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 /* linux_nat_new_fork hook.   */
  47
  48 static void
  49 x86_linux_new_fork (struct lwp_info *parent, pid_t child_pid)
  50 {
  51   pid_t parent_pid;
  52   struct x86_debug_reg_state *parent_state;
  53   struct x86_debug_reg_state *child_state;
  54
  55   /* NULL means no watchpoint has ever been set in the parent.  In
  56      that case, there's nothing to do.  */
  57   if (parent->arch_private == NULL)
  58     return;
  59
  60   /* Linux kernel before 2.6.33 commit
  61      72f674d203cd230426437cdcf7dd6f681dad8b0d
  62      will inherit hardware debug registers from parent
  63      on fork/vfork/clone.  Newer Linux kernels create such tasks with
  64      zeroed debug registers.
  65
  66      GDB core assumes the child inherits the watchpoints/hw
  67      breakpoints of the parent, and will remove them all from the
  68      forked off process.  Copy the debug registers mirrors into the
  69      new process so that all breakpoints and watchpoints can be
  70      removed together.  The debug registers mirror will become zeroed
  71      in the end before detaching the forked off process, thus making
  72      this compatible with older Linux kernels too.  */
  73
  74   parent_pid = ptid_get_pid (parent->ptid);
  75   parent_state = x86_debug_reg_state (parent_pid);
  76   child_state = x86_debug_reg_state (child_pid);
  77   *child_state = *parent_state;
  78 }
  79 \f
  80
  81 static void (*super_post_startup_inferior) (struct target_ops *self,
  82                                             ptid_t ptid);
  83
  84 static void
  85 x86_linux_child_post_startup_inferior (struct target_ops *self, ptid_t ptid)
  86 {
  87   x86_cleanup_dregs ();
  88   super_post_startup_inferior (self, 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 static const struct target_desc *
 106 x86_linux_read_description (struct target_ops *ops)
 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 = ptid_get_lwp (inferior_ptid);
 118   if (tid == 0)
 119     tid = ptid_get_pid (inferior_ptid); /* 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       switch (xcr0_features_bits)
 196         {
 197         case X86_XSTATE_AVX_MPX_AVX512_PKU_MASK:
 198           if (is_x32)
 199             /* No MPX, PKU on x32, fall back to AVX-AVX512.  */
 200             return tdesc_x32_avx_avx512_linux;
 201           else
 202             return tdesc_amd64_avx_mpx_avx512_pku_linux;
 203         case X86_XSTATE_AVX_AVX512_MASK:
 204           if (is_x32)
 205             return tdesc_x32_avx_avx512_linux;
 206           else
 207             return tdesc_amd64_avx_avx512_linux;
 208         case X86_XSTATE_MPX_MASK:
 209           if (is_x32)
 210             return tdesc_x32_avx_linux; /* No MPX on x32 using AVX.  */
 211           else
 212             return tdesc_amd64_mpx_linux;
 213         case X86_XSTATE_AVX_MPX_MASK:
 214           if (is_x32)
 215             return tdesc_x32_avx_linux; /* No MPX on x32 using AVX.  */
 216           else
 217             return tdesc_amd64_avx_mpx_linux;
 218         case X86_XSTATE_AVX_MASK:
 219           if (is_x32)
 220             return tdesc_x32_avx_linux;
 221           else
 222             return tdesc_amd64_avx_linux;
 223         default:
 224           if (is_x32)
 225             return tdesc_x32_linux;
 226           else
 227             return tdesc_amd64_linux;
 228         }
 229 #endif
 230     }
 231   else
 232     {
 233       const struct target_desc * tdesc
 234         = i386_linux_read_description (xcr0_features_bits);
 235
 236       if (tdesc == NULL)
 237         tdesc = i386_linux_read_description (X86_XSTATE_SSE_MASK);
 238
 239       return tdesc;
 240     }
 241
 242   gdb_assert_not_reached ("failed to return tdesc");
 243 }
 244 \f
 245
 246 /* Enable branch tracing.  */
 247
 248 static struct btrace_target_info *
 249 x86_linux_enable_btrace (struct target_ops *self, ptid_t ptid,
 250                          const struct btrace_config *conf)
 251 {
 252   struct btrace_target_info *tinfo;
 253
 254   errno = 0;
 255   tinfo = linux_enable_btrace (ptid, conf);
 256
 257   if (tinfo == NULL)
 258     error (_("Could not enable branch tracing for %s: %s."),
 259            target_pid_to_str (ptid), safe_strerror (errno));
 260
 261   return tinfo;
 262 }
 263
 264 /* Disable branch tracing.  */
 265
 266 static void
 267 x86_linux_disable_btrace (struct target_ops *self,
 268                           struct btrace_target_info *tinfo)
 269 {
