gdb/x86-linux-nat.c

   1 /* Native-dependent code for GNU/Linux x86 (i386 and x86-64).
   2
   3    Copyright (C) 1999-2017 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 "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 #include "linux-nat.h"
  31 #ifndef __x86_64__
  32 #include "i386-linux-nat.h"
  33 #endif
  34 #include "x86-linux-nat.h"
  35 #include "i386-linux-tdep.h"
  36 #ifdef __x86_64__
  37 #include "amd64-linux-tdep.h"
  38 #endif
  39 #include "x86-xstate.h"
  40 #include "nat/linux-btrace.h"
  41 #include "nat/linux-nat.h"
  42 #include "nat/x86-linux.h"
  43 #include "nat/x86-linux-dregs.h"
  44 #include "nat/linux-ptrace.h"
  45
  46 /* Per-thread arch-specific data we want to keep.  */
  47
  48 struct arch_lwp_info
  49 {
  50   /* Non-zero if our copy differs from what's recorded in the thread.  */
  51   int debug_registers_changed;
  52 };
  53
  54 \f
  55
  56 /* linux_nat_new_fork hook.   */
  57
  58 static void
  59 x86_linux_new_fork (struct lwp_info *parent, pid_t child_pid)
  60 {
  61   pid_t parent_pid;
  62   struct x86_debug_reg_state *parent_state;
  63   struct x86_debug_reg_state *child_state;
  64
  65   /* NULL means no watchpoint has ever been set in the parent.  In
  66      that case, there's nothing to do.  */
  67   if (parent->arch_private == NULL)
  68     return;
  69
  70   /* Linux kernel before 2.6.33 commit
  71      72f674d203cd230426437cdcf7dd6f681dad8b0d
  72      will inherit hardware debug registers from parent
  73      on fork/vfork/clone.  Newer Linux kernels create such tasks with
  74      zeroed debug registers.
  75
  76      GDB core assumes the child inherits the watchpoints/hw
  77      breakpoints of the parent, and will remove them all from the
  78      forked off process.  Copy the debug registers mirrors into the
  79      new process so that all breakpoints and watchpoints can be
  80      removed together.  The debug registers mirror will become zeroed
  81      in the end before detaching the forked off process, thus making
  82      this compatible with older Linux kernels too.  */
  83
  84   parent_pid = ptid_get_pid (parent->ptid);
  85   parent_state = x86_debug_reg_state (parent_pid);
  86   child_state = x86_debug_reg_state (child_pid);
  87   *child_state = *parent_state;
  88 }
  89 \f
  90
  91 static void (*super_post_startup_inferior) (struct target_ops *self,
  92                                             ptid_t ptid);
  93
  94 static void
  95 x86_linux_child_post_startup_inferior (struct target_ops *self, ptid_t ptid)
  96 {
  97   x86_cleanup_dregs ();
  98   super_post_startup_inferior (self, ptid);
  99 }
 100
 101 #ifdef __x86_64__
 102 /* Value of CS segment register:
 103      64bit process: 0x33
 104      32bit process: 0x23  */
 105 #define AMD64_LINUX_USER64_CS 0x33
 106
 107 /* Value of DS segment register:
 108      LP64 process: 0x0
 109      X32 process: 0x2b  */
 110 #define AMD64_LINUX_X32_DS 0x2b
 111 #endif
 112
 113 /* Get Linux/x86 target description from running target.  */
 114
 115 static const struct target_desc *
 116 x86_linux_read_description (struct target_ops *ops)
 117 {
 118   int tid;
 119   int is_64bit = 0;
 120 #ifdef __x86_64__
 121   int is_x32;
 122 #endif
 123   static uint64_t xcr0;
 124   uint64_t xcr0_features_bits;
 125
 126   /* GNU/Linux LWP ID's are process ID's.  */
 127   tid = ptid_get_lwp (inferior_ptid);
 128   if (tid == 0)
 129     tid = ptid_get_pid (inferior_ptid); /* Not a threaded program.  */
 130
 131 #ifdef __x86_64__
 132   {
 133     unsigned long cs;
 134     unsigned long ds;
 135
 136     /* Get CS register.  */
 137     errno = 0;
 138     cs = ptrace (PTRACE_PEEKUSER, tid,
 139                  offsetof (struct user_regs_struct, cs), 0);
 140     if (errno != 0)
 141       perror_with_name (_("Couldn't get CS register"));
 142
 143     is_64bit = cs == AMD64_LINUX_USER64_CS;
 144
 145     /* Get DS register.  */
 146     errno = 0;
 147     ds = ptrace (PTRACE_PEEKUSER, tid,
 148                  offsetof (struct user_regs_struct, ds), 0);
 149     if (errno != 0)
 150       perror_with_name (_("Couldn't get DS register"));
 151
 152     is_x32 = ds == AMD64_LINUX_X32_DS;
 153
 154     if (sizeof (void *) == 4 && is_64bit && !is_x32)
 155       error (_("Can't debug 64-bit process with 32-bit GDB"));
