbp);
 124
 125   return 1;
 126 }
 127
 128 void
 129 _initialize_amd64obsd_nat (void)
 130 {
 131   amd64_native_gregset32_reg_offset = amd64obsd32_r_reg_offset;
 132   amd64_native_gregset32_num_regs = ARRAY_SIZE (amd64obsd32_r_reg_offset);
 133   amd64_native_gregset64_reg_offset = amd64obsd_r_reg_offset;
 134
 135   /* Add some extra features to the common *BSD/amd64 target.  */
 136   obsd_add_target (amd64bsd_target ());
 137
 138   /* Support debugging kernel virtual memory images.  */
 139   bsd_kvm_add_target (amd64obsd_supply_pcb);
 140 }