gdb: AArch64: Support MTE on baremetal

This commit moves aarch64_linux_memtag_matches_p,
aarch64_linux_set_memtags, aarch64_linux_get_memtag, and
aarch64_linux_memtag_to_string hooks (plus the aarch64_mte_get_atag
function used by them), along with the setting of the memtag granule
size, from aarch64-linux-tdep.c to aarch64-tdep.c, making MTE available
on baremetal targets. Since the aarch64-linux-tdep.c layer inherits
these hooks from aarch64-tdep.c, there is no effective change for
aarch64-linux targets.

Helpers used both by aarch64-tdep.c and by aarch64-linux-tdep.c were
moved from arch/aarch64-mte-linux.{c,h} to new arch/aarch64-mte.{c,h}
files.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Tested-By: Luis Machado <luis.machado@arm.com>
Approved-By: Luis Machado <luis.machado@arm.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>

11 files changed, 308 insertions, 251 deletions

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 1c697bf..6744b82 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -746,6 +746,7 @@ ALL_64_TARGET_OBS = \
 	amd64-windows-tdep.o \
 	arch/aarch64.o \
 	arch/aarch64-insn.o \
+	arch/aarch64-mte.o \
 	arch/aarch64-mte-linux.o \
 	arch/aarch64-scalable-linux.o \
 	arch/amd64-linux-tdesc.o \
@@ -1551,6 +1552,7 @@ HFILES_NO_SRCDIR = \
 	arch/aarch32.h \
 	arch/aarch64.h \
 	arch/aarch64-insn.h \
+	arch/aarch64-mte.h \
 	arch/aarch64-mte-linux.h \
 	arch/aarch64-scalable-linux.h \
 	arch/amd64-linux-tdesc.h \
@@ -1664,6 +1666,7 @@ ALLDEPFILES = \
 	arch/aarch32.c \
 	arch/aarch64.c \
 	arch/aarch64-insn.c \
+	arch/aarch64-mte.c \
 	arch/aarch64-mte-linux.c \
 	arch/aarch64-scalable-linux.c \
 	arch/amd64.c \
diff --git a/gdb/NEWS b/gdb/NEWS
index 9a5543c..50c033a 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -17,6 +17,9 @@
   This may cause breakage when using an incompatible libc, like uclibc or
   newlib, or an older glibc.
 
+* MTE (Memory Tagging Extension) debugging is now supported on AArch64 baremetal
+  targets.
+
 *** Changes in GDB 15
 
 * The MPX commands "show/set mpx bound" have been deprecated, as Intel
diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
index a1296a8..ada9614 100644
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -48,6 +48,7 @@
 #include "record-full.h"
 #include "linux-record.h"
 
+#include "arch/aarch64-mte.h"
 #include "arch/aarch64-mte-linux.h"
 #include "arch/aarch64-scalable-linux.h"
 
@@ -2427,29 +2428,6 @@ aarch64_linux_gcc_target_options (struct gdbarch *gdbarch)
   return {};
 }
 
-/* Helper to get the allocation tag from a 64-bit ADDRESS.
-
-   Return the allocation tag if successful and nullopt otherwise.  */
-
-static std::optional<CORE_ADDR>
-aarch64_mte_get_atag (CORE_ADDR address)
-{
-  gdb::byte_vector tags;
-
-  /* Attempt to fetch the allocation tag.  */
-  if (!target_fetch_memtags (address, 1, tags,
-			     static_cast<int> (memtag_type::allocation)))
-    return {};
-
-  /* Only one tag should've been returned.  Make sure we got exactly that.  */
-  if (tags.size () != 1)
-    error (_("Target returned an unexpected number of tags."));
-
-  /* Although our tags are 4 bits in size, they are stored in a
-     byte.  */
-  return tags[0];
-}
-
 /* Implement the tagged_address_p gdbarch method.  */
 
 static bool
@@ -2466,132 +2444,6 @@ aarch64_linux_tagged_address_p (struct gdbarch *gdbarch, CORE_ADDR address)
   return true;
 }
 
