Re: [PATCH, v4] [AArch64] MTE corefile support

[Luis Machado <luis.machado@arm.com>]

ping?

On 5/3/22 22:56, Luis Machado via Gdb-patches wrote:
> v4:
> 
> - Updated documentation (added cross-references).
> - Updated the segment name from PT_ARM_MEMTAG_MTE to
>    PT_AARCH64_MEMTAG_MTE.
> 
> v3:
> 
> - Updated NEWS and documentation to be more thorough.
> 
> v2:
> 
> - Rework memory tag section handling to use generic section fields.
> 
> --
> 
> Teach GDB how to dump memory tags for AArch64 when using the gcore command
> and how to read memory tag data back from a core file generated by GDB
> (via gcore) or by the Linux kernel.
> 
> The format is documented in the Linux Kernel documentation [1].
> 
> Each tagged memory range (listed in /proc/<pid>/smaps) gets dumped to its
> own PT_AARCH64_MEMTAG_MTE segment. A section named ".memtag" is created for each
> of those segments when reading the core file back.
> 
> To save a little bit of space, given MTE tags only take 4 bits, the memory tags
> are stored packed as 2 tags per byte.
> 
> When reading the data back, the tags are unpacked.
> 
> I've added a new testcase to exercise the feature.
> 
> Build-tested with --enable-targets=all and regression tested on aarch64-linux
> Ubuntu 20.04.
> 
> [1] Documentation/arm64/memory-tagging-extension.rst (Core Dump Support)
> ---
>   gdb/Makefile.in                              |   1 +
>   gdb/NEWS                                     |  10 ++
>   gdb/aarch64-linux-tdep.c                     | 167 +++++++++++++++++++
>   gdb/arch/aarch64-mte-linux.c                 |  56 +++++++
>   gdb/arch/aarch64-mte-linux.h                 |  10 ++
>   gdb/corelow.c                                |  62 +++++++
>   gdb/defs.h                                   |   3 +-
>   gdb/doc/gdb.texinfo                          |  19 +++
>   gdb/gcore.c                                  |  83 ++++++++-
>   gdb/gdbarch-components.py                    |  35 ++++
>   gdb/gdbarch-gen.h                            |  26 +++
>   gdb/gdbarch.c                                |  96 +++++++++++
>   gdb/linux-tdep.c                             |  39 ++++-
>   gdb/memtag.c                                 |  61 +++++++
>   gdb/memtag.h                                 |  50 ++++++
>   gdb/testsuite/gdb.arch/aarch64-mte-gcore.c   |  93 +++++++++++
>   gdb/testsuite/gdb.arch/aarch64-mte-gcore.exp | 107 ++++++++++++
>   17 files changed, 910 insertions(+), 8 deletions(-)
>   create mode 100644 gdb/memtag.c
>   create mode 100644 gdb/memtag.h
>   create mode 100644 gdb/testsuite/gdb.arch/aarch64-mte-gcore.c
>   create mode 100644 gdb/testsuite/gdb.arch/aarch64-mte-gcore.exp
> 
> diff --git a/gdb/Makefile.in b/gdb/Makefile.in
> index 418094775a5..fac9364bea4 100644
> --- a/gdb/Makefile.in
> +++ b/gdb/Makefile.in
> @@ -1120,6 +1120,7 @@ COMMON_SFILES = \
>   	memattr.c \
>   	memory-map.c \
>   	memrange.c \
> +	memtag.c \
>   	minidebug.c \
>   	minsyms.c \
>   	mipsread.c \
> diff --git a/gdb/NEWS b/gdb/NEWS
> index 982f4a1a18c..3d925dc3663 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -3,6 +3,16 @@
>   
>   *** Changes since GDB 12
>   
> +* GDB now supports dumping memory tag data for AArch64 MTE.  It also supports
> +  reading memory tag data for AArch64 MTE from core files generated by
> +  the gcore command or the Linux kernel.
> +
> +  When a process uses memory-mapped pages protected by memory tags (for
> +  example, AArch64 MTE), this additional information will be recorded in
> +  the core file in the event of a crash or if GDB generates a core file
> +  from the current process state.  GDB will show this additional information
> +  automatically, or through one of the memory-tag subcommands.
> +
>   * GDB now supports hardware watchpoints on FreeBSD/Aarch64.
>   
>   * Remove support for building against Python 2, it is now only possible to
> diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
> index 55094b3d88b..12d98e71796 100644
> --- a/gdb/aarch64-linux-tdep.c
> +++ b/gdb/aarch64-linux-tdep.c
> @@ -53,6 +53,9 @@
>   
>   #include "gdbsupport/selftest.h"
>   
> +#include "elf/common.h"
> +#include "elf/aarch64.h"
> +
>   /* Signal frame handling.
>   
>         +------------+  ^
> @@ -1781,6 +1784,155 @@ aarch64_linux_report_signal_info (struct gdbarch *gdbarch,
>       }
>   }
>   
> +/* AArch64 Linux implementation of the gdbarch_create_memtag_section hook.  */
> +
> +static asection *
> +aarch64_linux_create_memtag_section (struct gdbarch *gdbarch, bfd *obfd,
> +				     CORE_ADDR address, size_t size)
> +{
> +  gdb_assert (obfd != nullptr);
> +  gdb_assert (size > 0);
> +
> +  /* Create the section and associated program header.  */
> +  asection *mte_section = bfd_make_section_anyway (obfd, "memtag");
> +
> +  if (mte_section == nullptr)
> +    return nullptr;
> +
> +  bfd_set_section_vma (mte_section, address);
> +  /* The size of the memory range covered by the memory tags.  We reuse the
> +     section's rawsize field for this purpose.  */
> +  mte_section->rawsize = size;
> +  /* Tags are stored packed as 2 tags per byte.  */
> +  bfd_set_section_size (mte_section, (size / AARCH64_MTE_GRANULE_SIZE) / 2);
> +  /* Make sure the section's flags has SEC_HAS_CONTENTS, otherwise BFD will
> +     refuse to write data to this section.  */
> +  bfd_set_section_flags (mte_section, SEC_HAS_CONTENTS);
> +
> +  /* Store program header information.  */
> +  bfd_record_phdr (obfd, PT_AARCH64_MEMTAG_MTE, 1, 0, 0, 0, 0, 0, 1,
> +		   &mte_section);
> +
> +  return mte_section;
> +}
> +
> +/* Maximum number of tags to request.  */
> +#define MAX_TAGS_TO_TRANSFER 1024
> +
> +/* AArch64 Linux implementation of the gdbarch_fill_memtag_section hook.  */
> +
> +static bool
> +aarch64_linux_fill_memtag_section (struct gdbarch *gdbarch, asection *osec)
> +{
> +  /* We only handle MTE tags for now.  */
> +
> +  size_t segment_size = osec->rawsize;
> +  CORE_ADDR start_address = bfd_section_vma (osec);
> +  CORE_ADDR end_address = start_address + segment_size;
> +
> +  /* Figure out how many tags we need to store in this memory range.  */
> +  size_t granules = aarch64_mte_get_tag_granules (start_address, segment_size,
> +						  AARCH64_MTE_GRANULE_SIZE);
> +
> +  /* If there are no tag granules to fetch, just return.  */
> +  if (granules == 0)
> +    return true;
> +
> +  CORE_ADDR address = start_address;
> +
> +  /* Vector of tags.  */
> +  gdb::byte_vector tags;
> +
> +  while (granules > 0)
> +    {
> +      /* Transfer tags in chunks.  */
> +      gdb::byte_vector tags_read;
> +      size_t xfer_len
> +	= (granules >= MAX_TAGS_TO_TRANSFER)?
