gdbserver/linux-i386-ipa.cc

   1 /* GNU/Linux/x86 specific low level interface, for the in-process
   2    agent library for GDB.
   3
   4    Copyright (C) 2010-2024 Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <sys/mman.h>
  22 #include "tracepoint.h"
  23 #include "gdbsupport/x86-xstate.h"
  24 #include "arch/i386-linux-tdesc.h"
  25 #include "arch/x86-linux-tdesc-features.h"
  26
  27 /* GDB register numbers.  */
  28
  29 enum i386_gdb_regnum
  30 {
  31   I386_EAX_REGNUM,              /* %eax */
  32   I386_ECX_REGNUM,              /* %ecx */
  33   I386_EDX_REGNUM,              /* %edx */
  34   I386_EBX_REGNUM,              /* %ebx */
  35   I386_ESP_REGNUM,              /* %esp */
  36   I386_EBP_REGNUM,              /* %ebp */
  37   I386_ESI_REGNUM,              /* %esi */
  38   I386_EDI_REGNUM,              /* %edi */
  39   I386_EIP_REGNUM,              /* %eip */
  40   I386_EFLAGS_REGNUM,           /* %eflags */
  41   I386_CS_REGNUM,               /* %cs */
  42   I386_SS_REGNUM,               /* %ss */
  43   I386_DS_REGNUM,               /* %ds */
  44   I386_ES_REGNUM,               /* %es */
  45   I386_FS_REGNUM,               /* %fs */
  46   I386_GS_REGNUM,               /* %gs */
  47   I386_ST0_REGNUM               /* %st(0) */
  48 };
  49
  50 #define i386_num_regs 16
  51
  52 #define FT_CR_EAX 15
  53 #define FT_CR_ECX 14
  54 #define FT_CR_EDX 13
  55 #define FT_CR_EBX 12
  56 #define FT_CR_UESP 11
  57 #define FT_CR_EBP 10
  58 #define FT_CR_ESI 9
  59 #define FT_CR_EDI 8
  60 #define FT_CR_EIP 7
  61 #define FT_CR_EFL 6
  62 #define FT_CR_DS 5
  63 #define FT_CR_ES 4
  64 #define FT_CR_FS 3
  65 #define FT_CR_GS 2
  66 #define FT_CR_SS 1
  67 #define FT_CR_CS 0
  68
  69 /* Mapping between the general-purpose registers in jump tracepoint
  70    format and GDB's register array layout.  */
  71
  72 static const int i386_ft_collect_regmap[] =
  73 {
  74   FT_CR_EAX * 4, FT_CR_ECX * 4, FT_CR_EDX * 4, FT_CR_EBX * 4,
  75   FT_CR_UESP * 4, FT_CR_EBP * 4, FT_CR_ESI * 4, FT_CR_EDI * 4,
  76   FT_CR_EIP * 4, FT_CR_EFL * 4, FT_CR_CS * 4, FT_CR_SS * 4,
  77   FT_CR_DS * 4, FT_CR_ES * 4, FT_CR_FS * 4, FT_CR_GS * 4
  78 };
  79
  80 void
  81 supply_fast_tracepoint_registers (struct regcache *regcache,
  82                                   const unsigned char *buf)
  83 {
  84   int i;
  85
  86   for (i = 0; i < i386_num_regs; i++)
  87     {
  88       int regval;
  89
  90       if (i >= I386_CS_REGNUM && i <= I386_GS_REGNUM)
  91         regval = *(short *) (((char *) buf) + i386_ft_collect_regmap[i]);
  92       else
  93         regval = *(int *) (((char *) buf) + i386_ft_collect_regmap[i]);
  94
  95       supply_register (regcache, i, &regval);
  96     }
  97 }
  98
  99 ULONGEST
 100 get_raw_reg (const unsigned char *raw_regs, int regnum)
 101 {
 102   /* This should maybe be allowed to return an error code, or perhaps
 103      better, have the emit_reg detect this, and emit a constant zero,
 104      or something.  */
 105
 106   if (regnum > i386_num_regs)
 107     return 0;
 108   else if (regnum >= I386_CS_REGNUM && regnum <= I386_GS_REGNUM)
 109     return *(short *) (raw_regs + i386_ft_collect_regmap[regnum]);
 110   else
 111     return *(int *) (raw_regs + i386_ft_collect_regmap[regnum]);
 112 }
 113
 114 #ifdef HAVE_UST
 115
 116 #include <ust/processor.h>
 117
 118 /* "struct registers" is the UST object type holding the registers at
 119    the time of the static tracepoint marker call.  This doesn't
 120    contain EIP, but we know what it must have been (the marker
 121    address).  */
 122
 123 #define ST_REGENTRY(REG)                        \
 124   {                                             \
 125     offsetof (struct registers, REG),           \
 126     sizeof (((struct registers *) NULL)->REG)   \
 127   }
 128
 129 static struct
 130 {
 131   int offset;
 132   int size;
 133 } i386_st_collect_regmap[] =
 134   {
 135     ST_REGENTRY(eax),
 136     ST_REGENTRY(ecx),
 137     ST_REGENTRY(edx),
 138     ST_REGENTRY(ebx),
 139     ST_REGENTRY(esp),
 140     ST_REGENTRY(ebp),
 141     ST_REGENTRY(esi),
 142     ST_REGENTRY(edi),
 143     { -1, 0 }, /* eip */
 144     ST_REGENTRY(eflags),
 145     ST_REGENTRY(cs),
 146     ST_REGENTRY(ss),
 147   };
 148
 149 #define i386_NUM_ST_COLLECT_GREGS \
 150   (sizeof (i386_st_collect_regmap) / sizeof (i386_st_collect_regmap[0]))