-/* Implement the memtag_matches_p gdbarch method.  */
-
-static bool
-aarch64_linux_memtag_matches_p (struct gdbarch *gdbarch,
-				struct value *address)
-{
-  gdb_assert (address != nullptr);
-
-  CORE_ADDR addr = value_as_address (address);
-
-  /* Fetch the allocation tag for ADDRESS.  */
-  std::optional<CORE_ADDR> atag
-    = aarch64_mte_get_atag (gdbarch_remove_non_address_bits (gdbarch, addr));
-
-  if (!atag.has_value ())
-    return true;
-
-  /* Fetch the logical tag for ADDRESS.  */
-  gdb_byte ltag = aarch64_mte_get_ltag (addr);
-
-  /* Are the tags the same?  */
-  return ltag == *atag;
-}
-
-/* Implement the set_memtags gdbarch method.  */
-
-static bool
-aarch64_linux_set_memtags (struct gdbarch *gdbarch, struct value *address,
-			   size_t length, const gdb::byte_vector &tags,
-			   memtag_type tag_type)
-{
-  gdb_assert (!tags.empty ());
-  gdb_assert (address != nullptr);
-
-  CORE_ADDR addr = value_as_address (address);
-
-  /* Set the logical tag or the allocation tag.  */
-  if (tag_type == memtag_type::logical)
-    {
-      /* When setting logical tags, we don't care about the length, since
-	 we are only setting a single logical tag.  */
-      addr = aarch64_mte_set_ltag (addr, tags[0]);
-
-      /* Update the value's content with the tag.  */
-      enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
-      gdb_byte *srcbuf = address->contents_raw ().data ();
-      store_unsigned_integer (srcbuf, sizeof (addr), byte_order, addr);
-    }
-  else
-    {
-      /* Remove the top byte.  */
-      addr = gdbarch_remove_non_address_bits (gdbarch, addr);
-
-      /* With G being the number of tag granules and N the number of tags
-	 passed in, we can have the following cases:
-
-	 1 - G == N: Store all the N tags to memory.
-
-	 2 - G < N : Warn about having more tags than granules, but write G
-		     tags.
-
-	 3 - G > N : This is a "fill tags" operation.  We should use the tags
-		     as a pattern to fill the granules repeatedly until we have
-		     written G tags to memory.
-      */
-
-      size_t g = aarch64_mte_get_tag_granules (addr, length,
-					       AARCH64_MTE_GRANULE_SIZE);
-      size_t n = tags.size ();
-
-      if (g < n)
-	warning (_("Got more tags than memory granules.  Tags will be "
-		   "truncated."));
-      else if (g > n)
-	warning (_("Using tag pattern to fill memory range."));
-
-      if (!target_store_memtags (addr, length, tags,
-				 static_cast<int> (memtag_type::allocation)))
-	return false;
-    }
-  return true;
-}
-
-/* Implement the get_memtag gdbarch method.  */
-
-static struct value *
-aarch64_linux_get_memtag (struct gdbarch *gdbarch, struct value *address,
-			  memtag_type tag_type)
-{
-  gdb_assert (address != nullptr);
-
-  CORE_ADDR addr = value_as_address (address);
-  CORE_ADDR tag = 0;
-
-  /* Get the logical tag or the allocation tag.  */
-  if (tag_type == memtag_type::logical)
-    tag = aarch64_mte_get_ltag (addr);
-  else
-    {
-      /* Remove the top byte.  */
-      addr = gdbarch_remove_non_address_bits (gdbarch, addr);
-      std::optional<CORE_ADDR> atag = aarch64_mte_get_atag (addr);
-
-      if (!atag.has_value ())
-	return nullptr;
-
-      tag = *atag;
-    }
-
-  /* Convert the tag to a value.  */
-  return value_from_ulongest (builtin_type (gdbarch)->builtin_unsigned_int,
-			      tag);
-}
-
-/* Implement the memtag_to_string gdbarch method.  */
-
-static std::string
-aarch64_linux_memtag_to_string (struct gdbarch *gdbarch, struct value *tag_value)
-{
-  if (tag_value == nullptr)
-    return "";
-
-  CORE_ADDR tag = value_as_address (tag_value);
-
-  return string_printf ("0x%s", phex_nz (tag, sizeof (tag)));
-}
 