> +	  MAX_TAGS_TO_TRANSFER * AARCH64_MTE_GRANULE_SIZE :
> +	  granules * AARCH64_MTE_GRANULE_SIZE;
> +
> +      if (!target_fetch_memtags (address, xfer_len, tags_read,
> +				 static_cast<int> (memtag_type::allocation)))
> +	{
> +	  warning (_("Failed to read MTE tags from memory range [%s,%s)."),
> +		     phex_nz (start_address, sizeof (start_address)),
> +		     phex_nz (end_address, sizeof (end_address)));
> +	  return false;
> +	}
> +
> +      /* Transfer over the tags that have been read.  */
> +      tags.insert (tags.end (), tags_read.begin (), tags_read.end ());
> +
> +      /* Adjust the remaining granules and starting address.  */
> +      granules -= tags_read.size ();
> +      address += tags_read.size () * AARCH64_MTE_GRANULE_SIZE;
> +    }
> +
> +  /* Pack the MTE tag bits.  */
> +  aarch64_mte_pack_tags (tags);
> +
> +  if (!bfd_set_section_contents (osec->owner, osec, tags.data (),
> +				 0, tags.size ()))
> +    {
> +      warning (_("Failed to write %s bytes of corefile memory "
> +		 "tag content (%s)."),
> +	       pulongest (tags.size ()),
> +	       bfd_errmsg (bfd_get_error ()));
> +    }
> +  return true;
> +}
> +
> +/* AArch64 Linux implementation of the gdbarch_decode_memtag_section
> +   hook.  Decode a memory tag section and return the requested tags.
> +
> +   The section is guaranteed to cover the [ADDRESS, ADDRESS + length)
> +   range.  */
> +
> +static gdb::byte_vector
> +aarch64_linux_decode_memtag_section (struct gdbarch *gdbarch,
> +				     bfd_section *section,
> +				     int type,
> +				     CORE_ADDR address, size_t length)
> +{
> +  gdb_assert (section != nullptr);
> +
> +  /* The requested address must not be less than section->vma.  */
> +  gdb_assert (section->vma <= address);
> +
> +  /* Figure out how many tags we need to fetch in this memory range.  */
> +  size_t granules = aarch64_mte_get_tag_granules (address, length,
> +						  AARCH64_MTE_GRANULE_SIZE);
> +  /* Sanity check.  */
> +  gdb_assert (granules > 0);
> +
> +  /* Fetch the total number of tags in the range [VMA, address + length).  */
> +  size_t granules_from_vma
> +    = aarch64_mte_get_tag_granules (section->vma,
> +				    address - section->vma + length,
> +				    AARCH64_MTE_GRANULE_SIZE);
> +
> +  /* Adjust the tags vector to contain the exact number of packed bytes.  */
> +  gdb::byte_vector tags (((granules - 1) >> 1) + 1);
> +
> +  /* Figure out the starting offset into the packed tags data.  */
> +  file_ptr offset = ((granules_from_vma - granules) >> 1);
> +
> +  if (!bfd_get_section_contents (section->owner, section, tags.data (),
> +				 offset, tags.size ()))
> +    error (_("Couldn't read contents from memtag section."));
> +
> +  /* At this point, the tags are packed 2 per byte.  Unpack them before
> +     returning.  */
> +  bool skip_first = ((granules_from_vma - granules) % 2) != 0;
> +  aarch64_mte_unpack_tags (tags, skip_first);
> +
> +  /* Resize to the exact number of tags that was requested.  */
> +  tags.resize (granules);
> +
> +  return tags;
> +}
> +
>   static void
>   aarch64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
>   {
> @@ -1864,6 +2016,21 @@ aarch64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
>   
>         set_gdbarch_report_signal_info (gdbarch,
>   				      aarch64_linux_report_signal_info);
> +
> +      /* Core file helpers.  */
> +
> +      /* Core file helper to create a memory tag section for a particular
> +	 PT_LOAD segment.  */
> +      set_gdbarch_create_memtag_section
> +	(gdbarch, aarch64_linux_create_memtag_section);
> +
> +      /* Core file helper to fill a memory tag section with tag data.  */
> +      set_gdbarch_fill_memtag_section
> +	(gdbarch, aarch64_linux_fill_memtag_section);
> +
> +      /* Core file helper to decode a memory tag section.  */
> +      set_gdbarch_decode_memtag_section (gdbarch,
> +					 aarch64_linux_decode_memtag_section);
>       }
>   
>     /* Initialize the aarch64_linux_record_tdep.  */
> diff --git a/gdb/arch/aarch64-mte-linux.c b/gdb/arch/aarch64-mte-linux.c
> index fc7a8cc00f7..3af6f364e91 100644
> --- a/gdb/arch/aarch64-mte-linux.c
> +++ b/gdb/arch/aarch64-mte-linux.c
> @@ -21,6 +21,62 @@
>   
>   /* See arch/aarch64-mte-linux.h */
>   
> +void
> +aarch64_mte_pack_tags (gdb::byte_vector &tags)
> +{
> +  /* Nothing to pack?  */
> +  if (tags.empty ())
> +    return;
> +
> +  /* If the tags vector has an odd number of elements, add another
> +     zeroed-out element to make it even.  This facilitates packing.  */
> +  if ((tags.size () % 2) != 0)
> +    tags.emplace_back (0);
> +
> +  for (int unpacked = 0, packed = 0; unpacked < tags.size ();
> +       unpacked += 2, packed++)
> +    tags[packed] = (tags[unpacked + 1] << 4) | tags[unpacked];
> +
> +  /* Now we have half the size.  */
> +  tags.resize (tags.size () / 2);
> +}
> +
> +/* See arch/aarch64-mte-linux.h */
> +
> +void
> +aarch64_mte_unpack_tags (gdb::byte_vector &tags, bool skip_first)
> +{
> +  /* Nothing to unpack?  */
> +  if (tags.empty ())
> +    return;
> +
> +  /* An unpacked MTE tags vector will have twice the number of elements
> +     compared to an unpacked one.  */
> +  gdb::byte_vector unpacked_tags (tags.size () * 2);
> +
> +  int unpacked = 0, packed = 0;
