gdb/amd64-obsd-nat.c

   1 /* Native-dependent code for OpenBSD/amd64.
   2
   3    Copyright (C) 2003-2021 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-bsd-nat.h"
  27 #include "amd64-nat.h"
  28 #include "obsd-nat.h"
  29
  30 /* Mapping between the general-purpose registers in OpenBSD/amd64
  31    `struct reg' format and GDB's register cache layout for
  32    OpenBSD/i386.
  33
  34    Note that most (if not all) OpenBSD/amd64 registers are 64-bit,
  35    while the OpenBSD/i386 registers are all 32-bit, but since we're
  36    little-endian we get away with that.  */
  37
  38 /* From <machine/reg.h>.  */
  39 static int amd64obsd32_r_reg_offset[] =
  40 {
  41   14 * 8,                       /* %eax */
  42   3 * 8,                        /* %ecx */
  43   2 * 8,                        /* %edx */
  44   13 * 8,                       /* %ebx */
  45   15 * 8,                       /* %esp */
  46   12 * 8,                       /* %ebp */
  47   1 * 8,                        /* %esi */
  48   0 * 8,                        /* %edi */
  49   16 * 8,                       /* %eip */
  50   17 * 8,                       /* %eflags */
  51   18 * 8,                       /* %cs */
  52   19 * 8,                       /* %ss */
  53   20 * 8,                       /* %ds */
  54   21 * 8,                       /* %es */
  55   22 * 8,                       /* %fs */
  56   23 * 8                        /* %gs */
  57 };
  58 \f
  59
  60 /* Support for debugging kernel virtual memory images.  */
  61
  62 #include <sys/types.h>
  63 #include <machine/frame.h>
  64 #include <machine/pcb.h>
  65
  66 #include "bsd-kvm.h"
  67
  68 static int
  69 amd64obsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  70 {
  71   struct switchframe sf;
  72   int regnum;
  73
  74   /* The following is true for OpenBSD 3.5:
  75
  76      The pcb contains the stack pointer at the point of the context
  77      switch in cpu_switch().  At that point we have a stack frame as
  78      described by `struct switchframe', which for OpenBSD 3.5 has the
  79      following layout:
  80
  81      interrupt level
  82      %r15
  83      %r14
  84      %r13
  85      %r12
  86      %rbp
  87      %rbx
  88      return address
  89
  90      Together with %rsp in the pcb, this accounts for all callee-saved
  91      registers specified by the psABI.  From this information we
  92      reconstruct the register state as it would look when we just
  93      returned from cpu_switch().
  94
  95      For core dumps the pcb is saved by savectx().  In that case the
  96      stack frame only contains the return address, and there is no way
  97      to recover the other registers.  */
  98
  99   /* The stack pointer shouldn't be zero.  */
 100   if (pcb->pcb_rsp == 0)
 101     return 0;
 102
 103   /* Read the stack frame, and check its validity.  */
 104   read_memory (pcb->pcb_rsp, (gdb_byte *) &sf, sizeof sf);
 105   if (sf.sf_rbp == pcb->pcb_rbp)
 106     {
 107       /* Yes, we have a frame that matches cpu_switch().  */
 108       pcb->pcb_rsp += sizeof (struct switchframe);
 109       regcache->raw_supply (12, &sf.sf_r12);
 110       regcache->raw_supply (13, &sf.sf_r13);
 111       regcache->raw_supply (14, &sf.sf_r14);
 112       regcache->raw_supply (15, &sf.sf_r15);
 113       regcache->raw_supply (AMD64_RBX_REGNUM, &sf.sf_rbx);
 114       regcache->raw_supply (AMD64_RIP_REGNUM, &sf.sf_rip);
 115     }
 116   else
 117     {
 118       /* No, the pcb must have been last updated by savectx().  */
 119       pcb->pcb_rsp += 8;
 120       regcache->raw_supply (AMD64_RIP_REGNUM, &sf);
 121     }
 122
 123   regcache->raw_supply (AMD64_RSP_REGNUM, &pcb->pcb_rsp);
 124   regcache->raw_supply (AMD64_RBP_REGNUM, &pcb->pcb_rbp);
 125
 126   return 1;
 127 }
 128
 129 static amd64_bsd_nat_target<obsd_nat_target> the_amd64_obsd_nat_target;
 130
 131 void _initialize_amd64obsd_nat ();
 132 void
 133 _initialize_amd64obsd_nat ()
 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 }