 /* AArch64 Linux implementation of the report_signal_info gdbarch
    hook.  Displays information about possible memory tag violations.  */
@@ -2900,24 +2752,6 @@ aarch64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
       /* Register a hook for checking if an address is tagged or not.  */
       set_gdbarch_tagged_address_p (gdbarch, aarch64_linux_tagged_address_p);
 
-      /* Register a hook for checking if there is a memory tag match.  */
-      set_gdbarch_memtag_matches_p (gdbarch,
-				    aarch64_linux_memtag_matches_p);
-
-      /* Register a hook for setting the logical/allocation tags for
-	 a range of addresses.  */
-      set_gdbarch_set_memtags (gdbarch, aarch64_linux_set_memtags);
-
-      /* Register a hook for extracting the logical/allocation tag from an
-	 address.  */
-      set_gdbarch_get_memtag (gdbarch, aarch64_linux_get_memtag);
-
-      /* Set the allocation tag granule size to 16 bytes.  */
-      set_gdbarch_memtag_granule_size (gdbarch, AARCH64_MTE_GRANULE_SIZE);
-
-      /* Register a hook for converting a memory tag to a string.  */
-      set_gdbarch_memtag_to_string (gdbarch, aarch64_linux_memtag_to_string);
-
       set_gdbarch_report_signal_info (gdbarch,
 				      aarch64_linux_report_signal_info);
 
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index e4bca6c..865b1c0 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -45,6 +45,7 @@
 
 #include "aarch64-tdep.h"
 #include "aarch64-ravenscar-thread.h"
+#include "arch/aarch64-mte.h"
 
 #include "record.h"
 #include "record-full.h"
@@ -4088,6 +4089,156 @@ aarch64_stack_frame_destroyed_p (struct gdbarch *gdbarch, CORE_ADDR pc)
   return streq (inst.opcode->name, "ret");
 }
 