 270   enum btrace_error errcode = linux_disable_btrace (tinfo);
 271
 272   if (errcode != BTRACE_ERR_NONE)
 273     error (_("Could not disable branch tracing."));
 274 }
 275
 276 /* Teardown branch tracing.  */
 277
 278 static void
 279 x86_linux_teardown_btrace (struct target_ops *self,
 280                            struct btrace_target_info *tinfo)
 281 {
 282   /* Ignore errors.  */
 283   linux_disable_btrace (tinfo);
 284 }
 285
 286 static enum btrace_error
 287 x86_linux_read_btrace (struct target_ops *self,
 288                        struct btrace_data *data,
 289                        struct btrace_target_info *btinfo,
 290                        enum btrace_read_type type)
 291 {
 292   return linux_read_btrace (data, btinfo, type);
 293 }
 294
 295 /* See to_btrace_conf in target.h.  */
 296
 297 static const struct btrace_config *
 298 x86_linux_btrace_conf (struct target_ops *self,
 299                        const struct btrace_target_info *btinfo)
 300 {
 301   return linux_btrace_conf (btinfo);
 302 }
 303
 304 \f
 305
 306 /* Helper for ps_get_thread_area.  Sets BASE_ADDR to a pointer to
 307    the thread local storage (or its descriptor) and returns PS_OK
 308    on success.  Returns PS_ERR on failure.  */
 309
 310 ps_err_e
 311 x86_linux_get_thread_area (pid_t pid, void *addr, unsigned int *base_addr)
 312 {
 313   /* NOTE: cagney/2003-08-26: The definition of this buffer is found
 314      in the kernel header <asm-i386/ldt.h>.  It, after padding, is 4 x
 315      4 byte integers in size: `entry_number', `base_addr', `limit',
 316      and a bunch of status bits.
 317
 318      The values returned by this ptrace call should be part of the
 319      regcache buffer, and ps_get_thread_area should channel its
 320      request through the regcache.  That way remote targets could
 321      provide the value using the remote protocol and not this direct
 322      call.
 323
 324      Is this function needed?  I'm guessing that the `base' is the
 325      address of a descriptor that libthread_db uses to find the
 326      thread local address base that GDB needs.  Perhaps that
 327      descriptor is defined by the ABI.  Anyway, given that
 328      libthread_db calls this function without prompting (gdb
 329      requesting tls base) I guess it needs info in there anyway.  */
 330   unsigned int desc[4];
 331
 332   /* This code assumes that "int" is 32 bits and that
 333      GET_THREAD_AREA returns no more than 4 int values.  */
 334   gdb_assert (sizeof (int) == 4);
 335
 336 #ifndef PTRACE_GET_THREAD_AREA
 337 #define PTRACE_GET_THREAD_AREA 25
 338 #endif
 339
 340   if (ptrace (PTRACE_GET_THREAD_AREA, pid, addr, &desc) < 0)
 341     return PS_ERR;
 342
 343   *base_addr = desc[1];
 344   return PS_OK;
 345 }
 346 \f
 347
 348 /* Create an x86 GNU/Linux target.  */
 349
 350 struct target_ops *
 351 x86_linux_create_target (void)
 352 {
 353   /* Fill in the generic GNU/Linux methods.  */
 354   struct target_ops *t = linux_target ();
 355
 356   /* Initialize the debug register function vectors.  */
 357   x86_use_watchpoints (t);
 358   x86_dr_low.set_control = x86_linux_dr_set_control;
 359   x86_dr_low.set_addr = x86_linux_dr_set_addr;
 360   x86_dr_low.get_addr = x86_linux_dr_get_addr;
 361   x86_dr_low.get_status = x86_linux_dr_get_status;
 362   x86_dr_low.get_control = x86_linux_dr_get_control;
 363   x86_set_debug_register_length (sizeof (void *));
 364
 365   /* Override the GNU/Linux inferior startup hook.  */
 366   super_post_startup_inferior = t->to_post_startup_inferior;
 367   t->to_post_startup_inferior = x86_linux_child_post_startup_inferior;
 368
 369   /* Add the description reader.  */
 370   t->to_read_description = x86_linux_read_description;
 371
 372   /* Add btrace methods.  */
 373   t->to_supports_btrace = linux_supports_btrace;
 374   t->to_enable_btrace = x86_linux_enable_btrace;
 375   t->to_disable_btrace = x86_linux_disable_btrace;
 376   t->to_teardown_btrace = x86_linux_teardown_btrace;
 377   t->to_read_btrace = x86_linux_read_btrace;
 378   t->to_btrace_conf = x86_linux_btrace_conf;
 379
 380   return t;
 381 }
 382
 383 /* Add an x86 GNU/Linux target.  */
 384
 385 void
 386 x86_linux_add_target (struct target_ops *t)
 387 {
 388   linux_nat_add_target (t);
 389   linux_nat_set_new_thread (t, x86_linux_new_thread);
 390   linux_nat_set_new_fork (t, x86_linux_new_fork);
 391   linux_nat_set_forget_process (t, x86_forget_process);
 392   linux_nat_set_prepare_to_resume (t, x86_linux_prepare_to_resume);
 393 }