gdb/x86-linux-nat.c

   1 /* Native-dependent code for GNU/Linux x86 (i386 and x86-64).
   2
   3    Copyright (C) 1999-2020 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 "inferior.h"
  22 #include "elf/common.h"
  23 #include "gdb_proc_service.h"
  24 #include "nat/gdb_ptrace.h"
  25 #include <sys/user.h>
  26 #include <sys/procfs.h>
  27 #include <sys/uio.h>
  28
  29 #include "x86-nat.h"
  30 #ifndef __x86_64__
  31 #include "i386-linux-nat.h"
  32 #endif
  33 #include "x86-linux-nat.h"
  34 #include "i386-linux-tdep.h"
  35 #ifdef __x86_64__
  36 #include "amd64-linux-tdep.h"
  37 #endif
  38 #include "gdbsupport/x86-xstate.h"
  39 #include "nat/linux-btrace.h"
  40 #include "nat/linux-nat.h"
  41 #include "nat/x86-linux.h"
  42 #include "nat/x86-linux-dregs.h"
  43 #include "nat/linux-ptrace.h"
  44
  45 /* linux_nat_target::low_new_fork implementation.  */
  46
  47 void
  48 x86_linux_nat_target::low_new_fork (struct lwp_info *parent, pid_t child_pid)
  49 {
  50   pid_t parent_pid;
  51   struct x86_debug_reg_state *parent_state;
  52   struct x86_debug_reg_state *child_state;
  53
  54   /* NULL means no watchpoint has ever been set in the parent.  In
  55      that case, there's nothing to do.  */
  56   if (parent->arch_private == NULL)
  57     return;
  58
  59   /* Linux kernel before 2.6.33 commit
  60      72f674d203cd230426437cdcf7dd6f681dad8b0d
  61      will inherit hardware debug registers from parent
  62      on fork/vfork/clone.  Newer Linux kernels create such tasks with
  63      zeroed debug registers.
  64
  65      GDB core assumes the child inherits the watchpoints/hw
  66      breakpoints of the parent, and will remove them all from the
  67      forked off process.  Copy the debug registers mirrors into the
  68      new process so that all breakpoints and watchpoints can be
  69      removed together.  The debug registers mirror will become zeroed
  70      in the end before detaching the forked off process, thus making
  71      this compatible with older Linux kernels too.  */
  72
  73   parent_pid = parent->ptid.pid ();
  74   parent_state = x86_debug_reg_state (parent_pid);
  75   child_state = x86_debug_reg_state (child_pid);
  76   *child_state = *parent_state;
  77 }
  78 \f
  79
  80 x86_linux_nat_target::~x86_linux_nat_target ()
  81 {
  82 }
  83
  84 void
  85 x86_linux_nat_target::post_startup_inferior (ptid_t ptid)
  86 {
  87   x86_cleanup_dregs ();
  88   linux_nat_target::post_startup_inferior (ptid);
  89 }
  90
  91 #ifdef __x86_64__
  92 /* Value of CS segment register:
  93      64bit process: 0x33
  94      32bit process: 0x23  */
  95 #define AMD64_LINUX_USER64_CS 0x33
  96
  97 /* Value of DS segment register:
  98      LP64 process: 0x0
  99      X32 process: 0x2b  */
 100 #define AMD64_LINUX_X32_DS 0x2b
 101 #endif
 102
 103 /* Get Linux/x86 target description from running target.  */
 104
 105 const struct target_desc *
 106 x86_linux_nat_target::read_description ()
 107 {
 108   int tid;
 109   int is_64bit = 0;
 110 #ifdef __x86_64__
 111   int is_x32;
 112 #endif
 113   static uint64_t xcr0;
 114   uint64_t xcr0_features_bits;
 115
 116   /* GNU/Linux LWP ID's are process ID's.  */
 117   tid = inferior_ptid.lwp ();
 118   if (tid == 0)
 119     tid = inferior_ptid.pid (); /* Not a threaded program.  */
 120
 121 #ifdef __x86_64__
 122   {
 123     unsigned long cs;