+/* Helper to get the allocation tag from a 64-bit ADDRESS.
+
+   Return the allocation tag if successful and nullopt otherwise.  */
+
+std::optional<CORE_ADDR>
+aarch64_mte_get_atag (CORE_ADDR address)
+{
+  gdb::byte_vector tags;
+
+  /* Attempt to fetch the allocation tag.  */
+  if (!target_fetch_memtags (address, 1, tags,
+			     static_cast<int> (memtag_type::allocation)))
+    return {};
+
+  /* Only one tag should've been returned.  Make sure we got exactly that.  */
+  if (tags.size () != 1)
+    error (_("Target returned an unexpected number of tags."));
+
+  /* Although our tags are 4 bits in size, they are stored in a
+     byte.  */
+  return tags[0];
+}
+
+/* Implement the memtag_matches_p gdbarch method.  */
+
+static bool
+aarch64_memtag_matches_p (struct gdbarch *gdbarch,
+			  struct value *address)
+{
+  gdb_assert (address != nullptr);
+
+  CORE_ADDR addr = value_as_address (address);
+
+  /* Fetch the allocation tag for ADDRESS.  */
+  std::optional<CORE_ADDR> atag
+    = aarch64_mte_get_atag (gdbarch_remove_non_address_bits (gdbarch, addr));
+
+  if (!atag.has_value ())
+    return true;
+
+  /* Fetch the logical tag for ADDRESS.  */
+  gdb_byte ltag = aarch64_mte_get_ltag (addr);
+
+  /* Are the tags the same?  */
+  return ltag == *atag;
+}
+
+/* Implement the set_memtags gdbarch method.  */
+
+static bool
+aarch64_set_memtags (struct gdbarch *gdbarch, struct value *address,
+		     size_t length, const gdb::byte_vector &tags,
+		     memtag_type tag_type)
+{
+  gdb_assert (!tags.empty ());
+  gdb_assert (address != nullptr);
+
+  CORE_ADDR addr = value_as_address (address);
+
+  /* Set the logical tag or the allocation tag.  */
+  if (tag_type == memtag_type::logical)
+    {
+      /* When setting logical tags, we don't care about the length, since
+	 we are only setting a single logical tag.  */
+      addr = aarch64_mte_set_ltag (addr, tags[0]);
+
+      /* Update the value's content with the tag.  */
+      enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+      gdb_byte *srcbuf = address->contents_raw ().data ();
+      store_unsigned_integer (srcbuf, sizeof (addr), byte_order, addr);
+    }
+  else
+    {
+      /* Remove the top byte.  */
+      addr = gdbarch_remove_non_address_bits (gdbarch, addr);
+
+      /* With G being the number of tag granules and N the number of tags
+	 passed in, we can have the following cases:
+
+	 1 - G == N: Store all the N tags to memory.
+
+	 2 - G < N : Warn about having more tags than granules, but write G
+		     tags.
+
+	 3 - G > N : This is a "fill tags" operation.  We should use the tags
+		     as a pattern to fill the granules repeatedly until we have
+		     written G tags to memory.
+      */
+
+      size_t g = aarch64_mte_get_tag_granules (addr, length,
+					       AARCH64_MTE_GRANULE_SIZE);
+      size_t n = tags.size ();
+
+      if (g < n)
+	warning (_("Got more tags than memory granules.  Tags will be "
+		   "truncated."));
+      else if (g > n)
+	warning (_("Using tag pattern to fill memory range."));
+
+      if (!target_store_memtags (addr, length, tags,
+				 static_cast<int> (memtag_type::allocation)))
+	return false;
+    }
+  return true;
+}
+
+/* Implement the get_memtag gdbarch method.  */
+
+static struct value *
+aarch64_get_memtag (struct gdbarch *gdbarch, struct value *address,
+		    memtag_type tag_type)
+{
+  gdb_assert (address != nullptr);
+
+  CORE_ADDR addr = value_as_address (address);
+  CORE_ADDR tag = 0;
+
+  /* Get the logical tag or the allocation tag.  */
+  if (tag_type == memtag_type::logical)
+    tag = aarch64_mte_get_ltag (addr);
+  else
+    {
+      /* Remove the top byte.  */
+      addr = gdbarch_remove_non_address_bits (gdbarch, addr);
+      std::optional<CORE_ADDR> atag = aarch64_mte_get_atag (addr);
+
+      if (!atag.has_value ())
+	return nullptr;
+
+      tag = *atag;
+    }
+
+  /* Convert the tag to a value.  */
+  return value_from_ulongest (builtin_type (gdbarch)->builtin_unsigned_int,
+			      tag);
+}
+
+/* Implement the memtag_to_string gdbarch method.  */
+
+static std::string
+aarch64_memtag_to_string (struct gdbarch *gdbarch, struct value *tag_value)
+{
+  if (tag_value == nullptr)
+    return "";
+
+  CORE_ADDR tag = value_as_address (tag_value);
+
+  return string_printf ("0x%s", phex_nz (tag, sizeof (tag)));
+}
+
 /* AArch64 implementation of the remove_non_address_bits gdbarch hook.  Remove
    non address bits from a pointer value.  */
 
@@ -4504,6 +4655,23 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 					aarch64_pseudo_register_reggroup_p);
   set_gdbarch_cannot_store_register (gdbarch, aarch64_cannot_store_register);
 
