gdb/nat/aarch64-mte-linux-ptrace.c

   1 /* Common Linux native ptrace code for AArch64 MTE.
   2
   3    Copyright (C) 2021-2022 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 "gdbsupport/common-defs.h"
  21 #include "gdbsupport/byte-vector.h"
  22
  23 #include "linux-ptrace.h"
  24
  25 #include "arch/aarch64.h"
  26 #include "arch/aarch64-mte-linux.h"
  27 #include "nat/aarch64-linux.h"
  28 #include "nat/aarch64-mte-linux-ptrace.h"
  29
  30 #include <sys/uio.h>
  31
  32 /* Helper function to display various possible errors when reading
  33    MTE tags.  */
  34
  35 static void ATTRIBUTE_NORETURN
  36 aarch64_mte_linux_peek_error (int error)
  37 {
  38   switch (error)
  39     {
  40     case EIO:
  41       perror_with_name (_("PEEKMTETAGS not supported"));
  42       break;
  43     case EFAULT:
  44       perror_with_name (_("Couldn't fetch allocation tags"));
  45       break;
  46     case EOPNOTSUPP:
  47       perror_with_name (_("PROT_ME not enabled for requested address"));
  48     default:
  49       perror_with_name (_("Unknown MTE error"));
  50       break;
  51     }
  52 }
  53
  54 /* Helper function to display various possible errors when writing
  55    MTE tags.  */
  56
  57 static void ATTRIBUTE_NORETURN
  58 aarch64_mte_linux_poke_error (int error)
  59 {
  60   switch (error)
  61     {
  62     case EIO:
  63       perror_with_name (_("POKEMTETAGS not supported"));
  64       break;
  65     case EFAULT:
  66       perror_with_name (_("Couldn't store allocation tags"));
  67       break;
  68     case EOPNOTSUPP:
  69       perror_with_name (_("PROT_ME not enabled for requested address"));
  70     default:
  71       perror_with_name (_("Unknown MTE error"));
  72       break;
  73     }
  74 }
  75
  76 /* Helper to prepare a vector of tags to be passed on to the kernel.  The
  77    main purpose of this function is to optimize the number of calls to
  78    ptrace if we're writing too many tags at once, like a pattern fill
  79    request.
  80
  81    Return a vector of tags of up to MAX_SIZE size, containing the tags that
  82    must be passed on to the kernel, extracted from TAGS, starting at POS.
  83    GRANULES is the number of tag granules to be modified.  */
  84
  85 static gdb::byte_vector
  86 prepare_tag_vector (size_t granules, const gdb::byte_vector &tags, size_t pos,
  87                     size_t max_size)
  88 {
  89   gdb::byte_vector t;
  90
  91   if (granules == 0)
  92     return t;
  93
  94   gdb_assert (tags.size () > 0 && max_size > 0);
  95
  96   if (granules > AARCH64_MTE_TAGS_MAX_SIZE)
  97     t.resize (AARCH64_MTE_TAGS_MAX_SIZE);
  98   else
  99     t.resize (granules);
 100
 101   size_t tag_count = tags.size ();
 102
 103   for (size_t i = 0; i < t.size (); i++)
 104     t[i] = tags[(pos + i) % tag_count];
 105
 106   return t;
 107 }
 108
 109 /* See nat/aarch64-mte-linux-ptrace.h */
 110
 111 bool
 112 aarch64_mte_fetch_memtags (int tid, CORE_ADDR address, size_t len,
 113                            gdb::byte_vector &tags)
 114 {
 115   size_t ntags = aarch64_mte_get_tag_granules (address, len,
 116                                                AARCH64_MTE_GRANULE_SIZE);
 117
 118   /* If the memory range contains no tags, nothing left to do.  */
 119   if (ntags == 0)
 120     return true;
 121
 122   gdb_byte tagbuf[ntags];
 123
 124   struct iovec iovec;
 125   iovec.iov_base = tagbuf;
 126   iovec.iov_len = ntags;
 127
 128   tags.clear ();
 129   bool done_reading = false;
 130
 131   /* The kernel may return less tags than we requested.  Loop until we've read
 132      all the requested tags or until we get an error.  */
 133   while (!done_reading)
 134     {
 135       /* Attempt to read ntags allocation tags from the kernel.  */
 136       if (ptrace (PTRACE_PEEKMTETAGS, tid, address, &iovec) < 0)
 137         aarch64_mte_linux_peek_error (errno);
 138
 139       /* Make sure the kernel returned at least one tag.  */
 140       if (iovec.iov_len <= 0)
 141         {
 142           tags.clear ();
 143           return false;
 144         }
 145
 146       /* Copy the tags the kernel returned.  */
 147       for (size_t i = 0; i < iovec.iov_len; i++)
 148         tags.push_back (tagbuf[i]);
 149
 150       /* Are we done reading tags?  */
 151       if (tags.size () == ntags)
 152         done_reading = true;
 153       else
 154         {
 155           address += iovec.iov_len * AARCH64_MTE_GRANULE_SIZE;
 156           iovec.iov_len = ntags - iovec.iov_len;
 157         }
 158     }
 159   return true;
 160 }
 161
 162 /* See nat/aarch64-mte-linux-ptrace.h */
 163
 164 bool
 165 aarch64_mte_store_memtags (int tid, CORE_ADDR address, size_t len,
 166                            const gdb::byte_vector &tags)
 167 {
 168   if (tags.size () == 0)
 169     return true;
 170
 171   /* Get the number of tags we need to write.  */
 172   size_t ntags = aarch64_mte_get_tag_granules (address, len,
 173                                                AARCH64_MTE_GRANULE_SIZE);
 174
 175   /* If the memory range contains no tags, nothing left to do.  */
 176   if (ntags == 0)
 177     return true;
 178
 179   bool done_writing = false;
 180   size_t tags_written = 0;
 181
 182   /* Write all the tags, AARCH64_MTE_TAGS_MAX_SIZE blocks at a time.  */
 183   while (!done_writing)
 184     {
 185       gdb::byte_vector t = prepare_tag_vector (ntags - tags_written, tags,
 186                                                tags_written,
 187                                                AARCH64_MTE_TAGS_MAX_SIZE);
 188
 189       struct iovec iovec;
 190       iovec.iov_base = t.data ();
 191       iovec.iov_len = t.size ();
 192
 193       /* Request the kernel to update the allocation tags.  */
 194       if (ptrace (PTRACE_POKEMTETAGS, tid, address, &iovec) < 0)
 195         aarch64_mte_linux_poke_error (errno);
 196
 197       /* Make sure the kernel wrote at least one tag.  */
 198       if (iovec.iov_len <= 0)
 199         return false;
 200
 201       tags_written += iovec.iov_len;
 202
 203       /* Are we done writing tags?  */
 204       if (tags_written == ntags)
 205         done_writing = true;
 206       else
 207         address += iovec.iov_len * AARCH64_MTE_GRANULE_SIZE;
 208     }
 209
 210   return true;
 211 }