 151
 152 void
 153 supply_static_tracepoint_registers (struct regcache *regcache,
 154                                     const unsigned char *buf,
 155                                     CORE_ADDR pc)
 156 {
 157   int i;
 158   unsigned int newpc = pc;
 159
 160   supply_register (regcache, I386_EIP_REGNUM, &newpc);
 161
 162   for (i = 0; i < i386_NUM_ST_COLLECT_GREGS; i++)
 163     if (i386_st_collect_regmap[i].offset != -1)
 164       {
 165         switch (i386_st_collect_regmap[i].size)
 166           {
 167           case 4:
 168             supply_register (regcache, i,
 169                              ((char *) buf)
 170                              + i386_st_collect_regmap[i].offset);
 171             break;
 172           case 2:
 173             {
 174               unsigned long reg
 175                 = * (short *) (((char *) buf)
 176                                + i386_st_collect_regmap[i].offset);
 177               reg &= 0xffff;
 178               supply_register (regcache, i, &reg);
 179             }
 180             break;
 181           default:
 182             internal_error ("unhandled register size: %d",
 183                             i386_st_collect_regmap[i].size);
 184           }
 185       }
 186 }
 187
 188 #endif /* HAVE_UST */
 189
 190
 191 /* This is only needed because reg-i386-linux-lib.o references it.  We
 192    may use it proper at some point.  */
 193 const char *gdbserver_xmltarget;
 194
 195 /* Attempt to allocate memory for trampolines in the first 64 KiB of
 196    memory to enable smaller jump patches.  */
 197
 198 static void
 199 initialize_fast_tracepoint_trampoline_buffer (void)
 200 {
 201   const CORE_ADDR buffer_end = 64 * 1024;
 202   /* Ensure that the buffer will be at least 1 KiB in size, which is
 203      enough space for over 200 fast tracepoints.  */
 204   const int min_buffer_size = 1024;
 205   char buf[IPA_BUFSIZ];
 206   CORE_ADDR mmap_min_addr = buffer_end + 1;
 207   ULONGEST buffer_size;
 208   FILE *f = fopen ("/proc/sys/vm/mmap_min_addr", "r");
 209
 210   if (!f)
 211     {
 212       snprintf (buf, sizeof (buf), "mmap_min_addr open failed: %s",
 213                 safe_strerror (errno));
 214       set_trampoline_buffer_space (0, 0, buf);
 215       return;
 216     }
 217
 218   if (fgets (buf, IPA_BUFSIZ, f))
 219     sscanf (buf, "%llu", &mmap_min_addr);
 220
 221   fclose (f);
 222
 223   buffer_size = buffer_end - mmap_min_addr;
 224
 225   if (buffer_size >= min_buffer_size)
 226     {
 227       if (mmap ((void *) (uintptr_t) mmap_min_addr, buffer_size,
 228                 PROT_READ | PROT_EXEC | PROT_WRITE,
 229                 MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
 230                 -1, 0)
 231           != MAP_FAILED)
 232         set_trampoline_buffer_space (mmap_min_addr, buffer_end, NULL);
 233       else
 234         {
 235           snprintf (buf, IPA_BUFSIZ, "low-64K-buffer mmap() failed: %s",
 236                     safe_strerror (errno));
 237           set_trampoline_buffer_space (0, 0, buf);
 238         }
 239     }
 240   else
 241     {
 242       snprintf (buf, IPA_BUFSIZ, "mmap_min_addr is %d, must be %d or less",
 243                 (int) mmap_min_addr, (int) buffer_end - min_buffer_size);
 244       set_trampoline_buffer_space (0, 0, buf);
 245     }
 246 }
 247
 248 /* Return target_desc to use for IPA, given the tdesc index passed by
 249    gdbserver.  */
 250
 251 const struct target_desc *
 252 get_ipa_tdesc (int idx)
 253 {
 254   uint64_t xcr0 = x86_linux_tdesc_idx_to_xcr0 (idx);
 255
 256   return i386_linux_read_description (xcr0);
 257 }
 258
 259 /* Allocate buffer for the jump pads.  On i386, we can reach an arbitrary
 260    address with a jump instruction, so just allocate normally.  */
 261
 262 void *
 263 alloc_jump_pad_buffer (size_t size)
 264 {
 265   void *res = mmap (NULL, size, PROT_READ | PROT_WRITE | PROT_EXEC,
 266                     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 267
 268   if (res == MAP_FAILED)
 269     return NULL;
 270
 271   return res;
 272 }
 273
 274 void
 275 initialize_low_tracepoint (void)
 276 {
 277   initialize_fast_tracepoint_trampoline_buffer ();
 278   for (int i = 0; i < x86_linux_i386_tdesc_count (); i++)
 279     i386_linux_read_description (x86_linux_tdesc_idx_to_xcr0 (i));
 280 }