+  /* Set the allocation tag granule size to 16 bytes.  */
+  set_gdbarch_memtag_granule_size (gdbarch, AARCH64_MTE_GRANULE_SIZE);
+
+  /* Register a hook for checking if there is a memory tag match.  */
+  set_gdbarch_memtag_matches_p (gdbarch, aarch64_memtag_matches_p);
+
+  /* Register a hook for setting the logical/allocation tags for
+     a range of addresses.  */
+  set_gdbarch_set_memtags (gdbarch, aarch64_set_memtags);
+
+  /* Register a hook for extracting the logical/allocation tag from an
+     address.  */
+  set_gdbarch_get_memtag (gdbarch, aarch64_get_memtag);
+
+  /* Register a hook for converting a memory tag to a string.  */
+  set_gdbarch_memtag_to_string (gdbarch, aarch64_memtag_to_string);
+
   /* ABI */
   set_gdbarch_short_bit (gdbarch, 16);
   set_gdbarch_int_bit (gdbarch, 32);
diff --git a/gdb/aarch64-tdep.h b/gdb/aarch64-tdep.h
index 0e6024b..50166fb 100644
--- a/gdb/aarch64-tdep.h
+++ b/gdb/aarch64-tdep.h
@@ -203,4 +203,6 @@ void aarch64_displaced_step_fixup (struct gdbarch *gdbarch,
 
 bool aarch64_displaced_step_hw_singlestep (struct gdbarch *gdbarch);
 
+std::optional<CORE_ADDR> aarch64_mte_get_atag (CORE_ADDR address);
+
 #endif /* aarch64-tdep.h */
diff --git a/gdb/arch/aarch64-mte-linux.c b/gdb/arch/aarch64-mte-linux.c
index e0b441e..49426d7 100644
--- a/gdb/arch/aarch64-mte-linux.c
+++ b/gdb/arch/aarch64-mte-linux.c
@@ -75,59 +75,3 @@ aarch64_mte_unpack_tags (gdb::byte_vector &tags, bool skip_first)
   tags = std::move (unpacked_tags);
 }
 
-/* See arch/aarch64-mte-linux.h */
-
-size_t
-aarch64_mte_get_tag_granules (CORE_ADDR addr, size_t len, size_t granule_size)
-{
-  /* An empty range has 0 tag granules.  */
-  if (len == 0)
-    return 0;
-
-  /* Start address */
-  CORE_ADDR s_addr = align_down (addr, granule_size);
-  /* End address */
-  CORE_ADDR e_addr = align_down (addr + len - 1, granule_size);
-
-  /* We always have at least 1 granule because len is non-zero at this
-     point.  */
-  return 1 + (e_addr - s_addr) / granule_size;
-}
-
-/* See arch/aarch64-mte-linux.h */
-
-CORE_ADDR
-aarch64_mte_make_ltag_bits (CORE_ADDR value)
-{
-  return value & AARCH64_MTE_LOGICAL_MAX_VALUE;
-}
-
-/* See arch/aarch64-mte-linux.h */
-
-CORE_ADDR
-aarch64_mte_make_ltag (CORE_ADDR value)
-{
-  return (aarch64_mte_make_ltag_bits (value)
-	  << AARCH64_MTE_LOGICAL_TAG_START_BIT);
-}
-
-/* See arch/aarch64-mte-linux.h */
-
-CORE_ADDR
-aarch64_mte_set_ltag (CORE_ADDR address, CORE_ADDR tag)
-{
-  /* Remove the existing tag.  */
-  address &= ~aarch64_mte_make_ltag (AARCH64_MTE_LOGICAL_MAX_VALUE);
-
-  /* Return the new tagged address.  */
-  return address | aarch64_mte_make_ltag (tag);
-}
-
-/* See arch/aarch64-mte-linux.h */
-
-CORE_ADDR
-aarch64_mte_get_ltag (CORE_ADDR address)
-{
-  CORE_ADDR ltag_addr = address >> AARCH64_MTE_LOGICAL_TAG_START_BIT;
-  return aarch64_mte_make_ltag_bits (ltag_addr);
-}
diff --git a/gdb/arch/aarch64-mte-linux.h b/gdb/arch/aarch64-mte-linux.h
index 460b10e..686749f 100644
--- a/gdb/arch/aarch64-mte-linux.h
+++ b/gdb/arch/aarch64-mte-linux.h
@@ -29,12 +29,6 @@
 /* The MTE regset consists of a single 64-bit register.  */
 #define AARCH64_LINUX_SIZEOF_MTE 8
 