> +
> +  if (skip_first)
> +    {
> +      /* We are not interested in the first unpacked element, just discard
> +	 it.  */
> +      unpacked_tags[unpacked] = (tags[packed] >> 4) & 0xf;
> +      unpacked++;
> +      packed++;
> +    }
> +
> +  for (; packed < tags.size (); unpacked += 2, packed++)
> +    {
> +      unpacked_tags[unpacked] = tags[packed] & 0xf;
> +      unpacked_tags[unpacked + 1] = (tags[packed] >> 4) & 0xf;
> +    }
> +
> +  /* Update the original tags vector.  */
> +  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)
>   {
> diff --git a/gdb/arch/aarch64-mte-linux.h b/gdb/arch/aarch64-mte-linux.h
> index d158926feff..8a145b447aa 100644
> --- a/gdb/arch/aarch64-mte-linux.h
> +++ b/gdb/arch/aarch64-mte-linux.h
> @@ -32,6 +32,7 @@
>   
>   /* 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
>   
> @@ -71,4 +72,13 @@ extern CORE_ADDR aarch64_mte_set_ltag (CORE_ADDR address, CORE_ADDR tag);
>      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.  */
> +void aarch64_mte_pack_tags (gdb::byte_vector &tags);
> +
> +/* Given a TAGS vector containing 2 MTE tags per byte, unpack the data as
> +   1 tag per byte and resize the vector.  If SKIP_FIRST is TRUE, skip the
> +   first unpacked element.  Otherwise leave it in the unpacked vector.  */
> +void aarch64_mte_unpack_tags (gdb::byte_vector &tags, bool skip_first);
> +
>   #endif /* ARCH_AARCH64_LINUX_H */
> diff --git a/gdb/corelow.c b/gdb/corelow.c
> index 8c33fb7ebb2..8b8994f80db 100644
> --- a/gdb/corelow.c
> +++ b/gdb/corelow.c
> @@ -52,6 +52,7 @@
>   #include <unordered_set>
>   #include "gdbcmd.h"
>   #include "xml-tdesc.h"
> +#include "memtag.h"
>   
>   #ifndef O_LARGEFILE
>   #define O_LARGEFILE 0
> @@ -101,6 +102,13 @@ class core_target final : public process_stratum_target
>   
>     bool info_proc (const char *, enum info_proc_what) override;
>   
> +  bool supports_memory_tagging () override;
> +
> +  /* Core file implementation of fetch_memtags.  Fetch the memory tags from
> +     core file notes.  */
> +  bool fetch_memtags (CORE_ADDR address, size_t len,
> +		      gdb::byte_vector &tags, int type) override;
> +
>     /* A few helpers.  */
>   
>     /* Getter, see variable definition.  */
> @@ -1162,6 +1170,60 @@ core_target::info_proc (const char *args, enum info_proc_what request)
>     return true;
>   }
>   
> +/* Implementation of the "supports_memory_tagging" target_ops method.  */
> +
> +bool
> +core_target::supports_memory_tagging ()
> +{
> +  /* Look for memory tag sections.  If they exist, that means this core file
> +     supports memory tagging.  */
> +
> +  return (bfd_get_section_by_name (core_bfd, "memtag") != nullptr);
> +}
> +
> +/* Implementation of the "fetch_memtags" target_ops method.  */
> +
> +bool
> +core_target::fetch_memtags (CORE_ADDR address, size_t len,
> +			    gdb::byte_vector &tags, int type)
> +{
> +  struct gdbarch *gdbarch = target_gdbarch ();
> +
> +  /* Make sure we have a way to decode the memory tag notes.  */
> +  if (!gdbarch_decode_memtag_section_p (gdbarch))
> +    error (_("gdbarch_decode_memtag_section not implemented for this "
> +	     "architecture."));
> +
> +  memtag_section_info info;
> +  info.memtag_section = nullptr;
> +
> +  while (get_next_core_memtag_section (core_bfd, info.memtag_section,
> +				       address, info))
> +  {
> +    size_t adjusted_length
> +      = (address + len < info.end_address)? len : (info.end_address - address);
> +
> +    /* Decode the memory tag note and return the tags.  */
> +    gdb::byte_vector tags_read
> +      = gdbarch_decode_memtag_section (gdbarch, info.memtag_section, type,
> +				       address, adjusted_length);
> +
> +    /* Transfer over the tags that have been read.  */
> +    tags.insert (tags.end (), tags_read.begin (), tags_read.end ());
> +
> +    /* ADDRESS + LEN may cross the boundaries of a particular memory tag
> +       segment.  Check if we need to fetch tags from a different section.  */
> +    if (!tags_read.empty () && (address + len) < info.end_address)
> +      return true;
> +
> +    /* There are more tags to fetch.  Update ADDRESS and LEN.  */
> +    len -= (info.end_address - address);
> +    address = info.end_address;
> +  }
> +
> +  return false;
> +}
> +
>   /* Get a pointer to the current core target.  If not connected to a
>      core target, return NULL.  */
>   
> diff --git a/gdb/defs.h b/gdb/defs.h
> index 99bfdd526ff..51a7576a56a 100644
> --- a/gdb/defs.h
> +++ b/gdb/defs.h
> @@ -344,7 +344,8 @@ extern const char *pc_prefix (CORE_ADDR);
>   
>   typedef int (*find_memory_region_ftype) (CORE_ADDR addr, unsigned long size,
>   					 int read, int write, int exec,
> -					 int modified, void *data);
> +					 int modified, bool memory_tagged,
> +					 void *data);
>   
>   /* * Possible lvalue types.  Like enum language, this should be in
>      value.h, but needs to be here for the same reason.  */
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 38ad2ac32b0..36f10f20cfb 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -25555,6 +25555,25 @@ options that can be controlled at runtime and emulates the @code{prctl}
>   option @code{PR_SET_TAGGED_ADDR_CTRL}.  For further information, see the
>   documentation in the Linux kernel.