 124     unsigned long ds;
 125
 126     /* Get CS register.  */
 127     errno = 0;
 128     cs = ptrace (PTRACE_PEEKUSER, tid,
 129                  offsetof (struct user_regs_struct, cs), 0);
 130     if (errno != 0)
 131       perror_with_name (_("Couldn't get CS register"));
 132
 133     is_64bit = cs == AMD64_LINUX_USER64_CS;
 134
 135     /* Get DS register.  */
 136     errno = 0;
 137     ds = ptrace (PTRACE_PEEKUSER, tid,
 138                  offsetof (struct user_regs_struct, ds), 0);
 139     if (errno != 0)
 140       perror_with_name (_("Couldn't get DS register"));
 141
 142     is_x32 = ds == AMD64_LINUX_X32_DS;
 143
 144     if (sizeof (void *) == 4 && is_64bit && !is_x32)
 145       error (_("Can't debug 64-bit process with 32-bit GDB"));
 146   }
 147 #elif HAVE_PTRACE_GETFPXREGS
 148   if (have_ptrace_getfpxregs == -1)
 149     {
 150       elf_fpxregset_t fpxregs;
 151
 152       if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
 153         {
 154           have_ptrace_getfpxregs = 0;
 155           have_ptrace_getregset = TRIBOOL_FALSE;
 156           return i386_linux_read_description (X86_XSTATE_X87_MASK);
 157         }
 158     }
 159 #endif
 160
 161   if (have_ptrace_getregset == TRIBOOL_UNKNOWN)
 162     {
 163       uint64_t xstateregs[(X86_XSTATE_SSE_SIZE / sizeof (uint64_t))];
 164       struct iovec iov;
 165
 166       iov.iov_base = xstateregs;
 167       iov.iov_len = sizeof (xstateregs);
 168
 169       /* Check if PTRACE_GETREGSET works.  */
 170       if (ptrace (PTRACE_GETREGSET, tid,
 171                   (unsigned int) NT_X86_XSTATE, &iov) < 0)
 172         have_ptrace_getregset = TRIBOOL_FALSE;
 173       else
 174         {
 175           have_ptrace_getregset = TRIBOOL_TRUE;
 176
 177           /* Get XCR0 from XSAVE extended state.  */
 178           xcr0 = xstateregs[(I386_LINUX_XSAVE_XCR0_OFFSET
 179                              / sizeof (uint64_t))];
 180         }
 181     }
 182
 183   /* Check the native XCR0 only if PTRACE_GETREGSET is available.  If
 184      PTRACE_GETREGSET is not available then set xcr0_features_bits to
 185      zero so that the "no-features" descriptions are returned by the
 186      switches below.  */
 187   if (have_ptrace_getregset == TRIBOOL_TRUE)
 188     xcr0_features_bits = xcr0 & X86_XSTATE_ALL_MASK;
 189   else
 190     xcr0_features_bits = 0;
 191
 192   if (is_64bit)
 193     {
 194 #ifdef __x86_64__
 195       return amd64_linux_read_description (xcr0_features_bits, is_x32);
 196 #endif
 197     }
 198   else
 199     {
 200       const struct target_desc * tdesc
 201         = i386_linux_read_description (xcr0_features_bits);
 202
 203       if (tdesc == NULL)
 204         tdesc = i386_linux_read_description (X86_XSTATE_SSE_MASK);
 205
 206       return tdesc;
 207     }
 208
 209   gdb_assert_not_reached ("failed to return tdesc");
 210 }
 211 \f
 212
 213 /* Enable branch tracing.  */
 214
 215 struct btrace_target_info *
 216 x86_linux_nat_target::enable_btrace (ptid_t ptid,
 217                                      const struct btrace_config *conf)
 218 {
 219   struct btrace_target_info *tinfo = nullptr;
 220   try
 221     {
 222       tinfo = linux_enable_btrace (ptid, conf);
 223     }
 224   catch (const gdb_exception_error &exception)
 225     {
 226       error (_("Could not enable branch tracing for %s: %s"),