-/* We have one tag per 16 bytes of memory.  */
-#define AARCH64_MTE_GRANULE_SIZE 16
-#define AARCH64_MTE_TAG_BIT_SIZE 4
-#define AARCH64_MTE_LOGICAL_TAG_START_BIT 56
-#define AARCH64_MTE_LOGICAL_MAX_VALUE 0xf
-
 /* Memory tagging definitions.  */
 #ifndef SEGV_MTEAERR
 # define SEGV_MTEAERR 8
@@ -50,27 +44,6 @@ enum class aarch64_memtag_type
   mte_allocation
 };
 
-/* Return the number of tag granules in the memory range
-   [ADDR, ADDR + LEN) given GRANULE_SIZE.  */
-extern size_t aarch64_mte_get_tag_granules (CORE_ADDR addr, size_t len,
-					    size_t granule_size);
-
-/* Return the 4-bit tag made from VALUE.  */
-extern CORE_ADDR aarch64_mte_make_ltag_bits (CORE_ADDR value);
-
-/* Return the 4-bit tag that can be OR-ed to an address.  */
-extern CORE_ADDR aarch64_mte_make_ltag (CORE_ADDR value);
-
-/* Helper to set the logical TAG for a 64-bit ADDRESS.
-
-   It is always possible to set the logical tag.  */
-extern CORE_ADDR aarch64_mte_set_ltag (CORE_ADDR address, CORE_ADDR tag);
-
-/* Helper to get the logical tag from a 64-bit ADDRESS.
-
-   It is always possible to get the logical tag.  */
-extern CORE_ADDR aarch64_mte_get_ltag (CORE_ADDR address);
-
 /* Given a TAGS vector containing 1 MTE tag per byte, pack the data as
    2 tags per byte and resize the vector.  */
 extern void aarch64_mte_pack_tags (gdb::byte_vector &tags);
diff --git a/gdb/arch/aarch64-mte.c b/gdb/arch/aarch64-mte.c
new file mode 100644
index 0000000..908e12c
--- /dev/null
+++ b/gdb/arch/aarch64-mte.c
@@ -0,0 +1,77 @@
+/* Common AArch64 functionality for MTE
+
+   Copyright (C) 2021-2024 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "arch/aarch64-mte.h"
+
+/* See arch/aarch64-mte.h */
+
+size_t
+aarch64_mte_get_tag_granules (CORE_ADDR addr, size_t len, size_t granule_size)
+{
+  /* An empty range has 0 tag granules.  */
+  if (len == 0)
+    return 0;
+
+  /* Start address */
+  CORE_ADDR s_addr = align_down (addr, granule_size);
+  /* End address */
+  CORE_ADDR e_addr = align_down (addr + len - 1, granule_size);
+
+  /* We always have at least 1 granule because len is non-zero at this
+     point.  */
+  return 1 + (e_addr - s_addr) / granule_size;
+}
+
+/* See arch/aarch64-mte.h */
+
+CORE_ADDR
+aarch64_mte_make_ltag_bits (CORE_ADDR value)
+{
+  return value & AARCH64_MTE_LOGICAL_MAX_VALUE;
+}
+
+/* See arch/aarch64-mte.h */
+
+CORE_ADDR
+aarch64_mte_make_ltag (CORE_ADDR value)
+{
+  return (aarch64_mte_make_ltag_bits (value)
+	  << AARCH64_MTE_LOGICAL_TAG_START_BIT);
+}
+
+/* See arch/aarch64-mte.h */
+
+CORE_ADDR
+aarch64_mte_set_ltag (CORE_ADDR address, CORE_ADDR tag)
+{
+  /* Remove the existing tag.  */