>   
> +@value{GDBN} supports dumping memory tag data to core files through the
> +@command{gcore} command and reading memory tag data from core files generated
> +by the @command{gcore} command or the Linux kernel.
> +
> +When a process uses memory-mapped pages protected by memory tags (for
> +example, AArch64 MTE), this additional information will be recorded in
> +the core file in the event of a crash or if @value{GDBN} generates a core file
> +from the current process state.
> +
> +The memory tag data will be used so developers can display the memory
> +tags from a particular memory region (using the @samp{m} modifier to the
> +@command{x} command, using the @command{print} command or using the various
> +@command{memory-tag} subcommands.
> +
> +In the case of a crash, @value{GDBN} will attempt to retrieve the memory tag
> +information automatically from the core file, and will show one of the above
> +messages depending on whether the synchronous or asynchronous mode is selected.
> +@xref{Memory Tagging}. @xref{Memory}.
> +
>   @node i386
>   @subsection x86 Architecture-specific Issues
>   
> diff --git a/gdb/gcore.c b/gdb/gcore.c
> index fdb22b72a07..b81ef81ab84 100644
> --- a/gdb/gcore.c
> +++ b/gdb/gcore.c
> @@ -349,6 +349,12 @@ make_output_phdrs (bfd *obfd, asection *osec)
>     int p_flags = 0;
>     int p_type = 0;
>   
> +  /* Memory tag segments have already been handled by the architecture, as
> +     those contain arch-specific information.  If we have one of those, just
> +     return.  */
> +  if (startswith (bfd_section_name (osec), "memtag"))
> +    return;
> +
>     /* FIXME: these constants may only be applicable for ELF.  */
>     if (startswith (bfd_section_name (osec), "load"))
>       p_type = PT_LOAD;
> @@ -371,7 +377,8 @@ make_output_phdrs (bfd *obfd, asection *osec)
>   
>   static int
>   gcore_create_callback (CORE_ADDR vaddr, unsigned long size, int read,
> -		       int write, int exec, int modified, void *data)
> +		       int write, int exec, int modified, bool memory_tagged,
> +		       void *data)
>   {
>     bfd *obfd = (bfd *) data;
>     asection *osec;
> @@ -454,6 +461,45 @@ gcore_create_callback (CORE_ADDR vaddr, unsigned long size, int read,
>     return 0;
>   }
>   
> +/* gdbarch_find_memory_region callback for creating a memory tag section.
> +   DATA is 'bfd *' for the core file GDB is creating.  */
> +
> +static int
> +gcore_create_memtag_section_callback (CORE_ADDR vaddr, unsigned long size,
> +				      int read, int write, int exec,
> +				      int modified, bool memory_tagged,
> +				      void *data)
> +{
> +  /* Are there memory tags in this particular memory map entry?  */
> +  if (!memory_tagged)
> +    return 0;
> +
> +  bfd *obfd = (bfd *) data;
> +
> +  /* Ask the architecture to create a memory tag section for this particular
> +     memory map entry.  It will be populated with contents later, as we can't
> +     start writing the contents before we have all the sections sorted out.  */
> +  asection *memtag_section
> +    = gdbarch_create_memtag_section (target_gdbarch (), obfd, vaddr, size);
> +
> +  if (memtag_section == nullptr)
> +    {
> +      warning (_("Couldn't make gcore memory tag segment: %s"),
> +	       bfd_errmsg (bfd_get_error ()));
> +      return 1;
> +    }
> +
> +  if (info_verbose)
> +    {
> +      gdb_printf (gdb_stdout, "Saved memory tag segment, %s bytes "
> +			      "at %s\n",
> +		  plongest (bfd_section_size (memtag_section)),
> +		  paddress (target_gdbarch (), vaddr));
> +    }
> +
> +  return 0;
> +}
> +
>   int
>   objfile_find_memory_regions (struct target_ops *self,
>   			     find_memory_region_ftype func, void *obfd)
> @@ -483,6 +529,7 @@ objfile_find_memory_regions (struct target_ops *self,
>   			   (flags & SEC_READONLY) == 0, /* Writable.  */
>   			   (flags & SEC_CODE) != 0, /* Executable.  */
>   			   1, /* MODIFIED is unknown, pass it as true.  */
> +			   false, /* No memory tags in the object file.  */
>   			   obfd);
>   	    if (ret != 0)
>   	      return ret;
> @@ -496,6 +543,7 @@ objfile_find_memory_regions (struct target_ops *self,
>   	     1, /* Stack section will be writable.  */
>   	     0, /* Stack section will not be executable.  */
>   	     1, /* Stack section will be modified.  */
> +	     false, /* No memory tags in the object file.  */
>   	     obfd);
>   
>     /* Make a heap segment.  */
> @@ -506,6 +554,7 @@ objfile_find_memory_regions (struct target_ops *self,
>   	     1, /* Heap section will be writable.  */
>   	     0, /* Heap section will not be executable.  */
>   	     1, /* Heap section will be modified.  */
> +	     false, /* No memory tags in the object file.  */
>   	     obfd);
>   
>     return 0;
> @@ -555,6 +604,20 @@ gcore_copy_callback (bfd *obfd, asection *osec)
>       }
>   }
>   
> +/* Callback to copy contents to a particular memory tag section.  */
> +
> +static void
> +gcore_copy_memtag_section_callback (bfd *obfd, asection *osec)
> +{
> +  /* We are only interested in "memtag" sections.  */
> +  if (!startswith (bfd_section_name (osec), "memtag"))
> +    return;
> +
> +  /* Fill the section with memory tag contents.  */
