gdb/amd64-obsd-nat.c

   1 /* Native-dependent code for OpenBSD/amd64.
   2
   3    Copyright (C) 2003-2019 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
  22 /* Local non-gdb includes.  */
  23 #include "amd64-bsd-nat.h"
  24 #include "amd64-nat.h"
  25 #include "amd64-tdep.h"
  26 #include "gdbcore.h"
  27 #include "obsd-nat.h"
  28 #include "regcache.h"
  29 #include "target.h"
  30
  31 /* Mapping between the general-purpose registers in OpenBSD/amd64
  32    `struct reg' format and GDB's register cache layout for
  33    OpenBSD/i386.
  34
  35    Note that most (if not all) OpenBSD/amd64 registers are 64-bit,
  36    while the OpenBSD/i386 registers are all 32-bit, but since we're
  37    little-endian we get away with that.  */
  38
  39 /* From <machine/reg.h>.  */
  40 static int amd64obsd32_r_reg_offset[] =
  41 {
  42   14 * 8,                       /* %eax */
  43   3 * 8,                        /* %ecx */
  44   2 * 8,                        /* %edx */
  45   13 * 8,                       /* %ebx */
  46   15 * 8,                       /* %esp */
  47   12 * 8,                       /* %ebp */
  48   1 * 8,                        /* %esi */
  49   0 * 8,                        /* %edi */
  50   16 * 8,                       /* %eip */
  51   17 * 8,                       /* %eflags */
  52   18 * 8,                       /* %cs */
  53   19 * 8,                       /* %ss */
  54   20 * 8,                       /* %ds */
  55   21 * 8,                       /* %es */
  56   22 * 8,                       /* %fs */
  57   23 * 8                        /* %gs */
  58 };
  59 \f
  60
  61 /* Support for debugging kernel virtual memory images.  */
  62
  63 #include <sys/types.h>
  64 #include <machine/frame.h>
  65 #include <machine/pcb.h>
  66
  67 #include "bsd-kvm.h"
  68
  69 static int
  70 amd64obsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  71 {
  72   struct switchframe sf;
  73   int regnum;
  74
  75   /* The following is true for OpenBSD 3.5:
  76
  77      The pcb contains the stack pointer at the point of the context
  78      switch in cpu_switch().  At that point we have a stack frame as
  79      described by `struct switchframe', which for OpenBSD 3.5 has the
  80      following layout:
  81
  82      interrupt level
  83      %r15
  84      %r14
  85      %r13
  86      %r12
  87      %rbp
  88      %rbx
  89      return address
  90
  91      Together with %rsp in the pcb, this accounts for all callee-saved
  92      registers specified by the psABI.  From this information we
  93      reconstruct the register state as it would look when we just
  94      returned from cpu_switch().
  95
  96      For core dumps the pcb is saved by savectx().  In that case the
  97      stack frame only contains the return address, and there is no way
  98      to recover the other registers.  */
  99
 100   /* The stack pointer shouldn't be zero.  */
 101   if (pcb->pcb_rsp == 0)
 102     return 0;
 103
 104   /* Read the stack frame, and check its validity.  */
 105   read_memory (pcb->pcb_rsp, (gdb_byte *) &sf, sizeof sf);
 106   if (sf.sf_rbp == pcb->pcb_rbp)
 107     {
 108       /* Yes, we have a frame that matches cpu_switch().  */
 109       pcb->pcb_rsp += sizeof (struct switchframe);
 110       regcache->raw_supply (12, &sf.sf_r12);
 111       regcache->raw_supply (13, &sf.sf_r13);
 112       regcache->raw_supply (14, &sf.sf_r14);
 113       regcache->raw_supply (15, &sf.sf_r15);
 114       regcache->raw_supply (AMD64_RBX_REGNUM, &sf.sf_rbx);
 115       regcache->raw_supply (AMD64_RIP_REGNUM, &sf.sf_rip);
 116     }
 117   else
 118     {
 119       /* No, the pcb must have been last updated by savectx().  */
 120       pcb->pcb_rsp += 8;
 121       regcache->raw_supply (AMD64_RIP_REGNUM, &sf);
 122     }
 123
 124   regcache->raw_supply (AMD64_RSP_REGNUM, &pcb->pcb_rsp);
 125   regcache->raw_supply (AMD64_RBP_REGNUM, &pcb->pcb_rbp);
 126
 127   return 1;
 128 }
 129
 130 static amd64_bsd_nat_target<obsd_nat_target> the_amd64_obsd_nat_target;
 131
 132 void
 133 _initialize_amd64obsd_nat (void)
 134 {
 135   amd64_native_gregset32_reg_offset = amd64obsd32_r_reg_offset;
 136   amd64_native_gregset32_num_regs = ARRAY_SIZE (amd64obsd32_r_reg_offset);
 137   amd64_native_gregset64_reg_offset = amd64obsd_r_reg_offset;
 138
 139   add_inf_child_target (&the_amd64_obsd_nat_target);
 140
 141   /* Support debugging kernel virtual memory images.  */
 142   bsd_kvm_add_target (amd64obsd_supply_pcb);
 143 }