 156   }
 157 #elif HAVE_PTRACE_GETFPXREGS
 158   if (have_ptrace_getfpxregs == -1)
 159     {
 160       elf_fpxregset_t fpxregs;
 161
 162       if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
 163         {
 164           have_ptrace_getfpxregs = 0;
 165           have_ptrace_getregset = TRIBOOL_FALSE;
 166           return tdesc_i386_mmx_linux;
 167         }
 168     }
 169 #endif
 170
 171   if (have_ptrace_getregset == TRIBOOL_UNKNOWN)
 172     {
 173       uint64_t xstateregs[(X86_XSTATE_SSE_SIZE / sizeof (uint64_t))];
 174       struct iovec iov;
 175
 176       iov.iov_base = xstateregs;
 177       iov.iov_len = sizeof (xstateregs);
 178
 179       /* Check if PTRACE_GETREGSET works.  */
 180       if (ptrace (PTRACE_GETREGSET, tid,
 181                   (unsigned int) NT_X86_XSTATE, &iov) < 0)
 182         have_ptrace_getregset = TRIBOOL_FALSE;
 183       else
 184         {
 185           have_ptrace_getregset = TRIBOOL_TRUE;
 186
 187           /* Get XCR0 from XSAVE extended state.  */
 188           xcr0 = xstateregs[(I386_LINUX_XSAVE_XCR0_OFFSET
 189                              / sizeof (uint64_t))];
 190         }
 191     }
 192
 193   /* Check the native XCR0 only if PTRACE_GETREGSET is available.  If
 194      PTRACE_GETREGSET is not available then set xcr0_features_bits to
 195      zero so that the "no-features" descriptions are returned by the
 196      switches below.  */
 197   if (have_ptrace_getregset == TRIBOOL_TRUE)
 198     xcr0_features_bits = xcr0 & X86_XSTATE_ALL_MASK;
 199   else
 200     xcr0_features_bits = 0;
 201
 202   if (is_64bit)
 203     {
 204 #ifdef __x86_64__
 205       switch (xcr0_features_bits)
 206         {
 207         case X86_XSTATE_MPX_AVX512_MASK:
 208         case X86_XSTATE_AVX512_MASK:
 209           if (is_x32)
 210             return tdesc_x32_avx512_linux;
 211           else
 212             return tdesc_amd64_avx512_linux;
 213         case X86_XSTATE_MPX_MASK:
 214           if (is_x32)
 215             return tdesc_x32_avx_linux; /* No MPX on x32 using AVX.  */
 216           else
 217             return tdesc_amd64_mpx_linux;
 218         case X86_XSTATE_AVX_MPX_MASK:
 219           if (is_x32)
 220             return tdesc_x32_avx_linux; /* No MPX on x32 using AVX.  */
 221           else
 222             return tdesc_amd64_avx_mpx_linux;
 223         case X86_XSTATE_AVX_MASK:
 224           if (is_x32)
 225             return tdesc_x32_avx_linux;
 226           else
 227             return tdesc_amd64_avx_linux;
 228         default:
 229           if (is_x32)
 230             return tdesc_x32_linux;
 231           else
 232             return tdesc_amd64_linux;
 233         }
 234 #endif
 235     }
 236   else
 237     {
 238       switch (xcr0_features_bits)
 239         {
 240         case X86_XSTATE_MPX_AVX512_MASK:
 241         case X86_XSTATE_AVX512_MASK:
 242           return tdesc_i386_avx512_linux;
 243         case X86_XSTATE_MPX_MASK:
 244           return tdesc_i386_mpx_linux;
 245         case X86_XSTATE_AVX_MPX_MASK:
 246           return tdesc_i386_avx_mpx_linux;
 247         case X86_XSTATE_AVX_MASK:
 248           return tdesc_i386_avx_linux;
 249         default:
 250           return tdesc_i386_linux;
 251         }
 252     }
 253
 254   gdb_assert_not_reached ("failed to return tdesc");
 255 }
 256 \f
 257
 258 /* Enable branch tracing.  */
 259
 260 static struct btrace_target_info *
 261 x86_linux_enable_btrace (struct target_ops *self, ptid_t ptid,
 262                          const struct btrace_config *conf)
 263 {
 264   struct btrace_target_info *tinfo;
 265
 266   errno = 0;
 267   tinfo = linux_enable_btrace (ptid, conf);
 268
 269   if (tinfo == NULL)
 270     error (_("Could not enable branch tracing for %s: %s."),
 271            target_pid_to_str (ptid), safe_strerror (errno));
 272
 273   return tinfo;
 274 }
 275
 276 /* Disable branch tracing.  */
 277
 278 static void
 279 x86_linux_disable_btrace (struct target_ops *self,
 280                           struct btrace_target_info *tinfo)
 281 {
 282   enum btrace_error errcode = linux_disable_btrace (tinfo);
 283
 284   if (errcode != BTRACE_ERR_NONE)
 285     error (_("Could not disable branch tracing."));
 286 }
 287
 288 /* Teardown branch tracing.  */
 289