> +  if (!gdbarch_fill_memtag_section (target_gdbarch (), osec))
> +    error (_("Failed to fill memory tag section for core file."));
> +}
> +
>   static int
>   gcore_memory_sections (bfd *obfd)
>   {
> @@ -567,13 +630,27 @@ gcore_memory_sections (bfd *obfd)
>   	return 0;			/* FIXME: error return/msg?  */
>       }
>   
> +  /* Take care of dumping memory tags, if there are any.  */
> +  if (!gdbarch_find_memory_regions_p (target_gdbarch ())
> +      || gdbarch_find_memory_regions (target_gdbarch (),
> +				      gcore_create_memtag_section_callback,
> +				      obfd) != 0)
> +    {
> +      if (target_find_memory_regions (gcore_create_memtag_section_callback,
> +				      obfd) != 0)
> +	return 0;
> +    }
> +
>     /* Record phdrs for section-to-segment mapping.  */
>     for (asection *sect : gdb_bfd_sections (obfd))
>       make_output_phdrs (obfd, sect);
>   
> -  /* Copy memory region contents.  */
> +  /* Copy memory region and memory tag contents.  */
>     for (asection *sect : gdb_bfd_sections (obfd))
> -    gcore_copy_callback (obfd, sect);
> +    {
> +      gcore_copy_callback (obfd, sect);
> +      gcore_copy_memtag_section_callback (obfd, sect);
> +    }
>   
>     return 1;
>   }
> diff --git a/gdb/gdbarch-components.py b/gdb/gdbarch-components.py
> index e8f20c83ff0..6fa1b7591db 100644
> --- a/gdb/gdbarch-components.py
> +++ b/gdb/gdbarch-components.py
> @@ -1522,6 +1522,41 @@ Find core file memory regions
>       invalid=True,
>   )
>   
> +Method(
> +    comment="""
> +Given a bfd OBFD, segment ADDRESS and SIZE, create a memory tag section to be dumped to a core file
> +""",
> +    type="asection *",
> +    name="create_memtag_section",
> +    params=[("bfd *", "obfd"), ("CORE_ADDR", "address"), ("size_t", "size")],
> +    predicate=True,
> +    invalid=True,
> +)
> +
> +Method(
> +    comment="""
> +Given a memory tag section OSEC, fill OSEC's contents with the appropriate tag data
> +""",
> +    type="bool",
> +    name="fill_memtag_section",
> +    params=[("asection *", "osec")],
> +    predicate=True,
> +    invalid=True,
> +)
> +
> +Method(
> +    comment="""
> +Decode a memory tag SECTION and return the tags of type TYPE contained in
> +the memory range [ADDRESS, ADDRESS + LENGTH).
> +If no tags were found, return an empty vector.
> +""",
> +    type="gdb::byte_vector",
> +    name="decode_memtag_section",
> +    params=[("bfd_section *", "section"), ("int", "type"), ("CORE_ADDR", "address"), ("size_t", "length")],
> +    predicate=True,
> +    invalid=True,
> +)
> +
>   Method(
>       comment="""
>   Read offset OFFSET of TARGET_OBJECT_LIBRARIES formatted shared libraries list from
> diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h
> index 882b9057b1a..1d19f51f21d 100644
> --- a/gdb/gdbarch-gen.h
> +++ b/gdb/gdbarch-gen.h
> @@ -874,6 +874,32 @@ typedef int (gdbarch_find_memory_regions_ftype) (struct gdbarch *gdbarch, find_m
>   extern int gdbarch_find_memory_regions (struct gdbarch *gdbarch, find_memory_region_ftype func, void *data);
>   extern void set_gdbarch_find_memory_regions (struct gdbarch *gdbarch, gdbarch_find_memory_regions_ftype *find_memory_regions);
>   
> +/* Given a bfd OBFD, segment ADDRESS and SIZE, create a memory tag section to be dumped to a core file */
> +
> +extern bool gdbarch_create_memtag_section_p (struct gdbarch *gdbarch);
> +
> +typedef asection * (gdbarch_create_memtag_section_ftype) (struct gdbarch *gdbarch, bfd *obfd, CORE_ADDR address, size_t size);
> +extern asection * gdbarch_create_memtag_section (struct gdbarch *gdbarch, bfd *obfd, CORE_ADDR address, size_t size);
> +extern void set_gdbarch_create_memtag_section (struct gdbarch *gdbarch, gdbarch_create_memtag_section_ftype *create_memtag_section);
> +
> +/* Given a memory tag section OSEC, fill OSEC's contents with the appropriate tag data */
> +
> +extern bool gdbarch_fill_memtag_section_p (struct gdbarch *gdbarch);
> +
> +typedef bool (gdbarch_fill_memtag_section_ftype) (struct gdbarch *gdbarch, asection *osec);
> +extern bool gdbarch_fill_memtag_section (struct gdbarch *gdbarch, asection *osec);
> +extern void set_gdbarch_fill_memtag_section (struct gdbarch *gdbarch, gdbarch_fill_memtag_section_ftype *fill_memtag_section);
> +
> +/* Decode a memory tag SECTION and return the tags of type TYPE contained in
> +   the memory range [ADDRESS, ADDRESS + LENGTH).
> +   If no tags were found, return an empty vector. */
> +
> +extern bool gdbarch_decode_memtag_section_p (struct gdbarch *gdbarch);
> +
> +typedef gdb::byte_vector (gdbarch_decode_memtag_section_ftype) (struct gdbarch *gdbarch, bfd_section *section, int type, CORE_ADDR address, size_t length);
> +extern gdb::byte_vector gdbarch_decode_memtag_section (struct gdbarch *gdbarch, bfd_section *section, int type, CORE_ADDR address, size_t length);
> +extern void set_gdbarch_decode_memtag_section (struct gdbarch *gdbarch, gdbarch_decode_memtag_section_ftype *decode_memtag_section);
> +
>   /* Read offset OFFSET of TARGET_OBJECT_LIBRARIES formatted shared libraries list from
>      core file into buffer READBUF with length LEN.  Return the number of bytes read
>      (zero indicates failure).
> diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
> index a588bdef61a..f5dbacb14e7 100644
> --- a/gdb/gdbarch.c
> +++ b/gdb/gdbarch.c
> @@ -171,6 +171,9 @@ struct gdbarch
>     gdbarch_iterate_over_regset_sections_ftype *iterate_over_regset_sections;
>     gdbarch_make_corefile_notes_ftype *make_corefile_notes;
>     gdbarch_find_memory_regions_ftype *find_memory_regions;
> +  gdbarch_create_memtag_section_ftype *create_memtag_section;
> +  gdbarch_fill_memtag_section_ftype *fill_memtag_section;
> +  gdbarch_decode_memtag_section_ftype *decode_memtag_section;
>     gdbarch_core_xfer_shared_libraries_ftype *core_xfer_shared_libraries;
>     gdbarch_core_xfer_shared_libraries_aix_ftype *core_xfer_shared_libraries_aix;
>     gdbarch_core_pid_to_str_ftype *core_pid_to_str;
> @@ -527,6 +530,9 @@ verify_gdbarch (struct gdbarch *gdbarch)
>     /* Skip verify of iterate_over_regset_sections, has predicate.  */
>     /* Skip verify of make_corefile_notes, has predicate.  */
>     /* Skip verify of find_memory_regions, has predicate.  */
> +  /* Skip verify of create_memtag_section, has predicate.  */
> +  /* Skip verify of fill_memtag_section, has predicate.  */
> +  /* Skip verify of decode_memtag_section, has predicate.  */
>     /* Skip verify of core_xfer_shared_libraries, has predicate.  */
>     /* Skip verify of core_xfer_shared_libraries_aix, has predicate.  */
>     /* Skip verify of core_pid_to_str, has predicate.  */
> @@ -1096,6 +1102,24 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
>     gdb_printf (file,
>                         "gdbarch_dump: find_memory_regions = <%s>\n",
>                         host_address_to_string (gdbarch->find_memory_regions));
> +  gdb_printf (file,
> +                      "gdbarch_dump: gdbarch_create_memtag_section_p() = %d\n",
> +                      gdbarch_create_memtag_section_p (gdbarch));
> +  gdb_printf (file,
> +                      "gdbarch_dump: create_memtag_section = <%s>\n",
> +                      host_address_to_string (gdbarch->create_memtag_section));
> +  gdb_printf (file,
> +                      "gdbarch_dump: gdbarch_fill_memtag_section_p() = %d\n",
> +                      gdbarch_fill_memtag_section_p (gdbarch));
> +  gdb_printf (file,
> +                      "gdbarch_dump: fill_memtag_section = <%s>\n",
> +                      host_address_to_string (gdbarch->fill_memtag_section));
> +  gdb_printf (file,
> +                      "gdbarch_dump: gdbarch_decode_memtag_section_p() = %d\n",
> +                      gdbarch_decode_memtag_section_p (gdbarch));
> +  gdb_printf (file,
> +                      "gdbarch_dump: decode_memtag_section = <%s>\n",
> +                      host_address_to_string (gdbarch->decode_memtag_section));
>     gdb_printf (file,
>                         "gdbarch_dump: gdbarch_core_xfer_shared_libraries_p() = %d\n",
>                         gdbarch_core_xfer_shared_libraries_p (gdbarch));
> @@ -3744,6 +3768,78 @@ set_gdbarch_find_memory_regions (struct gdbarch *gdbarch,
>     gdbarch->find_memory_regions = find_memory_regions;
>   }
>   
> +bool
> +gdbarch_create_memtag_section_p (struct gdbarch *gdbarch)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  return gdbarch->create_memtag_section != NULL;
> +}
> +
> +asection *
> +gdbarch_create_memtag_section (struct gdbarch *gdbarch, bfd *obfd, CORE_ADDR address, size_t size)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  gdb_assert (gdbarch->create_memtag_section != NULL);
> +  if (gdbarch_debug >= 2)
> +    gdb_printf (gdb_stdlog, "gdbarch_create_memtag_section called\n");
> +  return gdbarch->create_memtag_section (gdbarch, obfd, address, size);
> +}
> +
> +void
> +set_gdbarch_create_memtag_section (struct gdbarch *gdbarch,
> +                                   gdbarch_create_memtag_section_ftype create_memtag_section)
> +{
> +  gdbarch->create_memtag_section = create_memtag_section;
> +}
> +
> +bool
> +gdbarch_fill_memtag_section_p (struct gdbarch *gdbarch)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  return gdbarch->fill_memtag_section != NULL;
> +}
> +
> +bool
> +gdbarch_fill_memtag_section (struct gdbarch *gdbarch, asection *osec)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  gdb_assert (gdbarch->fill_memtag_section != NULL);
> +  if (gdbarch_debug >= 2)
> +    gdb_printf (gdb_stdlog, "gdbarch_fill_memtag_section called\n");
> +  return gdbarch->fill_memtag_section (gdbarch, osec);
> +}
> +
> +void
> +set_gdbarch_fill_memtag_section (struct gdbarch *gdbarch,
> +                                 gdbarch_fill_memtag_section_ftype fill_memtag_section)
> +{
> +  gdbarch->fill_memtag_section = fill_memtag_section;
> +}
> +
> +bool
> +gdbarch_decode_memtag_section_p (struct gdbarch *gdbarch)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  return gdbarch->decode_memtag_section != NULL;
> +}
> +
> +gdb::byte_vector
> +gdbarch_decode_memtag_section (struct gdbarch *gdbarch, bfd_section *section, int type, CORE_ADDR address, size_t length)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  gdb_assert (gdbarch->decode_memtag_section != NULL);
> +  if (gdbarch_debug >= 2)
> +    gdb_printf (gdb_stdlog, "gdbarch_decode_memtag_section called\n");
> +  return gdbarch->decode_memtag_section (gdbarch, section, type, address, length);
> +}
> +
> +void
> +set_gdbarch_decode_memtag_section (struct gdbarch *gdbarch,
> +                                   gdbarch_decode_memtag_section_ftype decode_memtag_section)
> +{
> +  gdbarch->decode_memtag_section = decode_memtag_section;
> +}
> +
>   bool
>   gdbarch_core_xfer_shared_libraries_p (struct gdbarch *gdbarch)
>   {
> diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
> index 4e728a06e7e..8a83ed320cf 100644
> --- a/gdb/linux-tdep.c
> +++ b/gdb/linux-tdep.c
> @@ -42,6 +42,7 @@
>   #include "gcore.h"
>   #include "gcore-elf.h"
>   #include "solib-svr4.h"
> +#include "memtag.h"
>   
>   #include <ctype.h>
>   #include <unordered_map>
> @@ -1320,6 +1321,7 @@ typedef int linux_find_memory_region_ftype (ULONGEST vaddr, ULONGEST size,