 227              target_pid_to_str (ptid).c_str (), exception.what ());
 228     }
 229
 230   return tinfo;
 231 }
 232
 233 /* Disable branch tracing.  */
 234
 235 void
 236 x86_linux_nat_target::disable_btrace (struct btrace_target_info *tinfo)
 237 {
 238   enum btrace_error errcode = linux_disable_btrace (tinfo);
 239
 240   if (errcode != BTRACE_ERR_NONE)
 241     error (_("Could not disable branch tracing."));
 242 }
 243
 244 /* Teardown branch tracing.  */
 245
 246 void
 247 x86_linux_nat_target::teardown_btrace (struct btrace_target_info *tinfo)
 248 {
 249   /* Ignore errors.  */
 250   linux_disable_btrace (tinfo);
 251 }
 252
 253 enum btrace_error
 254 x86_linux_nat_target::read_btrace (struct btrace_data *data,
 255                                    struct btrace_target_info *btinfo,
 256                                    enum btrace_read_type type)
 257 {
 258   return linux_read_btrace (data, btinfo, type);
 259 }
 260
 261 /* See to_btrace_conf in target.h.  */
 262
 263 const struct btrace_config *
 264 x86_linux_nat_target::btrace_conf (const struct btrace_target_info *btinfo)
 265 {
 266   return linux_btrace_conf (btinfo);
 267 }
 268
 269 \f
 270
 271 /* Helper for ps_get_thread_area.  Sets BASE_ADDR to a pointer to
 272    the thread local storage (or its descriptor) and returns PS_OK
 273    on success.  Returns PS_ERR on failure.  */
 274
 275 ps_err_e
 276 x86_linux_get_thread_area (pid_t pid, void *addr, unsigned int *base_addr)
 277 {
 278   /* NOTE: cagney/2003-08-26: The definition of this buffer is found
 279      in the kernel header <asm-i386/ldt.h>.  It, after padding, is 4 x
 280      4 byte integers in size: `entry_number', `base_addr', `limit',
 281      and a bunch of status bits.
 282
 283      The values returned by this ptrace call should be part of the
 284      regcache buffer, and ps_get_thread_area should channel its
 285      request through the regcache.  That way remote targets could
 286      provide the value using the remote protocol and not this direct
 287      call.
 288
 289      Is this function needed?  I'm guessing that the `base' is the
 290      address of a descriptor that libthread_db uses to find the
 291      thread local address base that GDB needs.  Perhaps that
 292      descriptor is defined by the ABI.  Anyway, given that
 293      libthread_db calls this function without prompting (gdb
 294      requesting tls base) I guess it needs info in there anyway.  */
 295   unsigned int desc[4];
 296
 297   /* This code assumes that "int" is 32 bits and that
 298      GET_THREAD_AREA returns no more than 4 int values.  */
 299   gdb_assert (sizeof (int) == 4);
 300
 301 #ifndef PTRACE_GET_THREAD_AREA
 302 #define PTRACE_GET_THREAD_AREA 25
 303 #endif
 304
 305   if (ptrace (PTRACE_GET_THREAD_AREA, pid, addr, &desc) < 0)
 306     return PS_ERR;
 307
 308   *base_addr = desc[1];
 309   return PS_OK;
 310 }
 311 \f
 312
 313 void
 314 _initialize_x86_linux_nat ()
 315 {
 316   /* Initialize the debug register function vectors.  */
 317   x86_dr_low.set_control = x86_linux_dr_set_control;
 318   x86_dr_low.set_addr = x86_linux_dr_set_addr;
 319   x86_dr_low.get_addr = x86_linux_dr_get_addr;
 320   x86_dr_low.get_status = x86_linux_dr_get_status;
 321   x86_dr_low.get_control = x86_linux_dr_get_control;
 322   x86_set_debug_register_length (sizeof (void *));
 323 }