 290 static void
 291 x86_linux_teardown_btrace (struct target_ops *self,
 292                            struct btrace_target_info *tinfo)
 293 {
 294   /* Ignore errors.  */
 295   linux_disable_btrace (tinfo);
 296 }
 297
 298 static enum btrace_error
 299 x86_linux_read_btrace (struct target_ops *self,
 300                        struct btrace_data *data,
 301                        struct btrace_target_info *btinfo,
 302                        enum btrace_read_type type)
 303 {
 304   return linux_read_btrace (data, btinfo, type);
 305 }
 306
 307 /* See to_btrace_conf in target.h.  */
 308
 309 static const struct btrace_config *
 310 x86_linux_btrace_conf (struct target_ops *self,
 311                        const struct btrace_target_info *btinfo)
 312 {
 313   return linux_btrace_conf (btinfo);
 314 }
 315
 316 \f
 317
 318 /* Helper for ps_get_thread_area.  Sets BASE_ADDR to a pointer to
 319    the thread local storage (or its descriptor) and returns PS_OK
 320    on success.  Returns PS_ERR on failure.  */
 321
 322 ps_err_e
 323 x86_linux_get_thread_area (pid_t pid, void *addr, unsigned int *base_addr)
 324 {
 325   /* NOTE: cagney/2003-08-26: The definition of this buffer is found
 326      in the kernel header <asm-i386/ldt.h>.  It, after padding, is 4 x
 327      4 byte integers in size: `entry_number', `base_addr', `limit',
 328      and a bunch of status bits.
 329
 330      The values returned by this ptrace call should be part of the
 331      regcache buffer, and ps_get_thread_area should channel its
 332      request through the regcache.  That way remote targets could
 333      provide the value using the remote protocol and not this direct
 334      call.
 335
 336      Is this function needed?  I'm guessing that the `base' is the
 337      address of a descriptor that libthread_db uses to find the
 338      thread local address base that GDB needs.  Perhaps that
 339      descriptor is defined by the ABI.  Anyway, given that
 340      libthread_db calls this function without prompting (gdb
 341      requesting tls base) I guess it needs info in there anyway.  */
 342   unsigned int desc[4];
 343
 344   /* This code assumes that "int" is 32 bits and that
 345      GET_THREAD_AREA returns no more than 4 int values.  */
 346   gdb_assert (sizeof (int) == 4);
 347
 348 #ifndef PTRACE_GET_THREAD_AREA
 349 #define PTRACE_GET_THREAD_AREA 25
 350 #endif
 351
 352   if (ptrace (PTRACE_GET_THREAD_AREA, pid, addr, &desc) < 0)
 353     return PS_ERR;
 354
 355   *base_addr = desc[1];
 356   return PS_OK;
 357 }
 358 \f
 359
 360 /* Create an x86 GNU/Linux target.  */
 361
 362 struct target_ops *
 363 x86_linux_create_target (void)
 364 {
 365   /* Fill in the generic GNU/Linux methods.  */
 366   struct target_ops *t = linux_target ();
 367
 368   /* Initialize the debug register function vectors.  */
 369   x86_use_watchpoints (t);
 370   x86_dr_low.set_control = x86_linux_dr_set_control;
 371   x86_dr_low.set_addr = x86_linux_dr_set_addr;
 372   x86_dr_low.get_addr = x86_linux_dr_get_addr;
 373   x86_dr_low.get_status = x86_linux_dr_get_status;
 374   x86_dr_low.get_control = x86_linux_dr_get_control;
 375   x86_set_debug_register_length (sizeof (void *));
 376
 377   /* Override the GNU/Linux inferior startup hook.  */
 378   super_post_startup_inferior = t->to_post_startup_inferior;
 379   t->to_post_startup_inferior = x86_linux_child_post_startup_inferior;
 380
 381   /* Add the description reader.  */
 382   t->to_read_description = x86_linux_read_description;
 383
 384   /* Add btrace methods.  */
 385   t->to_supports_btrace = linux_supports_btrace;
 386   t->to_enable_btrace = x86_linux_enable_btrace;
 387   t->to_disable_btrace = x86_linux_disable_btrace;
 388   t->to_teardown_btrace = x86_linux_teardown_btrace;
 389   t->to_read_btrace = x86_linux_read_btrace;
 390   t->to_btrace_conf = x86_linux_btrace_conf;
 391
 392   return t;
 393 }
 394
 395 /* Add an x86 GNU/Linux target.  */
 396
 397 void
 398 x86_linux_add_target (struct target_ops *t)
 399 {
 400   linux_nat_add_target (t);
 401   linux_nat_set_new_thread (t, x86_linux_new_thread);
 402   linux_nat_set_new_fork (t, x86_linux_new_fork);
 403   linux_nat_set_forget_process (t, x86_forget_process);
 404   linux_nat_set_prepare_to_resume (t, x86_linux_prepare_to_resume);
 405 }