>   					    ULONGEST offset, ULONGEST inode,
>   					    int read, int write,
>   					    int exec, int modified,
> +					    bool memory_tagged,
>   					    const char *filename,
>   					    void *data);
>   
> @@ -1470,10 +1472,11 @@ parse_smaps_data (const char *data,
>     return smaps;
>   }
>   
> -/* See linux-tdep.h.  */
> +/* Helper that checks if an address is in a memory tag page for a live
> +   process.  */
>   
> -bool
> -linux_address_in_memtag_page (CORE_ADDR address)
> +static bool
> +linux_process_address_in_memtag_page (CORE_ADDR address)
>   {
>     if (current_inferior ()->fake_pid_p)
>       return false;
> @@ -1505,6 +1508,30 @@ linux_address_in_memtag_page (CORE_ADDR address)
>     return false;
>   }
>   
> +/* Helper that checks if an address is in a memory tag page for a core file
> +   process.  */
> +
> +static bool
> +linux_core_file_address_in_memtag_page (CORE_ADDR address)
> +{
> +  if (core_bfd == nullptr)
> +    return false;
> +
> +  memtag_section_info info;
> +  return get_next_core_memtag_section (core_bfd, nullptr, address, info);
> +}
> +
> +/* See linux-tdep.h.  */
> +
> +bool
> +linux_address_in_memtag_page (CORE_ADDR address)
> +{
> +  if (!target_has_execution ())
> +    return linux_core_file_address_in_memtag_page (address);
> +
> +  return linux_process_address_in_memtag_page (address);
> +}
> +
>   /* List memory regions in the inferior for a corefile.  */
>   
>   static int
> @@ -1593,6 +1620,7 @@ linux_find_memory_regions_full (struct gdbarch *gdbarch,
>   		map.offset, map.inode, map.read, map.write, map.exec,
>   		1, /* MODIFIED is true because we want to dump
>   		      the mapping.  */
> +		map.vmflags.memory_tagging != 0,
>   		map.filename.c_str (), obfd);
>   	}
>       }
> @@ -1621,12 +1649,14 @@ static int
>   linux_find_memory_regions_thunk (ULONGEST vaddr, ULONGEST size,
>   				 ULONGEST offset, ULONGEST inode,
>   				 int read, int write, int exec, int modified,
> +				 bool memory_tagged,
>   				 const char *filename, void *arg)
>   {
>     struct linux_find_memory_regions_data *data
>       = (struct linux_find_memory_regions_data *) arg;
>   
> -  return data->func (vaddr, size, read, write, exec, modified, data->obfd);
> +  return data->func (vaddr, size, read, write, exec, modified, memory_tagged,
> +		     data->obfd);
>   }
>   
>   /* A variant of linux_find_memory_regions_full that is suitable as the
> @@ -1675,6 +1705,7 @@ static int
>   linux_make_mappings_callback (ULONGEST vaddr, ULONGEST size,
>   			      ULONGEST offset, ULONGEST inode,
>   			      int read, int write, int exec, int modified,
> +			      bool memory_tagged,
>   			      const char *filename, void *data)
>   {
>     struct linux_make_mappings_data *map_data
> diff --git a/gdb/memtag.c b/gdb/memtag.c
> new file mode 100644
> index 00000000000..af86137c49d
> --- /dev/null
> +++ b/gdb/memtag.c
> @@ -0,0 +1,61 @@
> +/* GDB generic memory tagging functions.
> +
> +   Copyright (C) 2022 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 "defs.h"
> +#include "memtag.h"
> +#include "bfd.h"
> +
> +/* See memtag.h */
> +
> +bool
> +get_next_core_memtag_section (bfd *abfd, asection *section,
> +			      CORE_ADDR address, memtag_section_info &info)
> +{
> +  /* If the caller provided no SECTION to start from, search from the
> +     beginning.  */
> +  if (section == nullptr)
> +    section = bfd_get_section_by_name (abfd, "memtag");
> +
> +  /* Go through all the memtag sections and figure out if ADDRESS
> +     falls within one of the memory ranges that contain tags.  */
> +  while (section != nullptr)
> +    {
> +      size_t memtag_range_size = section->rawsize;
> +      size_t tags_size = bfd_section_size (section);
> +
> +      /* Empty memory range and empty tag dump should not happen.  */
> +      gdb_assert (memtag_range_size != 0);
> +      gdb_assert (tags_size != 0);
> +
> +      CORE_ADDR start_address = bfd_section_vma (section);
> +      CORE_ADDR end_address = start_address + memtag_range_size;
> +
> +      /* Is the address within [start_address, end_address)?  */
> +      if (address >= start_address
> +	  && address < end_address)
> +	{
> +	  info.start_address = start_address;
> +	  info.end_address = end_address;
> +	  info.memtag_section = section;
> +	  return true;
> +	}
> +      section = bfd_get_next_section_by_name (abfd, section);
> +    }
> +  return false;
> +}
> diff --git a/gdb/memtag.h b/gdb/memtag.h
> new file mode 100644
> index 00000000000..fe908c1e5e3
> --- /dev/null
> +++ b/gdb/memtag.h
> @@ -0,0 +1,50 @@
> +/* GDB generic memory tagging definitions.
> +   Copyright (C) 2022 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 MEMTAG_H
> +#define MEMTAG_H
> +
> +#include "bfd.h"
> +
> +struct memtag_section_info
> +{
> +  /* The start address of the tagged memory range.  */
> +  CORE_ADDR start_address;
> +  /* The final address of the tagged memory range.  */
> +  CORE_ADDR end_address;
> +  /* The section containing tags for the memory range
> +     [start_address, end_address).  */
> +  asection *memtag_section;
> +};
> +
> +/* Helper function to walk through memory tag sections in a core file.
> +
> +   Return TRUE if there is a "memtag" section containing ADDRESS.  Return FALSE
> +   otherwise.
> +
> +   If SECTION is provided, search from that section onwards. If SECTION is
> +   nullptr, then start a new search.
> +
> +   If a "memtag" section containing ADDRESS is found, fill INFO with data
> +   about such section.  Otherwise leave it unchanged.  */
> +
> +bool get_next_core_memtag_section (bfd *abfd, asection *section,
> +				   CORE_ADDR address,
> +				   memtag_section_info &info);
> +
> +#endif /* MEMTAG_H */
> diff --git a/gdb/testsuite/gdb.arch/aarch64-mte-gcore.c b/gdb/testsuite/gdb.arch/aarch64-mte-gcore.c
> new file mode 100644
> index 00000000000..b20ebcff424
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-mte-gcore.c
> @@ -0,0 +1,93 @@
> +/* This test program is part of GDB, the GNU debugger.
> +
> +   Copyright 2021 Free Software Foundation, Inc.
