gdb/nat/x86-linux.c

   1 /* Native-dependent code for GNU/Linux x86 (i386 and x86-64).
   2
   3    Copyright (C) 1999-2024 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 "x86-linux.h"
  21 #include "x86-linux-dregs.h"
  22 #include "nat/gdb_ptrace.h"
  23 #include <sys/user.h>
  24
  25 /* Per-thread arch-specific data we want to keep.  */
  26
  27 struct arch_lwp_info
  28 {
  29   /* Non-zero if our copy differs from what's recorded in the
  30      thread.  */
  31   int debug_registers_changed;
  32 };
  33
  34 /* See nat/x86-linux.h.  */
  35
  36 void
  37 lwp_set_debug_registers_changed (struct lwp_info *lwp, int value)
  38 {
  39   if (lwp_arch_private_info (lwp) == NULL)
  40     lwp_set_arch_private_info (lwp, XCNEW (struct arch_lwp_info));
  41
  42   lwp_arch_private_info (lwp)->debug_registers_changed = value;
  43 }
  44
  45 /* See nat/x86-linux.h.  */
  46
  47 int
  48 lwp_debug_registers_changed (struct lwp_info *lwp)
  49 {
  50   struct arch_lwp_info *info = lwp_arch_private_info (lwp);
  51
  52   /* NULL means either that this is the main thread still going
  53      through the shell, or that no watchpoint has been set yet.
  54      The debug registers are unchanged in either case.  */
  55   if (info == NULL)
  56     return 0;
  57
  58   return info->debug_registers_changed;
  59 }
  60
  61 /* See nat/x86-linux.h.  */
  62
  63 void
  64 x86_linux_new_thread (struct lwp_info *lwp)
  65 {
  66   lwp_set_debug_registers_changed (lwp, 1);
  67 }
  68
  69 /* See nat/x86-linux.h.  */
  70
  71 void
  72 x86_linux_delete_thread (struct arch_lwp_info *arch_lwp)
  73 {
  74   xfree (arch_lwp);
  75 }
  76
  77 /* See nat/x86-linux.h.  */
  78
  79 void
  80 x86_linux_prepare_to_resume (struct lwp_info *lwp)
  81 {
  82   x86_linux_update_debug_registers (lwp);
  83 }
  84
  85 #ifdef __x86_64__
  86 /* Value of CS segment register:
  87      64bit process: 0x33
  88      32bit process: 0x23  */
  89 #define AMD64_LINUX_USER64_CS 0x33
  90
  91 /* Value of DS segment register:
  92      LP64 process: 0x0
  93      X32 process: 0x2b  */
  94 #define AMD64_LINUX_X32_DS 0x2b
  95 #endif
  96
  97 /* See nat/x86-linux.h.  */
  98
  99 x86_linux_arch_size
 100 x86_linux_ptrace_get_arch_size (int tid)
 101 {
 102 #ifdef __x86_64__
 103   unsigned long cs;
 104   unsigned long ds;
 105
 106   /* Get CS register.  */
 107   errno = 0;
 108   cs = ptrace (PTRACE_PEEKUSER, tid,
 109                offsetof (struct user_regs_struct, cs), 0);
 110   if (errno != 0)
 111     perror_with_name (_("Couldn't get CS register"));
 112
 113   bool is_64bit = cs == AMD64_LINUX_USER64_CS;
 114
 115   /* Get DS register.  */
 116   errno = 0;
 117   ds = ptrace (PTRACE_PEEKUSER, tid,
 118                offsetof (struct user_regs_struct, ds), 0);
 119   if (errno != 0)
 120     perror_with_name (_("Couldn't get DS register"));
 121
 122   bool is_x32 = ds == AMD64_LINUX_X32_DS;
 123
 124   return x86_linux_arch_size (is_64bit, is_x32);
 125 #else
 126   return x86_linux_arch_size (false, false);
 127 #endif
 128 }