+  address &= ~aarch64_mte_make_ltag (AARCH64_MTE_LOGICAL_MAX_VALUE);
+
+  /* Return the new tagged address.  */
+  return address | aarch64_mte_make_ltag (tag);
+}
+
+/* See arch/aarch64-mte.h */
+
+CORE_ADDR
+aarch64_mte_get_ltag (CORE_ADDR address)
+{
+  CORE_ADDR ltag_addr = address >> AARCH64_MTE_LOGICAL_TAG_START_BIT;
+  return aarch64_mte_make_ltag_bits (ltag_addr);
+}
diff --git a/gdb/arch/aarch64-mte.h b/gdb/arch/aarch64-mte.h
new file mode 100644
index 0000000..7d8445e
--- /dev/null
+++ b/gdb/arch/aarch64-mte.h
@@ -0,0 +1,51 @@
+/* Common AArch64 definitions for MTE
+
+   Copyright (C) 2021-2024 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef ARCH_AARCH64_MTE_H
+#define ARCH_AARCH64_MTE_H
+
+
+/* We have one tag per 16 bytes of memory.  */
+#define AARCH64_MTE_GRANULE_SIZE 16
+#define AARCH64_MTE_TAG_BIT_SIZE 4
+#define AARCH64_MTE_LOGICAL_TAG_START_BIT 56
+#define AARCH64_MTE_LOGICAL_MAX_VALUE 0xf
+
+/* Return the number of tag granules in the memory range
+   [ADDR, ADDR + LEN) given GRANULE_SIZE.  */
+extern size_t aarch64_mte_get_tag_granules (CORE_ADDR addr, size_t len,
+					    size_t granule_size);
+
+/* Return the 4-bit tag made from VALUE.  */
+extern CORE_ADDR aarch64_mte_make_ltag_bits (CORE_ADDR value);
+
+/* Return the 4-bit tag that can be OR-ed to an address.  */
+extern CORE_ADDR aarch64_mte_make_ltag (CORE_ADDR value);
+
+/* Helper to set the logical TAG for a 64-bit ADDRESS.
+
+   It is always possible to set the logical tag.  */
+extern CORE_ADDR aarch64_mte_set_ltag (CORE_ADDR address, CORE_ADDR tag);
+
+/* Helper to get the logical tag from a 64-bit ADDRESS.
+
+   It is always possible to get the logical tag.  */
+extern CORE_ADDR aarch64_mte_get_ltag (CORE_ADDR address);
+
+#endif /* ARCH_AARCH64_MTE_H */
diff --git a/gdb/configure.tgt b/gdb/configure.tgt
index 8326c45..5fb14b6 100644
--- a/gdb/configure.tgt
+++ b/gdb/configure.tgt
@@ -59,7 +59,8 @@ amd64_tobjs="ravenscar-thread.o amd64-ravenscar-thread.o \
 case "${targ}" in
 aarch64*-*-*)
 	cpu_obs="aarch32-tdep.o aarch64-tdep.o arch/aarch32.o \
-		 arch/aarch64-insn.o arch/aarch64.o  ravenscar-thread.o \
+		 arch/aarch64-insn.o arch/aarch64.o arch/aarch64-mte.o \
+		 ravenscar-thread.o \
 		 aarch64-ravenscar-thread.o";;
 
 alpha*-*-*)
diff --git a/gdb/nat/aarch64-mte-linux-ptrace.c b/gdb/nat/aarch64-mte-linux-ptrace.c
index 9e2a2ce..c2e7029 100644
--- a/gdb/nat/aarch64-mte-linux-ptrace.c
+++ b/gdb/nat/aarch64-mte-linux-ptrace.c
@@ -22,6 +22,7 @@
 #include "linux-ptrace.h"
 
 #include "arch/aarch64.h"
+#include "arch/aarch64-mte.h"
 #include "arch/aarch64-mte-linux.h"
 #include "nat/aarch64-linux.h"
 #include "nat/aarch64-mte-linux-ptrace.h"