> +
> +   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/>.  */
> +
> +/* Exercise AArch64's Memory Tagging Extension with tagged pointers.  */
> +
> +/* This test was based on the documentation for the AArch64 Memory Tagging
> +   Extension from the Linux Kernel, found in the sources in
> +   Documentation/arm64/memory-tagging-extension.rst.  */
> +
> +#include <errno.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <sys/auxv.h>
> +#include <sys/mman.h>
> +#include <sys/prctl.h>
> +
> +/* From arch/arm64/include/uapi/asm/hwcap.h */
> +#define HWCAP2_MTE              (1 << 18)
> +
> +/* From arch/arm64/include/uapi/asm/mman.h */
> +#define PROT_MTE  0x20
> +
> +/* From include/uapi/linux/prctl.h */
> +#define PR_SET_TAGGED_ADDR_CTRL 55
> +#define PR_GET_TAGGED_ADDR_CTRL 56
> +#define PR_TAGGED_ADDR_ENABLE	(1UL << 0)
> +#define PR_MTE_TCF_SHIFT	1
> +#define PR_MTE_TCF_SYNC		(1UL << PR_MTE_TCF_SHIFT)
> +#define PR_MTE_TAG_SHIFT	3
> +
> +void
> +access_memory (unsigned char *tagged_ptr)
> +{
> +  tagged_ptr[0] = 'a';
> +}
> +
> +int
> +main (int argc, char **argv)
> +{
> +  unsigned char *tagged_ptr;
> +  unsigned long page_sz = sysconf (_SC_PAGESIZE);
> +  unsigned long hwcap2 = getauxval(AT_HWCAP2);
> +
> +  /* Bail out if MTE is not supported.  */
> +  if (!(hwcap2 & HWCAP2_MTE))
> +    return 1;
> +
> +  /* Enable the tagged address ABI, synchronous MTE tag check faults and
> +     allow all non-zero tags in the randomly generated set.  */
> +  if (prctl (PR_SET_TAGGED_ADDR_CTRL,
> +	     PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_SYNC
> +	     | (0xfffe << PR_MTE_TAG_SHIFT),
> +	     0, 0, 0))
> +    {
> +      perror ("prctl () failed");
> +      return 1;
> +    }
> +
> +  /* Create a mapping that will have PROT_MTE set.  */
> +  tagged_ptr = mmap (0, page_sz, PROT_READ | PROT_WRITE,
> +		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> +  if (tagged_ptr == MAP_FAILED)
> +    {
> +      perror ("mmap () failed");
> +      return 1;
> +    }
> +
> +  /* Enable MTE on the above anonymous mmap.  */
> +  if (mprotect (tagged_ptr, page_sz, PROT_READ | PROT_WRITE | PROT_MTE))
> +    {
> +      perror ("mprotect () failed");
> +      return 1;
> +    }
> +
> +  access_memory (tagged_ptr);
> +
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.arch/aarch64-mte-gcore.exp b/gdb/testsuite/gdb.arch/aarch64-mte-gcore.exp
> new file mode 100644
> index 00000000000..8a19c4b449e
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-mte-gcore.exp
> @@ -0,0 +1,107 @@
> +# Copyright (C) 2018-2021 Free Software Foundation, Inc.
> +#
> +# 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/>.
> +
> +# This file is part of the gdb testsuite.
> +
> +# Test generating and reading a core file with MTE memory tags.
> +
> +if {![is_aarch64_target]} {
> +    verbose "Skipping ${gdb_test_file_name}."
> +    return
> +}
> +
> +standard_testfile
> +if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
> +    return -1
> +}
> +
> +if ![runto_main] {
> +    untested "could not run to main"
> +    return -1
> +}
> +
> +# Targets that don't support memory tagging should not execute the
> +# runtime memory tagging tests.
> +if {![supports_memtag]} {
> +    unsupported "memory tagging unsupported"
> +    return -1
> +}
> +
> +gdb_breakpoint "access_memory"
> +
> +if [gdb_continue "access_memory"] {
> +    return -1
> +}
> +
> +# Set each tag granule to a different tag value, from 0x0 to 0xf.
> +set atag_msg "Allocation tag\\(s\\) updated successfully\."
> +for {set i 15} {$i >= 0} {incr i -1} {
> +    set index [expr [expr 15 - $i] * 16]
> +    set tag [format "%02x" $i]
> +    gdb_test "memory-tag set-allocation-tag &tagged_ptr\[$index\] 1 $tag" \
> +	     $atag_msg \
> +	     "set memory tag of &tagged_ptr\[$index\] to $tag"
> +}
> +
> +# Run until a crash and confirm GDB displays memory tag violation
> +# information.
> +gdb_test "continue" \
> +    [multi_line \
> +	"Program received signal SIGSEGV, Segmentation fault" \
> +	"Memory tag violation while accessing address $hex" \
> +	"Allocation tag $hex" \
> +	"Logical tag $hex\." \
> +	"$hex in access_memory \\(.*\\) at .*" \
> +	".*tagged_ptr\\\[0\\\] = 'a';"] \
> +	 "display tag violation information for live process"
> +
> +# Generate the core file.
> +set core_filename [standard_output_file "$testfile.core"]
> +set core_generated [gdb_gcore_cmd "$core_filename" "generate core file"]
> +
> +if { !$core_generated } {
> +    return -1
> +}
> +
> +clean_restart $binfile
> +
> +# Load the core file and make sure we see the tag violation fault
> +# information.
> +gdb_test "core $core_filename" \
> +    [multi_line \
> +	"Core was generated by.*\." \
> +	"Program terminated with signal SIGSEGV, Segmentation fault" \
> +	"Memory tag violation while accessing address $hex" \
> +	"Allocation tag 0xf" \
> +	"Logical tag 0x0\." \
> +	"#0.*$hex in access_memory \\(.*\\) at .*" \
> +	".*tagged_ptr\\\[0\\\] = 'a';"] \
> +	 "core file shows tag violation information"
> +
> +# Make sure we have the tag_ctl register.
> +gdb_test "info register tag_ctl" \
> +	 "tag_ctl.*$hex.*${::decimal}" \
> +	 "tag_ctl is available"
> +
> +# Check if the tag granules have the expected values.  If they do, that
> +# means the core file saved the tags properly and GDB has read them
> +# correctly.
> +for {set i 15} {$i >= 0} {incr i -1} {
> +    set index [expr [expr 15 - $i] * 16]
> +    set tag [format "%x" $i]
> +    gdb_test "memory-tag print-allocation-tag &tagged_ptr\[$index\]" \
> +	     "= 0x$tag" \
> +	     "memory tag of &tagged_ptr\[$index\] is correct"
> +}